TECHNICAL REPORTS SERIES No. 54 Application of Food

TECHNICAL REPORTS SERIES No. 5 4

Application of

Food Irradiation in

Developing Countries JOINT FAO/ IAEA DIVISION OF ATOMIC ENERGY IN AGRICULTURE ( ^ к

{ < £ Й INTERNATIONAL ATOMIC ENERGY AGENCY,VIENNA, 1966

APPLICATION OF FOOD IRRADIATION

IN DEVELOPING COUNTRIES

The following States ate Members of the International Atomic Energy Agency:

AFGHANISTAN FEDERAL REPUBLIC OF NICARAGUA ALBANIA GERMANY NIGERIA ALGERIA GABON NORWAY ARGENTINA GHANA PAKISTAN AUSTRALIA GREECE PARAGUAY AUSTRIA GUATEMALA PERU BELGIUM HAITI PHILIPPINES BOLIVIA HOLY SEE POLAND BRAZIL HONDURAS PORTUGAL

'BULGARIA HUNGARY ROMANIA BURMA ICELAND SAUDI ARABIA BYELORUSSIAN SOVIET INDIA SENEGAL

SOCIALIST REPUBLIC INDONESIA SOUTH AFRICA CAMBODIA IRAN SPAIN CAMEROON IRAQ SUDAN CANADA ISRAEL SWEDEN CEYLON ITALY SWITZERLAND CHILE IVORY COAST SYRIA CHINA JAMAICA THAILAND COLOMBIA JAPAN TUNISIA CONGO, DEMOCRATIC KENYA TURKEY

REPUBLIC OF REPUBLIC OF KOREA UKRAINIAN SOVIET SOCIALIST COSTA RICA KUWAIT REPUBLIC CUBA LEBANON UNION OF SOVIET SOCIALIST CYPRUS LIBERIA REPUBLICS CZECHOSLOVAK SOCIALIST LIBYA UNITED ARAB REPUBLIC

REPUBLIC LUXEMBOURG UNITED KINGDOM OF GREAT DENMARK MADAGASCAR BRITAIN AND NORTHERN DOMINICAN REPUBLIC MALI IRELAND ECUADOR MEXICO UNITED STATES OF AMERICA EL SALVADOR MONACO URUGUAY ETHIOPIA MOROCCO VENEZUELA FINLAND NETHERLANDS VIET-NAM FRANCE NEW ZEALAND YUGOSLAVIA

The Agency's Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; It entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is "to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world".

@ IAEA, 1966

Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Kärntner Ring 11, Vienna I, Austria.

Printed by the IAEA in Austria May 1966

TECHNICAL REPORTS SERIES No.54

APPLICATION OF FOOD IRRADIATION IN DEVELOPING COUNTRIES

R E P O R T O F A P A N E L O N A P P L I C A T I O N O F F O O D IRRADIATION IN D E V E L O P I N G COUNTRIES,

H E L D IN VIENNA, 3-6 A U G U S T 1964

I N T E R N A T I O N A L A T O M I C E N E R G Y A G E N C Y VIENNA, 1966

International Atomic Energy Agency. Applications of food irradiation in developing

countries. Report of a Panel ... held in Vienna, 3-6 August 1964. Vienna, the Agency, 1966. 183 p. (IAEA, Technical reports series no. 54)

664.8.039.5

A P P L I C A T I O N O F F O O D IRRADIATION IN D E V E L O P I N G C O U N T R I E S IAEA, VIENNA, 1966

STl/DOC/lO/54

FOREWORD

A Panel on the Application of Food Irradiation in Developing Countries was convened in Vienna by the International Atomic Energy Agency in August 1964. The meeting was motivated by the desire to assist in solving problems in the preservation of food in geographical areas where at present much food is lost through spoilage, deterioration and insect infestation; by minimizing such losses more food could be made available to the world population. It was thought that, if it was at all practicable, radiation treat-ment should be brought to bear on these problems.

The primary purpose was to advise the Director General of the Inter-national Atomic Energy Agency on how the Agency can best fulfil its role in this area. The members of the panel were selected for their competence and experience in the various technical fields and in handling various classes of food. There were 13 experts in attendance, with four observers from research organizations, and two representatives from the Food and Agri-culture Organization in Rome.

Since research has indicated great potential in the use of ionizing radi-ation in food preservation and since wheat, potatoes and bacon treated with ionizing radiation have been cleared for human consumption by certain governments, it seemed evident that investigations should be undertaken to exploit this new processing method for the benefit of the developing countries. Radiation treatment also has a potential to help increase the exchange of food products between countries through extending the useful life of certain fresh products and by killing organisms of quarantine and public health significance.

The deliberations of this panel resulted in several worthwhile recommen-dations that will be taken into consideration by the Agency in planning its future programmes and in extending those now in effect. It was recommend-ed that the Agency publish the proceedings of the panel, and the papers that were presented before it, in order that these might be made available to workers in the various countries for their information and guidance.

In presenting this• compilation the Agency wishes to express its gratitude to all participants for their advice, for the thoroughness with which they went over the problems and for their recommendations. Dr. Lars-Eric Ericson, on his untimely death, was succeeded as scientific secretary by Dr. Harry E. Goresline of the Food and Agriculture Organization of the United Nations, jointly with Dr. M . Fried.

The Panel wishes to be recorded as standing in silence as a tribute to the m e m o r y of Dr. Lars-Eric Ericson who has served as a source of inspiration and leadership in the formation of this Panel. He was dedicated to his work in food irradiation and those of us who knew him feel deeply his loss and will long remember him.

CONTENTS

T E R M S O P R E F E R E N C E

W O R K OF THE P A N E L

R E P O R T OF T H E P A N E L I. Research and development on the application of ionizing

energy in the developing countries 2 II. Education 2 III. Programme of activity for specific problem areas

A. Radiation preservation of fish and marine products B. Disinfestation of dried sind smoked fish C. Radiation preservation and disinfestation of fruits and

vegetables and their products D. Virus inactivation

PAPERS P R E S E N T E D B E F O R E T H E P A N E L Food preservation problems in developing countries 9

S. A. Goldblith The United States Atomic Energy Commission programme on

marine products irradiation 19 K. G. Shea

A discussion of the radiation preservation of fish in developing countries 39 D.N. Rhodes, T.A. Roberts and G. Hobbs

Research in the USSR on the conservation of fish and fish products by gamma irradiation 65 A. V. Kardashev

Insect infection of African dried or smoked fish and the possibility of its control by irradiation 73 J. Daget

Disinsectization of African dried and smoked fish by means of irradiation 85 M. H. Boisot and M. Gauzit

Clostridium botulinum, type E, in relation to irradiation treatment of fresh fish, with special reference to tropical conditions 95 K. Abrahamsson, N. Molin and N. N. de Silva

Prospects and needs for radiation disinfestation of packed fruits and vegetables 105 A. S. Talhouk

Radiation preservation of some fruits and vegetables 115 S.D. Dharkar

Use of ionizing radiations to prolong the storage life of fruit and berries (Review of work in the USSR) 123 V. I. Rogachev

Irradiation studies of fruit and vegetables in Latin America 143 J. Samn-Sâder'

Data on radiosensitization of fruit-spoilage fungi by chemical sensitizers 147 S. G. Georgopoulos, E. Georgiadou and B. Maoris

Radiosensitivity of purified and crude pectic enzyme preparations 151 K. Vas and G. Proszt

Radiation inactivation of foot and mouth disease virus 159 D. Massa

Report of the meeting of the PAO/WHO/IAEA expert committee on the technical basis for legislation on the wholesomeness sind microbiological safety of irradiated food .... 173 H. E. Goresline

Problems of the pasteurization of fruit juices by irradiation 177 K. Kaindl, H. Altmann, H. Gaisch, K. Prosenz and G. Stehlik

List of Participants 181

TERMS OF REFERENCE The terms of reference of the Panel on the Application of Food Irradi-

ation in Developing Countries are: (1) To consider the food problems existing in developing countries con-

cerned with: food preservation; insect control in stored products such as cereals, dried fruits and similar products; destruction of pathogenic microorganisms and other infective agents, including parasites, in foods; extension of the period of use and distribution of fresh products such as fruits, vegetables, meats and fish; inhibition of sprouting of certain vegetables; and the retardation of maturing of certain fruits.

(2) To suggest how the ionizing radiation process might be applied for the solution of some of these problems.

(3) To recommend investigations that should be undertaken and research projects that should be considered to collect scientific data and infor-mation which could eventually provide for a wider application of this new method of food processing, and lead to the solution of important food problems. The panel is not required to evaluate the suitability or effectiveness

of the process, since the feasibility has been adequately proven; or to be concerned with radiological health protection for personnel engaged in the production of irradiated food; or to consider legislative implications con-cerned with the production of irradiated food products and/or their distri-bution in international trade.

WORK OF THE P A N E L The sessions of the panel were held under the chairmanship of

Dr. Samuel A. Goldblith. During the sessions of the panel as a whole tech-nical papers on various subjects of interest were presented by members, describing results of radiation research or discussing conditions existing in particular geographic areas. This valuable information and the open dis-cussions by the.members were taken into consideration by the panel in ar-riving at conclusions and recommendations.

To further facilitate the work of the panel four smaller groups were formed to deal with specific areas of interest, the membership being made up of specialists in the specific fields. In sessions of these groups the problems were discussed, information and research data on the subject were laid before the members, the papers presented before the general sessions were discussed, and from this material conclusions were drawn. The work and discussions of each of the groups resulted in reports that were brought before the sessions of the panel as a whole for discussion arid consideration.

From such procedures the following report was developed setting forth the observations, suggestions and recommendations of the panel.

REPORT OF THE P A N E L The Panel on the Application of Food Irradiation in Developing Countries

has taken under consideration the material in the many technical papers that have been presented, the valuable information and personal experience laid

1

2 REPORT OF THE PANEL

before it by the specialists in the various fields of food handling and preser-vation, and the interchange of ideas brought about by the many discussions on the various subjects. These items have been of great value in arriving at unified opinions on the subjects laid before us and have made it possible for the panel to arrive at this unified report of its proceedings.

It is the opinion of the panel that: (a) Food irradiation has now reached a stage where some potential appli-

cations of ionizing energy in developing countries, in specific topics of interest, are possible. These m a y offer a real potential in elimi-nating some of the losses of food from insect and microbial damage and the prevention of the transmission of disease organisms and pests in products of export.

(b) The use of ionizing energy for the preservation of foods is still in the research and development stage and it is only now beginning to emerge as a method of food preservation in the well-developed areas of the world. Yet, in the opinion of this panel, there are potential benefits which m a y accrue if this technique is considered for study, research, and even in some cases, potential application to the developing countries.

(c) During this meeting background papers on certain possible areas of interest were presented to the panel, and there were detailed discussions on the entire problem of food irradiation, out of which emerged a series of recommendations, and like the three Princes of Serendip, additional ideas and recommendations of potential value to the developing countries arose which had not been foreseen. The following general observations and suggestions were made by the

panel:

I. R E S E A R C H A N D D E V E L O P M E N T O N T H E APPLICATION OF IONIZING E N E R G Y IN T H E D E V E L O P I N G COUNTRIES

The panel has concluded that many important problems within the subject matter under discussion can only be solved by radiation research within the geographical area in which the problems exist. In certain areas facilities exist for carrying out research, but in other locations radiation centres will be needed to serve large areas which are concerned with similar problems of food conservation. These radiation centres could, and preferably should, be run on an international basis so as to be able to establish close co-operation between irradiation specialists from the developed countries and specialists in local food technology working side by side, in the same es-tablishment, on real and urgent problems of the areas concerned.

It is recommended that the Agency survey the need for establishing such centres and the potential location for such centres in relation to existing problems that show promise of solution by the use of ionizing radiation.

II. E D U C A T I O N

The panel feels strongly that to effect optimal utilization of the above facilities, educational and training programmes for scientists in the develop-


ing countries should be encouraged. The panel also believes that it would be fruitless to establish radiation centres without providing for a sufficient number of properly educated men and women in this field.

III. P R O G R A M M E O F ACTIVITY F O R SPECIFIC P R O B L E M AREAS

The panel selected the following categories of interest for discussion and consideration:

A. Radiation preservation of fish and marine products B. Disinfestation of dried and smoked fish C. Radiation preservation and disinfestation of fruits and vegetables

and their products D. Virus inactivation. The following material sets forth the unanimous opinions of the panel

in these specific areas.

A. Radiation preservation of fish and marine products

Summary and conclusions

It is difficult to make a general judgement concerning the possibilities of the application of radiation in fish and marine technology to the countries of the world because of the variation in the specific local conditions and in their differing technical development. It seems likely, however, that at the present time, irradiation preservation of fresh fish is applicable to some of the more advanced developing countries.

The panel feels that the state of technology is such that for selected countries or areas, exploratory economic analyses and feasibility studies should be made to determine promising applications. Subsequently, the possibilities of scientific and applied research under local conditions should be considered.

There are two general processes to consider: (1) Radiation sterilization. The sterilization of raw fish is unacceptable because of subsequent deterioration by enzymes, because of moisture loss due to structural breakdown and because of off-flavours. It may be possible to successfully adapt this process to cooked fish and to certain local highly spiced or fermented products. Considering the different food habits in dif-ferent countries,' experiments should be carried out to determine the accept-ability of the food treated in the above manner. (2) Radiation pasteurization. The present state of knowledge indicates that this application is technically feasible for certain fish and marine products if used in combination with refrigeration. However, the economics of this process must be studied under local commercial conditions before judge-ment can be rendered on the feasibility of the application.

The potential danger of pathogenic Clostridia, particularly Clostridium botulinum, type E, must be considered carefully. To avoid the growth of such bacteria storage temperatures must be adequately controlled. For this reason in countries where such temperature control is not possible radi-ation pasteurization cannot be recommended at present.


It is possible that a combination of sufficient heat together with irradi-ation and proper packaging will result in total destruction of pathogenic Clostridia and give a safe product. There are, however, few data avail-able on the effect of ionizing radiations on Clostridium botulinum, type E, and on its ecology. Much work has to be done to determine the potential danger of this type of organism. Special emphasis should be paid to the occurrence and pathogenicity of this organism in fish and marine products in tropical regions. It is considered that such investigations should precede the possible application of food irradiation to fish in tropical areas. It is also believed that information which could be gained from investigations of this kind will also be of great potential value for other projects concerned with the development of improved methods for food preservation in the de-veloping countries.

Re commendations

(1) The panel recommends that the Agency (IAEA) sponsor research particularly in the field of the ecology of Clostridium botulinum, type E, to determine its distribution and potential danger.

(2) It is recommended that IAEA co-ordinate the research already going on in different laboratories in this field and increase the research potential by making additional research grants available.

B. Disinfestation of dried and smoked fish


Insect infestation of dried fish in certain developing countries causes losses of economic importance and it is believed that radiation treatment can provide a useful method of reducing such losses.

A radiation treatment becomes economically more attractive as the total amount processed increases. Thus, for a practicable application, a con-siderable quantity of material to be treated is essential, and the rate of pro-duction must be spread evenly over a sufficient part of the year.

In most instances the dried fish are collected from widely separated small fishing areas and are generally already infested on arrival at the con-centration point.

The major problem in insect control of these products is one of packaging to prevent reinfestation and this is not confined solely to the consideration of a radiation process. Unless an inexpensive insect-proof package can be found, no sophisticated disinfestation method is worthwhile applying.

Existing knowledge of applying radiation techniques for disinfestation of food products appears to be sufficient for the proposed application to dried and smoked fish.

Recommendations

(1) It is recommended that a survey be made by an international organi-zation to determine more accurately the extent of the loss of fish which


occurs between drying and arrival at the central store and between arrival at the store and the point of consumption. Based on data available to the panel it appears at the present time that only the latter losses can be prevented by irradiation disinfestation.

(2) It is recommended that an insect-proof package of suitable strength and of reasonable cost be found or developed. Such a package must not intro-duce a health hazard.

(3) Since dried and smoked fish products are easily transported it is recommended that studies on insect destruction, using doses based on exist-ing knowledge, be carried out under practical conditions by transporting materials to an existing research establishment for irradiation. These ex-periments should be designed

(a) To confirm the effectiveness of the dose against the insects; (b) To produce material for quality assessments; (c) To produce material to be returned to the local handling chain in

order to test packaging, storage behaviour, effectiveness against reinfestation, etc.

(4) It is recommended that the studies outlined above be used to provide data with which to determine whether the present methods used by the local industry could be improved, and whether the elimination of wastage achievable is sufficient to justify the expense of setting up an irradiation plant large enough to deal with the quantities of material available.

C. Radiation preservation and disinfestation of fruits and vegetables and their products


It is recognized that the information on hand indicates some distinct possibilities for the application of ionizing radiations for the practical pre-servation of fruits, fruit juices and vegetables. To warrant its use, any new method of food processing should perform tasks not previously possible or provide advantages in quality or economy. It is the view of the panel that these requirements are satisfied in many instances when fruits, fruit juices and vegetables are treated with ionizing radiations.

There are several ways in which irradiation might act in preserving fruits and vegetables, such as:

(a) Through the extension of the shelf life of certain fruits by destruc-tion or retardation of the growth of microorganisms;

(b) Through physiological effects such as the inhibition of the sprouting of potatoes and onions or through altering the rate of ripening of fruit;

(c) Through the destruction or sterilization of insects such as those which infest dried fruit.

The application of irradiation for all of these three purposes has been extensively studied. The inhibition of sprouting in potatoes by irradiation has reached the point where it is being applied on a practical scale in certain countries.

Much work has also been done on the prolongation of the useful shelf life of fruits and vegetables, mostly based on the control of microbial


spoilage. In spite of this, the evidence available on the benefits which may be derived from irradiation is not sufficiently clear to warrant a proposal of extensive large-scale usage. However, the indications of potential use-fulness are strong enough to suggest the need for further research and de-velopment work. It should be noted also that in the irradiation of plant ma-terial for the control of microorganisms, the occurrence of possible physiological side-effects cannot be excluded even if these are not now recognized.

Present indications are that irrädiation of fresh fruits, fruit juices or vegetables in the approximate dose range of 0.1 - 0. 5 Mrad often results in increased storage life. Higher radiation dosages in many cases cause undesirable changes in the texture or other properties of fresh fruits, fruit juices and vegetables. Therefore, radiation dosages above this range are not now recommended for such plant material. Higher dosages of radiation could be used to reduce microbial infection of spices and to render coconut meat free of Salmonella, and to treat dehydrated fruits and vegetables, reduce the microbial population and to enhance the rate of rehydration.

The papers presented to the panel described a number of instances which, together with other information available to panel members, indicate that there are many instances where irradiation m a y be successfully used for the prolongation of storage life of fruits, vegetables and of fruit juices by the control of microbial populations and insect infestation.

With great variations in the nature and characteristics of foods of plant origin and the substantial variations shown in their response to ionizing radi-ations, it is impossible to deal here with every separate instance or to give general statements which would hold true in all cases. Therefore, only the possibilities with some plant products, and particularly of fruits and vege-tables, will be noted to provide a basis for the recommendations given below.

The substantial progress in grain irradiation for elimination of insect damage and for sprout-inhibition of potatoes and onions by radiation are too well known to discuss here, and these instances of radiation preservation have been dealt with recently by other groups. In addition, the panel agreed that insect control in dried fruit has been studied to an extent justifying re-commendation for the practical use of this method where economic and regu-latory considerations permit its application. The panel felt that the prolon-gation of storage life of mangoes, citrus fruit, grapes, peaches, apricots, strawberries, cherries and tomatoes by the use of ionizing radiations is particularly promising. Several other items, such as the irradiation of bananas and papaya to delay ripening and the radiation preservation of fruit juices, m a y turn out to be practical after further research.

It is clear that m u c h more experimental information will have to be collected on the effect of ionizing radiations on plant material. In particular, the panel wishes to emphasize the need for more research to provide infor-mation on the following points:

(a) The physiological changes caused by irradiating fruits and vegetables; (b) The effects of irradiation on the natural resistance of fruits and

vegetable tissues to infection and breakdown; (c) The sensitization of microorganisms and insects by the use of agents

which will enhance the effectiveness of irradiation.


The panel also agreed that the usual factors determining the practical feasibility of food preservation techniques should also be taken into con-sideration for radiation preservation before large-scale operations are planned. For any food processing facility to be feasible and effective several criteria must be satisfied, but in particular the raw materials must be avail-able in uniform quality and maturity for prolonged continuous periods.

The panel believes that much of the needed research and development effort in this field must be carried out where research facilities, radiation sources and trained personnel are now available. It considers it highly de-sirable that some of the work be carried out in the countries where the raw materials are produced and where the process would be applied eventually, even if such countries now have no adequate facilities for such work. In addition to the obvious training aspects, this is desirable because many fruits and vegetables are produced only in certain areas and cannot be transported elsewhere for useful experiments. Further reasons for doing this are the differences which m a y exist in the prevailing insects and microbial flora in different countries.

Recommendations (1) It is recommended that the IAEA support requests from developing

countries to apply radiation preservation to products which satisfy the follow-ing requirements:

(a) That the irradiated products be of substantial importance to the economy of the country;

(b) That the scientific background information be sufficient to warrant such tests;

(c) That there be, in the country, a definite expectation that local tech-nical skills will be available for the eventual operation of such a production facility.

(2) The panel recommends that the irradiation treatment of potatoes, onions and dried fruit be tested and applied in some developing countries.

(3) The panel also recommends that further research on the radiation preservation of fruits, vegetables and fruit juices be encouraged, par-ticularly concerning the following matters:

(a) The biochemical mechanisms through which changes occur in ir-radiated plant material;

(b) The microbial and entomological aspects of food preservation by ionizing radiations (sensitization, resistant mutations, etc.);

(c) The application of combination food processing methods involving the use of ionizing radiations;

(d) The design and use of packaging materials and packages specifi-cally suitable for use with irradiated fruits, fruit juices and vegetables.

D. Virus inactivation

Summary and conclusions The panel notes that knowledge on the effects of ionizing energy on

viruses (particularly those associated with animal products), has just begun to be accumulated. The data thus far obtained, while not too extensive and


limited to several strains of the foot and mouth disease virus, have indi-cated a logarithmic destruction of the virus by ionizing energy.

The panel feels that further research should be encouraged and spon-sored on these and other viruses which are the etiological agents of exotic diseases of tremendous economic importance such as Rinder pest, African Swine Fever, Swine Fever, etc.

Radiation m a y offer a possible means of reducing or eliminating the virus titer in such products as glands, hair, straw bedding, hides, bone, fabrics used for packaging, etc., where undesirable side effects are not of extreme importance. The feasibility of this application, however, must be proven by extensive laboratory experimentation.

In addition, further studies are needed on the effects of ionizing energy on viruses in situ in meat, lymph nodes, fat, bones, etc., and for products consumed by m a n directly as in cured meat, or indirectly as in processed products such as gelatin.

Research to date has suggested the advisability of further research on the possible application of ionizing energy, either per se, or in combi-nation with other physical or chemical agents for the inactivation of theinfec-tivity of virus in the production of vaccines for Foot and Mouth Disease, Rinder pest, etc.

Recommendation

The panel recommends support of research on the quantitative effects of ionizing energy on certain viruses in situ important in animal food pro-duction, in vaccines and in products manufactured from animal materials.

FOOD PRESERVATION PROBLEMS IN DEVELOPING COUNTRIES

S.A. GOLDBLITH DEPARTMENT OF NUTRITION AND FOOD SCIENCE,

MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE, MASS., UNITED STATES OF AMERICA

Abstract — Résumé — Аннотация — Resumen

FOOD PRESERVATION PROBLEMS IN DEVELOPING COUNTRIES. This paper presents the basic problems relating to food preservation indeveloping countries as well as outlining the relative importance ot these problems among the whole group of basic socio-economic problems of the world today. Statistics are presented ( u s i n g

the USA as an example of a well-developed country) on the importance of technology in the production and preservation of foods. The food preservation problems of the developing countries are outlined in a general manner with specific illustrations of the problems themselves and the magnitude of these problems. These dau are presented in such a manner as to be consistent with the topic of the panel itself.

PROBLEMES DE LA CONSERVATION DES DENREES ALIMENTAIRES DANS LES PAYS EN VOIE DE DE-VELOPPEMENT. L'auteur expose les problèmes essentiels de la conservation des denrées alimentaires dans les pays en voie de développement et il étudie leur importance par rapport a celle des autres grands problèmes socio-économiques du monde actuel. En prenant les Etats-Unis comme exemple de pays parvenu à un stade de développement avancé, il fournit des statistiques montrant l'importance de la technologie dans la production et la conservation des denrées alimentaires. Cet exposé général est accompagné d'exemples concrets qui donnent une idée de l'ampleur des problèmes de la conservation des denrées alimentaires dans les pays en voie de développement. Ces renseignements sont présentés de manière à cadrer avec le sujet de la réunion.

ПРОБЛЕМЫ СОХРАНЕНИЯ ПРОДУКТОВ ПИТАНИЯ В РАЗВИВАЮЩИХСЯ СТРАНАХ. Излагаются основные проблемы, связанные с сохранением пищевых продуктов в развиваю-щихся странах, а также подчеркивается относительная важность этих проблем среди всей совокупности основных социально-экономических проблем в мире в настоящее время. Пред-ставляется статистика (с использованием США в качестве примера хорошо развитой страны) относительно важного значения техники в производстве и сохранении пищевых продуктов . Проблемы сохранения пищевых продуктов в развивающихся странах намечаются в общих чер-тах с конкретными примерами самих проблем и указанием их размаха. Эти данные представ-ляются таким образом, чтобы это было совместимо с темой самого совещания экспертов.

PROBLEMAS DE CONSERVACION DE ALIMENTOS EN LOS PAISES EN DESARROLLO. En la memoria se exponen los problemas fundamentales que plantea la conservación de alimentos en los países en desarrollo y se señala su importancia relativa dentro del conjunto de problemas básicos economicosociales que preocupan actualmente al mundo. Se dan datos estadísticos (tomando a los Estados Unidos como ejemplo de país ade-lantado) sobre la importancia de la tecnología para la producción y conservación de alimentos. Los problemas de conservación de alimentos en los países en desarrollo se exponen en líneas generales con ejemplos específicos de su índole y magnitud. Los datos se presentan de forma que resulten de utilidad para el estudio del tema de la reunión.

Ionizing energy has long been recommended in both the sc ient i f ic as well as the unscientific press as a panacea for the alleviation of many of the problems associated with the food supply and its conservation in both the developing as well as in the well-developed countries. Proposals have been made for the use of ionizing energy, varying in scope from that of the disinfestation of insects in grains to the sterilization of foods and from the

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TABLE IV

S O M E STATISTICS O N A R E A A N D P O P U L A T I O N O F S E L E C T E D C O U N T R I E S (Source: Statistical Abstract of the United States, 1963)

Country Area Population Population Annual rate (Square mi les ) (1960) per square of increase

m i l e (1958 -61 )

m

USA 3 615 211 1 7 9 3 2 3 000 51 1 . 7

Argentina 1 0 7 2 070 20 006 000 20 1 . 7

Brazil 3 2 8 6 4 7 8 7 0 9 67 000 22 3. 6

Costa Rica 19 575 801 000 a 43 4 . 4

Ecuador 104 506 3 203 000 a 33 3. 2

Guatemala 42 042 2 791 000 a 67. 3. 1

Honduras 43 277 1 883 000 b 4 4 3 . 0

El Salvador 8 260 2 501 0 0 0 b 3 2 8 3. 6

India 1 1 7 4 826 434 885 000 b 3 7 6 2. 2

Panama 2 8 7 5 3 1 0 7 6 0 0 0 39 2 . 7

Philippines 115 707 27 088 000 248 3 . 3

Thailand 1 9 8 4 5 6 2 6 2 5 8 000 137 3 . 0

О О 5 со r* I—I H a

a 1950 data. b 1961 data.

FOOD PRESERVATION PROBLEMS 11

setting up of shipboard irradiators to the development of self-contained nuclear power plants and associated irradiation facilities.

This paper presents the overall problems existent today in man's food supply in a number of areas of the world with which the writer is personally familiar, and outlines some of the challenges for ionizing energy in relation to solving some of these problems. It is only since the early 1900s that we can really say that the better-developed countries of the world began to evidence some concern about their more unfortunate brethren in other parts of the globe. As the famous historian Arnold Toynbee has stated: "Our age will be remembered chiefly neither for its horrifying crime, nor its as-tonishing inventions, but for its having been the first since the dawn of civili-zation in which people dared to think it practicable to make the benefits of civilization available for the whole human race."

The United Nations and its various agencies have done m u c h to tackle the problems associated with food, agriculture and public health in these countries. Various private philanthropic agencies have also accomplished much in respect to providing some of the basic needs of m a n in the under-developed and developing countries. However, much more remains to be done. These needs are not only because hunger exists today all over the world, with about one-third to one-half of the world's population being hungry or malnourished, but also because, if even conservative forecasts of popu-lation growth are fulfilled, we will qeed to double our food production in the next 20 yr, if we indeed fill all the "mouths of the world".

Professor Calder [1] in an excellent paper in 1963 stated that: "It has taken mankind over 200 000 yr to get up to a population level of three billion. " If our present daily rate of population increase of 140 000 continues, it will take only 40 yr to double our present population. Some interesting statistics in this respect are presented in Table I.

This prediction is a dire one if w e recognize that it is not sufficient to state simply that the potential calorie production in the world or protein production in the world can keep up with this increase. Rather, as Dr. Calder points out, these figures must not be distorted by surpluses that exist but are not or cannot be distributed'. W e must be concerned with getting the necessary food into hungry bellies'. Surpluses in the United States of America or in Western Europe do not necessarily mean that the growing population of a country such as India will be well fed1. According to one estimation, about one-third of the world's population eats three-quarters of the world's food supply.

Thus, the basic problem probably relates to specific countries and indeed specific areas within a country. W e must address ourselves to the basic problems of how ionizing energy can help local and specific situations. W e must avoid generalization and really dig into these illustrations and examples. Admittedly, the problems are global in scope but the situations themselves are local, and the answers are going to be obtained on a local basis although, without question, many of the possibilities of a specific use of radiation ap-plied to a specific local problem will have application in many other areas of the globe.

TABLE II

S O M E STATISTICS O N A G R I C U L T U R A L L A B O U R F O R C E IN T H E U N I T E D S T A T E S O F A M E R I C A (Source: Statistical Abstract of the United States, 1963)

1 2 3 4 Year Total population Total labour force Total labour force Ratio of 2 : 4

employed in agriculture

1940 132 594 000 56180 000 9 540 000 1 3 . 3 : 1

1950 151868 000 64 749 000 7497 000 20. 5 : 1

1955 165 931000 68 896 000 6 718 000 2 4 . 7 : 1

1960 180676000 7 3 1 2 6 0 0 0 5 7 2 3 0 0 0 3 1 . 6 : 1

1963 188447000 7 4 3 8 2 0 0 0 4 3 3 7 0 0 0 4 3 . 5 : 1


TABLE III

F A R M O U T P U T I N D E X E S IN T H E U N I T E D S T A T E S O F A M E R I C A , 1940-1962*

(Source: Statistical Abstract of the United States, 1963)

Year Ir.dex of farm output

1940 10

1950 86

1955 96

1960 103

1962 108

* Farm output 1957-1959 = 100

T H E SITUATION IN T H E W E L L - D E V E L O P E D C O U N T R I E S

Using the USA as an example, we can see that as technology is developed and as it is applied to agriculture, we have less and less people working in agricultural production (Table II) and a better and more efficient output from farms (Table III). Thus agriculture, transportation, science and technology in the well-developed countries afford the inhabitants thereof a surplus of food, fresh and processed, produced by relatively few people.

In the USA the food industry is the largest single industry, approximately 85 billion dollars out of a gross national product of about 554 billion dollars. Of this 85 billion dollars, a goodly portion is in the form of processed foods. As an example, and admittedly an extreme one, it is estimated that some 80% of all the citrus produced in the state of Florida is processed, either frozen, canned, or dehydrated1.

T H E SITUATION IN T H E D E V E L O P I N G C O U N T R I E S

It is interesting to compare the number of people needed to provide for the foodstuffs in different parts of the globe (Table IV). There are several important points which bear emphasizing. First of all, the better-developed countries are m o r e efficient in terms of food production per se and in the use of their employable population in providing foodstuffs for the entire population. A second point relates to the fact that developing countries are, by and large, in a state of caloric and/or protein deficit, which, unless some-thing is done to the contrary, will only becojne more serious. The Food and Agriculture Organization estimates that in the Far East, the region which contains over half the world's population, some 300-500 million people are undernourished and an additional 500 million do not get enough food of the right kind [2] . This becomes even more apparent if we examine Table V.

14 GOLDBLITH

TABLE IV

R E G I O N A L D I S T R I B U T I O N O F T H E W O R L D ' S F A R M A N D N O N - F A R M P O P U L A T I O N , 1958

(Source: Development Through Food, F r e e d o m from Hunger Campaign }

Basic Study No. 2, F A O , R o m e , Italy)

Area Population on the farm Total population in area

0")

Far East 70 1 506 000 000

Europe 31 417 000 000

USSR 48 207 000 000

North America 16 191000 000

Latin America 59 196000 000

Africa 72 203 000 000

Near East 70 125000000

Oceania 28 15000 000

TABLE V

R E G I O N A L S H A R E O F T H E W O R L D ' S A G R I C U L T U R A L P R O D U C T I O N A N D P O P U L A T I O N , 1958

(Source: Population and Food Supply, Freedom from Hunger Campaign, Basic Study No. 7, F A O , Rome, Italy)

Region Agricultural Population Index of per capita production Cla) production

Oft) (World over = 100)

Western Europe 15 11 133

Eastern Europe (including USSR) 17 10 162

Northern America 21 7 316

Latin America 8 7 121

Far East 28 53 53

Near East 4 4 90

Africa 4 7 60

Oceania 3 1 583

World total 100 100 100


It is now well-known that many people, especially weanling children, suffer from protein deficiency. This is true in Central America, India, Africa and parts of South America. Yet all of these areas are, or should be, good producers of foodstuffs. It is obvious that the first and primary need of these countries is an increased food supply. This can be achieved if a second necessity is supplied, namely, education to achieve higher agri-cultural productivity. But higher agricultural productivity in itself is not sufficient. To this must be added better transportation facilities in these areas and development of organized food preservation industries.

Better transportation can indeed help to avoid the paradox of food surplus on one side of a mountain chain and starvation on the other. Organized food preservation can indeed help to convert the perishable agricultural surpluses into stable commodities for future consumption.

In addition, the development of a food processing industry could lead to foreign exchange and a better economy for the entire country. One of the best examples of the latter is Argentina who, in times when it has good crops and large exports, has obtained an improved standard of living for its in-habitants. Argentina, however, could utilize better means of conservation and food technology and with this could improve its economic status tremen-dously. Thus the emergence of food science and technology as a discipline is badly needed in these countries.

The role of education in food science and technology cannot be over-stressed. The developing countries, almost without exception, lack an organized educational discipline in food science and technology and have, by any standards, a poorly developed food processing industry. By and large, most of the developing countries do not lack natural resources insofar as foodstuffs are concerned. What they do lack is a sufficient core of educated m e n and w o m e n who can understand the problems, who .can approach them scientifically, and who can educate sufficient numbers to carry out the solu-tions. Back-yard farming must be converted and transformed into organized agriculture if the developing countries are to increase their food output.

Education is not simply to be construed as university education, but rather education at all levels. Illiteracy must be wiped out in order for a population to become developed, a population that can understand the problems, solve these problems, and can overcome local prejudice, taboos and superstition.

Thus, the problems of food preservation in the developing countries are not simply problems in food preservation. They include all the socio-economic problems as well. The problems of food preservation themselves may be summarized as follows:

(1) To increase the yield of crops per land area. (2) To improve the types of crops in terms of optimizing the particular

species for a given area, climatic condition and disease resistance. (3) To develop a food processing industry based on good quality standards

so that the products may not only serve for the country itself, but also may be used for export and development of foreign exchange.

(4) To improve the public health aspects and sanitation of the? crops, animal foodstuffs and the foods processed therefrom.

(5) To improve storage conditions for foods in the developing countries.

16 GOLDBLITH

It is difficult to obtain accurate data on the consumption and require-ments of foodstuffs for various countries of the world. This becomes particu-larly true for the more underdeveloped countries. The Food and Agriculture Organization certainly found this out as a result of their world surveys. Documentation of food spoilage and wastage in the developing countries is even more difficult to pinpoint accurately, and it is even harder to document these data for underdeveloped countries. Thus, the best that we can probably say, with some modicum of accuracy, is

(1) There is both a caloric and a protein deficiency in various under-developed regions of the world.

(2) There is a definite wastage of food brought about through lack of knowledge, lack of processing equipment, and lack of trained and educated personnel to set up and operate food conservation pro-g r a m m e s using existing technology.

(3) This wastage of foods is not limited merely to vegetable and fruit crops but to animal products as well.

For some years, food scientists have been concerned with the problems of spoilage of animal foods - beef, poultry, eggs, etc. - in tropical regions where refrigeration is, for all practical purposes, non-existent and where power is simply not available or available in limited quantities and at high prices. Some workers, such as Deatherage and his group [3], have studied the potential use of antibiotics as a means of extending the marketability of fresh meat an additional 48 h. This process has not been widely adopted. There are a number of reasons for this into which I will not go. Never-theless, it illustrates a method that has had wide experimentation in an at-tempt to solve one of the big problems of food spoilage in the tropics.

Another example of animal food spoilage can be gleaned if we but address ourselves to the question of how many tons of fish are not caught each year in tropical regions, because there is no method of preservation which will en-able one to process and transport the products into inland regions of Brazil, Central America, or Africa where protein deficiency is indeed a problem. While exact figures are not available, it is well-known to inhabitants of the areas cited that the potential of the oceans of the world have not been tapped because of lack of transportation, refrigeration and processing facilities.

With respect to fruits and vegetables, again quantitative data are not available. However, it is estimated that in Pakistan about 25% of the total yield of fruit is wasted annually because of the fruit preservation industry being in its infancy [4] . Moreover, the total production of all kinds of fruits is still not sufficient to meet the demands of its 100 million people.

Another and major problem in developing countries relates to milk pre-servation. The importance of this in terms of infant feeding is obvious.

In terms of agricultural practice, an additional basic problem relates to the development of methods for the preservation of silage for animal feeding.

Lastly, I am sure that you are all familiar with the importance attached to groundnuts, such as peanuts, as sources of protein for undernourished areas. In recent years, the existence of a powerful toxin (Aflatoxin) produced by the growth of certain strains of Aspergillus flavus on peanuts has been demonstrated. The toxin produced by the growth of the Aspergillus on peanuts is toxigenic in very minute quantities. Thus, means must be found for pre-


venting the growth of this mould under the favourable conditions of tempera-ture and humidity that exist in the tropical and subtropical regions. The entire development and the rationale of using groundnuts and other vegetable proteins for human feeding may be dependent entirely on finding a means of obviating the production of this toxin. This may, of course, be achieved by either reducing the storage temperature or humidity (a practical impossi-bility in the tropics) or trying to destroy the mould on the peanuts by ex-posure either to chemicals or to ionizing energy. This toxin, and the mould producing it, has been demonstrated in corn and cottonseed as well as in peanuts; both of these crops have also been advocated for inexpensive protein supplementation for undernourished children in the underdeveloped regions of the world.

All of the above must be considered with due regard to the fact that suggested measures for solving these problems should not raise the cost of the food supply beyond the purchasing capacity of those of the most limited income in the particular area.

I fear that I have gone far beyond the subject assigned me. I have dwelled a great deal on the world problems. This I have done advisedly, as I have felt that we need to understand that the solution to the problems of food preservation in developing countries concerns us all. Moreover, I hope I have presented the problems in such a way as to suggest the proper place for ionizing energy.

Lastly, we must r e m e m b e r that in the long run we can do best when we teach each country how to help itself using its own people and its own resources.

R E F E R E N C E S

[1] CALDER, R., "The mathematics of hunger", in Food Supplies and Population Growth, Oliver and Boyd, Edinburgh (1963) 9-12.

[2] Population and Food Supply, Freedom from Hunger Campaign, Basic Study No. 7, UN Sales No. 62.1. 22. [3] DEATHERAGE, F. E., Use of antibiotics in the preservation of meats and other food products, Amer. J.

publ. Health £7 5 (1957) 594-600. [4] TYSSER, H. F., Ed., The Fruit Annual, British-Continental Trade Press, Ltd., London (1964) 609 pp.

THE UNITED STATES ATOMIC ENERGY COMMISSION

PROGRAMME ON MARINE PRODUCTS IRRADIATION

К. G. SHEA RADIATION PROCESSED FOODS SECTION, DIVISION OF ISOTOPES DEVELOPMENT,

UNITED STATES ATOMIC ENERGY COMMISSION, WASHINGTON, D . C . ,

UNITED STATES OF AMERICA


THE UNITED STATES ATOMIC ENERGY COMMISSION PROGRAMME ON MARINE PRODUCTS IRRADI-ATION. The USAEC progsamme organization on radiation treatment of marine products is described. Various elements of the programme including microbiology, facility design, construction and economics are reviewed and analysed. The importance of the Cl. botulinum, type E, question is discussed as well as the design, capa-bilities and proposed use of the soon-completed marine products pilot plant, located at Gloucester, Massachusetts. An evaluation is made of present status and future outlook.

PROGRAMME DE LA COMMISSION DE L'ENERGIE ATOMIQUE DES ETATS-UNIS SUR LE TRAITEMENT DES PRODUITS DE LA MER PAR LES RAYONNEMENTS. Le mémoire expose le programme de la CEA-EU sur le traitement des produits de la mer par les rayonnements. Il contient la description et l'analyse critique de divers éléments du programme, notamment la microbiologie, l 'étude des installations, leur construction et les prix de revient. L'auteur examine l ' importance de Cl. botulinum de type E ainsi que l 'e tude, la capacité et les possibilités d'emploi de l'usine pilote de traitement des produits de la mer dont la construction sera prochainement achevée à Gloucester (Massachusetts). Il fait le point de l'état actuel de la question et des perspectives d'avenir.

П Р О Г Р А М М А КОМИССИИ ПО АТОМНОЙ Э Н Е Р Г И И С О Е Д И Н Е Н Н Ы Х Ш Т А Т О В А М Е -Р И К И ПО О Б Л У Ч Е Н И Ю М О Р С К И Х П Р О Д У К Т О В . Д а е т с я описание о р г а н и з а ц и о н н ы х основ п р о г р а м м ы КАЭ США в о б л а с т и радиационной обработки морских п р о д у к т о в . Р а с с м а т р и в а -ются и а н а л и з и р у ю т с я р а з л и ч н ы е э л е м е н т ы п р о г р а м м ы , в том числе вопросы микробиологии, конструкции у с т а н о в к и , проблемы с т р о и т е л ь с т в а и экономики . О б с у ж д а е т с я вопрос о в а ж н о -сти C l . b o t u l i n u m типа Е , а т а к ж е к о н с т р у к ц и я , мощность и п р е д п о л а г а е м а я сфера и с п о л ь -з о в а н и я опытной у с т а н о в к и для о б р а б о т к и м о р с к и х п р о д у к т о в , с т р о и т е л ь с т в о которой с к о р о будет з а в е р ш е н о в Г л о с т е р е , штат М а с с а ч у з е т с . Д а е т с я оценка положения в настоящее в р е -м я и п е р с п е к т и в на б у д у щ е е .

PROGRAMA DE LA COMISION DE ENERGIA ATOMICA DE LOS ESTADOS UNIDOS SOBRE IRRADIACION DE PRODUCTOS MARINOS. La memor ia descr ibe la estructura d e l programa de la Comisión de Energía

Atómica de los Estados Unidos sobre la irradiación de productos marines y estudia y analiza diversos elementos

del programa: microbiología, diseño de instalaciones, construcción, aspectos económicos, e tc . Se examina

la importancia del Cl. botulinum tipo E y se describe el diseño, posibilidades de utilización y empleo proyectado

de la planta experimental para productos marinos de Gloucester (Massachusetts), que se terminerá en breve. Se

analiza la situación actual y las perspectivas futuras.

The United States Atomic Energy Commiss ion (USAEC) p r o g r a m m e in rad ia t ion pas t eu r i za t ion of foods has been wel l publ ic ized. The USAEC's p r i m e objective, d i rected toward civilian consumption, is to develop rad i -

19

20 SHEA

ation pasteurized products, especially fish and fruit products, which can last for three or four times their normal storage period while under re-frigeration.

Technological aspects of the U S A E C programme are sponsored by the Division of Isotopes Development, while research to establish the whole-someness and safety of the foods under study is the responsibility of the Division of Biology and Medicine (See Appendix 1). This report concerns itself primarily with the programme of the Division of Isotopes Development and especially that part of the programme concerning marine products (see Appendix 2). In this programme we aim to

(a) Develop radiation pasteurization of selected products to the point of technical and economic feasibility, and

(b) Develop prototype commercial radiation facilities.

R E S E A R C H R E S U L T S

Radiation pasteurization has been shown in laboratory research to ex-tend the refrigerated shelf life of marine products for thirty days or more, permitting an expansion of fresh fish markets to areas presently inacces-sible. Table I summarizes several typical results attainable with radiation. Two products, shrimp and haddock, have successfully undergone large-scale consumer feeding tests which were made in co-operation with the Depart-ment of the A r m y at Ft. Lee, Va.

Similarly, research in depth is proceeding on marine products. Miyauchi et al. [1], for example, found that when radiation pasteurized samples became unacceptable as a result of bacterial spoilage (usually samples ir-radiated below 0.4 Mrad), good agreement was found in evaluating the change in quality by total bacterial counts, yeasts and mould counts^ total volatile base, and trimethyl-amine nitrogen content. In samples whpre a combina-tion of higher irradiation dose and low storage temperature inhibited bac-terial spoilage other objective tests are needed and should be developed to measure the decrease in quality.

TABLE I

T Y P I C A L S H E L F L I F E E X T E N S I O N S

Product Dose (rad)

Normal shelf l i fe (d)

Irradiated shelf l i fe (d)

Shrimp

Crab

Haddock

Clams

150 000

200 000

200 000

400 000

14-21

7

12-14

5

21-40

35

30

30

USAEC MARINE PRODUCTS IRRADIATION 2 1

Another interesting observation was that bacterial populations must be approximately 100 times larger on irradiated products than on non-irradiated products to bring about flavour and odour changes.

One area of research involves the effects of irradiation on lipides of fish, to develop means of retarding undesirable changes [2]. The rancidity that develops in stored fish is the result of oxidative reactions. W o r k is being done with docosahexaenoic acid, a long chain fatty acid. Irradiation per se does not cause observable or measurable changes in this highly re-active fatty acid. However, we know that changes involving fatty acids do go on at a higher rate in the irradiated marine product. Current work is concerned with the influence of metal ions on model systems. Novak and Liuzzo [3] have demonstrated that melanosis, a black discolouration that occurs in shrimp from the action of phenol oxidases, can be controlled by low doses apparently through some intermediary interference. They are also doing work on the isolation and identification of the flavour components of shrimp and the changes which they undergo during irradiation. An at-tempt is being m a d e to recombine these components to duplicate original shrimp flavour. The most significant changes identified in the irradiated shrimp occurred in the reduction of trimethylamine and ammonia and an increase' in the methylamine content.

R A D I A T I O N M I C R O B I O L O G Y

The relation of resistance of microorganisms .to radiation is another area of work being supported. It is a fact that bacterial counts show extreme variation in samples of irradiated fish or shell fish after 14-21 d of storage at 33°F. These variations can range from no bacteria on one sample to as great as millions of bacteria per gram on another sample from the same lot of fish. To control those variations, it will ultimately be necessary to under-stand some of the factors that contribute to radiation resistance or radiation sensitivity.

Microorganisms are more susceptible to ionizing radiation when they are in the logarithmic phase of growth. Previous research has shown that the lipide content of the bacterial cells is correlated with the growth rate of the bacteria. In other words, as the bacterial growth rate increases the cellular lipide content decreases. It can therefore be hypothesized that the cellular lipides act as a protective agent providing a sparing effect on other critical parts of the cell. The degree of unsaturation of fatty acids m a y also play an important role in bacterial resistance as well as the role of the changed chemical composition of these fish flesh, e.g. an increase in inosine and hypoxanthine.

The areas of present and required research in regard to the special area of microbial flora on irradiated marine products might be summarized as follows :

(1) The shifting ecology of the irradiated flora caused by variation in irradi-ation resistance and the unique spoilage patterns resulting

(2) Whether or not a significant number of those microorganisms which survive are mutants, and their disease producing role, if any

(3) The extent of increase in radioresistance

22 SHEA

(4) The s y n e r g i s t i c r a d i o l e t h a l e f f e c t s of food add i t ives such as n i t r i t e s , n i t r a t e s , s o d i u m c h l o r i d e , a n t i b i o t i c s (Ty los in ) , c o n c o m i t a n t hea t and p o s s i b l e o t h e r a g e n t s .

With r e g a r d t o i t e m (1) above it h a s b e e n shown [4] t ha t the only o r g a -n i s m s s u r v i v i n g 0 .5 M r a d w e r e m e m b e r s of t h e g e n u s m i c r o c o c c i , s p o r e f o r m e r s , a n d p o s s i b l y a r a d i a t i o n r e s i s t a n t f o r m of S a l m o n e l l a t y p h o s a . E r d m a n e t a l . [5] p r e s e n t e d d a t a showing t h a t r e d u c e d r e s i s t a n c e to r a d i -a t ion could o c c u r t o a d e g r e e i v a r i a b l e wi th the b a c t e r i a l s p e c i e s . With E s c h e r i c h i a c o l i t h e d o s e r e q u i r e d , s u b s e q u e n t t o t h e d e v e l o p m e n t of r e -s i s t a n c e , w a s a p p r o x i m a t e l y doub led . R e s i s t a n c e s m u c h h i g h e r w e r e de -ve loped in l a t e r w o r k . S ign i f ican t changes a l s o o c c u r r e d in b i o c h e m i c a l r e -a c t i o n s . It w a s f e l t , t h e r e f o r e , t h a t r a d i a t i o n - r e s i s t a n t m u t a n t s h a d d e -v e l o p e d .

F i n a l l y , t he s y n e r g i s t i c e f f e c t of food add i t i ve s m a y wel l p r o v e of va lue , not only in p o s s i b l y l o w e r i n g the b u r d e n p l a c e d on r a d i a t i o n s t e r i l i z e d foods by the 12D r e q u i r e m e n t but a l s o in the p a s t e u r i z e d food p r o g r a m m e . In the f o r m e r c a s e va lue m a y b e d e r i v e d f r o m a l e s s e n e d i nc idence of o f f - f l a v o u r , o d o u r o r t e x t u r e . In o t h e r c a s e s , i t s p a r t i c u l a r v a l u e m a y p e r t a i n t o t h e c o n t r o l of p a t h o g e n s .

T h e whole q u e s t i o n of m i c r o b i o l o g y and p a t h o g e n i c i t y i s u n d e r r e v i e w . T h i s a r e a a s s u m e s c o n s i d e r a b l e i m p o r t a n c e w i t h r e l a t i o n t o t h e l o w d o s e t r e a t m e n t of i r r a d i a t e d f o o d s , p a r t i c u l a r l y t h o s e f o o d s above pH 4 .5 . The m a j o r p r o b l e m is r e l a t e d t o t h e p u t r e f a c t i v e a n a e r o b e s . T h e r e a r e s o m e r e l a t i v e l y n e w m i c r o b i o l o g i c a l p r o b l e m s i n t h i s f i e l d ; f o r e x a m p l e , C l o s t r i d i u m w e l c h i i ( a l s o c a l l e d CI. p e r f r i n g e n s ) i s now r e c o g n i z e d a s a c a u s a t i v e a g e n t of food p o i s o n i n g and h a s b e e n a s s o c i a t e d w i t h f i s h . A p -p a r e n t l y d a t a c o n c e r n i n g t h e r a d i a t i o n r e s i s t a n c e of CI . w e l c h i i s p o r e s i s s c a r c e . F t i r t h e r i t h a s b e e n r e c e n t l y i n d i c a t e d t h a t a l l of t h e C l o s t r i d i u m bo tu l inum s t r a i n s , A, B, C, D, E, and F , have been found to c a u s e bo tu l i sm in h u m a n s a s a r e s u l t of ea t ing po isoned food. This o b s e r v a t i o n i s impor t an t t o t h e food i n d u s t r y in g e n e r a l and could h a v e i m p o r t a n t f u t u r e i m p l i c a t i o n s in any r a d i a t i o n p a s t e u r i z a t i o n p r o g r a m m e .

S tud ie s of t h e c o n d i t i o n s f o r g e r m i n a t i o n of C l o s t r i d i u m bo tu l inum s p o r e s in v a r i o u s s u b s t r a t e s , b o t h t h e o r e t i c a l l y sind a s r e l a t e d t o u l t i m a t e hold ing c o n d i t i o n s , a r e i n d i c a t e d .

V e g e t a t i v e c e l l s of s o m e p a t h o g e n i c b a c t e r i a , s u c h a s S t r e p t o c o c c u s f a e c a l i s , c e r t a i n s a l m o n e l l a e , e t c . , h a v e b e e n s h o w n t o b e c o n s i d e r a b l y m o r e r a d i a t i o n r e s i s t a n t t h a n E . co l i , w h i c h i s o f t e n u s e d a s a t e s t o r g a -n i s m w h e n d e t e r m i n i n g t h e s a n i t a r y q u a l i t y of f o o d s . T h i s too could b e of c o n c e r n in e s t a b l i s h i n g i r r a d i a t i o n p a s t e u r i z a t i o n l e v e l s .

T h e s e r i o u s n e s s of CI. b o t u l i n u m , T y p e E , t o t h e e n t i r e food p r e s e r -v a t i o n i n d u s t r y w a s h i g h l i g h t e d when n ine d e a t h s in 1963 w e r e a t t r i b u t e d to CI. b o t u l i n u m , T y p e E, in c o m m e r c i a l l y c a n n e d o r s m o k e d f i s h [6]. While i n d e e d a c a u s e of c o n c e r n t o food p r o c e s s o r s , s t i l l a p r o p e r p e r s p e c t i v e in i n t e r p r e t i n g t h e s e a c c i d e n t s m u s t be app l ied . The magn i f i cen t r e c o r d , c o m -p i l e d in g e n e r a l b y t h e f o o d p r o c e s s i n g and d i s t r i b u t i o n i n d u s t r y , m u s t b e c o n s i d e r e d . T h e y m a y f u r t h e r b e a t t e s t e d t o by t h e f a c t t ha t t h e s e a r e t h e f i r s t s u c h i n c i d e n t s s i n c e 1926.

A s p e c i a l a d v i s o r y c o m m i t t e e to the Food and Drug Admin i s t r a t i on (FDA)f

appo in ted to a p p r a i s e the b o t u l i n u m o u t b r e a k s in s m o k e d f i sh , r e c o m m e n d e d

USAEC MARINE PRODUCTS IRRADIATION 23

t h a t c e r t a i n r e s t r i c t i o n s b e app l i ed in the d i s t r i b u t i o n of s m o k e d f i s h p r o -d u c t s . The Food and Drug A d m i n i s t r a t i o n adopted t h e s e r e c o m m e n d a t i o n s , app ly ing p r o p o s e d r e s t r i c t i o n s t o s m o k e d f i s h p r o d u c t s o r i g i n a t i n g in t h e G r e a t Lakes a r e a [7]. O the r p roduc t s and o ther loca t ions w e r e not a f fec ted .

In m i d - J a n u a r y 1964, a p a n e l of n e a r l y 300 of t he c o u n t r y ' s e x p e r t s in mic rob io logy m e t in Cincinnat i to eva lua te the p rob lem of botul ism in genera l . A b a s i c ou tcome, of t he m e e t i n g w a s t h e r e a l i z a t i o n tha t r e l a t i v e l y l i t t l e i s known about CI . b o t u l i n u m . Much of t h e p r e s e n t r e s e a r c h in t h i s c o u n t r y h a s been s p o n s o r e d th rough the e f f o r t s . of the USAEC and the United Sta tes A r m y and a d m i n i s t e r e d u n d e r t h e i r p r o g r a m m e s f o r r ad ia t ion p r e s e r v a t i o n of foods . Such work inc luded the d e t e r m i n a t i o n of heat and i r r a d i a t i o n r e s i -s t a n c e of Type E s p o r e s in s e a f o o d s u b s t r a t e s , a s we l l a s the e f f e c t of ad-d i t i ve s . The Type E s p o r e s w e r e found to have a D-va lue of a p p r o x i m a t e l y 0 .13 M r a d and a r e a m o n g t h e l e a s t r e s i s t a n t t o r a d i a t i o n of t h e v a r i o u s s t r a i n s .

O V E R A L L P R O G R E S S

Tab le II s e t s f o r t h the c u r r e n t o v e r a l l USAEC p r o j e c t s chedu l e . P r o -g r a m m e p r o g r e s s m a y be s u m m a r i z e d by s t a t i ng tha t o v e r a l l r e s u l t s con-t i n u e to be qu i t e p r o m i s i n g . H o w e v e r , p r o b l e m s do e x i s t . T h e b o t u l i s m

TABLE П

U S A E C F O O D P R O G R A M M E T A R G E T S F O R T H E C A L E N D A R Y E A R *

. D i v i s i o n of I s o t o p e s D e v e l o p m e n t

i960 1961 1962 1963 1964 1965 1966 1967 1968 1969 I. RESEARCH & DEVELOPMENT

a. Feasibility

b. Programming

c. Market Analyses

d. Experimental Research

Fruit Fish

e. Packaging

f . Wholesomeness**

g. Public Education

h. Field Studies

П. EQUIPMENT

a. I r radiator Design

b. Research I r radia tors

c. Mobile Irradiator

d. MPDI

e. Bulfegrain

f . Hawaiian Irradiator

g. On-ship i r radia tors

1П. COMMERCIALIZATION

a. FDA Petitions

b. Industrial Use

I 1

3 с

* For notes t o Table II, see Appendix 3. * * Programme cognizance by Division of Biology and Medicine.

24 SHEA

problem has caused the entire fishing industry, as well as appropriate Government departments to reappraise processing and distribution practices, with particular reference to eliminating this potential hazard. The pro-gramme, as related to fish and other marine products, is directly affected. Studies on CI. botulinum, Type E, have been sponsored by the Division of Biology and Medicine for the past three years (see Appendix 1). Intensified research on this organism is required to assure compliance with all Food and Drug Administration standards. It is anticipated that the additional re-search work will require approximately twelve to eighteen months to obtain sufficient data for the submission of petitions to the Food and Drug Admini-stration for clearance of irradiated marine products.

I R R A D I A T O R S

That portion of our programme related to irradiator development is pro-ceeding well and generally on schedule. Table III summarizes the units which support the programme.

In Fig. 1 a floor plan of the Marine Products Development Irradiator is shown.

FIG. 1. Floor plan of the Marine Products Development Irradiator

When the unit becomes operational, large-scale shipping, storage and acceptability testing will be instituted, with the objective of proving-out on a commercial scale the laboratory research results. The fishing industry has expressed its interest in participating in these tests. Successful demon-

USAEC MARINE PRODUCTS IRRADIATION

TABLE III

I R R A D I A T O R S

25

Type Purpose Comments

Research

Mobile

On-site research support

Feasibility and large scale demonstration; prove-out lab parameters

Four units operating: University of California, Massachusetts Institute of Technology, University of Washington, University of Florida, Designed for about 30 000 Ci cobalt -60.

Semi -commerc ia l scale. Under design; completion by spring, 1965. Initial use with fruits, West Coast area. Cost: $ 350 000. Employs 100 000 Ci cobalt -60.

On-ship Research One unit under construction. Small scale, 100 lb/h, for immediate processing at sea. Cost: $ 40000 . Employs6500 Ci cobalt -60.

Bulk grain Commercial prototype

Marine products Semi-production

Under construction, location Savannah, Georgia. Bulk grain and packaged product capability. Cost: $ 200 000. Employs 20 000 Ci cobalt -60.

Under construction*, location, Glou-cester, Mass. Up to 1 - t / h capacity. Completion scheduled late summer 1964. Cost: $ 600 000. Employs 250 000 CI cobalt -60.

Hawaiian Research, semi-production of tropical fruits

Proposed in FY 65 budget. Quarantine control an important aspect of this research. $ 350 000 requested. Employs 400 000 Ci cobal t -60 .

* See Fig. 1.

stration with the Marine Products Development Irradiator, coupled with Food and Drug Administration marine product clearances, will provide the basis for commercial radiation processing of fish.

Food and Drug Administration clearances

One of the better indicators of progress of the overall programme, which assumes product development and completion of wholesomeness and public health safety requirements, is the status of petitioning action with the Food and Drug Administration. Table IV summarizes the present and applied for petitioning actions. W e hope to have a petition on marine products before the United States Food and Drug Administration within four months.

TABLE IV to оз

R E G U L A T I O N S A N D P E T I T I O N S O N

R A D I A T I O N P R E S E R V A T I O N O F F O O D S

Product Petitioner Source Dose FDA filing FDA approval Federal Register Ref.

(vol . and page)

Bacon Bacon

Bacon

Bacon Wheat, wheat

products

Wheat, wheat products

White potatoes

Oranges

Packaging, materials

Bacon

US Army General Electric

US Army

USAEC Brownell et a l .

High Voltage Engng Corp. US Army

US Army/USAEC

USAEC

Radiation Dynamics, Inc.

6 0Co 5-MeV electron 10-MeV electron 13,Cs

2.2 MeV, or less, gamma energy

s 5 MeV

2.2 MeV, or less, gamma energy 50Co 13'G>

2 .2-MeV, or . less, gamma

energy X-ray from 5- MeV electrons

4 . 5 - 5.6 Mrad 4 .5 - 5.6 Mrad

4 . 5 - 5.6 Miad

4.Б - 6.6 Mrad 20 000 - 50 000 rad

75000 - 200 000 rad 75 000 - 100 000 rad 1 Mrad or less

4 . 5 - 5.6 Mrad

7 / 2 7 / 6 2 5 / 2 9 / 6 3

8 / 6 / 6 3

1 0 / 3 0 / 6 3 9 / 1 1 / 6 2

20 000 - 50 000 rad 1 2 / 1 7 / 6 3

5000 - 10 000 rad 4 / 2 1 / 6 3

1 2 / 1 1 / 6 3 1 / 2 3 / 6 4

7 / 2 3 / 6 4

2 / 8 / 6 3 8 / 2 3 / 6 3

Pending

4 / 1 / 6 4 8 / 2 1 / 6 3

Pending

7 / 8 / 6 4

Pending Pending

28 FR 1465 28 FR 9526

28 FR 9329

28 FR 11797 28 FR 9208

28 FR 13797

28 FR 5588

28 FR 13797 28 FR 2318

29 FR 9910

a m >


Where applicable, the US A r m y is making available the results of its long-term feeding studies already completed, which the Food and Drug Ad-ministration has agreed to consider for low dose clearance. In most cases, however, additional^ animal feeding studies of short term nature are to be carried out before petitions are submitted. These studies will be sponsored by the Division of Biology and Medicine. Since the clearance of sterilized bacon on 8 Feb. 1963, a widespread increase of industry interest in food irradiation has been especially notable, primarily from two segments; (a) food processors and (b) manufacturers and designers of. irradiation equipment and facilities.

E C O N O M I C S

The question of economics, of course, serves as the final incentive for adopting any new process. In the case of certain radiation-pasteurized fruits, we are finding that where chemicals can now do an acceptable job, such as with the use of diphenol on oranges, radiation offers no distinct economic advantages. On the other hand, one is aware of the attention cur-rently being given to the matter of chemical additives in food by the appro-priate Government departments. Radiation would stand as the prime alter-nate in the event that the use of certain chemicals was no longer permitted for public health reasons. Highly perishable fruit do offer distinct economic advantages. In the case of the reduction of strawberry losses previously noted, a 20-cent irradiation cost would save 75 cents worth of berries.

Economics of fish pasteurization look promising. F r o m a survey of several hundred processors and distributors in the industry, 60% indicated that a radiation cost of 1 to 3 <?/lb could be tolerated. W e feel these costs can be met. Our marketing and economic analyses are continuing, through the US Department of Agriculture and the US Department of the Interior, with the objective of further determining where radiation can make significant contributions to the food industry.

C O N C L U S I O N S

Recently the US Department of Commerce, with the support of the USAEC, queried food industry leaders concerning their interest in food irradiation. The general acceptance of the future success of this coming technology was a dominant feature of the reply.

It is encouraging to note that after lOyr of intensive research on this subject and after thousands of animal and human feeding tests, there is no evidence to indicate that radiation-processed foods are harmful to man. The potential of this process is such as to encourage continued development, to secure the approval of the Food and Drug Administration for a greater number of products and to recognize and accept radiation treatment as a logical and important adjunct to our existing potential of food processing and distribution.

By the nature of the process and the need to obtain Food and Drug Ad-ministration clearances item by item (or at least by class of item), it can

28 SHEA

be expected that individual foods will reach production at widely different times. There are also sufficient difficulties with flavour, colour, odour and texture caused by the ionizing radiation treatment, as to require re-search for many years, a situation similar to that still existing in the can-ning industry today.

R E F E R E N C E S

[1] M1YAUCH1, D., et al., Application of Radiation on Pasteurization Processes to Pacific Crab and Flounder, US DC Rpt 18036, Off. Techn. Service (April 1963).

[2] STOUT, V. F., Effects of Ionizing Radiation on Lipids of Fish, USDC Rpt 18657,Off. Techn. Service (April 1963).

[3] NOVAK, A.F. , LIUZZO, J. A. , Radiation Pasteurization of Shrimp, Louisiana State University, USDC Rpt ORO-601,Off. Techn. Service.

[4] ANDERSON, A.W. , Oregon State University, personal communication. [5] ERDMAN, I .E. , THATCHER, F.S. , MacQUEEN, K. F., Studies on the irradiation of microorganisms in

relation to food preservation.il Irradiation resistant mutants, Canad. J. Microbiology 7 (1961) 207-15. [6] Morbidity and Mortality Weekly Report 13 1 Communicable Disease Center, Altanta, Georgia (10 Jan. 1964). [7] Pressrelease, US Department of Health, Education and Welfare, Washington, D .C . ( 25 Oct. 1963).

A P P E N D I X 1

CONTRACT STUDIES FOR THE PROGRAMME ON RADIATION PASTEURIZATION OF

FOODS, WHICH ARE SUPPORTED BY THE DIVISION OF BIOLOGY AND MEDICINE*

SUMMARY

The main objectives of these contract studies are to determine the wholesomeness, nutritional adequacy and biological safety of low-dose irradiated foods which are of interest to the Commission's irradiated food programme. The studies pertain to the areas of wholesomeness, microbiology, biochemistry and physiology of low-dose irradiated marine products and fruits. The data acquired from these studies are needed to satisfy requirements outlined by the United States Food and Drug Administration (FDA). A summary of these con-tracts follows.

Two-year animal feeding studies on irradiated soft-shell clams and short-term protein availability studies on haddock, flounder, crab, shrimp and soft-shell clams have been initiated (University of Illinois). The protein availability data will essentially complete the required wholesomeness data for haddock, crab, shrimp and flounder. Long-term animal feeding studies on irradiated strawberries will also be conducted (Industrial Bio-Test Laboratories, Inc.)

Two studies on growth and toxin production of various strains of CI. botulinum, Type E, in various sub-strates and marine homogenates, under a variety of temperature conditions, are in progress. (University of Michigan and Continental Can Company, Inc.)

The natural incidence of CI. botulinum, Type E, spores in Pacific coastal sea muds, crab gut and flounder is also being determined (Bureau of Commercial Fisheries, Seattle).

* Courtesy of Dr. L. Whitehair, Division of Biology and Medicine, USAEC.


A study was recently initiated to determine possible toxin formation in irradiated haddock fillets and soft-shell clams which have been inoculated with three levels of CI. botulinum. Type E, spores and stored for ex-tended periods of time under specified temperature conditions ranging from 32-45°F. (Massachusetts Institute of Technology).

Microbiological and biochemical studies on irradiated fish are under way at the University of Washington. Efforts have been concentrated on the bacteriological safety of radiation-pasteurized sea foods. Potentially pathogenic organisms are being studied to determine their sensitivity to radiation, outgrowth after irradiation, and physiological changes after irradiation. Biochemical studies are designed to identify products and mecha-nisms involved in the tissue changes and relate them to radiation dose levels.

Basic studies on the radiation biochemistry of fruits are being conducted at the University of California, Davis. Observations 0:1 the primary cytoplasmic events during the course of radiation damage and which may be responsible for textural changes are being explored. Investigations on the radiation physiology and •micro-biology of fmit détériorât'on are also being conducted under another contract at the University of California, Davis.

The biochemical and physiological changes in the tissue of fresh fruits and vegetables (associated with extension of shelf- l i fe by means of radiation) are being studied at Cornell University (Geneva Agricultural Experiment Station). Softening changes which occur in plant tissue during and after exposure to radiation are being investigated.

Fundamental flavour and odour studies on volatiles from irradiated fish are being conducted by the Bureau of Commercial Fisheries at Gloucester. Attempts will be made to correlate gas chromatogram patterns with detailed results of organoleptic testing on the same fish products.

Biochemical alterations in the protein moiety of haemoproteins (fish myoglobin) as a result of radiation are being studied at the University of California, Berkeley.

Future studies will be directed by findings in current studies and by requirements outlined by the FDA. The findings in each of the above-outlined studies will be consolidated with previous results obtained in the

US Army's Radiation Sterilization of Foods Program and with results of studies supported by the Division of Isotopes Development. These data will be submitted to the FDA in the form of petition requests for approval of low-dose irradiated foods for human consumption.

LIST OF CONTRACTS OF THE DIVISION OF BIOLOGY AND MEDICINE

1. University of Illinois, Urbana, 111. Investigator: Elwood F. Reber Title: The Wholesomeness Evaluation of Radiation Sub-Sterilized Food Products (Protein availability studies

on irradiated soft shell clams, haddock, crab and flounder and 2-yr chronic studies on soft-shell iclams).

2. Industrial Bio-Test Laboratories, Northbrook, 111. Investigator: Margaret Ives Title: Wholesomeness Investigation of Radiation-Pasteurized Foods in the USAEC Food Irradiation Program:

Sub-Sterilized Strawberries.

3. AME Associates, Princeton, N.J. Investigator: R. W. Fogleman Title: Short-Term Sub-Acute Animal Feeding Studies on Radiation-Pasteurized Foods.

4. US Army Material Command Investigator: US Army Title: (Provisions for irradiation services for foods which are to be evaluated for wholesomeness in the

USAEC Food Irradiation Program)

5. University of Michigan, Ann Arbor, Mich. Investigator: John Graikoski and Lloyd L. Kempe Title: A Study on the Effect of Ionizing Radiation on Resistance, Germination, and Toxin Synthesis of

CI. botulinum Spores, Types A, B, and E.

3 0 SHEA

6. Continental Can Company, Inc. , Chicago, 111. Investigators: Bruce Morgan, Wayne Segner and Clarence F. Schmidt Title: Growth Characteristics of CI. botulinum. Type E, in the Temperature Range of 34-50°F.

7. Massachusetts Institute of Technology Investigators: S .A. Goldblith and J.T.R. Nickerson Title: The Effects of Gamma Rays on Haddock and Clams Inoculated with Clostridium botulinum, Type E.

8. US Department of Interior, Bureau of Commercial Fisheries, Seattle, Wash. Investigator: Melvin K. Eklund Title: The Significance of Clostridium botulinum, Type E, in the Application of Radiation-Pasteurization

Process to Pacific Crab Meat and Flounder

9. Louisiana State University, Baton Rouge, La. Investigator: Robert M. Grodner Title: Examination of Gamma Irradiated Gulf Shrimp for Clostridium botulinum and Type E toxin

10. University of Washington, Seattle, Wash. Investigator: A .M. Dollar and John Liston Title: Study of the Basic Microbiological and Biochemical Factors Involved in the Irradiation Preservation

of Marine Products.

11. US Department of Interior, Bureau of Commercial Fisheries, Gloucester, Mass. Investigator: Joseph Slavin, Maynard Steinberg, Louis Ronsivalle Title: Study of Radiation-Pasteurized Fishery Products - Fundamental Flavor and Odor Studies.

12. University of California, Davis, Calif. Investigator: Roger J. Romani Title: Radiation Biochemistry of Fruit.

13. University of California, Davis, Calif. Investigators; Noel F. Sommer and E. C. Maxie Title: The Radiation Physiology and Microbiology of Fruit Deterioration.

14. Cornell University (Geneva Agricultural Experiment Station) Geneva, New York Investigator: Louis M. Massey Title: Biochemistry and Physiology of Irradiated Fruits and Vegetables.

15. University of California, Berkeley, Calif. Investigator: W. Duane Brown Title: Radiation of Heme Proteins.


A P P E N D I X 2

LIST OF

DIVISION OF ISOTOPES DEVELOPMENT CONTRACTS WITH SUMMARY

SCOPE OF WORK

1. Massachusetts Institute of Technology Department of Food Technology Cambridge, Mass. Dr. J.T.R. Nickerson

SIMULTANEOUS RADIATION-LOW HEAT TREATMENT OF HADDOCK

Synergistic effects of low thermal heat and radiation will be determined on haddock fillets. Bacterial destruction in cultures held at temperatures between 110 and 130°F and irradiated from 250 000 to 350 000 rad will be compared to bacterial destruction at 32 to 35°F. Five aerobes and three anaerobes typical of spoilage flora in irradiated haddock will be investigated. Storage life and organoleptic acceptance of haddock irradiated at the aforementioned elevated temperatures, then cooled and stored at 32 and 43°F will be determined.

2. US Department of the Interior Bureau of Commercial Fisheries Foot of Emerson Avenue Gloucester, Mass. Mr. Joseph Slavin

RADIATION PRESERVATION OF FISHERY PRODUCTS

To conduct ( l )qual i ty studies on cod, pollock and ocean perch (2) studies to determine the ef fect of pre-irradiation quality level on post-irradiation storage life (3) packaging studies to determine the most suitable materials for use with irradiation pasteurized sea foods (4) applied flavour and odour studies to related changes in composition of the volatiles of radiation quality level on post-irradiation storage life.

3. US Department of the Interior Bureau of Commercial Fisheries 2725 Montlake Boulevard East Seattle, Wash. Dr. David Miyauchi

APPLICATION OF RADIATION-PASTEURIZATION PROCESSES TO PACIFIC CRAB AND FLOUNDER, USDI TECHNOLOGICAL

LABORATORY

Objective is to develop a practical procedure for radiation processing of Pacific crab meat and flounder. The first task will be the determination of pre- and post-irradiation conditions. Acceptability tests and packag-ing studies will be included. A second task is to develop objective methods for measuring the acceptability of radiation pasteurized Pacific crab meat and flounder by correlating sensory and microbiological evaluation with physical and chemical alterations in these samples. Finally behaviour of highly unsaturated fatty esters, typical models of fish lipides in the preservation of fishery products by irradiation.

32 SHEA

4. Louisiana State University Baton Rouge 3, La. Dr. Arthur Novak

RADIATION PASTEURIZATION OF SHRIMP AND OYSTERS

Investigators will continue to conduct research on the radiation pasteurization of shrimp. Completion work will include sub-projects such as semi-commercial testing in at least two large cities; acceptability testing at Ft. Lee, Va. , isolation and identification of flavour components and changes which they undergo during irradiation; and exploration of changes in enzyme systems of irradiated shrimp.

Initial studies to develop radiation-processed oysters will begin during this contract period, to include optimum dose in relation to storage time, temperature and post-irradiation storage

5. Oregon State University Department of Food Science and Technology Corvallis, Oregon Dr. Russell O. Sinnhuber

EFFECTS OF IRRADIATION ON THE MICROBIAL FLORA SURVIVING IRRADIATION PASTEURIZATION .

OF SEA FOODS

At pasteurizing levels of radiation, study the shift in natural microbiological flora of sea foods due to the variation in radiation resistance and determine: (a) the effect the survivors play in the spoilage of food; (b) their pathogenicity Specific objectives include: (1) Study the shift in the natural microbial flora, including yeasts and moulds, induced by irradiation. (2) Determine possible mutagenic ef fect of radiation on marine microorganisms and its role in spoilage. (3) Investigate complementary effects of approved food additives and radiation to determine dose reduction

effects.

6. University of Michigan Chemical and Metallurgical Engineering Dept. Ann Arbor, Michigan Dr. Lloyd L. Kempe, Professor

IRRADIATION PASTEURIZATION OF FOODS

The University of Michigan,acting as the prime contractor, will co-ordinate the technical efforts involved and will furnish irradiation support in a joint fish-fruit programme with USDI, Ann Arbor, and Michigan State University. Related work, not directly in this contract will be arranged with the Division of Biology and Medi-cine concerning an extension of CI. botulinum studies to fresh water fish. At Michigan State University the extension of the shelf life of fruits and vegetables by irradiation pasteurization will be studied under conditions of growth, harvest and storage as practiced in Michigan. These studies will include microbiological, nutritional and organoleptic changes which occur during storage of irradiated products. Pasteurization effects of fast electrons and gamma radiation will be compared. At the BCF, Ann Arbor, Mich., studies are proposed con-cerning the shelf l ife of fresh water fish treated by irradiation. This would include yellow perch, chub and other species of fresh water fish from the Great Lakes.

7. US Department of the Interior Bureau of Commercial Fisheries Ann Arbor, Mich. (See No. 6. )


8. University of California Department of Pomology Davis, Calif. Dr. E. C. Maxie

RADIATION TECHNOLOGY IN CONJUNCTION WITH POST-HARVEST PROCEDURES AS A MEANS OF

EXTENDING THE SHELF LIFE OF FRUITS AND VEGETABLES

Conduct research and development on selected fruits to determine the effects of pre- and post-harvest techniques to extend storage life. Studies shall include but not be limited to shelf life extension as a function of radiation dose and dose rate; the effects of modified environments (temperature, humidity, atmosphere) during and after irradiation; research on the physiological state of the commodity as influenced by irradiation; acceptability testing. Operate Mark II irradiator.

9. University of Florida Department of Food Technology and Nutrition Agricultural Experiment Station Gainesville, Fla. Dr. R.A. Dennison

EFFECT OF LOW LEVEL IRRADIATION UPON THE PRESERVATION OF FOOD PRODUCTS,

UNIVERSITY OF FLORIDA

To determine the effects of low level irradiation upon fresh tomatoes and citrus as measured in terms of quality, extension of shelf life, microbiological and biochemical changes. Optimum radiation levels, in-fluences of atmospheric and temperature conditions during irradiation, the influence of variety, fruit maturity and seasonal variability will be determined. Associated studies of post-irradiation storage conditions will be investigated, especially atmospheric and temperature conditions. Many studies have indicated the change which may occur under such conditions. It is necessary to establish whether the same change occurs with varie-ties and conditions in Southeast USA.

10. Michigan State University Department of Food Science Lansing, Mich. (See No. 6)

11. US Department of Agriculture Crops Branch, Marketing Economics Division Economic Research Service 1

Washington 25, D. C. Dr. Norris A. Pritchard, Chief

MARKETING FEASIBILITY STUDY OF RADIATION-PASTEURIZED FRESH STRAWBERRIES,

PEACHES, TOMATOES, GRAPES, ORANGES AND GRAPEFRUIT

Like all new processes, a point is reached where economic feasibility for commercial adoption must be determined. To develop these objectives with respect to radiation pasteurization, information is needed in relation to trade and consumer acceptance, comparative costs of the various methods of radiation processing relative to other processes currently in use, and the probable impact of this method on prices, supplies, and market structure of the agricultural products involved. Of the five selected fruits and vegetables, strawberries

3 4 SHEA

were selected for intensive study because of the relatively large body of related research already developed from them, and because gross marketing spoilage loss for fresh strawberries is about 25% of fresh farm weight.

In Phase I, a survey of market economic feasibility with respect to radiation pasteurization of fresh straw-berries, peaches, citrus, grapes and tomatoes has been carried out. Handlers, processors, wholesalers, re-tailers and institutional users of these commodities have been interviewed.

Phase II, now under way, will provide estimates on normal marketing spoilage and loss. It will include a comparison of typical fresh-strawberry marketing practices with expected marketing practices for radiation-pasteurized strawberries together with a comparison of the economic factor of both forms.

12. Market Development Branch Bureau of Commercial Fisheries Fish and Wildlife Service Department of the Interior Washington 25, D. C. Mr. A.L. Morel

MARKET RESEARCH ON IRRADIATED FISHERY PRODUCTS

This contract is for a two-phase market research study concerning the marketing of irradiation fishery products.

In conducting the first phase, now completed, marketing specialists have contacted over 600 producers, processors, distributors, wholesalers, and retailers in an effort to determine approximately, (a) the losses in-volved in marketing fresh fishery products compared with fish and shellfish that have been radiation pasteurized, and (b) the potential impact of radiation pasteurization on marketing supplies and structures. Results are now being tabulated and analysed.

The second phase of this programme will be conducted for the Bureau of Commercial Fisheries by a com-mercial research firm and will involve a highly qualitative study among consumers of fish and shellfish to determine what bind of an educational programme is required to market irradiated fish most successfully. In essence, this would involve a study of attitudes held, information, misinformation, and psychological images as related to fish in general and irradiated fish in particular. The aim is to include a sample of approximately 2500 consumers from all geographic and city size strata. The second phase will be initiated before the first phase is completed. Questionnaires, approved by the Bureau of the Budget, will be prepared for use in both phases of this project.

13. Hazleton Laboratories, Inc. P. O. Box 30 Falls Church, Va. Mr. Edward Garlock

EXTRACTIVE STUDIES - PACKAGING

A petition requesting clearance of a number of packaging products to be used in conjunction with radiation pasteurization was filed with the FDA on 27 Jan. 1964 (FAP 1297). Materials included cellophane; glassine paper, paraffin and microcrystalline wax-coated paperboard; polyolefin films produced from polypropylene, polyethylene or ethylene-alkene-1 copolymers; polystyrene; rubber hydrochloride film; and vinylidene chloride-vinyl chloride copolymer f i lm (Satan). The petition was based on extractive studies conducted by the con-tractor.

14. Hazleton Laboratories, Inc. P. O. Box 30 Falls Church, Va. Dr. O.E. Paynter


FOOD ADDITIVE PETITION PREPARATION

During this contract period, a petition has been completed and submitted to FDA requesting clearance for the radiation pasteurization of oranges and lemons.' Other petitions are currently being prepared for peaches, nectarines and carrots.

15. Western Nuclear Corporation P. O. Box 1156 Idaho Falls, Idaho Dr. George A. Freund

LARGE SCALE POTATO IRRADIATION

In conjunction with several potato growers and processors in southern Idaho, approximately 18 000 lb of potatoes will be irradiated and undergo evaluation by users as chips, french fries, frozen, e tc . As of this date, radiation is nearly complete, and evaluation is to begin.

16. Southern Interstate Nuclear Board Suite 664, 800 Peachtree St . , N.W. Atlanta 8, Ga. Robert H. Gifford .

APPLICABILITY OF RADIATION-PASTEURIZED FRUITS TO THE SOUTH

Contractor will summarize technical status of radiation pasteurization of fruits of specific interest to the South, identify economic benefits to be gained, and evaluate the potential and prospects of commercialization of this area. With respect to additional research and development found to be necessary, such scope will be identified with respect to effort, t ime and funding required.

П . Processing Equipment Company Lodi, N. J. H. C. Cusumano

SERVICE CONTRACT FOR RESEARCH IRRADIATORS

This is to furnish preventive maintenance for the four installed research irradiators. The first service period is approximately 12 months from the start of operation for each irradiator. The second and more com-prehensive servicing is scheduled 12 months after the first.

18. University of Hawaii Honolulu, Hawaii Dr. Edward Ross

SHELF LIFE EXTENSION RELATED TO DISINFESTATION OF FRUITS AND VEGETABLES

• BY GAMMA IRRADIATION

Certain tropical fruits such as mangoes and papayas promise to benefit greatly from irradiation. For example, mangoes cannot be sent to the mainland due to an internal infestation presently uncontrollable. Papayas are treated with hot water to control fruit fly but quality is affected. Disinfestation can be accomplished by irradiation. The results of this work can be extrapolated to other semi-tropical areas.

36 SHEA

19. Arthur D. Little, Inc. Cambridge, Mass. Mr. David Rest

STUDY OF ECONOMICS OF CONTROLLING SALMONELLA IN FOODS BY THE USE OF IONIZING RADIATION

Recent intense industry interest has been generated by the potentials of the radiation process concerning shelf l ife extension and control of the food poisoning organisms, such as Salmonella, in poultry and poultry products. A thorough analysis of process status, potential, and future research requirement will be made.

20. US Department of Commerce Washington, D .C.

PROSPECTS FOR COMMERCIALIZATION OF THE POTENTIAL RADIATION PRESERVATION OF FOODS

An economic analysis of current status and prospects. Designed to serve as the basis for the ultimate preparation of a Handbook for management that will assist in the orderly absorption of this new technology by the food and related industries.

21. Hallam Nuclear Power Facility Hallam, Nebr.

RADIATION TEST FACILITY

A test facility, using the sodium coolant z3Na which is converted to radioactive MNa in the Hallam Nuclear Power Facility. The facility will be used for both technological and wholesomeness experimentation.

A P P E N D I X 3

NOTES TO TABLE II

I. RESEARCH AND DEVELOPMENT

a. Feasibility 1. Massachusetts Institute of Technology feasibility studies on radiation preservation of fish (completed)

2. Stanford Research Institute studies on radiation feasibility of fruits and vegetables (completed)

b. Programming Massachusetts Institute of Technology and Stanford Research Institute studies on fish and fruit, respectively (completed)

c . Market analyses 1. US Department of Interior studies on market feasibility of fishery products 1960 (completed)


2. US Department of Agriculture market feasibility on radiation processing of fruits 1962-63 (in progress)

3. US Department of Interior study on market feasibility of radiation processed fish 1963 (in progress)

Experimental research

1. Fish (in progress) a. US Department of Interior, Gloucester (haddock, clam, ocean perch, cod) b. Massachusetts Institute of Technology (haddock) c. US Department of Interior, Seattle (crab, flounder, halibut) d. US Department of Interior, Ann Arbor (white fish, chub) e . Louisiana State University (shrimp, oysters) f. Oregon State University (halibut)

2. Fruit (in progress) a. University of California, Davis (strawberries, peaches, oranges, nectarines, other) b. University of Michigan (strawberries, peaches, cherries) c . Florida State University (citrus, tomatoes, peaches) d. US Department of Agriculture, Fresno (shipping tests variety of products) e . University of Hawaii (in progress)

Packaging Continental Can study 1961-62 to determine additional work required to successfully use packaging processes with radiation processed food. Extractives on packaging material culminating in petitions to the Federal Drug Administration for appropriate use for Hazleton Laboratories, Inc. (completed) Petition submitted Nov.1963.

Wholesomeness Another important area of the programme is the wholesomeness and public health safety aspects of radiation processed foods. Contract work is being sponsored by the Division of Biology and Medicine (See table)

Public education Establishment of public education programme in 1964 by US Department of Interior, Washington, D. C. , implementation by US Department of Interior, and US Department of Commerce, beginning 1965. (in progress)

Field studies Use of Atomic Energy of Canada Limited mobile irradiator 1963-64. Use of Marine Products Development Irradiator and Atomic Energy Commission mobile irradiator beginning latter 1964.

EQUIPMENT

Irradiator design

Irradiator design development of design concept primarily by Brookhaven National Laboratory for equipment adequate to support food irradiation research, 1960-62. Design concepts of advanced irradiators including mobile and semi-production types 1963-64 by Brookhaven National Laboratory, Vitro, Associated Nucleonics. Further source and design studies as required through 1967.

Research irradiator Installation of four research irradiators employing 30 000 Ci cobalt-60 each at Massachusetts Institute of Technology, University of California, University of Washington and University of Florida, 1961-64.

Mobile irradiator Completion of construction early 1965 for use in large scale shipping tests with fruits. Costs: $ 350 000. Employs 150 000 Ci cobalt-60

3 8 SHEA

d. Marine Products Development Irradiator Completion scheduled for late summer 1964 at Gloucester, Mass., for semi-commercial scale production and shipping tests. Costs: $ 600000.Employs 250 000 Ci of cobalt-60. US Department of the Interior operation begins FY-68.

e . Bulk grain Completion early 1965. Bulk grain capacity (5000 lb/h) as well as packaged product capability. Dis-infestation purposes. Costs: $ 200 000.Employs 20 000 a cobalt-60. US Department of Agriculture ope-ration begins FY-67

f. On-ship ' A portable 12-t unit containing 20 000 Ci o f cobalt-60, for use primarily aboard fishing vessels to process the catch as landed. Costs: $ 35000.

g. Hawaiian irradiator Semi-production unit for (a) shelf life extension of tropical fruits, and (b) quarantine control. S 350 000 re-quested for FY-65; completion by late FY-66. Employs 400 000 Ci cobalt-60.

1П. COMMERCIALIZATION

a. Food and Drug Administration 1963: Petition for radiation-processed citrus submitted to Food and Drug Administration in September. A more detailed plan of petition action is outlined in Table IV.

b. Industrial use Expected to begin in early 1965 for one or more products, increased industrial participation through end of programme.

A DISCUSSION OF THE RADIATION PRESERVATION

OF FISH IN DEVELOPING COUNTRIES

D . N . RHODES A N D T . A . ROBERTS

AGRICULTURAL RESEARCH C O U N C I L .

LOW TEMPERATURE RESEARCH S T A T I O N ,

CAMBRIDGE, ENGLAND

A N D

G. HOBBS

DEPARTMENT OF SCIENTIFIC A N D INDUSTRIAL RESEARCH,

TORRY RESEARCH S T A T I O N ,

ABERDEEN, SCOTLA N D

ОБСУЖДЕНИЕ ПРОБЛЕМЫ СОХРАНЕНИЯ Р Ы Б Ы С ПОМОЩЬЮ ОБЛУЧЕНИЯ В РАЗ-ВИВАЮЩИХСЯ СТРАНАХ. Обсуждаются накопленные к настоящему времени знания отно-сительно сохранения рыбы в р е з у л ь т а т е процесса радиационной пастеризации и стерилиза-ции в связи с применением этих процессов в развивающихся с т р а н а х . Р а с с м а т р и в а ю т с я органолептические, бактериологические, технологические и экономические факторы. Опи-сываются роль CI. botulinum типа Е в качестве патогена особой важности в процессе радиа-ционной пастеризации рыбы, а также свойства и характеристики роста спор этого организма. Сопоставляютря случаи отравления пищевых продуктов, приписываемого этому организму, и текущая экологическая информация.

LA CONSERVACION DE PESCADO POR IRRADIACION EN LOS PAISES EN DESARROLLO. La memoria examina los actuales conocimientos sobre la conservación de pescado porradiopasteurizaciónyradioesterilízación desde el punto de vista del empleo de esos procesos en los pafses en desarrollo. Se estudian los aspectos organo-lépticos, bacteriológicos, tecnólogicos y económicos. Se describe la función del Cl. botulinum tipo E como agente patógeno de especial importancia en la radiopasteurización del pescado, así como las propiedades y características de crecimiento de sus esporas. Se indica la frequencia de los casos registrados de intoxicación alimentaria atribuidos a dicho bacilo y se citan los datos ecológicos de que se dispone.

3 9

A DISCUSSION OF THE RADIATION PRESERVATION OF FISH IN DEVELOPING COUNTRIES. The present knowledge concerning the preservation of fish by radiation pasteurization and sterilization processes is discussed in relation to the application of these processes in the developing countries. Organoleptic, bacteriological, technological and economic factors are considered. The role of CL botulinum, type E, as a pathogen of special significance in radiation pasteurization of fish, and the properties and growth characteristics of the spores of this organism are described. The recorded occurrence of food poisoning incidents attributed to this organism and the current ecological information are collated.

ETUDE DE LA CONSERVATION DU POISSON AU MOYEN DES RAYONNEMENTS DANS LES PAYS EN VOIE DE DEVELOPPEMENT. L'auteur fair un exposé sur l'état actuel des connaissances en matière de pasteuri-sation et de stérilisation du poisson au moyen des rayonnements et sur les applications que ces procédés reçoivent dans les pays en voie de développement. La question est etudiée du point de vue organoleptique, bactériologique, technique et économique. Le mémoire décrit le rôle de Cl. botulinum, de type E en tant qu'organisme pathogène d'une importance particulière dans la radiopasteurisation du poisson ainsi que les propriétés et les caractéristiques de développement de ses spores. L'auteur présente un ensemble de cas d'empoisonnement alimentaire attribués à cet organisme ainsi que les données écologiques actuelles.


4 0 RHODES et a l .

An assessment of a new process for the preservation of food m a y be conveniently divided into three aspects for consideration: acceptability, tech-nology and economics. Acceptability covers all aspects of the relationship of the product to the consumer; technology, the problems of production, pro-cessing and distribution; and economics, the costs of the process in relation-ship to its benefits to industry and the consumer. These factors have been studied extensively in the United Kingdom, in various European countries and in the United States of America for the preservation of fish by an ir-radiation treatment, but very few of the premises assumed in these studies are valid when considering the situation in tropical countries with less ad-vanced technologies. This paper attempts a reappraisal of the problems (all of which are by no means satisfactorily solved in the former cases) in the light of what we know of the conditions likely to obtain in the latter.

The effects of radiation processing on the wholesomeness of food are not considered here except where problems specific to fish arise. A full discussion of the general aspects of wholesomeness has appeared in the re-port of the 1961 F A O / W H O /IAEA meeting held at Brussels.

P R E S E N T K N O W L E D G E

The radiation preservation of most species of Atlantic and Pacific sea fish (and of some river and lake fish) commonly consumed in North America and Europe has been extensively studied during the past decade. Broadly speaking, species with unpigmented flesh and low fat content which comprise the major part of the Atlantic catch (cod, halibut, haddock, plaice, sole) can be irradiated to a dose up to 0. 5 Mrad without change in organoleptic quality. This treatment extends the storage life of the fish by a factor of about four times at temperatures between 0 and 5°C. Some important fatty species (herring) have also been successfully treated at this dose level, de-spite the highly unsaturated nature of the fats, if packaged in vacuum in materials with low permeability to oxygen. Pigmented fatty fish such as salmon or tuna suffer serious adverse effects at dose levels even as low as 0. 1 Mrad. Doses in the range of 1 - 2 Mrad have proved satisfactory in the treatment of some crustacea after the blanching procedures normally applied to these sea foods, but at the dose level necessary for sterilization (5 Mrad), all fish suffer severe changes in odour and flavour typical of high dose treatment of any high protein wet food.

Leaving aside the blanched crustacea, it has been generally concluded, on organoleptic grounds, that fish treated at levels above 0. 5 Mrad would not be acceptable to the average consumer in competition with the normal fresh supplies but that, in England and the United States at least, advantages could accrue to both consumer and supplier from a process based on the innocuous dose levels below 0. 5 Mrad and that such a process would be viable commercially (see, for example, Rhodes [39]). These conclusions have been based upon nutritional, bacteriological and organoleptic studies, and on the economics of the catching, distributing and retailing industries in the developed countries, where no more than the m i n i m u m extension of storage life compatible with the improvement of the distribution methods is required, and where it is possible to ensure that reasonable accuracy of

RADIATION PRESERVATION OF FISH 4 1

storage temperature and control of shelf life would be exerted if the process were put into practice. The application of possible processes in the tropical countries is now examined.

R A D I A T I O N - P A S T E U R I Z A T I O N P R O C E S S E S

I. Treatment of raw fish

The Western consumer is accustomed to buy fish in the fresh state and to cook it by a wide variety of methods; the larger part of fish sold is, there-fore, in the native state and most of the work on preservation has been directed towards extending the shelf life in this form.

(a) Microbiological factors

(i) Spoilage organisms. A pasteurizing dose of 0. 5 Mrad will reduce the total count of microorganisms on fish by a factor of 106- 107 times (Fig. 1). The flora consists mainly of Pseudomonads and Achromobacter, the normal food spoilage organisms, growth of which produces the unpleasant

DOSE (krafi )

FIG. 1. Radiation sensitivity of various common food-spoilage organisms Data from: 1. LEY, F. , FREEMAN, B.M. , HOBBS, B.C. , J. Hyg.,Camb. 61 (1963) 515. 2. SCHMIDT-LORENZ, W. , FARKAS, J. , Arch. f. Mikrobiol. 39 (1961) 1. 3. WOESE, C. , J. Bact. 77 (1959) 38. 4. MATSUYAMA, A. , THORNLEY, M.J . , INGRAM, M. , J. appl. Bact. 27 (19Ö4) 110 and 125. 5. INGRAM, M . , THORNLEY, M.J . , J. appl. Bact. 24 (1961) 94. 6. ANDERSON, A. W. et al. , Food Tech. 10 (1956) 575. 7. ROBERTS, T. A. . INGRAM, M. , to be published.

4 2 RHODES e t a l .

100

и0

20

4

\ ° 4

\

>

0 20 40 60

TEMPERATURE (°F)

FIG. 2. Relationship between incubation time for visible gas production and temperature for four strains of CI. botulinum, type E [SCHMIDT, C. F . , LECHOWICH, R. V. , FOLINAZZO, J. Food Sei. 20 (1961) 626. ]

odours associated with spoilage. Commercial fish in Europe may have been kept on melting ice (the c o m m o n method of preservation) for as long as 15 d before it reaches the consumer, and the bacterial count during this time reaches about 106-107 organisms per gram. The rate of growth of spoilage organisms is, of course, greatly accelerated at higher temperatures and it would be of paramount importance in applying radiation pasteurization to ensure that the fish was as fresh as possible at thfe time of treatment. Thus treatment with 0. 5 Mrad will reduce the bacterial count to very small numbers, and the Pseudomonads and Achromobacter are virtually eliminated by this dose. W h e n the residual flora eventually reasserts itself during storage, its growth is revealed by the appearance of sweetish, sour or yeasty odours differing widely from the normal putrid smells.

The available evidence indicates that the spoilage flora of ocean fish caught in the tropics does not differ greatly from the above, provided that the fish is handled in the same way, that is mixed with melting ice as soon as possible after death. Tropical inshore and river fish, however, living in water at higher temperatures might carry a higher proportion of meso-philic organisms which, because of their generally higher resistance to ra-diation, would survive in larger numbers after treatment. Although this would not affect the storage characteristics of pasteurized fish stored below 10°C, the process might be less effective if the product were stored at temperatures above 15°C.

(ii) Pathogenic bacteria. The vegetative cells of pathogenic bacteria such as the salmonellae or Clostridia are sensitive to radiation and are virtu-ally eliminated from foods by doses in the pasteurizing range (Fig. 1). The Clostridia will survive such treatments, however, if they are present in the form of spores which are far more resistant (Fig. 1). In the normal storage of foods their presence causes no anxiety since the growth of the commonly occurring Clostridium welchii or Clostridium botulinum, typés A and B, is inhibited completely at temperatures below 10° C. With fish, the situation is complicated by the possible presence of spores of CI. botulinum, type E, which differs from the others in that its spores can germinate and

RADIATION PRESERVATION OF FISH

TABLE I

O U T G R O W T H O F C L O S T R I D I U M B O T U L I N U M , T Y P E E *

43

Period to outgrowth (d) . , .. „ . , at incubation temperatures of: Medium Spore inoculum

46°F 42°F 40'F 38°F

Beef stew 2 X 10® 11-•20 13-•29 18-•49 > 90

Haddock 2 X 106 7-•10 15-•22 > 9 6 >365

Sole 2 X 106 6-• 8 15-•20 31-•47 -

Shrimp 2 X 10 6 10-•20 60-•>74 > 7 4 -

Sole 2 X 10 3 13-•15 20-•34 40 -

* Strains: Alaska, Beluga, Minneapolis, 8E [ 3 8 ] .

produce toxin at temperatures as low as 3. 3°C. The relationship between temperature and time to produce measurable signs of outgrowth has been given by Schmidt and his co-workers (Fig. 2 and Table I). In ordinary fish the putrefactive bacteria grow much more rapidly and render the foodstuff offensive (or recognizably "bad")'before the spores have germinated and produced toxin; in a radiation-pasteurized product, however, the spoilage bacteria are destroyed while the spores of CI. botulinum, type E, are re-duced by a factor of about 102 (Table II). Thus no odoriferous warning.of a possibly dangerous outgrowth of spores will be detectable since the times given by Schmidt (Fig. 2) could be less than the shelf life of pasteurized fish. Extreme caution is necessary, therefore, in advocating the storage of ir-radiated fish under conditions where the storage temperature could exceed 3. 3°C. In the work in the United Kingdom (Rhodes [39] ) the most lenient conditions considered safe for discussion were given as 20 d at 4. 4°C, and 10 d at this temperature was suggested as the limit of a safe storage life for packaged irradiated fish in commercial practice. The greatest»safety lies in the careful control of temperature as close to 0 eC as possible while in commercial storage, retail display or in the hands of the consumer. In the last case the package might well be held after purchase for some time under varying conditions of storage, perhaps without refrigeration, a risk which would be minimized by printed instructions urging refrigerated storage and immediate consumption. An additional safeguard in Western countries arises from the fact that botulism results from the ingestion of preformed toxin, and that the toxin is readily destroyed by mild heating (Table III). As fish is never consumed in England uncooked, the heating during cooking would be sufficient and could be relied upon to destroy the dangerous toxin.

In the tropical countries, where domestic refrigeration is far less com-m o n and the regulation of commercial installations is made more difficult by the high ambient temperatures and where the transport and distribution industries are less highly organized, the dangers arising from the possible growth of CI. botulinum, type E, during inadequate storage are manifestly


TABLE II

THE RADIATION RESISTANCE OF SPORES OF CLOSTRIDIUM BOTULINUM. ТУРЕ E

Strain

Dose (Mrad)

Doverall (in beef stew)

[37 ]

^exponential (aqueous suspension)

. [36]

Dose (Mrad) to inactivate 106 spores [36]

Alaska

Beluga

Iwanai

/ Minneapolis

VH

8E

16/63

1537/62

4318/63

0.137

' 0 .136

0 .125

0.128

0.138

0 .13

0.080

0. 075

0.12

0. 084

0.12

0. 16 (0 .18 in broth)

0. 10

0. 065

1. 01

0 .70

0. 73 (1. 01 in broth)

0 .95

0. 84

0 . 9 5

1 .18 (1. 29 in broth)

0. 92

0. 73

Note: Irradiated in aqueous suspension at ambient temperature or at 0 - 3°C in broth.

greatly increased. Moreover the safety factors described are all more dif-ficult to apply or control, andlocal culinary methods may not include heating sufficient to inactivate toxin.

(iii) The ecology of CI. botulinum, type E. Considerations of the signi-ficance of this organism as a possible cause of food poisoning must include an estimate of the likelihood of its occurrence in any particular location. Forexample, up to the present time no positive identification of the organism has been made on fish caught in the North Sea or the Atlantic Ocean and landed in England. Present knowledge of the/distribution is summarized in Fig. 3 where the location of food poisoning outbreaks or isolations of the or-ganism itself from sea muds, soils or fish are shown. Further details of particular events are given in Tables IV and V, and fatalities are sum-marized in Table VI. It is clear that spores of CI. botulinum, type E, occur in soils and hence are washed into rivers and lakes, and persist in those portions of the oceans which are relatively enclosed and from which the dis-charged river waters are not readily dispersed. Thus the sea m u d s and fish of the Baltic Sea show a high incidence of contamination whereas the adjacent, but highly scoured waters of the North Sea have, so far, shown uniformly negative results. Most other positive identifications have occurred in land-locked waters or lakes.

Very few observations have been made in tropical regions or in the southern hemisphere; thus the appearance of restriction to the northern climes rests, more likely, upon the paucity of data rather than on fact. Positive


TABLE III

T H E H E A T R E S I S T A N C E O F C L O S T R I D I U M B O T U L I N U M , T Y P E E, T O X I N *

Inactivation factor for heating at 60°C in cooked-meat medium fluid for: pH

5 min 10 min 20 min 40 min

7 . 5 105 -

6 . 3 10 4 10 4 105

5 . 5 - 10 3 105

5. 2 - 1 0 4 1 05 1 05

4. 9 - 10 2 102 103

4 . 6 - 1 0 1 103 103

4 . 3 - 1 0 1 103 104

4 . 0 - 1 0 3 10S 105

3 . 5 105

* From Ref. [ 3 4 ] .

identifications have been made on the coasts of the Mediterranean and the Black Seas and in the soil of Israel, and negative identifications in Spain, Ceylon and Tasmania. Further work on the ecology of this organism is. now in progress in a number of laboratories in Europe and the USA, but, to our knowledge, none in the tropics.

No reliable estimate of the level of infection of CI. botulinum, type E, in terms of numbers of spores per fish or of the proportion of fish infected can be deduced from the data published to date. It has been shown experi-mentally that the time to develop a given potency of toxin under standard conditions is affected by the initial concentration of spores in the range of 102 - 10® per gram (Table VII). It cannot be suggested, however, that the level in fish now commonly eaten in Scandinavia, for example, can approach even the lower of these figures.

A further factor influencing the outgrowth of spores of this organism is the presence of sodium chloride in the suspending medium. Levels above 3. 0% inhibit growth at low temperatures (Table VIII), whereas there is a sensitizing effect at lower concentrations (Tables IX and X).

(b) Organoleptic factors

Fresh fish pasteurized by radiation will retain its quality during storage at 0°C for about 20 d and at 4°С for about 10 d. During this time there is

FIG. 3. The locations of reported incidents involving CI. botulinum, type E, and positive and negative isolations of the organism (1932-64) • Outbreak O Isolate ® Negative search

RADIATION PRESERVATION OF FISH 47

TABLE IV

LOCATION AND ORIGIN OF RECORDED OUTBREAKS OF CLOSTRIDIUM BOTULINUM, TYPE E

Deaths/cases Date Location Origin ? = type E Ref.

not isolated

1932

1934

Cooperstown, N.Y.

Westchester, N. Y.

1934-35 N. W. Shores of Caspian Sea Astrakahn Guryev

1938 Leningrad

1940 nr. Whitehorse, Yukon

1941 San Francisco, Calif.

Labrador smoked salmon 1 /3

commercially canned sprats 1 /3

salted uncooked meat and 2 / 3 ? blubber from seal J 5 / Î}

smoked herring 1 /1

salmon eggs 3 /5 г

locally canned Yugoslav

[ 1 , 1 6 , 1 7 , 2 1 ]

[ 1 , 1 6 , 1 7 , 2 1 ]

[16] [16]

[ 1 , 1 6 ]

[16]

mushrooms 1 /3 [6 ]

1944 Nanaimo, B.C. home-canned salmon 3 /3 [ 2 , 1 6 ]

1945 Markham Bay, N.W.T. seal meat 7/8? [ 1 6 , 1 9 ]

1947 Kotzebue, Alaska beluga flippers 2 /3? [16 ]

1948 Noatak, Alaska beluga flippers 1/2? [16]

1948 Ketchikan, Alaska salmon eggs 1/2? [16 ]

1949 Vancouver, В. C. pickled (vinegared) herring 1/2 • [18]

1950 Point Hope, Alaska raw beluga flipper 0 /5 [16]

1951 Iwanai, Hokkaido, Japan herring 'izushi' 4 / 1 4 [7 ]

1951 Fredriksberg, Denmark home-pickled herring 0/6 [ 8 ]

1951-52 France fish-borne botulism ? [ 3 , 3 0 , 3 1 ]

1952 Selawik, Alaska beluga flipper 1/1 [16]

1952 Natal, B.C. home-pickled trout 1 /1 [ 1 6 , 1 9 ]

1952 • Okkoppe, Hokkaido sole 'izushi' 0 /4 [7 ]

Memanbetsu, Hokkaido sole 'izushi' 2 / 5 [ 7 ]

1953 Saroma, Hokkaido sole 'izushi' 1 /5 [7 ]

Tenno, Hokkaido gilthead 'izushi' 2 / 4 [28]

1954 Abashiri, Hokkaido sole 'izushi' 1 /5 [ 7 ]

Onbetsu, Hokkaido hata-hata (sandfish) 'izushi' 1/2 [7]

Bella Bella, B.C. salmon egg 'cheese' 1 /3 [16 ]

1955 Kitami, Hokkaido trout eggs 1/2 [7 ]

Otaru, Hokkaido mackerel 'izushi' 1 /5 [7 ]

48 RHODES et a l .

TABLE IV (cont.)

Deaths/cases Date Location Origin î = type E Ref.

not isolated

1955 Morai, Hokkaido salmon 'izushi' 2 / 1 1 [ 7 ]

Kamiyama, Hokkaido sanma 'izushi' 3 / 3 [ 7 ]

1956 Kushiro, Hokkaido yamabe 'izushi' 3 / 1 2 [ 7 ]

Zenikamezawa, Hokkaido hata-hata 'izushi' 4 / 1 1 [ 7 ]

Wakkanai, Hokkaido sole 'izushi' 2 / 5 [ 7 ]

Ungadlek, Labrador uncooked seal flipper 6 / 8 [ 1 6 ]

Kotzebue, Alaska beluga flipper 1 /2 [ 1 6 ]

1957 Betsukai, Hokkaido hata-hata 'izushi' 0 / 4 [ 7 ]

Wakkanai, Hokkaido sole 'izushi' 4 / 5 [ 7 ]

Kitami Esashi, Hokkaido sole 'izushi' 1 /1 [ 7 ]

Mashike, Hokkaido hata-hata 'izushi' 9 / 3 5 [ 7 ]

Prince Rupert, B.C. uncooked salmon eggs 3 / 3 [ 1 6 ]

1951-57 Hokkaido, Japan 'izushi' 16 outbreaks trout eggs 1 outbreak 39/129

[ 1 1 , 2 8 ] [ 7 , 1 6 ]

1959 Scammon Bay, Alaska grey whale fluke 1/7 [ 1 6 ]

1958 /9 Hydaburg, Alaska salmon eggs 2 / 2 [ 1 6 ]

1960 Penticton, B.C. Holland herring exported in brine 0 / 1 1 5 , 1 6 ]

Hopedale, Labrador uncooked seal flipper 2 / 4 ) [ 1 6 ]

nr. Hopedale, Labrador dried seal meat 1 / 2 Î [ 1 6 ]

Nain, Labrador uncooked seal flipper o / i г [ 1 6 ]

Minneapolis, Minn., USA vacuum-packed smoked ciscoes 2 / 2 [ 1 ]

Malmö, Sweden pickled herring 0 / 2 [ 9 ]

Odessa, USSR i / г [13

Ketchican, Alaska salmon egg 'cheese' 2 / 2 [ 1 6 ]

1961 Forks, Wash. , USA salmon eggs 1 / 4

Paulatuk, N. W.T . seal meat 7 / 8 î [ 1 9 ]

nr. Copenhagen, Denmark salted herring 0 / 1 [ 1 ]

Norway (in mink) fish meal • - [ 2 6 ]

1962 HSlsingborg, Sweden unknown. 1 / 1 [10]

Kristinehamn, Sweden commercial ly canned boiled herring in gelatin 0 / 3 [ 1 ]


TABLE IV (cont. )

4 9

Date Location Origin Deaths/cases

î = type E not isolated

Ref.

1959-62 Ketchikan area, В. C. salmon eggs 6 / 1 1

Î

t l ]

to 1962 Hokkaido, Japan 28 outbreaks 42 /222 [ 2 9 ]

Honshu, Japan 20 outbreaks (1 trout egg , 1 commercial ly

canned mackerel, 2 herring kirikomi, remainder 'izushi')

37 /82 [ 2 9 ]

1963 Oppland, S.E.Norway 'rakefisk' 1 / 5 [ 2 2 ]

Knoxville, Tenn. , USA vacuum-packed smoked whitefish chubs 2 / 7 [ 2 4 ]

Nashville, T e n n . , USA vacuum-packed smoked whitefish chubs 3 / 5 [ 2 4 ]

Huntsville, A l a . , USA vacuum-packed smoked whitefish chubs 0 / 1 [ 2 4 ]

Kalamazoo, Mich. , USA smoked whitefish 2 / 2 [ 2 4 ]

Kentucky, USA vacuum-packed smoked whitefish chubs 0 / 2 [ 2 4 ]

Detroit, M i c h . , USA Japanese tuna (canned in Calif .) 2 / 3 [ 1 ]

Denmark uncooked trout 1 / 1 [ 2 2 ]

Iwate, Japan 'menuke izushi' 2 / 5 [ 4 1 ]

a slow decline in acceptability in which the characteristic fresh odour and flavour disappear leaving a rather tasteless product. Little further change occurs until the surviving microorganisms begin to multiply and finally spoilage occurs.

At higher temperatures these changes are all accelerated and, although few results on fish are available, at 10 and 15°C the storage life can be esti-mated from experiments on chicken carcasses given the same dose iRhodes and Shepherd, unpublished data]. These results are summarized in TableXI, which covers the main species of fish of commercial importance, in Europe which do not suffer pigment destruction on irradiation. All storage results were obtained on fish packaged in the absence of air in plastic materials of low oxygen permeability. Other results on fish of low fat content (cod, had-dock) have shown similar stability in cheaper plastic materials more per-meable to oxygen; for short-term storage such materials might prove adequate.

(c) Discussion

At present, the overriding factor in considering radiation pasteurization of fish must be the possibility of outgrowth of CI. botulinum, type E, spores

50 RHODES et a l .

TABLE V

POSITIVE AND NEGATIVE ISOLATION OF CLOSTRIDIUM BOTULINUM, TYPE E

Date Location Origin Ref.

POSl t lVE

1 9 3 4 - 3 5

1945

1957

1951

Sea of Azov (Soviet Ukraine) intestine of sturgeon

1955-

1956

1 9 5 8 - 5 9

1954

1961

1 9 6 1 - 6 4

N a n a i m o , B . C .

Agluitsok Bay, Greenland

Straits of Georgia, Vancouver

N. Central , France

Lake St. Martin, Manitoba

Bute Inlet , Smith Inlet , Soda Creek , Prince Rupert, Pitt Lake , Canada

Lake Abashiri

Sea of Okhotsk

Hachiro Lagoon

dead fish from Hachiro Lagoon

Hokkaido, Japan

Copenhagen, Denmark

Grand Forks, В. C.

Sweden and Baltic

Israel

Texas , USA

Germany., Augsburg, Wiesbaden, Grossenbrode, Trave

N i c e , France

soil

sea bottom 4 samples , 1 strain

salmon

fresh-water perch 1 / 1 7 6 fish 163 fresh water

13 salt water

intestinal contents of mul l e t

Samples Strains

257 15 (bottom mud, t idal mud, sand)

2000

50

146

12

flsh sand shore bottom

6

2

18

10

315 (soil) 7

15 (sea mud and harbour) 12

from cucumber relish pH 4 . 4 and pickled tomatoes pH 4 . 2

650 (sand, soi l , mud, fish) 100

potatoes 3 samples

Galvaston, shore sample

potato sand sand sand

sand

[ 4 , 1 6 ]

[2]

[ 1 6 , 2 3 ]

[21]

[ 3 ]

[1]

[1.16]

[11,16]

[ 1 2 , 1 6 ]

[ 1 , 1 3 ]

[ 2 3 ]

[ 1 4 , 2 7 ]

[ 1 4 ]

[ 2 5 ]

[ 2 5 ] [ 2 5 ] [ 2 5 ] [ 2 5 ]

[ 2 5 ]


TABLE V (cont.)

51

Date Location Origin Ref.

1964 Great Lakes [32 ]

NEGATIVE

Vancouver beaches (sand) 20 '

Hooper Bay, Alaska 80

Norwegian Sea (sea bot tom) 19

Bristol Bay, N. Alaska 19 [1 ]

St. Paul Island (sand) (fish and seal intestine)

50 15

Bering and Chukchi Seas (sea bo t tom) 30

Canadian Far North (sea bot tom) 28

Great Britain (vacuum packed c o m m e r c i a l fish bought in re ta i l shops throughout Great Britain) 235

. [33 ]

Aberdeen harbour (mud) 12

N. Sea and Barrents Sea (mud) 20

Haddock and cod (intestines) 96

N. Sea herr ing (caught off Shetland Isles) 100

Spain (sand) 2 j [25] '

Ceylon (sand) 1 j [25] '

d u r i n g t h e p r o l o n g e d s t o r a g e p e r i o d s m a d e p o s s i b l e by t h e t r e a t m e n t . P a s t e u r i z i n g d o s e s do not e l i m i n a t e s p o r a l in fec t ion , a l though the n u m b e r s a r e r e d u c e d by at l e a s t 100 fo ld ( T a b l e II), and only if t he t e m p e r a t u r e of s t o r a g e both b e f o r e and a f t e r t r e a t m e n t can be adequa te ly con t ro l l ed within d e f i n e d l i m i t s can t h e p r o c e s s be s a f e l y a p p l i e d . The a p p l i c a t i o n of such c o n t r o l s p r e s u p p o s e s a highly o rgan ized d i s t r ibu t ion s y s t e m such a s obtains in s o m e W e s t e r n c o u n t r i e s . In the developing coun t r i e s with f e w e r handling and t r a n s p o r t f a c i l i t i e s and w h e r e lack of r e f r i g e r a t i o n i s coupled with high ambien t t e m p e r a t u r e s a f a r l e s s sa t i s f ac to ry si tuation a r i s e s . Considerat ion of the p r e s e n t knowledge of the r a t e s of development of CI. botulinum, typeE, l e a d s t o t h e c o n c l u s i o n t ha t , if t h e o r g a n i s m i s indeed p r e s e n t in t r o p i c a ! f i s h , r a d i a t i o n p a s t e u r i z a t i o n could not be r e c o m m e n d e d a s a p r e s e r v a t i o n p r o c e s s .

It i s not c e r t a i n that the o r g a n i s m i s endemic to a l l t r o p i c a l w a t e r s , just a s , in N o r t h e r n w a t e r s , i t s d i s t r i b u t i o n i s not u n i v e r s a l . D i r e c t e x p e r i -

52 RHODES e t a l .

TABLE VI

G E O G R A P H I C D I S T R I B U T I O N O F V E R I F I E D O U T B R E A K S O F C L O S T R I D I U M B O T U L I N U M , T Y P E E *

Place of occur rence Outbreaks Cases Deaths

Japan , Hokkaido 29 227 44

N. Honshu 20 82 37

USA. Alaska 7 19 6

Other states 11 34 15

C a n a d a , British Co lumbia 8 20 11

Labrador 3 10 8

Sweden 3 6 1

Denmark 3 8 1

USSR 2 2 2

Norway 1 5 1

* FromRefs . [ 1 , 2 2 , 2 4 ] . Note: T h e outbreaks in Japan have occurred since 1951.

TABLE VII

E F F E C T O F I N O C U L U M L E V E L ON O U T G R O W T H O F S P O R E S O F C L O S T R I D I U M B O T U L I N U M , T Y P E E *

Average period for outgrowth (d) for: Inoculum

50°F 46°F

2 x l 0 6 6 10

106 - 10

105 8 15

104 ' 10 15

103 12 16

102 13 19

* Strain: Minneapolis . Source: Schmid t , C . F . , Segner , W. P . , Boltz, J. K. , in prepara t ion .


TABLE VIII

E F F E C T OF SODIUM CHLORIDE AND INCUBATION T E M P E R A T U R E ON OUTGROWTH OF CLOSTRIDIUM BOTULINUM, T Y P E E,

IN TPG MEDIUM*

Per cent sal t added Tempera tu re

(*F) Growth No growth

98 2 . 5 3 . 0

85 3 . 5 4. 0

70 4. 0 4. 5

60 3. 0 4. 0

50 3, 0 3. 5

46 3. 0 3. 5

Strain: Minneapol is [ 3 8 ] .

TABLE IX

E F F E C T OF SODIUM CHLORIDE ON OUTGROWTH OF CLOSTRIDIUM BOTULINUM. T Y P E E, IN HADDOCK

AT S U B - O P T I M A L T E M P E R A T U R E S *

Outgrowth (d) a t incubat ion temperatures of: Sal t concent ra t ion . ° r

(% added) 46°F 42°F 40°F 38°F

0 6 - 1 0 12-22 23-> 96 > 51

0 . 5 6 - 8 12-16 19-28 > 5 1

1. 0 6- 9 12-21 17-33 4 1 - > 5 1

1. 5 8 - 1 0 15-22 20-43 -

2 . 0 12-17 24-38 28-69

* Strains: Alaska, Beluga, Minneapol is , 8E [ 3 8 ] .

menta l ev idence i s m e a g r e , but t h e r e i s no r e a s o n to think that f i s h caught in the open oceans in the South will be any m o r e l ikely to c a r r y the s p o r e s than those f r o m the Atlant ic which, to date, have been uniformly f r e e of i n -fect ion. On the other hand the isolat ion of spores in the soi ls of I s rae l and on the M e d i t e r r a n e a n c o a s t s s u g g e s t s tha t the s i t ua t ion in enc lo sed t r o p i c a l s e a s such a s the M e d i t e r r a n e a n , the Red Sea and the P e r s i a n Gulf wi l l be ana logous t o tha t in the B a l t i c and tha t the m u d s and f i s h in t h e s e w a t e r s

54 RHODES e t a l .

TABLE X

E F F E C T O F L O W L E V E L S O F SODIUM C H L O R I D E ON T H E O U T G R O W T H O F C L O S T R I D I U M B O T U L I N U M . T Y P E E ,

S P O R E S IN H A D D O C K

Beluga 8E Per cent NaCl

40"F , 38"F 40"F 38"F

0 4 2 - 6 1 >365 23 -35 > 3 6 5

0. 5 21-26 67-170 19-26 > 3 6 5

1 . 0 21 41 -48 19-23 64-204

Source: Segner, W. P. , Boltz, J. K. , Schmidt , C. F. , in preparat ion.

TABLE XI

S T O R A G E L I F E O F RAW F I S H T R E A T E D W I T H A P A S T E U R I Z I N G DOSE O F 0. 3 M r a d AND H E L D IN A N A E R O B I C P A C K A G E S

Tempera tu re of storage *C (°F) As first

class a r t i c le

Storage l i f e (d)

T o spoilage by microorganisms

0 (32)

5 (39)

10 (50)

20 (68)

20-30

10-16

5

2

> 60 "I

> 3 0 J Measured [39 ]

. 10 "I Estimated

2 J (see text)

wil l c a r r y the s p o r e s . In add i t ion a l l r i v e r o r lake f i sh wi l l be highly s u s -pec t . Until t h e s e ques t ions a r e c la r i f i ed by exper iment no radiat ion pas teur iz ing p r o c e s s can be safe ly r ecommended f o r t rop ica l r aw f i sh .

If it i s a s s u m e d that CI. botul inum, t y p e E , i s absent , the s to rage s tab i l i t ies a t v a r i o u s t e m p e r a t u r e s g iven in T a b l e XI m a y be t a k e n a s i n d i c a t i o n s of t he b e n e f i t l i ke ly t o a c c r u e f r o m r a d i a t i o n p a s t e u r i z a t i o n when the p r o d u c t i s packed in oxygen proof m a t e r i a l s . The ac tua l length of s a t i s f a c t o r y s to rage m u s t depend upon the def in i t ion of the l e v e l of o rganolep t ic acceptabi l i ty . It i s c l e a r , f o r example , that the concept of f i r s t c l a s s quali ty in the compe t i -t ive a t m o s p h e r e of W e s t e r n food r e t a i l i ng i s f a r too s t r ingen t to be r easonab ly appl ied in many o ther loca t ions . Raw f i sh , held until the onset of mic rob ia l spo i l age , r e m a i n s in a p e r f e c t l y edible condi t ion but l o s e s s o m e of the c h a r a c t e r i s t i c qua l i t i e s of the f r e s h f l e s h ; the f i s h p ro t e in r e t a i n s a l l of i t s


n u t r i t i o n a l q u a l i t i e s and s t o r e d f i s h , when cooked and s e r v e d with su i t ab le s a u c e s and f l a v o u r i n g s , i s e n t i r e l y a c c e p t a b l e . In the context of opening up new s o u r c e s of p r o t e i n f o r u n d e r n o u r i s h e d p o p u l a t i o n s t h e r a d i a t i o n -p a s t e u r i z e d p roduc t would s u f f e r no drawback f r o m the acceptabi l i ty f a c t o r .

It i s c l e a r f r o m T a b l e XI tha t without r e f r i g e r a t i o n only m i n o r advan tages in s t o r a g e l i f e could be gained f r o m the p a s t e u r i z a t i o n t r e a t m e n t ; at 20° С f o r e x a m p l e only one o r two days could be ga ined . R e f r i g e r a t i o n would n e -c e s s a r i l y be i n c o r p o r a t e d into an i r r ad i a t i on fac i l i ty f o r pas teur iza t ion ; thus s t o r age a f t e r t r e a t m e n t would be poss ib le fo r some t ime at low t e m p e r a t u r e s , even if d is t r ibut ion in insula ted con ta iners only were poss ib le t h e r e a f t e r . S torage l i fe at t e m p e r a t u r e s below 5°C is i n c r e a s e d to.between four and eight weeks ; thus the p r o c e s s g ives added t ime f o r d i s t r ibu t ion to dis tant m a r k e t s o r s h o r t - t e r m p r e s e r v a t i o n f o r r e g u l a r i z i n g f l u c t u a t i o n s in supply and d e -m a n d . However , t h e s e s t o r a g e t i m e s a r e insuf f ic ien t to p r e s e r v e f i sh f r o m one s e a s o n a l peak of ca tching to the next .

II. Combination with heat treatment

P r o t e o l y t i c o r o t h e r e n z y m a t i c c h a n g e s in f i s h m u s c l e a r e h a r d l y m e a s u r a b l e even a f t e r the m a x i m u m t i m e s and t e m p e r a t u r e s of s to rage given in T a b l e XI. No need h a s a r i s e n , t h e r e f o r e , t o c o n s i d e r t he inc lus ion of a hea t ing t r e a t m e n t t o inac t iva te the t i s s u e e n z y m e s b e f o r e i r r a d i a t i o n f o r t he p a s t e u r i z a t i o n t r e a t m e n t s a l r e a d y d i s c u s s e d . M o r e o v e r , in the United Kingdom at l eas t , the c o n s u m e r demands f i sh in the raw s ta te , and t h e r e a r e many t e c h n i c a l ob j ec t ions to a p a r t i a l l y cooked p roduc t , such a s l o s s of we igh t f r o m exuded f l u id , r e s t r i c t i o n of p o s s i b l e m e t h o d s f o r c o m p l e t i n g t h e cook ing p r o c e s s , u n a t t r a c t i v e a p p e a r a n c e of t he h e a t e d f i s h , e t c . In the con tex t of a new m a r k e t f o r f i s h and t h e open ing of a new s o u r c e of p r o t e i n , t h e s e ob jec t ions b e c o m e of s e c o n d a r y i m p o r t a n c e s ince they a r e b a s e d on e i t h e r c o m m e r c i a l c o n s i d e r a t i o n s o r p r e j u d i c e . In f ac t , the c o m -b i n a t i o n of a m i l d h e a t t r e a t m e n t and r a d i a t i o n p a s t e u r i z a t i o n o f f e r s a n u m b e r of s u b s t a n t i a l a d v a n t a g e s in p r o c e s s i n g .

(a) CI . bo tu l inum, type E

R e f e r e n c e to T a b l e XII shows that the s p o r e s of CI. botu l inum, type E , a r e r e a d i l y d e s t r o y e d by h e a t . T h e m o s t r e s i s t a n t of the s t r a i n s l i s t e d i s r educed 1010-fold by exposu re to 100°C f o r only 20 s and mos t o ther s t r a i n s t e s t e d a r e m u c h m o r e e a s i l y i n a c t i v a t e d t h a n t h i s . A h e a t t r e a t m e n t s u f f i c i e n t t o b r i n g the whole of a p i e c e of f i s h t o 100° С would , t h e r e f o r e , be su f f i c i en t to e l i m i n a t e s p o r e s of CI. bo tu l inum, type E , when the t i m e -t e m p e r a t u r e e x p o s u r e was i n t eg ra t ed over the whole p r o c e s s . The addi t ion of a r a d i a t i o n p a s t e u r i z a t i o n would c o m p l e t e t h e k i l l of the s p o i l a g e o r g a -n i s m s and add a f u r t h e r 100-fold reduc t ion in CI. botulinum, type E, s p o r e s . T h e r e s u l t a n t p r o d u c t would be c o n s i d e r a b l y m o r e s t a b l e in s t o r a g e t h a n raw p a s t e u r i z e d f i s h b e c a u s e of the i n c r e a s e d combined b a c t e r i c i d a l e f f ec t s and of the i n a c t i v a t i o n of e n z y m e s and the s t a b i l i z a t i o n of p r o t e i n s by d e -n a t u r a t i o n . Such a p roduc t wil l not r e q u i r e the r i g o r o u s con t ro l of s t o r a g e t e m p e r a t u r e n e c e s s a r y f o r the r a w f i sh . Some danger could s t i l l a r i s e f r o m

56 RHODES e t a l .

TABLE XII

THE HEAT RESISTANCE OF SPORES OF CLOSTRIDIUM BOTULINUM. T Y P E E

Strain Country of

origin Hea ted in z - v a l u e

D(min) a t 80еС (176°F)

Ref.

103 Canada M / 1 5 phosphate buffer pH 7. 0 17. 0 3. 3 [34 ]

108 USSR M / 1 5 phosphate buffer pH 7. 0 1 1 . 0 0. 54 [34 ]

Tenno Japan M / 1 5 phosphate buffer pH 7. 0 9 . 3 0 . 8 [ 2 8 ]

Minneapol is USA M / 1 5 phosphate buffer pH 7. 0 15 .0 2 . 4 [ 3 5 ]

Minneapol i s USA TPG m e d i u m 15; 5 1 . 7 8 [35 ]

Alaska USA water 1 0 . 5 0 . 6 [36 ]

Beluga Canada water 9 . 5 0 . 7 5 • [36 ]

Iwanai Japan water 10 .0 1 . 0 [36 ]

Minneapol is USA water 10. 5 0. 87 [ 3 6 ]

8E USSR water 7 . 4 0. 8 [36 ]

1957 /61 Sweden water 10. 8 1 . 2 5 [36 ]

1937/62 Sweden water 10. 7 0. 83 [ 3 6 ]

1 6 / 6 3 Sweden water 9. 0 < 0 . 3 3 [36 ]

4 3 1 8 / 6 3 Norway water 10. 0 0. 66 [36 ]

the p r e s e n c e of s p o r e s of CI. bo tu l inum, t y p e s A o r B, but the l ikel ihood of t h e s e o c c u r r i n g on f i s h in the t r o p i c s i s not known; m o r e o v e r the ou t -growth of s p o r e s of t he se types i s inhibited complete ly at t e m p e r a t u r e s b e -low 10°C.

(b) Organolept ic f a c t o r s

F i s h m u s c l e p r o t e o l y t i c e n z y m e s a r e d e s t r o y e d by hea t ing at 65. 5°C f o r 5 min o r 71°C f o r 15 s . (Sinnhuber and L a n d e r s [40]), E i t h e r t r e a t -ment i s suff icient to coagulate the musc le prote in and to give the appearance of a 'cooked1 f i s h . To achieve these condit ions at the cen t re of a solid slab of t i s s u e en ta i l s much m o r e d r a s t i c condi t ions at the s u r f a c e ; f o r example , in t h e e x p e r i m e n t s quoted 2 - c m l a y e r s of m i n c e d m u s c l e w e r e p l a c e d in w a t e r at 71 o r 77°С f o r 15 and 18 min , r e s p e c t i v e l y , fol lowed by a 7 - m i n cooling per iod. In p rac t i ce boiling water or s t eam is likely to be used. After cooling, the f l e s h could be s e p a r a t e d f r o m the bone, e . g. f r o m whole f i sh , and p a c k a g e d , t h u s avo id ing t h e i nc lu s ion of u s e l e s s f lu id and the d a n g e r of b o n e s p u n c t u r i n g p l a s t i c w r a p s .

The s to rage c h a r a c t e r i s t i c s of such a product have not been studied, but spo i lage wil l r e s u l t f r o m the growth of su rv iv ing m i c r o o r g a n i s m s a s in the


c a s e of unhea ted f i s h , and the h igher f i g u r e s in Tab le XI a r e p robab ly c lose t o what migh t be expec t ed . It i s l ike ly , h o w e v e r , tha t l i t t l e change in o r g a n o l e p t i c qua l i t i e s would be de t ec t ab l e in the hea ted f i s h unde r the con -d i t i o n s s p e c i f i e d and t h e a c c e p t a b i l i t y would be w e l l m a i n t a i n e d . Should t i m e s of t h e s o r t g iven be of v a l u e in p a r t i c u l a r c i r c u m s t a n c e s t h e c o m -b ina t i on of h e a t and r a d i a t i o n i s l i ke ly t o p r o v i d e the b e t t e r p r o c e s s .

F u r t h e r p r a c t i c a l work i s n e c e s s a r y to develop data on which to a s s e s s m a x i m u m d o s e s tha t c an be app l i ed to the v a r i o u s s p e c i e s of f i s h f o r c o n -sumpt ion by the p a r t i c u l a r popula t ion u n d e r d i s c u s s i o n . Such s t u d i e s m u s t include the indigenous cooking p r o c e s s e s and the local t a s t e s and p r e f e r e n c e s It i s not improbab le that h igher dose l eve l s than those de te rmined in England m a y b e a c c e p t a b l e e l s e w h e r e wi th a c o n s e q u e n t i m p r o v e m e n t in t h e p e r -f o r m a n c e of t he p r o c e s s in p r a c t i c e .

RADIATION S T E R I L I Z A T I O N

T r e a t m e n t of m o s t m e a t s and f i s h at the s t e r i l i z a t i o n dose l eve l of 5 Mrad h a s been r e j e c t e d a s a poss ib le c o m m e r c i a l p r o c e s s in Wes te rn con-d i t i o n s . When a b a l a n c e h a s t o be s t r u c k b e t w e e n t h e e f f i c i en t u t i l i z a t i o n of n a t u r a l food r e s o u r c e s f o r the supply of p r o t e i n to u n d e r n o u r i s h e d popu-l a t i o n s and the a c c e p t a b i l i t y of t h e p r o d u c t , a d i f f e r e n t conc lu s ion m a y be r e a c h e d . N e v e r t h e l e s s , an unappe t iz ing p r o t e i n , unconsumed, con t r i bu t e s no th ing t o t h e n u t r i t i v e v a l u e of a m e a l and the e n j o y m e n t of e a t i n g i s not a monopoly of W e s t e r n p a l a t e s ; thus the ma in tenance of the highest poss ib le qua l i t y m u s t be an i m p o r t a n t a i m of any p r e s e r v a t i o n p r o c e s s . F i s h h a s a del ica te f lavour a.nd i s popular ly cooked in a bland fashion so that any modi-f i c a t i o n in i t s na t i ve o d o u r o r f l a v o u r i s r e a d i l y d e t e c t e d . In the t r o p i c a l coun t r i e s , whe re cu l inary techniques make much m o r e f requent use of highly f l a v o u r e d s p i c e s , c o n d i m e n t s o r v e g e t a b l e s , s l ight c h a n g e s in the o r i g i n a l f l a v o u r of f i s h might we l l b e of l e s s c o n s e q u e n c e .

Such q u e s t i o n s r e q u i r e p r a c t i c a l i nves t i ga t i on .

Storage stability and microbiology

F i s h t r e a t e d with 5 Mrad wil l r e m a i n unspoiled indefini tely by the growth of m i c r o o r g a n i s m s a t any t e m p e r a t u r e a s long a s t h e p a c k a g i n g m a t e r i a l r e m a i n s in tac t . S i m i l a r l y a l l p r o b l e m s of b a c t e r i a l pa thogens a r e obviated and no r e s t r i c t i o n on s t o r a g e t e m p e r a t u r e app l i e s .

Raw s t e r i l e f i s h wi l l d e t e r i o r a t e a s in T a b l e XI and a t the h i g h e r t e m p e r a t u r e s the ac t ion of p ro t eo ly t i c and l ipoly t ic e n z y m e s wil l eventual ly d e s t r o y t h e s t r u c t u r e of t h e t i s s u e and r e n d e r t h e food i n e d i b l e . T o t a k e f u l l advan tage of a s t e r i l i z a t i o n p r o c e s s a hea t ing s t ep to inac t iva te the enzyme i s e s s e n t i a l [40] . In t h i s c a s e the m a j o r cause of de t e r i o r a t i on wil l b e c o m e c h e m i c a l , r e a c t i o n s of the b rowning type between s u g a r s and amino c o m p o u n d s t o give b r o w n c o l o u r e d compounds and b u r n t f l a v o u r s be ing the m o s t l i ke ly a t e l e v a t e d t e m p e r a t u r e s . The shel f l i f e at 0 - 1 0 ° С shou ld be in the r eg ion of many y e a r s and even at 20°C t h e r e should be ample s tabi l i ty t o c a r r y o v e r f i s h f r o m one annual h a r v e s t to the next .

58 RHODES e t a l .

T h e s t e r i l i z a t i o n t r e a t m e n t h a s , t h e r e f o r e , only t h e c h a n g e s in odour and f l a v o u r to i t s d i s advan t age and, a s shown below, the i n c r e a s e d cos t of p r o c e s s i n g .

PACKAGING

Al l r a d i a t i o n p r é s e r v a t i o n p r o c e s s e s depend upon t h e d e s t r u c t i o n of b a c t e r i a i n s i d e an h e r m e t i c a l l y s e a l e d c o n t a i n e r which t h e n p r e v e n t s r e -c o n t a m i n a t i o n of t h e föod by a d v e n t i t i o u s m i c r o o r g a n i s m s . T h e p r o c e s s a c c e l e r a t e s autoxidat ion of fa t by f o r m i n g f r e e r a d i c a l s hence the packaging m a t e r i a l mus t be suff ic ient ly impe rmeab le to prevent the i n g r e s s of sufficient oxygen to cause r anc id i ty . This will depend upon the na tu re of the f a t s p r e -sen t , the t e m p é r a t u r e of s t o r a g e and the r a t e at which oxygen i s consumed by o ther s y s t e m s in the t i s sue ; in raw mea t s , f o r example , oxygen i s rapidly ut i l ized by the t i s sue enzyme s y s t e m s .

T h e w o r k in the Uni ted Kingdom on f i s h p a s t e u r i z a t i o n [39] h a s b e e n c a r r i e d out u s ing a r e s i n - c e l l o p h a n e - p o l y e t h y l e n e l a m i n a t e d p l a s t i c which h a s p r o v e d e n t i r e l y s a t i s f a c t o r y f o r ind iv idua l p a c k e t s con ta in ing 0. 25 kg of f i sh f i l l e t . T h i s i s not the l imi t of s i z e s ince the s a m e m a t e r i a l ha s been used t o p a c k 15-kg s i d e s of l a m b f o r e x p e r i m e n t a l t r a n s p o r t by ship to A u s t r a l i a and New Z e a l a n d . It would a p p e a r f r o m o u r w o r k that p l a s t i c p a c k s can b e u s e d s u c c e s s f u l l y f o r f i l l e t s and whole f i s h , p r o v i d e d tha t no s h a r p p r o j e c t i o n s a r e al lowed to puncture the f i l m . Th is could be prevented by f i r s t wrapp ing in some p ro t ec t i ve m a t e r i a l such a s stout pape r , e tc .

R e m o v a l of oxygen f r o m the package b e f o r e sea l ing i s b e s t achieved by evacuat ion, m a c h i n e s f o r evacuat ing and sea l ing under vacuum being read i ly ava i l ab le . Al te rna t ive ly n i t rogen gas may be in jec ted to a sui table p r e s s u r e to r e l i eve t ens ion on the f i l m a f t e r packing. Until the ac tua l p r o c e s s and the condi t ions of s t o r a g e a r e def ined, the exact extent of p r e c a u t i o n s n e c e s s a r y to e x c l u d e oxygen canno t be p r e d i c t e d . In the s h o r t - t e r m p a s t e u r i z a t i o n p r o c e s s developed f o r poul t ry c a r c a s s e s , f o r example , light polythene packs w e r e suf f ic ien t [Rhodes and Shepherd, unpublished].

F o r l o n g - t e r m s t o r a g e , p o s s i b l e with the s t e r i l i z e d f i s h , a subs t an t i a l c o n t a i n e r would be r e q u i r e d and n o r m a l m e t a l cans a r e ind ica ted . In such a c a s e the f i s h m a y be v a c u u m packed in p l a s t i c in un i t s su i t ab l e f o r c o n -s u m p t i o n , a s b e f o r e , and m e r e l y s e a l e d in c a n s , t h u s obv ia t ing the m o r e d i f f i cu l t and e x p e n s i v e p r o c e s s of g a s p a c k i n g m e t a l c o n t a i n e r s .

S P E C I E S

An a n a l y s i s of T a b l e s XIII and XIV shows f i r s t l y tha t f r e s h - w a t e r f i s h c o m p r i s e a l a r g e p r o p o r t i o n of the to ta l edible ca tch in t r o p i c a l w a t e r s and tha t it f o r m s the m a j o r f i s h food in f o u r As i an coun t r i e s ; secondly , tha t the commones t of the sa l t w a t e r spec i e s a r e the h e r r i n g , anchovy, and s a r d i n e s in group D and the mul le t , j ack and sea b a s s in group B.

Li t t le can be said of the poss ib i l i t i e s of radia t ion p r e s e r v a t i o n of f r e s h -w a t e r f i s h excep t to apply the g e n e r a l p r inc ip les - d e r i v e d f r o m the e x p e r i -m e n t a l w o r k d e s c r i b e d . It i s unlikely that any s p e c i e s with p igmented f l e s h


and high fa t content , of the s a l m o n o r tuna type , wi l l p rove su i t ab le f o r r a -d ia t ion t r e a t m e n t . The p i g m e n t s a r e l ikely to be l ab i l e and to be d e s t r o y e d at low dose l e v e l s and the f l a v o u r change's, a r e a l s o m a r k e d . O the r s p e c i e s with white f l e sh , e spec ia l ly those with low fa t content, should r eac t s imi l a r ly t o the c o r r e s p o n d i n g s a l t w a t e r s p e c i e s and m a y b e expec ted to be s a t i s f a c t o r y .

TABLE XIII

F I S H H A R V E S T E D IN T R O P I C A L W A T E R S AS R E C O R D E D IN F AO Y E A R B O O K O F F I S H E R Y S T A T I S T I C S (1961)

C a t c h in mi l l ion m e t r i c tons for: Species

Asia Afr ica Oceania

A. Fresh-water fish 3. 06 0. 50 -

B. Mul l e t , j a c k , sea bass 2. 37 0 . 2 1 0. 04

C . Tuna , boni to , m a c k e r e l 1 . 3 1 0 . 1 2 0. 02

D. Herring, sardine , anchovy 1. 26 0. 96 -

E. Flounder, ha l ibu t , sole 0. 62 - -

F. Cod, h a k e , haddock 0 . 4 4 0 . 1 0 -

G. Shark, ray 0 . 1 7 - 0 . 0 1

H. Sa lmon, t rout , smel t 0 . 1 8 - -

I. Crus tacean 0. 30 0. 02 0. 02

J. Mollusc 1 . 1 9 - 0. 02

Unident i f ied 5. 27 0. 56 0. 01

Of the s p e c i e s of s e a f i s h l i s t e d , t h o s e in g roups С and H of Tab le XIII a r e p igmented and a r e not su i tab le f o r rad ia t ion p r e se rva t i on in the raw s ta te o r even a f t e r smoking; however , they c o m p r i s e a group of minor impor tance . The m o s t i m p o r t a n t g roup , D, con t a in s f i s h of high f a t content when h a r -v e s t e d at the height of t h e i r nu t r i t i ona l cyc le . However , in the work in Eng land , h e r r i n g w a s found to be e n t i r e l y s a t i s f a c t o r y a t two d a t e s of h a r v e s t i n g , p r o v i d e d tha t t he f i s h w e r e t r e a t e d and s t o r e d in the a b s e n c e of oxygen, f o r e x a m p l e , s e a l e d in l a m i n a t e d p l a s t i c . No e x p e r i m e n t s on h e a t - t r e a t e d h e r r i n g have been r e p o r t e d , nor have high dose t r e a t m e n t s been a t t e m p t e d on t h i s s p e c i e s . G r o u p B, t he s e c o n d in i m p o r t a n c e , c o n t a i n s s p e c i e s c o m p a r a b l e in fa t content with the cod and halibut of no r the rn wa te r s , a s f a r a s can be judged f r o m the r a t h e r s c a n t y a n a l y s e s a v a i l a b l e . It m a y be p red i c t ed , t h e r e f o r e , tha t t h e s e f i sh wil l be sui table f o r radia t ion p a s t e u r -i za t ion , r aw or cooked,- and wi l l be l e a s t a f fec ted even at the h igher l eve l s .

The only o ther s ea food commonly consumed in quantity a r e the mol luscs (g roup J ) . W o r k in the USA h a s shown tha t both cooked c l a m s and s h r i m p give good r e s u l t s when p r o c e s s e d by i r r a d i a t i o n ; t hus it s e e m s wor thwhi le tha t t h e s e s u p p l i e s should be c o n s i d e r e d .


TABLE XIV

PREDOMINANT SPECIES OF FISH IN 1961 HARVEST BY COUNTRY

Major groups Minor groups

Asia

Ceylon

China

Hong Kong

India

Israel

Japan

Korea

Pakistan

Philippines

Thai land

Turkey

Afr ica

Angola

Morocco

South Afr ica

Southwest Afr ica

Ocean ia

Australia

New Zea land

D . C

B.D

В

A , D , B

A

B . D . J

J,В

A

В

J, A

D

В

D

D

D

B.I

B.J

В

С

F . C . B

ECONOMICS

(a) Sh ip-based plant

It would s e e m a t t r a c t i v e to i r r a d i a t e f i s h on boa rd the catching v e s s e l immedia te ly a f t e r death o r in a fac to ry ship continuously supplied with very f r e s h f i sh f r o m a f l ee t of catching v e s s e l s s ince , in e i t he r case , ve ry high quality r a w m a t e r i a l would be avai lable . P r o c e s s i n g on the catching vesse l i s diff icult because (1) the weight and bulk of an isotope powered i r rad ia t ing plant a r e high and diff iculty a r i s e s in gett ing it into a no rma l t r a w l e r ; (2) to obta in any advantage the ca tch would need to be p r o c e s s e d within the t i m e t a k e n f o r the r e t u r n voyage; t h i s l e a d s to an e x c e s s i v e l y l a r g e throughput


r a t e and hence a l a r g e m a c h i n e ; (3) the cos t e f f i c i ency of an i so tope p lant d e p e n d s upon con t inuous u t i l i za t ion ; the w a s t e d t i m e whi le in p o r t would r a i s e the p r o c e s s i n g cos t p e r unit weight t r e m e n d o u s l y and (4) addi t iona l m a n p o w e r and s p a c e would be n e c e s s a r y to p r e p a r e and p a c k a g e the f i s h b e f o r e t r e a t m e n t . It s e e m s c l e a r tha t the f a c t o r y sh ip s c h e m e would b e the only one t e n a b l e , but t h i s could only be of va lue if a s t a b l e s t e r i l i z e d p roduc t w e r e be ing p roduced s ince , f o r the p a s t e u r i z e d p r o d u c t s , r a p i d d i s t r ibu t ion i s s t i l l n e c e s s a r y : s t e r i l i z e d f i s h could be a c c u m u l a t e d on the f a c t o r y ship f o r pe r iod i c col lec t ion by f e r r y i n g t e n d e r s f o r t r a n s p o r t to the land . Other conc lus ions might be a r r i v e d at if machine s o u r c e s w e r e used in p l ace of i sotope powered i r r a d i a t o r s but, at p r e s e n t , l i t t l e advantage i s ga ined in weight o r s i z e and the r e l a t i v e c o s t s cannot be r e a l i s t i c a l l y a s s e s s e d .

(b) S h o r e - b a s e d p l a n t s

It was concluded in the United Kingdom studies that the p rocess ing f a c t -ory w a s bes t s i ted at the l a rge f i sh ing p o r t s where good suppl ies of f i sh a r e avai lab le at mos t t i m e s of the y e a r . The cos t s of i r r ad i a t i on were then a c -c u r a t e l y a s s e s s e d f r o m the c o n s i d e r a b l e e x p e r i e n c e a l r e a d y gained in t h e r u n n i n g of c o m m e r c i a l i r r a d i a t i o n p l a n t s u s e d ma in ly f o r s t e r i l i z a t i o n of p h a r m a c e u t i c a l p r o d u c t s . T h e s e e s t i m a t e s a r e given in Table XV but it i s i m p o r t a n t to r e m e m b e r tha t the p r o c e s s i n g c o s t s given a r e ach ieved only if t h e th roughput f o r which the f a c i l i t y i s des igned i s m a i n t a i n e d Steadi ly and continuously ove r the whole y e a r . F u r t h e r it i s not pos s ib l e to exceed the m a x i m u m th roughpu t r a t e without d e c r e a s i n g the dose n o r can h i g h e r

TABLE x v

COSTS OF RADIATION PROCESSING *

Costs and other factors for annual throughput of: I t em

1 9 0 0 tons 7 600 tons 37 500 tons

Cost of bui ld ing, £ stg 35 000 45 000 50 000

Cost of coba l t , £ stg 13 000 51 600 258 000

T o t a l , £ stg 48 000 96 600 308 000

Processing cost , d. / l b 0. 71 0 . 3 8 0 . 2 5

Processing cost , US ^ / k g 1 . 8 5 1 . 0 0 0 . 6 5

Weight in f ac i l i ty , tons 2 . 2 3 . 8 7 . 4

H o l d - u p t i m e , hours 10 4 . 2 5 1 . 6 5

* Processing cost is ca l cu la t ed for dose of 0. 3 Mrad ; 2 4 - h day , 7-d week , 50-week year ; amor t i za t ion of c a p i t a l over 10 yr\ in teres t charge a t f f a , labour to run f a c i l i t y , over-heads» r e p l a c e m e n t of cobalt-, m a i n t e n a n c e . Cobal t 6 slf (84 US i) per cur ie .

62 RHODES e t a l .

d o s e s be g iven wi thou t r e d u c i n g t h e t h r o u g h p u t c o r r e s p o n d i n g l y . T h u s a f a c i l i t y des igned to give 0.5 M r a d t o 37 5 0 0 t / y r (as in co lumn 3, T a b l e XV) at a cos t of 0. 65 US «f/kg, could be used to give a s t e r i l i z ing dose of 3 Mrad to 3750 t / y r at a cos t of 6. 5 US £ /kg (although a fac i l i ty designed specif ical ly f o r the l a t t e r p a r a m e t e r s would be s l ight ly m o r e e f f ic ien t ) . Thus in des ign -ing an in s t a l l a t ion of t h i s type both the dose and the th roughput m u s t be d e -f i n e d . T h e f o r m e r i s f i x e d by t h e t y p e of p r o c e s s i n g d e s i r e d bu t , f o r t h e l a t t e r , both the amounts of sui table f i s h landed at the p o r t s and the regu la r i ty wi th which the l and ings o c c u r m u s t be known to compu te the m a x i m u m th roughpu t which can be m a i n t a i n e d s t ead i l y o v e r a 24 -h day, 7 - d week, 50-week y e a r (2 week se rv i c ing pe r iod) . S imi la r ly f o r f r e s h - w a t e r f i s h e r i e s a s u r v e y of the amount s landed and the s e a s o n a l va r i a t ion of landings i s n e -c e s s a r y . T h e f e a s i b i l i t y of i r r a d i a t i o n p r o c e s s i n g , wi th i t s heavy c a p i t a l i n v e s t m e n t and i n e s c a p a b l e runn ing c o s t s depends to a v e r y l a r g e extent on the de t a i l s of the supply of r a w m a t e r i a l s .

F r o m Table XV it can be s een tha t the c o s t s of r ad i a t i on p a s t e u r i z a t i o n a r e not e x c e s s i v e in t e r m s of W e s t e r n p r i c e s f o r f i s h , (0. 71 d. / l b i s about 2% of the r e t a i l p r i c e in E n g l a n d ) . F o r a s t e r i l i z a t i o n p r o c e s s t h i s c o s t would i n c r e a s e by t e n - f o l d b r i n g i n g the cos t of p r o c e s s i n g to 6 - 2 0 % of the r e t a i l p r i c e o r 1 0 - 3 0 % of the wholesa le p r i c e . Such an i n c r e a s e would c l e a r -ly need to be a c c o m p a n i e d by c o n s i d e r a b l e s av ings in was t age o r by i n -c r e a s e d c o n s u m p t i o n to m a k e it a v i a b l e c o m m e r c i a l p r o p o s i t i o n . In a d -d i t ion , t h e s e f i g u r e s could i n c r e a s e if t he p l an t i s not f u l l y u t i l i z e d .

The f i g u r e s given in Tab le XII show that v e r y l a r g e amoun t s of su i tab le f i sh a r e consumed in the t r o p i c a l coun t r i e s and, no doubt, much l a r g e r quan-t i t i e s could be m a d e a v a i l a b l e if s u i t a b l e h a r v e s t i n g and p r e s e r v a t i o n m e t h o d s w e r e d e v e l o p e d . M o r e d e t a i l e d i n f o r m a t i o n on t h e g e o g r a p h i c a l concen t r a t i on and p a r t i c u l a r l y the s e a s o n a l v a r i a b i l i t y of t he supp l i e s m u s t be ga the red b e f o r e the economics of the p a r t that r ad ia t ion p r o c e s s i n g could p lay can be a c c u r a t e l y a s s e s s e d .

R E F E R E N C E S

[ 1 ] DOLMAN, C.E. , IIDA, H. , Canad. J. publ. Hlth 54 (1963) 293. [2] DOLMAN, C.E. , KERR, D . E . , Canad. J. publ. Hlth 36 (1947) 48. [3 ] PREVOT, A. R. , HUET, M. , Bull. Acad. Nat. Med. 25, 26 (1951) 432. [4 ] DOLMAN, C.E. , CHANG, H. , Canad. J. publ. Hlth 44 (1953) 231. [5 ] DOLMAN, С . E . , Cand. med. Ass. J. 84 (1961) 191. [6 ] GEIGER, J . C . , J. Amer. med. Ass. 117 (1941) 22. [ 7 ] IIDA, H. e t al. , Japan. J. med. Sei. Biol. 11 (1958) 215. [ 8 ] PEDERSEN, H. О. , Nord. Vet-Med. 5 (1953) 700. [ 9 ] ENGLESON, G. e t a l . , Nord. Vet-Med. 67 (1962) 339.

[10] JOHANNSEN, A . , Nord. Vet-Med. 14 (1962) 780. [11] NAKAMURA, Y. e t al . , Japan, J. med. Sei. Biol. 9 (1956) 45. [12] SAITO, S. , FUJISAWA, S. , Akita. med. J. 8 1 (through 16) (1956). [13] TAKEUCHI, K. , Japan, J. publ. Hlth 7 (1960) 573. [14] JOHANNSEN, A. , Nord. Vet-Med. 14 (1962) 441. [15] JOHNSTON, R.W. et al. , Pub!. Hlth Rpt 78 (1963) 561. [16] DOLMAN, C.E. , Arctic 13 (1960) 230. [17] HAZEN, E.L. , Science 87 (1938) 413.


[18] DOLMAN, С. E. et al. , Canad. J. publ. Hlth 41 (1950) 215. [19] DOLMAN, С. E. , Canad. med. Ass. J. 68 (1953) 538. [20] GUNNISON, J.B. et al. , Proc. Soc. exptl Biol.Med. 35 (1936) 278. [21] DOLMAN, С. е . , Japan. J. med. Sei. Biol. 10 (1957)~383. [22] SKULBERG, A. , personal communicat ion, 1963. [23] PEDERSON, H.O. , J. appl. Bact. 18 (1955) 619. [24] Communicable Disease Centre, Morbidity and Mortality 12 (1963) 40-43. [25] JOHANNSEN, A . , personal communicat ion, 1964. [26] SKULBERG, A . , Nord. Vet-Med. 13 (1961) 87. [27] JOHANNSEN, A. , J. appl. Bact. 26 (1963) 43. [28] SAKAGUCHI, G. et al. , Japan. J. med. Sei. Biol. 7 (1954) 539. [29] NAKAMURA, Y. , Japan. J. med. Sei. Biol. 16 (1963) 304. [30] PREVOT, A.-R. et al. , Bull, de l 'Acad. Nat. de Médecine 136 (1952) 323. [31] PREVOT. A.-R. et a l . , Bull, de l 'Acad. Nat. de Médecine 136 (1952) 663. [32] FOSTER, E.M. , personal communicat ion, 1964. [33] Torry Research Station, Aberdeen, Scotland, Annual Report (1963). [34] OHYE, D. F , , SCOTT, W.J. , Austral. J. Biol. Sei. 10 (1957) 85. [35] SCHMIDT, С. F. , personal communication. [36] ROBERTS, T. A. , INGRAM, M. , in press, 1964. [37] SCHMIDT, С. F. , NANK, W.K. , LECHOWICH, R. V. , J. Food Sei. 27 (1962) 77. [38] Continental Can Co. , USAEC Contract AT (11-1) 1183-, Annual Report 1963. [39] RHODES, D. N . , Low Temperature Research Station Ree, Mem. 365, Food Irradiation, in press, 1963. [40] SINNHUBER, R.O. , LANDERS, M . K . , J. Food Sei. 29 (1964) 190. [41] SAKAGUCHI, G. , personal communicat ion.

RESEARCH IN THE USSR ON THE CONSERVATION OF FISH AND FISH PRODUCTS BY GAMMA IRRADIATION

A. V. KARDASHEV ALL-UNION RESEARCH INSTITUTE FOR THE

SEA-FISHING INDUSTRY AND OCEANOGRAPHY ÍVNIR01 MOSCOW, USSR


RESEARCH IN THE USSR ON THE CONSERVATION OF FISH AND FISH PRODUCTS BY GAMMA IRRADI-ATION. Research which has been carried out shows that gamma rays from cobalt-60 can be used to prolong the storage t ime for fresh fish (by irradiation with pasteurizing doses and, for certain types of fish, with sterili-zing doses). It is also possible to prepare stable fish conserves using irradiation doses of 1.5 to 2.0 Mrad.

RECHERCHES EFFECTUEES EN UNION SOVIETIQUE SUR LA CONSERVATION PAR IRRADIATION GAMMA DU POISSON ET DES PRODUITS DERIVES. Les études faites jusqu'à présent ont montré qu ' i l é tai t possible

d'utiliser les rayons gamma du cobalt-60 pour prolonger la durée de conservation du poisson frais, l'irradiation

ayant lieu à des doses de pasteurisation ou, pour certaines espèces, à des doses de stérilisation; on peut aussi

fabriquer des conserves de poisson dont la durée est prolongée par exposition à des doses de 1,5 à 2,0 Mrad.

И С С Л Е Д О В А Н И Е В С С С Р ПО К О Н С Е Р В И Р О В А Н И Ю Р Ы Б Ы И Р Ы Б Н Ы Х П Р О Д У К Т О В Г А М М А - И З Л У Ч Е Н И Е М . П р о в е д е н н ы е и с с л е д о в а н и я п о к а з а л и в о з м о ж н о с т ь и с п о л ь з о в а н и я г а м м а - л у ч е й к о б а л ь т а - 6 0 для удлинения с р о к о в хранения с в е ж е й рыбы,при облучении п а с т е -ризующими д о з а м и , и для некоторых видов рыб - стерилизующими дозами , а также приготовле-ния стойких консервов из рыбы при облучении дозами 1,5 - 2 ,0 Мрад .

INVESTIGACIONES HECHAS EN LA UNION SOVIETICA SOBRE LA CONSERVACION DEL PESCADO Y DE SUS DERIVADOS MEDIANTE RAYOS GAMMA. Las investigaciones han demostrado que se puede utilizar la radiación gamma del cobalto-60 para prolongar la conservación del pescado fresco. La irradiación se hace empleando las dosis de pasteurización y, para ciertos tipos de pescado, las de esteri l ización. También se pueden preparar conservas de pescado duraderas por irradiación a dosis comprendidas entre 1,5 y 2,0 Mrad.

In the f i r s t stage of the r e sea r ch programme on the use of ionizing radi-ation in the Soviet fishing industry, studies were carr ied out to determine the effect of cobalt-60 gamma radiation on different types of fish and fish products. Various types of fish and fish products were subjected to doses of 0.2-2.0Mrad: f r e s h - w a t e r f ish - pike pe rch (Lucioperca lucioperca) , pike (Esox lucius), catfish (Silurus glanis), carp (Cyprinus carpio), roach (Rutilus rutilus), e tc . ; sa l t -water fish - cod (Gadus morrhua), haddock(Melanogrammus aeglefinus). Atlant ic h e r r i n g (Clupea ha rengus harengus) . Atlantic h o r s e m a c k e r e l (Trachurus t rachurus) , Baltic her r ing (Clupea harengus membras) , anchovy (Engraulis encrasicholus) , e tc . ; f ish products - salted and pickled herr ing, sa l ted and pickled anchovy and Bal t ic he r r ing , blanched, f r i ed and stuffed fish, f i s h c a k e s , hot-smoked fish, f r ied fish in tomato sauce and in vegetable marinade.

In a l l c a s e s i r r a d i a t e d s a m p l e s were main ta ined at t e m p e r a t u r e s of 0-5°C and 16-18°C until spoilage occu r r ed . Organolept ic (colour, smel l , taste, consistency), physico-chemical and chemical changes were determined

65

66 KARDASHEV

in c o n t r o l and i r r a d i a t e d s a m p l e s and t h e s t e r i l i z i n g e f f e c t of t h e r a d i a t i o n w a s s t u d i e d .

R a d i a t i o n s e n s i t i v i t y w a s found t o b e h i g h e s t in t h e c a s e of f r e s h - w a t e r f i s h and f i s h with a s u b s t a n t i a l fa t content ( s e e Tab l e I). At dose s of 0.5 Mrad and o v e r , c o n s i d e r a b l e o r g a n o l e p t i c c h a n g e s w e r e o b s e r v e d ( r ad i a t ion odour and f l a v o u r ) . When the f i s h in q u e s t i o n w e r e s t o r e d , a f t e r having been sub-j e c t e d to h i g h e r d o s e s of r a d i a t i o n ( s e e T a b l e I) and a l s o a f t e r hav ing b e e n f r i e d , t he o d o u r d i s a p p e a r e d .

F r i e d f i s h , s l i gh t l y s a l t e d h e r r i n g and f r i e d f i s h c a k e s w e r e a l s o f a i r l y s e n s i t i v e to r a d i a t i o n . Oxida t ive changes in f a t s w e r e o b s e r v e d . In the c a s e of f r i e d f i s h in t o m a t o s a u c e and i n v e g e t a b l e m a r i n a d e , p r a c t i c a l l y no c h a n g e s in qua l i ty w e r e , o b s e r v e d at any of t h e d o s e s u s e d and t h e c u l i n a r y p r o p e r t i e s of t he p r o d u c t s w e r e not a f f e c t e d .

T h e m a x i m u m s t o r a g e p e r i o d f o r f i s h a n d f i s h p r o d u c t s a s a f u n c t i o n of d o s e and t e m p e r a t u r e , and a l s o of t h e s p e c i f i c q u a l i t i e s of t h e f i s h and f i s h p r o d u c t s , a r e shown in Tab l e II . F o r t h e d e t e r m i n a t i o n of the m a x i m u m s t o r a g e p e r i o d s , m i c r o b i o l o g i c a l , o r g a n o l e p t i c and c h e m i c a l i n d i c a t o r s (n i t rogen content of vo la t i l e b a s e s , fa t cons tan t , e t c . ) w e r e taken into account

T h e m o s t p r o m i s i n g t y p e s of f i s h f o r p u r p o s e s of i r r a d i a t i o n a r e t h e fo l lowing m a s s c o m m e r c i a l v a r i e t i e s : f r e s h - w a t e r f i s h - p ike and c a t f i s h ; s a l t - w a t e r f i s h - cod and haddock. A f t e r i r r a d i a t i o n t h e s e f i sh can be s t o r ed f o r s u f f i c i e n t l y long p e r i o d s to m e e t p r a c t i c a l r e q u i r e m e n t s . T h e s t o r a g e p e r i o d f o r f r e s h f i s h s u b j e c t e d to p a s t e u r i z i n g d o s e s of up t o 0.6 M r a d i s l i m i t e d by the s e c o n d a r y g r o w t h of m i c r o f l o r a , wh ich a r e g e n e r a l l y not p u t r e f a c t i v e ( the m o s t c o m m o n t y p e s a r e y e a s t s , c o c c i and m o u l d s ) . F o l -lowing d o s e s of 1 - 2 M r a d the l imi t ing f a c t o r s a r e autolyt ic p r o c e s s e s and the a u t o - o x i d a t i o n of f a t s ( even when the f i s h a r e i r r a d i a t e d in a l a r g e l y oxygen-f r e e e n v i r o n m e n t ) .

S p o i l a g e c a u s e d by a u t o l y t i c p r o c e s s e s o c c u r s m o s t r a p i d l y in the c a s e of i r r a d i a t e d a n c h o v i e s ; a f t e r t h a t c o m e h e r r i n g , B a l t i c h e r r i n g , h o r s e m a c k e r e l , c a r p , c a t f i s h , p ike , h a d d o c k a n d c o d . Spo i l age f r o m a u t o -o x i d a t i v e f a t s p o i l a g e i s found in a n c h o v i e s , h e r r i n g , c a r p , c a t f i s h , i . e . in o r d e r of d e c r e a s i n g n o n - s a t u r a t i o n of the f a t s in the f i s h .

T h e s t o r a g e p e r i o d i s a l s o l i m i t e d by t h e exuding of f lu id f r o m the f i sh , t h e a m o u n t of f l u i d e x u d e d d e p e n d i n g on t h e s i z e of t h e d o s e a n d , d u r i n g s t o r a g e , on the ac t iv i ty of the p r o t e o l y t i c e n z y m e s and the t e m p e r a t u r e . The l i m i t i n g f a c t o r in the c a s e of f r i e d f i s h i s t he spo i lage of the f r y i n g fa t .

F r i e d f i s h i n t o m a t o s a u c e o r in v e g e t a b l e m a r i n a d e , w h i c h h a s b e e n s u b j e c t e d to d o s e s of 1 . 0 - 2 . 0 M r a d , c a n b e p r e s e r v e d f o r l e n g t h y p e r i o d s w i t h o u t any c h a n g e in p r o p e r t i e s ( o v e r two y e a r s ) and t h e q u a l i t y i s b e t t e r t han tha t of s i m i l a r p r o d u c t s s t e r i l i z e d in an au toc lave . T a s t e , cons i s t ency , c o l o u r and c u l i n a r y a r o m a a r e a l l p r e s e r v e d ; t h e r e i s none of the o d o u r o r f l a v o u r a s s o c i a t e d with au toc l av ing and t h e r e i s no d e t e r i o r a t i o n of the f l e s h . No ox ida t ion of the f r y i n g fa t i s o b s e r v e d .

Al l t h e s e i n d i c a t i o n s have been c o n f i r m e d by ob jec t ive d a t a .

USSR RESEARCH ON FISH 67

TABLE I

MAXIMUM DOSES O F G A M M A R A D I A T I O N WHICH HAVE P R A C T I C A L L Y NO E F F E C T ON T H E Q U A L I T Y O F

F I S H AND F I S H P R O D U C T S

. ,. , Doses (Mrad) : Fish or fish

product After i r radiat ion After storage at After frying 0 - 5 e C (30 d)

Fresh-water fish

Carp Pike Catf ish

0. 5 0. 6

1. 0

1 .0 1. 5 1. 5

1. 5 1. 5 2 . 0

Sal t -wate r fish

At lan t ic herring Balt ic herring Horse m a c k e r e l Haddock Cod

0. 5 0 . 5 0 . 5 1 . 0 1 .0

1 .0 • 1 . 0 l . o a 1 . 5 1 . 5 '

1. 5 2. 0 2. 0

Fried fish

(Cod, pike, p ike perch, carp)

Fried fish cakes Fried fish in

t oma to sauce or vege tab le mar inade

Hot-smoked cod Slightly salted

herring Pickled herring

0. 5 1.0

2.0 1.0

0. 5 1 . 5

2.0 1 . 5

1 . 0 1 . 5

1. 5 (heating) 1. 5 (heating)

a After 10-15 d storage.

Changes in the properties of fish and fish products following irradiation and subsequent storage

Organolept ic i n d i c a t o r s

Following the admin i s t r a t ion of doses of 0 .2 Mrad upwards , p rofess iona l t a s t e r s a r e ab le t o d e t e c t c h a n g e s in the m a i n o r g a n o l e p t i c p r o p e r t i e s of f r e s h f i s h . T h e s u r f a c e of t h e f i s h b e c o m e s du l l , t he e y e s a r e d i m m e d , c r o s s - s e c t i o n s of the f lesh r e v e a l colour changes and the re is a slight " r a d i -at ion odour " . F o r doses of up to 0 . 6 - 1 . 0 Mrad these changes a r e sl ight and not p e r c e p t i b l e to the n o n - s p e c i a l i s t . S p e c t r o p h o t o m e t r y r e v e a l s c o l o u r c h a n g e s (haema t in p igmen t s ) in t h e f l e s h with d o s e s of 0. 2 M r a d and o v e r ; t h e s e i n c r e a s e with i nc r ea s ing rad ia t ion doses and a lso depend on the degree

6 8 KARDASHEV

TABLE II

M A X I M U M S T O R A G E P E R I O D S F O R I R R A D I A T E D S P E C I M E N S

Fish or fish product

Storage t empera tu re

CQ 0. 2 Mrad

M a x i m u m storage period (d) for doses of :

0. 6 Mrad 1. 0 Mrad 1. 5 Mrad

Herring 0 - 5 20 30 60 60 16-18 5 5 10 10

Horse m a c k e r e l 0 - 5 10 15 20 30 16-18 3 5 10 10

Carp 0 - 5 15 30 50 50 16-18 5 15 20 20

Pike 0 - 5 30 60 90 120 16-18 5 15 20 30

Catf ish 0 - 5 15 30 50 90 16-18 5 15 20 20

Cod and haddock 0 - 5 30 60 120 180 16-18 10 30 60 90

Fried fish in tomato sauce 0 - 5 60 180 l y r Over 2 yr or v e g e t a b l e 16-18 15 60 180 2 yr mar inade

Fried fish 0 - 5 15 30 60 60 16-18 3 5 10 10

Note : Storage periods have been rounded off to the nearest convenient lower number .

of oxygen r e m o v a l b e f o r e i r r a d i a t i o n . When the dose i s i n c r e a s e d , as was pointed out above, t h e r e i s an i n c r e a s e in the amount of fluid and fat exuded f r o m the f l e sh of the f i sh (F ig . 1) and the cons i s t ency of the l a t t e r i n c r e a s e s . If the s t o r a g e pe r iod i s p ro longed , f luid cont inues to be exuded but t h e r e i s no l o n g e r any dose dependence s i n c e an auto ly t ic p r o c e s s i s fundamen ta l ly involved . Ob jec t ive r e s e a r c h me thods a l s o r e v e a l an i n c r e a s e in the con-s i s t e n c y of the f l e s h with i n c r e a s e d dose .

The n a t u r a l a r o m a of the f i sh b e c o m e s f a i n t e r and an ex t raneous odour i s s u p e r i m p o s e d on the n a t u r a l odour; in the c a s e of f r e s h - w a t e r f ish t h e r e i s a s l ight odour of burn t f i sh f l esh ; with s a l t - w a t e r f ish t h e r e is a sme l l of s h r i m p s o r c r a b s . T h e s e odours a r e eas i ly not iceable at doses of 0 . 6 - 1 . 0 M r a d and above.

F o l l o w i n g p r o l o n g e d s t o r a g e (and f r y i n g ) the " i r r a d i a t i o n o d o u r " of i r r a d i a t e d f i s h g e n e r a l l y d i s a p p e a r s . In the c a s e of n o n - s t e r i l i z i n g doses , however , a p e c u l i a r odour i s p roduced which depends on the type of m i c r o -

USSR RESEARCH ON FISH 6 9

FIG. 1. Fluid exuded from herring fat and flesh as a function of radiation dose (ml/100 g tissue)

f l o r a deve loped . At d o s e s of 1 .5 -2 .0 Mrad an au to lysa te odour (p leasan t in the c a s e of s o m e types of f i sh) deve lops .

In i r r a d i a t e d h o t - s m o k e d f i s h a d e c r e a s e in the n a t u r a l a r o m a of t h e s m o k e d f i s h b e c o m e s n o t i c e a b l e with d o s e s of 1.0 M r a d and above . A f t e r m o r e than 30-d s t o r age at room t e m p e r a t u r e , however , and even a f t e r doses of 1.5 M r a d , t he n a t u r a l a r o m a of s m o k e d f i sh i s r e s t o r e d without any s e c o n d a r y o d o u r s .

In s a m p l e s of c u l i n a r y p r o d u c t s m a d e f r o m bo i l ed and f r i e d f i s h , t he organolept ic changes o c c u r r i n g immedia te ly following i r rad ia t ion were slight, up to doses of 1.5 Mrad . The s a m e applied to f r i ed f i sh in tomato sauce o r in vegetable m a r i n a d e up to doses of 2.0 Mrad.

In s a m p l e s of s l ight ly sa l t ed h e r r i n g and anchovies, the na tu ra l p leasant a r o m a of the m a t u r e f i s h b e c a m e f a i n t e r a f t e r i r r a d i a t i o n and was not r e -s t o r e d l a t e r , d e s p i t e a p r o l o n g e d auto ly t ic p r o c e s s . With p ick led h e r r i n g t h e r e w a s no n o t i c e a b l e l o s s of a r o m a and t a s t e a f t e r i r r a d i a t i o n and, a s a l s o i n t h e c a s e of s a l t e d h e r r i n g , no e x t r a n e o u s o d o u r w a s d e t e c t a b l e .

C h e m i c a l and p h y s i c o - c h e m i c a l d a t a

Rad ia t ion - induced p h y s i c o - c o l l o i d a l changes in p r o t e i n s o c c u r at lower doses than organolept ic and chemica l changes . Changes take place in the pH, e l e c t r o p h o r e t i c mob i l i t y , t h e con ten t of f r e e - s u l p h h y d r y l g r o u p s , and the hyd roph i ly of t h e t i s s u e s .

When f i s h a r e i r r a d i a t e d , d e n a t u r i n g p r o c e s s e s a r e found to o c c u r in the soluble p r o t e i n s . If the dose i s i n c r e a s e d f r o m 0.2 to 1.5 Mrad, 2 to 22% of t h e s o l u b l e p r o t e i n s in f r e s h f i s h b e c o m e d e n a t u r e d and t h e r e i s a de -c r e a s e in the h y d r o p h i l y of t he m u s c l e t i s s u e ( d e c r e a s e in b o u n d - w a t e r con ten t , i n c r e a s e in m o i s t u r e l i b e r a t i o n ; s e e F i g . 1).

Wi th i n c r e a s i n g d o s e t h e pH b e c o m e s h i g h e r i n f r e s h f i s h and l o w e r in he+.-smoked and f r i e d f i sh ; t h e r e i s a p a r t i c u l a r l y s h a r p d e c r e a s e in the e l e c t r o p h o r e t i c mob i l i t y of the globul in f r a c t i o n s of so lub le p r o t e i n s in m u s c l e t i s s u e ( s e e F i g . 2) . E l e c t r o p h o r e s i s a l s o r e v e a l s a c o n s i d e r a b l e d e c r e a s e in so lub i l i ty , m a i n l y in the globul in and to a l e s s e r ex ten t in the a lbumin f r a c t i o n s .

70 KARDASHEV

О 0.5 1.0 1.5 2.0 Mrad

FIG. 2. Electrophoregrams of soluble proteins of muscle tissue in herring irradiated with doses of 0.5 - 2.0 Mrad

D e t e r m i n a t i o n s of f r e e - s u l p h h y d r y l g r o u p s i n t h e h o m o g e n a t e of t h e m u s c l e t i s s u e s of f i s h show that the conten t of t h e s e g roups i n c r e a s e s 10-20% i m m e d i a t e l y a f t e r the i r r a d i a t i o n of f r e s h l y ki l led f i s h . A f t e r the i r r a d i a t i o n of thawed f i sh , which h a s a f r e e - s u l p h h y d r y l g r o u p content f ive to eight t i m e s g r e a t e r than f r e s h f i sh , t h e r e i s a d e c r e a s e of 9-18%. Fol lowing the i r r a d i -a t ion of chopped f i s h m i x e d with w a t e r t h e r e i s a l s o a d e c r e a s e in the f r e e -s u l p h h y d r y l g r o u p con t en t : 14-23% in the c a s e of chopped f r e s h f i sh ; 19-36% in the c a s e of thawed f i s h . If the chopped f i s h and w a t e r i s p l a c e d in a high v a c u u m , t h e l o s s of t h e f r e e - s u l p h h y d r y l g r o u p c o n t e n t c o n s t i t u t e s 4 - 9 % . T h e s e d e t e r m i n a t i o n s s h o w tha t i r r a d i a t i o n i s a c c o m p a n i e d by d e n a t u r a t i o n of f i s h p r o t e i n s , d e c a y of f r e e - s u l p h h y d r y l g r o u p s and a l s o by an o x y g e n e f f e c t ( d e c r e a s e in d e c a y of s u l p h h y d r y l g r o u p s in h igh v a c u u m ) . On t h e b a s i s of t h e s e e x p e r i m e n t s and of d i r e c t d e t e r m i n a t i o n s of t h e c o n t e n t of s u l p h u r - c o n t a i n i n g a m i n o - a c i d s , i t c a n be c o n c l u d e d t h a t , w h e n o x y g e n i s r e m o v e d , t h e r e i s a d e c r e a s e in the d i s i n t e g r a t i o n of v a l u a b l e a m i n o - a c i d s and a l s o , a s o r g a n o l e p t i c t e s t s s h o w , in t h e p r o d u c t i o n of an " i r r a d i a t i o n o d o u r " .

I r r a d i a t i o n i s a l so fo l lowed by d e a m i n a t i o n and hydro ly t i c d i s i n t eg ra t i on of the m u s c l e p r o t e i n s . At a dose of 1. 5 Mrad , depending on the type of f i s h invo lved , t he con ten t of v o l a t i l e n i t r o g e n i n c r e a s e s f r o m 50 to 180% and the con ten t of a m i n e - b o u n d n i t r o g e n i n c r e a s e s f r o m 52 to 140% as c o m p a r e d to the i n i t i a l c o n t e n t in t h e f r e s h f i s h .

In i r r a d i a t e d p r o d u c t s of f i s h tha t have b e e n s u b j e c t e d to hea t t r e a t m e n t t h e r e i s p r a c t i c a l l y no s i g n of d e a m i n a t i o n and h y d r o l y t i c d i s i n t e g r a t i o n of p r o t e i n . S t o r e d i r r a d i a t e d f r e s h f i s h i s found to u n d e r g o the u s u a l c h a n g e s in m u s c l e p r o t e i n a s s o c i a t e d wi th a u t o l y t i c p r o c e s s e s . In t h e c a s e of p r o -longed s t o r a g e of b o i l e d and f r i e d f i s h t r e a t e d wi th s t e r i l i z i n g d o s e s , t h e r e a r e , a s a r e s u l t of t h e r m a l i n a c t i v a t i o n of t i s s u e e n z y m e s , only v e r y s l i gh t hydro ly t ic p r o t e i n c h a n g e s as wel l a s co l lo ida l p ro t e in ge l aging accompanied by s y n e r e s i s p h e n o m e n a .

USSR RESEARCH ON FISH 71

TABLE III

C H A N G E S IN T H E N I T R O G E N O U S F R A C T I O N S O F M U S C L E TISSUES IN F I S H F O L L O W I N G I R R A D I A T I O N AND

A U T O C L A V I N G (% O F I N I T I A L C O N T E N T )

Irradiat ion Autoclaving Nitrogenous f ract ion (1. 5 Mrad) (60 min at 112°C)

Pike Cod Pike perch

Protein ni trogen - 4 . 9 - 1 . 8 - 1 5 . 2

Non-prote in nitrogen + 3 6 . 0 + 1 3 . 0 +253 .0

Amine-bound nitrogen + 5. 2 + 3 . 5 ^ +72. 0 -

+ 180 .0 +22 .0 + 2 6 . 0 Nitrogen of vo la t i l e

bases

Nitrogen of wa te r - _ 2Q_ g _ 3 1 . 5

soluble proteins +190. 0

Note : - losses, + increase.

F a t s e c r e t e d f r o m i r r a d i a t e d f i sh has been found to have a lower content of caro tenoid p igments and vi tamin A. At a dose of 1.5 Mrad about 10% of the v i t a m i n A d i s i n t e g r a t e s . S i m i l a r r e s u l t s have been ob ta ined in an e x p e r i -ment ön i r r a d i a t e d cacha lo t l i ve r : at doses of 0 .6-2.0 Mrad vi tamin A l o s s e s amounted to 4 .8-11.4%. The content of v i t amin B12 (cobalamin) in c a r p f l e sh d rops f r o m 44 to 69% when the dose i s i n c r e a s e d f r o m 0.2 to 1.5 Mrad .

De te rmina t ions c a r r i e d out on i r r a d i a t e d f i sh fa t s ( f rom cod and walleye po l lock l i v e r ) and on t i s s u e f a t s s e c r e t e d f r o m i r r a d i a t e d f i s h show t h a t ion iz ing r a d i a t i o n a f f e c t s t he s e n s i t i z a t i o n of au to -ox ida t i ve p r o c e s s e s and the i n t e n s i f i c a t i o n of fa t p o l y m e r i z a t i o n . In p r a c t i c e , however , t h e s e p r o -c e s s e s do not c a u s e any d e t e r i o r a t i o n in t h e qua l i t y of t he i r r a d i a t e d f i s h a t d o s e s of 0 . 2 - 1 . 5 M r a d , e x c e p t in t h e c a s e of h e r r i n g s , w h e r e t h e f a t s c o n t a i n h ighly u n s a t u r a t e d f a t t y a c i d s .

C o m p a r i s o n of the r e s u l t s obtained with rad ia t ion s t e r i l i z a t i on and with autoclaving (Table III) show that pro te in subs tances a r e l e s s subject to change with the f o r m e r than with the l a t t e r p r e s e r v i n g technique.

T h e i nves t i ga t i ons c a r r i e d out at t he Ai l -Union R e s e a r c h Ins t i tu te f o r the S e a - F i s h i n g I n d u s t r y and Oceanography (VNIRO) and at o t h e r i n s t i t u t e s which h a v e s t u d i e d the e f f e c t of i on i z ing r a d i a t i o n on m i c r o f l o r a and t h e nu t r i t iona l value of i r r a d i a t e d f i sh and f i sh p roduc t s demons t r a t e that i r r a d i -a t ion c o n s e r v a t i o n i s a u s e f u l t echn ique f o r p ro long ing the s t o r a g e p e r i o d s f o r f r e s h f i s h by m e a n s of p a s t e u r i z i n g d o s e s ( 0 . 2 - 1 . 0 Mrad ) and f o r o b -t a in ing s t a b l e c a n n e d f i s h by i r r a d i a t i n g wi th d o s e s of 1 . 5 - 2 . 0 M r a d ( th i s p r a c t i c a l l y i nvo lves s t e r i l i z a t i o n ) .

72 KARDASHEV

B I B L I O G R A P H Y

BIDENKO, M. S. , Ispolzovanie gamma-lučei dlya konservirovaniya rybnykh produktov (The Use of Gamma Rays for the Preservation of Fish Products), Ž. Ryb. Khoz. 5 (1958).

BIDENKO, M. S . , Vliyanie ioniziruyus'cikh izlučeny na udlinenie srokov khraneniya i izmeneniya kačestva preservov (žarenaya ryba v tomatnom souse) (The Influence of Gamma Radiation on the Duration of Storage Periods and on Qualitative Changes in Preserved Foods (Fried Fish in Tomato Sauce)), Trudy Balmiro VI (1960).

BONDAREV, G. I . , Oblučenie ioniziruyuščei radiatsiei piščevykh produktov i ikh prigodnost dlya pitaniya lyudei (The Treatment of Fish Products with Ionizing Radiation and the Suitability of Such Products for Human Consumption), Ž. Gigiena i sanitariya 4 (1960).

KARDASHEV, A. V. , Ispolzovanie ioniziruyuiSčikh izlučeny dlya konservirovaniya ryby i rybnykh produktov (The Use of Ionizing Radiations for the Preservation of Fish and Fish Products), Nauč-tekhn. informatsiya VNIRO 12 (1959).

KARDASHEV, A. V. , Ispolzovanie radioaktivnykh izotopov i izlučeny v rybnoi promyïlennosti (The Use of

Radioisotopes and Radiations in the Fishing Industry), Soveščanie po vnedreniyu rad. izotopov i yadernykh izlučeny v nar. khoz . , Sb. dokladov 2 (1960).

KARDASHEV. A. V. , Izmenenie svoistv svežei ryby pod vozdeistviem gamma-lučei (Changes in the Properties of Fresh Fish Following Exposure to Gamma Radiation), Trudy VNIRO 45 (1962).

INSECT INFECTION OF AFRICAN DRIED OR SMOKED FISH AND THE POSSIBILITY OF ITS CONTROL

BY IRRADIATION

J. DAGET

CHAD RESEARCH CENTER, FORT-LAMY, CHAD


INSECT INFECTION OF AFRICAN DRIED OR SMOKED FISH AND THE POSSIBILITY OF ITS CONTROL BY IRRADIATION. Most fishing interests in the interior of Africa find it impossible to arrange the trans-port of fresh fish from the fishing grounds to the centres of consumption and storage. Moreover, resort to deep-freezing or simple refrigeration is impossible or too expensive. It is therefore necessary to dry or smoke, on the spot, all fish which is not immediately consumed by the local population.

Drying and smoking offer many advantages in the developing countries, including low preparation costs, high nutritional value for low weight, and preservation and transport facilities. However, the dried or smoked fish is attacked by insects of the genera Dermestes and Necrobia and the damage is all the more serious since the fish is stored in large quantities. Chemical methods of disinsectization involve serious disadvantages. An attractive solution appears to be irradiation, which leads to the death or sterilization of the insects and which can be employed when the fish is already packed in hermetically sealed containers.

L'INFESTATION PAR LES INSECTES DU POISSON SECHE OU FUME EN AFRIQUE ET SON CONTROLE POSSIBLE AU MOYEN DES RAYONNEMENTS. Pour la plupart des pêcheries de l'intérieur de l'Afrique, il est impossible d'assurer le transport du poisson frais depuis les lieux de pêche jusqu'aux centres de consommation ou de stockage. Il est d'autre part impossible ou trop coûteux de recourir à la congélation ou à la simple réfrigération. Il faut donc traiter sur place par séchage ou fumage tous les produits de la pêche qui ne sont pas immédiatement autoconsommés.

Séchage et fumage présentent de nombreux avantages dans les pays en voie de développement: coût minime de la préparation, haute valeur nutritive sous un faible poids, facilité de conservation et de transport. Mais le poisson séché ou fumé est attaqué par des insectes, Dermestes et Necrobia, et les déprédations sont d'autant plus graves que le produit est stocké en masses plus importantes. Les procédés de désinsection par agents chimiques présentent de sérieux inconvénients. L'irradiation entrafhant la mort ou la stérilisation des insectes et permettant de traiter sous emballage hermétiquement clos est une solution a priori séduisante.

ЗАРАЖЕНИЕ НАСЕКОМЫМИ АФРИКАНСКОЙ СУШЕНОЙ ИЛИ КОПЧЕНОЙ РЫБЫ И ВОЗМОЖНОСТЬ ДЕЗИНСЕКЦИИ С ПОМОЩЬЮ ОБЛУЧЕНИЯ. Большинство рыбаков во внут-ренних частях Африки считает невозможным для себя вывозить свежую рыбу из мест ловли к центрам потребления и хранения. Более того, глубокое замораживание или простое хранение в холодильниках является невозможным или же обходится слишком дорого. Поэтому необхо-димо сушить* или коптить на месте всю рыбу, которая не потребляется немедленно местным населением .

Сушка и копчение имеют большие преимущества: сушеная рыба содержит много питательных веществ на весовую единицу, стоит дешево, ее удобно хранить и перевозить. Однако сушеная или копченая рыба поражается насекомыми типа Dermes t e s и гчеогосиа т и при хранении рыбы в больших количествах растет ущерб, причиняемый ими. Химические методы дезинсекции связаны с серьезными трудностями. Перспективным решением явля-ется , по-видимому, применение облучения, которое приводит к гибели или стерилизации на-секомых и которое можно применять, когда рыба уже упакована в герметически закрытые контейнеры.

INFESTACION POR INSECTOS DE PESCADOS SECOS O AHUMADOS EN AFRICA Y METODOS POSIBLES DE RADIODESINSECTACION. A la gran mayoría de las compañías pesqueras del interior de Africa les es imposible transportar el pescado fresco desde los lugares de pesca hasta los centros de consumo y almace-namiento. Por otra parte, es imposible o excesivamente constoso recurrir a la congelación o a la simple

73

74 DAGET

refrigeración. Por lo tanto, es preciso secar o ahumar in situ todo el pescado que no se venda inmediatamente a la población local.

El secado y ahumado ofrecen muchas ventajas para los países en desarrollo: coste mínimo de la prepara-ción, alto valor nutritivo con poco peso, y facilidades de conservación y transporte. Sin embargo, el pescado seco o ahumado es atacado por insectos de los géneros Dermestes y Necrobia, y los daños son tanto más graves cuanto mayor es la cantidad de pescado almacenado. Los métodos químicos de desinsectación entrañan graves inconvenientes. Una solución que parece interesante es la irradiación, que mata o esteriliza a los insectos y que puede emplearse aunque el pescado esté ya empacado en recipientes herméticos.

F i s h in Afr ica i s an important source of animal protein for the popu-lation. Fishing, whether it be i n d u s t r i a l - s c a l e d e e p - s e a f i sh ing or the family craft type of fishing carried on in the interior of the continent, plays a highly important part in the economy of many African countries. It should be pointed out that the f r e s h water of certain regions i s highly productive. Recent surveys conducted in Mali, a West African country, with no sea coadt, have shown that f ishing ranks third amongst the r e s o u r c e s of the national economy, after the cultivation of millet and the rearing of cattle. According to the f igures given, production attains 100 000 t of fresh fish a year, with a value of more than 50 million French francs. Fish i s reported to provide 20. 4% of the total protein consumed by the local population, and 3. 5% of the c a l o r i e s in i ts rat ions. Dried and smoked f i s h a l so f o r m the b a s i s of an export trade which ranks third af ter l ives tock and groundnuts.

Fish, however, i s the most delicate and perishable of foodstuffs. Many spec ies die immediately after they are taken from the water and somet imes even before this, for example when they are caught on lines or in fixed nets. As soon as death occurs, the high temperatures prevailing in tropical areas promote and accelerate autolysis of the t issues, the proliferation of bacteria, and all the processes of fermentation which very quickly lead to putrefaction. As in all the developing countries where lack of protein constitutes a more or l e s s urgent problem, the African governments have a considerable interest in ensuring that none of the nutritive value of f i sh caught in their territory i s los t . Therefore , when the f ishing grounds are distant f r o m the a r e a s where the f i sh i s consumed, or when production exceeds the absorption ca-pacity of the immediate area , the Afr ican governments require that pre-servat ion p r o b l e m s be so lved a s e f f e c t i v e l y and cheaply a s p o s s i b l e .

Drying, smoking and salting processes

There are severa l procedures for treating f i sh to preserve , if not i t s initial freshness and flavour, at least i ts value as a food product. Depending on the geographical situation of a country and i t s c l imate , on the state of its industrial development and i ts economic infrastructure, and on the tastes, habits and purchasing power of i t s inhabitants, various methods of preser -vation may be used. These methods, in the order of their complexity, in-clude drying, smoking, salting (often coupled with the two preceding pro-cesses ) , refrigeration at about 0°C using ice, freezing at a lower temperature and, lastly, canning coupled with steri l ization. In the developing countries of Africa it i s the s implest processes , namely, drying, smoking and salting, which are most frequently used s ince they have a number of advantages .

INSECT INFECTION OF DRIED OR SMOKED FISH 75

(1) No c o m p l i c a t e d hand l i ng and no e x p e n s i v e i n s t a l l a t i o n s a r e n e c e s s a r y . T h e s e two c o n d i t i o n s a r e of o v e r r i d i n g i m p o r t a n c e , s i n c e in A f r i c a c o a s t a l and inland f i sh ing i s done by l a r g e n u m b e r s of f i s h e r m e n s c a t t e r e d over wide-s p r e a d a r e a s . F i s h i n g c a m p s , t e m p o r a r y o r p e r m a n e n t , a r e a l w a y s e s t a b -l i s h e d on s i t e s c h o s e n f o r c o n v e n i e n c e of p l a c i n g and s u p e r v i s i n g the t a c k l e , t r a p s , p o t s , l i n e s o r n e t s , but m o s t o f t e n a c o n s i d e r a b l e d i s t a n c e f r o m the m a i n U n e s of c o m m u n i c a t i o n a n d f r o m a n y l a r g e r c e n t r e s . F u r t h e r m o r e , in a ho t and h u m i d c l i m a t e f i s h s p o i l s q u i c k l y a n d c a n n o t s t a n d long t r a n s -p o r t a t i o n . E x c e p t in s p e c i a l c a s e s , i t i s i m p o s s i b l e to c o n c e n t r a t e the f r e s h f i s h a t p o i n t s w h e r e i t c a n b e t r e a t e d on a n i n d u s t r i a l o r s e m i - i n d u s t r i a l s c a l e . P r e s e r v a t i o n m u s t t h e r e f o r e b e c a r r i e d out on t h e s p o t , a n d i m -m e d i a t e l y , by t h e f i s h e r m a n a n d h i s f a m i l y .

(2) Not o n l y a r e t h e n u t r i t i v e e l e m e n t s of t h e f l e s h of t h e f i s h p r e s e r v e d but t he food v a l u e of t he p r o d u c t f o r a g iven weight i s g r e a t l y i n c r e a s e d . In m o s t c a s e s , in f ac t , t he f i s h i s s i m p l y s c a l e d and gut ted ; l o s s e s du r ing p r e -p a r a t i o n a r e t h e r e f o r e r e d u c e d t o a m i n i m u m , a n d t h e p r i n c i p a l v a r i a b l e f a c t o r i s w a t e r con ten t , a m o u n t i n g to not m u c h m o r e than 20-25% in t h e end p r o d u c t . S o m e t i m e s a s m a l l a m o u n t of l i p i d e s i s a l s o l o s t d u r i n g p r e -p a r a t i o n . A r e c e n t s t udy of f i s h f r o m the S e n e g a l R i v e r y i e lded the f i g u r e s shown in T a b l e I f o r the c o m p o s i t i o n p e r 1000 g of f r e s h , whole f i s h . In t h i s t a b l e t h e w e i g h t of p h o s p h o r u s and c a l c i u m r e f e r s t o t h e e d i b l e p a r t of t h e f i s h , t h e p h o s p h o r u s a n d c a l c i u m of t h e b o n e s b e i n g i n c l u d e d i n t h e t o t a l w a s t e .

TABLE I

C O M P O S I T I O N O F 1 k g O F F R E S H , W H O L E F I S H

Fish Proteins Lipides P Ca Waste Fish

(g) (g) (g) (g) (g)

Hydrocyon 146 .7 5 2 . 4 0 . 2 2 0 .17 397

Clar ias 1 1 7 . 3 2 7 . 6 0 . 1 1 0 . 0 5 449

Citharinus 115 .5 19 .3 0 . 1 8 0 .17 528

Lates 132 .2 1 8 . 1 0 . 2 0 0 . 2 1 475

Ti lap ia 1 1 3 . 9 5 . 8 0 . 2 5 0 .37 577

Average 1 2 5 . 9 2 3 . 3 0 . 2 0 0 . 2 1 485

F r o m t h e s a m e s t u d y t h e c o m p o s i t i o n p e r 1000 g of d r i e d , w h o l e f i s h w a s o b t a i n e d ( s e e T a b l e II) . A c o m p a r i s o n of t h e s e two t a b l e s s h o w s t h a t whi l e 1 kg of f r e s h f i s h c o n t a i n s on an a v e r a g e 126 g of ed ib le p r o t e i n s , 1 kg o f d r i e d f i s h con ta in s 423 g, o r 3 . 3 t i m e s m o r e LCantrel le , P . and L a u r e n t , P . , " L e P o i s s o n de F l e u v e d a n s l ' O u e s t A f r i c a i n " , W e s t A f r i c a n R i v e r F i s h ( 1 9 6 1 ) ] .

76 DAGET

TABLE II

C O M P O S I T I O N O F 1 k g O F D R I E D , W H O L E F I S H

Fish Proteins Lipides P Ca Waste

Fish (g) (g) (g) (g) (g)

Hydiocyon 4 3 8 . 6 156 .6 0 . 6 4 0 . 4 9 290

Clarias 3 2 9 . 6 7 7 . 4 0 . 3 2 0 . 1 5 526

Citharinus 4 9 1 . 1 8 2 . 2 0 . 7 8 0 . 7 4 320

La tes 4 7 4 . 3 6 4 . 9 0 . 7 3 0 . 7 7 362

Ti lap ia 5 1 5 . 3 2 6 . 1 1 . 1 4 1 .66 340

Average 4 2 2 . 6 7 8 . 9 0 . 6 9 0 . 7 4 400

(3) Condi t ioning, s t o r i n g and m a r k e t i n g f a c i l i t i e s : Dr i ed , sa l t ed o r smoked f i s h k e e p s w e l l if i t i s p r o t e c t e d f r o m r a i n and an e x c e s s i v e l y humid a t m o -s p h e r e ; if t h e s e cond i t ions a r e not fu l f i l l ed mould a p p e a r s , the f lavour chan-ges , and the p r o c e s s e s of p u t r e f a c t i o n which have b e e n ha l ted by des s i ca t i ng , s a l t i n g o r s m o k i n g m a y r e c o m m e n c e . W h e n t h e c o n d i t i o n s a r e good t h e p roduc t can be s t o r e d l oose ly packed in b a r r e l s , wrapped in s a c k s o r mat t ing o r p a c k e d in w o o d e n c a s e s , and c a n s t a n d up to f r e q u e n t hand l ing and long-d i s t a n c e t r a n s p o r t . I t i s , h o w e v e r , a d v i s a b l e t o c o n s u m e s m o k e d f i s h a s s o o n a s p o s s i b l e , w h e r e a s d r i e d f i s h k e e p s m u c h l o n g e r wi thout l o s ing any of i t s q u a l i t i e s . In A f r i c a , w h e r e c o m m u n i c a t i o n r o u t e s a r e s t i l l inadequate and t r a n s p o r t i s g e n e r a l l y s low, d i f f i c u l t and u n c e r t a i n , t he d i s t r i b u t i o n of d r i e d , s a l t e d o r s m o k e d f i s h n e v e r t h e l e s s p r e s e n t s no d i f f i c u l t y , a n d t h e m o s t i s o l a t e d s m a l l m a r k e t s in t h e b u s h c a n a l w a y s be s u p p l i e d .

(4) Range of u s e s f o r t he c u s t o m e r : Depend ing on the d i s t r i c t and the l o c a l e a t i n g h a b i t s , d r i é d o r s m o k e d f i s h i s v e r y wide ly u s e d in A f r i c a n cooking . T h e p r u d e n t h o u s e w i f e a l w a y s k e e p s s o m e a t h o m e t o add t o the mi l l e t , r i c e o r m a n i o c s a u c e w h e n f r e s h f i s h and m e a t a r e not a v a i l a b l e , o r a r e beyond t h e r e a c h of h e r p u r s e . H o w e v e r , w h i l e s m o k e d f i s h i s u s e d i n A f r i c a n c u l i n a r y p r e p a r a t i o n s a s a d i s h in i t s e l f and i s p r e p a r e d a c c o r d i n g l y , d r i e d f i s h i s m o s t of ten u s e d a s a cond imen t . It has , in fac t , a v e r y s t rong f lavour a n d i s u s e d i n t h e s a m e w a y a s s a l t , r e d p e p p e r and o t h e r s p i c e s to m a k e highly s e a s o n e d s a u c e s to a c c o m p a n y r a t h e r dul l d i s h e s of c e r e a l s o r cooked t u b e r s . I t m a y b e s a i d t h a t s m o k e d f i s h i s e a t e n in l a r g e r a m o u n t s a t one t i m e , bu t a p p e a r s on ly i n f r e q u e n t l y on t h e m e n u , l i k e m e a t o r f r e s h f i s h . T h e f r e q u e n c y of i t s a p p e a r a n c e d e p e n d s on the l iv ing s t a n d a r d s of the c o n -s u m e r s . D r i e d f i s h i s e a t en in s m a l l e r quan t i t i e s , but m o r e r e g u l a r l y , s ince i t a c c o m p a n i e s t h e e v e r y d a y food in t h e f o r m of s a u c e s . In a n y c a s e , t h e con t r i bu t i on of d r i e d o r s m o k e d f i s h to the a n i m a l p r o t e i n content of the dai ly r a t i o n s i s f a r f r o m n e g l i g i b l e .

O f f s e t t i n g the a b o v e a d v a n t a g e s i s t h e f a c t t h a t d r i e d and s m o k e d f i s h , and even , a l though t o a l e s s e r extent , s a l t e d f i sh , a r e s u b j e c t to the s e r i o u s d r a w b a c k of being a t t a c k e d by i n s e c t s . The m o s t f o r m i d a b l e a r e D e r m e s t e s ,


above a l l the two s p e c i e s D. m a c u l a t u s and D. f r i t s c h i i , fol lowed by N e c r o b i a f u s c i p e s . B e f o r e e x a m i n i n g the way in which t h e s e i n s e c t s d e v e l o p and the m e t h o d s w h i c h c a n be e m p l o y e d t o r e d u c e and s t a m p out t h e i r a t t a c k s , we s h a l l g i v e a f e w d e t a i l s of t h e w a y s i n w h i c h f i s h i s m o s t c o m m o n l y p r e -p a r e d i n A f r i c a , f o r t h e p r o d u c t s w h i c h we s h a l l r e f e r to a s d r i e d f i s h and s m o k e d f i s h do not c o r r e s p o n d t o t h e g e n e r a l l y a c c e p t e d d e f i n i t i o n s .

D r i e d f i s h

S imple d ry ing in the a i r and in the sun i s obvious ly the l e a s t compl i ca t ed m e t h o d of p r e p a r a t i o n i m a g i n a b l e , and m u s t h a v e b e e n u s e d by m a n s i n c e v e r y a n c i e n t t i m e s . It i s p r a c t i c a b l e w h e r e v e r the r e l a t i v e h u m i d i t y d o e s no t e x c e e d 70 t o 7 5%; i n t h e s e c o n d i t i o n s , t h e f i s h g i v e s u p w a t e r t o t h e a t m o s p h e r e u n t i l i t c o n t a i n s n o t m o r e t h a n a b o u t 25%, w h i c h i s s u f f i c i e n t t o p r e v e n t t he d e v e l o p m e n t of m o u l d , b a c t e r i a and , g e n e r a l l y speak ing , a l l t h e p r o c e s s e s of p u t r e f a c t i o n . V e r y s m a l l f i s h may . be d r i e d a s t h e y a r e ; t h o s e of m e d i u m s i z e a r e s ca l ed , gu t ted and washed , while t h o s e a l i t t le l a r g e r a r e a l s o s p l i t in t w o and opened s o t h a t t he m u s c u l a r m a s s e s can d r y m o r e qu ick ly . D r y i n g i s u n s a t i s f a c t o r y with l a r g e o r v e r y th ick f i s h such a s Late s n i l o t i c u s : t h e o u t e r l a y e r s d r y , f o r m i n g a h a r d c r u s t u n d e r w h i c h t h e i n -s u f f i c i e n t l y d e h y d r a t e d f l e s h b e g i n s to r o t . T h e f i n a l p roduc t , if i t i s edible n o t w i t h s t a n d i n g , t h e n h a s a s l i g h t l y b i t t e r f l a v o u r . It s h o u l d be no t ed t h a t p r e l i m i n a r y f e r m e n t a t i o n and e v e n i n c i p i e n t p u t r e f a c t i o n a r e in no way d e -t r i m e n t a l — q u i t e t h e c o n t r a r y , i n f a c t — t o t h e p r e p a r a t i o n of d r i e d f i s h , p r o v i d e d t h a t t h i s f e r m e n t a t i o n c a n be s t opped a t a s u i t a b l e s t a g e by d e h y -d r a t i o n . In p r a c t i c e , t h e f i s h i s o f t e n l e f t t o s o a k in w a t e r f o r a l e n g t h of t i m e v a r y i n g wi th t h e s e a s o n , the s p e c i e s and the s i z e of the f i s h . In w a r m w e a t h e r , m o s t m e d i u m - s i z e d s p e c i e s r e m a i n in t h e w a t e r f o r a b o u t 24 h, wh i l e v e r y l a r g e o n e s m a y r e m a i n t h e r e f o r 24 to 48 h; in c o o l e r w e a t h e r , t h e s e t i m e s m a y be doub led o r e v e n t r e b l e d . It i s t h i s p r e l i m i n a r y f e r m e n -t a t i o n w h i c h g i v e s d r i e d f i s h i t s p a r t i c u l a r f l a v o u r , g r e a t l y a p p r e c i a t e d by the c o n s u m e r s f o r i t s enhanc ing e f f e c t on s a u c e s . F r o m the e c o n o m i c point of v i e w , t h i s d e t a i l of t h e p r e p a r a t i o n i s i m p o r t a n t , f o r f i s h w h i c h h a s a l -r e a d y t u r n e d bad and b e c o m e ined ib l e in the f r e s h s t a t e i s exce l l en t ly su i ted to d r y i n g ; not only d o e s i t s n u t r i t i v e value r e m a i n in tac t , but i t s c o m m e r c i a l va lue i s h a r d l y r e d u c e d .

F o r d r y i n g p r o p e r , the f i s h i s o f t en laid flat on the ground o r on w i c k e r -w o r k m a t s . A s one s i de only i s e x p o s e d to the sun, the f i s h m u s t be t u rn ed o v e r f r o m t i m e t o t i m e s o t ha t d r y i n g p r o c e e d s even ly . To avoid such m a -n i p u l a t i o n , t h e f i s h i s s o m e t i m e s h u n g up , t h r e a d e d on c o r d s o r s t i c k s s t r e t c h e d b e t w e e n two p o s t s . T h e d r y i n g t i m e v a r i e s depending on a i r t e m -p e r a t u r e , h y g r o m e t r y and s p e c i e s of f i s h . In a hot , d r y c l i m a t e , T i l a p i a , A l e s t e s , L a b e o and H y d r o c y o n , i . e . , g e n e r a l l y speak ing , a l l t he m e d i u m -s i z e d f i s h , d r y in 4 t o 8 d. * At t h e end of t h i s p e r i o d they a r e r e m o v e d f r o m the d r y i n g a r e a and p i led in s t o r a g e a r e a s . It s o m e t i m e s t a k e s 2 to 3 weeks to d r y v e r y l a r g e f i s h .

At t h e b e g i n n i n g of d r y i n g , f l i e s o f t e n l a y t h e i r e g g s on t h e f i s h which i s no t y e t d e h y d r a t e d , and m a g g o t s m a y a p p e a r . In m o s t c a s e s , t h e s e d i e v e r y qu i ck ly and f a l l onto the g r o u n d a s soon a s d e h y d r a t i o n i s p r o g r e s s i n g .

78 DAGET

N e v e r t h e l e s s , t o c u t s h o r t t h e p r e l i m i n a r y f e r m e n t a t i o n a n d t o a v o i d i t s d e g e n e r a t i n g i n to r e a l p u t r e f a c t i o n a c c o m p a n i e d by the d e v e l o p m e n t of t h e l a r v a e of t h e f l i e s , i n s h o r t , t o o b t a i n a good p r o d u c t of good a p p e a r a n c e wi th a l l the d e s i r e d g u s t a t o r y qua l i t i e s , a t l e a s t the beginning of dry ing m u s t be v e r y qu ick , and f o r t h i s r e a s o n t h e m e t h o d c a n n o t be u s e d i n h u m i d r e -g i o n s o r d u r i n g the t r o p i c a l r a i n s e a s o n .

D r i e d s a l t f i s h

D r y i n g a f t e r d r y - s a l t i n g o r s o a k i n g i n b r i n e i s r a r e l y u s e d in A f r i c a ; c o m p a r e d t o t h e s i m p l e d r y i n g j u s t d e s c r i b e d , t h i s m e t h o d of p r e s e r v a t i o n h a s t w o d i s a d v a n t a g e s .

(1) T h e p r o d u c t d o e s n o t h a v e t h e s a m e f l a v o u r , and f a n c i e r s of s a l t f i s h a r e t o be found only in c e r t a i n v e r y l i m i t e d a r e a s . C o n s u m e r s of d r i e d f i sh who h a v e been g iven s a l t f i s h to t a s t e do not th ink it c an r e p l a c e the p roduc t t o w h i c h t h e y a r e a c c u s t o m e d . U n l e s s , a s i s a l w a y s p o s s i b l e , t h e r e i s a r a d i c a l c h a n g e i n t a s t e s and e a t i n g h a b i t s , d r i e d s a l t f i s h c a n n o t r e p l a c e d r i e d f i s h o r e v e n s m o k e d f i s h on t h e p r e s e n t A f r i c a n m a r k e t .

(2) Salt i s t r a d i t i o n a l l y a p r o d u c t r e s e r v e d f o r f a m i l y cooking. Admit tedly , s o m e l i v e s t o c k b r e e d e r s give i t to t h e i r a n i m a l s , but only to t h o s e they t r e a t w i th t h e s a m e c o n s i d e r a t i o n a s t h e o t h e r m e m b e r s of t h e i r f a m i l y . In the Middle A g e s , s p e a k i n g of W e s t A f r i c a , F e r n a n d e z w r o t e : " T h e c h i e f s g ive m o r e gold in e x c h a n g e f o r s a l t t han f o r any o t h e r m e r c h a n d i s e " . Today, in s p i t e of t he f a c i l i t i e s f o r e x t r a c t i o n and t r a n s p o r t a f f o r d e d by m o d e r n t e c h -n i q u e s , s a l t r e m a i n s an e x p e n s i v e c o m m o d i t y i n t h e i n t e r i o r , and i s o f t en b r o u g h t f r o m a d i s t a n c e a t g r e a t e x p e n s e .

In c o n t r a s t to t h e s e d r a w b a c k s , i t h a s b e e n c l a i m e d tha t d r i e d sa l t f i s h i s no t a t t a c k e d by D e r m e s t e s , but p e r s o n a l e x p e r i e n c e c o m p e l s u s to s t a t e t ha t t h i s op in ion cou ld l e a d to g r a v e m i s c a l c u l a t i o n s . It i s t r u e tha t if s a l t f i s h a r e m i x e d wi th f i s h t ha t have s i m p l y b e e n d r i e d , t he f o r m e r wi l l not be a t t a c k e d by D e r m e s t e s w h i l e t h e l a t t e r w i l l be , bu t a l l t h i s p r o v e s i s t h a t D e r m e s t e s , g iven t h e c h o i c e , p r e f e r n o n - s a l t e d f i s h . H o w e v e r , when they have n o cho ice , t h e y t h r i v e v e r y we l l on s a l t f i s h . If a l l f i s h w e r e s y s t e m a -t i c a l l y s a l t e d , i t i s p r o b a b l e t h a t t he d a m a g e r e s u l t i n g f r o m a t t a c k s of D e r m e s t e s wou ld be a s s e r i o u s a s i t i s a t p r e s e n t f o r f i s h d r i e d w i thou t s a l t i n g .

S m o k e d f i s h

In A f r i c a , f i s h i s a l w a y s s m o k e d hot ; m o r e p r e c i s e l y , i t i s cooked and d r i e d o v e r a f i r e , and t h e only e f f e c t of t he s m o k e i s to g ive it an ind iv idua l f l a v o u r . T h i s me thod of s m o k i n g i s p o s s i b l e at any s e a s o n and in any c l ima te , even the m o s t humid , and when d ry ing i s i m p o s s i b l e . The f i s h to be smoked m u s t be p e r f e c t l y f r e s h , and m u s t t h e r e f o r e be p r e p a r e d a s soon a s poss ib le a f t e r i t i s c a u g h t . A c c o r d i n g t o the f i s h e r m e n , f i s h i n wh ich f e r m e n t a t i o n h a s begun b e c o m e s c r i s p d u r i n g and a f t e r smoking , and i s t h e r e f o r e i m p a i r e d . T h e r e i s t h e r e f o r e no p r e l i m i n a r y f e r m e n t a t i o n s t a g e in the p r e p a r a t i o n of s m o k e d f i s h , w i th the r e s u l t t ha t t he l a t t e r d o e s not h a v e the s t r o n g f l a v o u r


of d r i e d f i s h . T h e o v e n s v a r y i n s h a p e a n d d e s i g n , t h e e s s e n t i a l f e a t u r e be ing t h a t t he p r o d u c t t o be s m o k e d i s p l a c e d i m m e d i a t e l y above the h e a r t h and v e r y c l o s e to i t . At the beginning of the ope ra t i on the f i r e i s kept burning s t r o n g l y , so t h a t i t d r i e s the f i s h and p a r t i a l l y c o o k s the o u t e r l a y e r ; when t h i s i s done , t h e i n t e n s i t y of t h e f i r e i s r e d u c e d . Smoking g e n e r a l l y t a k e s f r o m t w o d a y s f o r s m a l l s p e c i e s t o f o u r d a y s f o r l a r g e o n e s .

Smoking r e q u i r e s m o r e c a r e and m o r e w o r k than d ry ing . The f i s h m u s t f i r s t be p r e p a r e d , t h a t i s s c a l e d , gu t t ed , w a s h e d and, if i t s s i z e d e m a n d s i t , . cu t i n t o p i e c e s , a s s o o n a s i t i s l a n d e d ; i t m u s t t h e n q u i c k l y be p l a c e d o v e r the h e a r t h w h e r e a f i r e m u s t be kept cons tan t ly burning and under s u p e r -v i s i o n ; f i n a l l y , t h e r e m u s t be an a d e q u a t e f u e l supp ly . Anything which can b u r n o r m a k e s m o k e i s s u i t a b l e , f r o m p a p y r u s s t e i n s t o d r i e d c o w d u n g . S o m e t i m e s s m a l l f i s h a r e s i m p l y p laced on a l a y e r of s t r a w o r d r i e d l e a v e s wh ich i s t h e n s e t on f i r e . T h e f i s h a r e m o r e o r l e s s c a r b o n i z e d ou twa rd ly , and d r y r a p i d l y t h e r e a f t e r . A l though th i s m e t h o d of p r e s e r v a t i o n i s b a s e d on the s a m e p r i n c i p l e a s the s m o k i n g d e s c r i b e d above, the ac t ion of t h e f i r e l a s t s too s h o r t a t i m e f o r the end p roduc t to be i m p r e g n a t e d by s m o k e ; what we have h e r e i s f i s h d r i e d a f t e r g r i l l i n g .

Infection by insects

A s h a s a l r e a d y b e e n s t a t e d , t he m o s t d a n g e r o u s i n s e c t s f o r d r i e d and s m o k e d f i s h a r e D e r m e s t e s , e s p e c i a l l y D. m a c u l a t u s which i s m u c h m o r e c o m m o n than D. f r i t s c h i i ; by c o m p a r i s o n , d a m a g e caused by Necrob ia f u s c i -p e s i s on a s m a l l s c a l e . A l l t h e s e i n s e c t s a r e c o l e o p t e r a whose a d u l t s a r e winged, which m e a n s tha t they can s p r e a d a l m o s t e v e r y w h e r e . T h e i r l a rvae , w h i c h a r e v e r y a c t i v e and p a r t i c u l a r l y v o r a c i o u s , a t t a c k a l l dr ieci a n i m a l m a t t e r , and not only f i s h . T h e s e i n s e c t s a r e t h e r e f o r e v e r y c o m m o n , but o f t e n p a s s u n n o t i c e d ; i t i s on ly w h e n c l i m a t i c c o n d i t i o n s a r e f a v o u r a b l e t o t h e m and w h e n t h e y f i n d a c o n s i d e r a b l e a c c u m u l a t i o n of d r i e d o r s m o k e d f i s h t h a t t h e y m u l t i p l y r a p i d l y and u l t i m a t e l y c a u s e c o n s i d e r a b l e d a m a g e .

D e r m e s t e s l a r v a e ha t ch two o r t h r e e d a y s a f t e r the eggs a r e l a id . The i n s e c t r e m a i n s a t t h e l a r v a l s t a g e f o u r t o e i g h t w e e k s a n d u n d e r g o e s n ine to twelve mou l t s , the exac t n u m b e r v a r y i n g to s o m e extent with t e m p e r a t u r e . When fu l ly deve loped , the l a r v a e , b l a c k i s h and c o v e r e d with h a i r s , r e a c h 10 t o 12 m m in l e n g t h . T h e s e l a r v a e a r e p h o t o p h o b i c ; t h e y b u r y t h e m s e l v e s in the f l e s h of the f i s h , in wh ich t h e y f u r r o w t u n n e l s in a l l d i r e c t i o n s . B e -f o r e c h a n g i n g in to i m a g o e s , t he l a r v a e p a s s t h r o u g h a n y m p h à l s t a g e which l a s t s f o r abou t a w e e k and c a n on ly o c c u r u n d e r c o v e r . At t h e m o m e n t of n y m p h o s i s t h e y t h e r e f o r e s e e k out a so f t m a t e r i a l to b u r r o w in to ; t he wood o r c l a y e y e a r t h f r o m w h i c h t h e w a r e h o u s e w a l l s a r e o f t e n bui l t s u i t s t h e m v e r y we l l . If n e c e s s a r y , t h e y can even u n d e r g o n y m p h o s i s in the f i s h w h e r e t h e y have l ived , bu t in t h i s c a s e the nymph , i n c a p a b l e of any m o v e m e n t , i s in d a n g e r of be ing d e v o u r e d by the o t h e r l a r v a e .

I n f e c t i o n by D e r m e s t e s b e c o m e s a d a n g e r a s s o o n a s t h e f i s h h a s a t -t a ined a c e r t a i n d e g r e e of d r y n e s s , when the l a r v a e of the f l i e s ican no longer d e v e l o p t h e r e . It i s c a u s e d e i t h e r by adult i n s e c t s which a r e ab le to f ly and l a y t h e i r e g g s on the f i s h , o r by the v e r y m o b i l e l a r v a e , w h i c h a r e a l w a y s looking f o r food. D r y i n g on the g round obv ious ly p r o m o t e s in fec t ion . How-

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e v e r , D e r m e s t e s and N e c r o b i a f e a r e x c e s s i v e hea t and l ight, while a c e r t a i n d e g r e e of humid i ty i s f a v o u r a b l e to t h e m . T h u s , they a r e above a l l n o c t u r -n a l i n s e c t s . D u r i n g the day and in b r igh t sun l igh t they a r e r a r e l y seen , but i t i s n e c e s s a r y on ly t o t u r n o v e r a b u n d l e of f i s h o r t o l i f t u p a w r a p p i n g m a t t o f ind u n d e r n e a t h a l a r g e n u m b e r of l a r v a e and f u l l - g r o w n i n s e c t s awai t ing , in a c c e p t a b l e s u r v i v a l condi t ions , the r educ t ion of t e m p e r a t u r e and l igh t a c c o m p a n y i n g n i g h t f a l l , so t h a t t h e y c a n a g a i n r e s u m e t h e i r a c t i v i t y . The b e d s of s t r a w o r w i c k e r - w o r k m a t s on which the f i s h e r m e n s p r e a d t h e i r f i s h , and the f i s h t h e m s e l v e s , in s o f a r a s t h e y m a i n t a i n a c e r t a i n J e g r e e of h u m i d i t y and p r e v e n t a r i s e in the t e m p e r a t u r e of the s o i l on wh ich t h e y a r e l a i d , a f f o r d e x c e l l e n t s h e l t e r f o r D e r m e s t e s when , a s a r e s u l t of e x -c e s s i v e e x p o s u r e t o t h e sun , t h e t e m p e r a t u r e of t h e f l e s h r e a c h e s a po in t a t w h i c h the l a r v a e a r e ob l iged to l e a v e . F r o m t h i s point of v iew, hang ing of t h e f i s h t h r o u g h o u t t h e d r y i n g p r o c e s s m u s t be s t r o n g l y r e c o m m e n d e d a s t h e b e s t p o s s i b l e p r o t e c t i o n a g a i n s t p r e c o c i o u s i n f e c t i o n by D e r m e s t e s and N e c r o b i a .

O n c e t h e f i s h a r e s u i t a b l y d r i e d o r s m o k e d , t he f i s h e r m e n m u s t h e a p t h e m u p and o f t e n c o v e r t h e m wi th a t a r p a u l i n o r a roof un t i l t h e y a r e so ld and d i s p a t c h e d to t h e m a r k e t i n g c e n t r e s . A l l t h e o p t i m u m c o n d i t i o n s f o r i n fec t ion a r e thus fu l f i l l ed , and if only the a t m o s p h e r i c condit ions a r e f a v o u r -a b l e , t h e D e r m e s t e s m u l t i p l y r a p i d l y . Many a t t e m p t s have b e e n m a d e t o a s s e s s the l o s s e s r e s u l t i n g f r o m t h e s e a t t a c k s of i n s e c t s , but it would s e e m tha t t h e q u e s t i o n i s d i f f i c u l t to a n s w e r p r e c i s e l y . The ex tent of the d a m a g e v a r i e s a g r e a t d e a l ; s o m e b a t c h e s of d r i e d , and e s p e c i a l l y of smoked , f i s h w h i c h h a v e b e e n so ld by t h e f i s h e r m e n i m m e d i a t e l y a f t e r p r e p a r a t i o n and which th roughou t the m a r k e t i n g p r o c e s s have been in condi t ions unfavourab le to i n f e c t i o n , m a y r e a c h t h e c o n s u m e r p r a c t i c a l l y u n h a r m e d . On the o t h e r h a n d , i t i s u n f o r t u n a t e l y no t u n c o m m o n t o f i n d b a t c h e s w h e r e t h e d a m a g e i s so e x t e n s i v e tha t a l l t ha t r e m a i n s i s the sk in and b o n e s of the f i s h with, at the bo t t om of the packages , a brown dus t c o n s i s t i n g of the d e j e c t a of the l a r v a e , m i x e d wi th the d e b r i s of exuv i ae and dead i n s e c t s . A l l the p r o t e i n pa r t , the on ly one of i n t e r e s t f r o m t h e po in t of v i e w of food , h a s d i s a p p e a r e d . A l l t h a t r e m a i n s i s w a s t e , c o m p l e t e l y i n e d i b l e and f i t on ly to be t h r o w n on a r e f u s e d u m p . In a l l the i n t e r m e d i a t e c a s e s of m o d e r a t e in fec t ion , the p r o -d u c t r e m a i n s m a r k e t a b l e ; t he c o n s u m e r s a r e r e s i g n e d t o s h a k i n g the f i s h to get r i d of what l a r v a e they can ; they then ea t what r e m a i n s ed ib le . A p r o -c e s s u s e d s o m e t i m e s , but which d o e s not s e e m v e r y e f fec t ive , i s to sp r ink le r e d p e p p e r on the f i s h to d r i v e out the i n s e c t s .

E x p e r t s have e s t i m a t e d tha t the l o s s e s due to i n s e c t s may r e a c h 25-30% of the t o t a l t onnage of d r i e d and s m o k e d f i s h m a r k e t e d in the r e g i o n s of the Midd le N i g e r and t h e C h a d B a s i n . A s t r a d e in e a c h of t h e s e r e g i o n s i s of the o r d e r of 12 OOOto 15 000 t, the t o t a l l o s s e s a r e be tween 6000 and 9000 t / y r , o r , in o t h e r w o r d s , 2500-3800 t of ed ib le p r o t e i n . T h e s e f i g u r e s have only a n i n d i c a t i v e v a l u e , but t h e y a r e s u f f i c i e n t t o show t h e i m p o r t a n c e of t h e p r o b l e m .

Measures taken against infection

V a r i o u s m e t h o d s of c o m b a t i n g i n f e c t i o n h a v e a l r e a d y b e e n t e s t e d and s o m e of t h e m h a v e , in p a r t i c u l a r c a s e s , g i v e n n o t e w o r t h y r e s u l t s . In the


R e p u b l i c of Chad and the n o r t h of t he F e d e r a l R e p u b l i c of C a m e r o o n , m o s t of t he f i s h caugh t i s A l e s t e s , e s p e c i a l l y A. b a r e m o z e ; t h e s e f i s h a r e sp l i t in two, gu t t ed and t h r e a d e d on s t i c k s , which a r e p l a c e d on wooden s u p p o r t s about 60 c m f r o m the g round ; d ry ing in the sun t a k e s four to f ive days . The p r o d u c t o b t a i n e d i s known l o c a l l y a s S a l a n g a , a n d i s t h e o b j e c t of a t r a d e r e a c h i n g s e v e r a l t h o u s a n d t o n s . It i s bought and pa id f o r in c a s h by S ta t e o r g a n i z a t i o n s , a t a p r i c e f i x e d f o r t he whole of t h e f i s h i n g s e a s o n . T h e s e p u r c h a s i n g condi t ions a r e su f f i c i en t l y advan tageous f o r f i s h e r m e n to s e l l t h e i r S a l a n g a a s i t i s p r o d u c e d , and c o n s e q u e n t l y b e f o r e it i s be ing a t t a c k e d by D e r m e s t e s . T h e S t a t e o r g a n i z a t i o n s wh ich b u y t h e f i s h i n bu lk r e c o n d i t i o n t h e m and d iv ide t h e m into u n i t s of 1000 f i s h each . E a c h of t h e s e i s wrapped in m a t t i n g m a d e of d o u m p a l m l e a v e s , and i s i m m e d i a t e l y s p r a y e d wi th an i n s e c t i c i d e so lu t ion . T h e b e s t r e s u l t s a r e ob ta ined with an aqueous so lu t ion of c o m m e r c i a l p r o d u c t s b a s e d on H - C - H , which have a good r e s i d u a l e f f e c t . The sp ray ing , which a f f e c t s only the outs ide of the bundles , mus t be r ep ea t ed e a c h t i m e t h e b a l e s of f i s h a r e h a n d l e d to any c o n s i d e r a b l e ex ten t , f o r e x -a m p l e a f t e r loading o r un load ing a l o r r y . They should a l s o be t r e a t e d aga in b e f o r e s t o r i n g i n t h e s h o p . At p r e s e n t t h e r e s p o n s i b l e a u t h o r i t i e s i n C a -m e r o o n and Chad e s t i m a t e t h a t Sa l anga c o n d i t i o n e d and t r e a t e d in t h i s way can e a s i l y be s t o r e d f o r a y e a r with no r i s k of d e t e r i o r a t i o n f r o m D e r m e s t e s .

When t h e s e f ind ings had been obtained, the Governmen t of Chad publ ished an o r d e r d a t e d 21 A p r i l 1964 p r o v i d i n g t h a t " b e f o r e t r a n s p o r t t o p l a c e s of c o n s u m p t i o n , a l l t he d r i e d f i s h known a s S a l a n g a ( A l e s t e s ) c a u g h t b e t w e e n Log o n e G a n a and L a k e Chad a n d i n t e n d e d f o r m a r k e t i n g in t h e R e p u b l i c of Chad m u s t be t r e a t e d wi th Em i n s e c t i c i d e . T h i s d i s i n f e c t i v e t r e a t m e n t w i l l be c a r r i e d out a t M i l e s i , in the c o v e r e d m a r k e t of t h e B a s - C h a r i F i s h e r m e n ' s C o - o p e r a t i v e . " T h i s t e r m c o - o p e r a t i v e should not be m i s u n d e r s t o o d . Unt i l t h e f i s h e r m e n a r e s u f f i c i e n t l y e d u c a t e d and t r a i n e d t o t a k e o v e r t h e i r own i n t e r e s t s , t he c o - o p e r a t i v e i s a S ta te body which f i x e s p r i c e s , s t a n d a r d i z e s packaging, p r o v i d e s p r o t e c t i o n aga ins t i n s e c t s dur ing s t o r a g e , and f a c i l i t a t e s m a r k e t i n g by p rov id ing c o n s u m e r s with a p roduc t of g u a r a n t e e d qual i ty . The o r g a n i z a t i o n w h i c h h a s b e e n s e t u p t e n d s to m a k e t h e S a l a n g a t r a d e a r e a l S t a t e m o n o p o l y , w i th a l l t h e a d v a n t a g e s and d i s a d v a n t a g e s w h i c h d i r e c t G o v e r n m e n t i n t e r v e n t i o n i n t r a d e c h a n n e l s a l w a y s i n v o l v e s . D i s i n s e c t i -z a t i o n i s on ly one a s p e c t of a c o m p l e x s e t of c o m m e r c i a l o p e r a t i o n s , and i t w i l l b e a f e w y e a r s b e f o r e a n y o b j e c t i v e a s s e s s m e n t of t h i s e x p e r i m e n t in Chad c a n be m a d e . I should a l s o l ike to e m p h a s i z e tha t t h i s p r o j e c t con-c e r n s on ly S a l a n g a , t h a t i s d r i e d A l e s t e s , i n t e n d e d f o r h o m e c o n s u m p t i o n in the c o t t o n - p i c k i n g r e g i o n s . It d o e s not c o v e r the t o t a l p roduc t ion , which c o n s i s t s p r i n c i p a l l y of s m o k e d f i s h e x p o r t e d to N i g e r i a .

In Mali the p r o b l e m of d i s i n s e c t i z a t i o n has not been s a t i s f a c t o r i l y solved, i n s p i t e of t h e i n v e s t i g a t i o n s a n d t e s t s w h i c h h a v e b e e n m a d e . T h e m a i n f a c t o r s i n t h e p r o b l e m a r e :

(1) T h e f i s h i n g g r o u n d s a r e s c a t t e r e d o v e r t h e w h o l e f l o o d r e g i o n of t h e M i d d l e N i g e r , a v a s t a r e a of 17 0 0 0 - 2 0 000 km2 in w h i c h t r a v e l b o t h on land and on w a t e r i s d i f f i cu l t , i n d e e d c o m p l e t e l y i m p o s s i b l e f o r a l a r g e p a r t of t he y e a r . L a r g e n u m b e r s of f i s h i n g c a m p s r e m a i n cu t off f r o m t h e r e s t of t he c o u n t r y f o r s e v e r a l m o n t h s , and the f i s h e r m e n t h u s have to keep t h e i r

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c a t c h wi th t h e m and c a n n o t d i s p o s e of i t u n t i l t he end of the s e a s o n . Dur ing t h i s p e r i o d n o t h i n g i s d o n e t o p r e v e n t i n f e c t i o n of t h e d r i e d f i s h . S o m e f i s h e r m e n , knowing the i n s e c t i c i d e e f f e c t of t he H - C - H based p o w d e r s which a r e n o w w i d e l y a v a i l a b l e , h a v e s c a t t e r e d s o m e on t h e i r d r i e d f i s h . T h e d e s i r e d r e s u l t w a s e a s i l y a t t a i n e d , t h e m o r e so s i n c e huge d o s e s w e r e e m -ployed , and the D e r m e s t e s d i s a p p e a r e d t e m p o r a r i l y . Howeve r , the Hea l th ' S e r v i c e h a s m o r e t h a n o n c e b e e n c o n f r o n t e d wi th c a s e s of p o i s o n i n g due t o t h e i n g e s t i o n of H - C - H . It would t h e r e f o r e be e x t r e m e l y d a n g e r o u s t o put i n s e c t i c i d e p r o d u c t s in the h a n d s of the f i s h e r m e n f o r the o s t e n s i b l e p u r p o s e of enab l ing t h e m to r e m o v e i n s e c t s f r o m t h e i r own s t o c k s of f i s h .

(2) T h e f i s h e r m e n d i s l i ke s e l l i ng t h e i r d r i e d f i s h a s and when it i s p roduced . In Mal i the t r a d e in f i s h i s f r e e and i s c o m p l e t e l y sub jec t to the law of supply and d e m a n d . P r i c e s u n d e r g o c o n t i n u a l f l uc tua t i ons , with a r e g u l a r t endency t o r i s e w h e n p r o d u c t i o n f a l l s off in t h e r a i n y s e a s o n . T h e f i s h e r m e n a r e a l w a y s w a r y of s e l l i n g t h e who le of t h e i r s t o c k a t t he p r i c e o f f e r e d by the b u y e r s ; r i g h t l y o r w r o n g l y , t h e y a l w a y s h o p e tha t , should t h e y wa i t a l i t t l e , p r i c e s w i l l r i s e . T h e p r o f i t hoped f o r o f t en d o e s not m a t e r i a l i z e , but a few w e e k s of v a c i l l a t i o n a r e enough f o r the D e r m e s t e s to mu l t i p ly .

(3) A l m o s t a l l t h e d r i e d and s m o k e d f i s h i s m a r k e t e d a t Mopt i , w h e r e i t i s c o l l e c t e d in l a r g e c e m e n t e d w a r e h o u s e s . H e r e the f i s h i s r e c o n d i t i o n e d , s o r t e d , p a c k e d a n d d i s p a t c h e d by l o r r y t o t h e l a r g e c o n s u m e r c e n t r e s of Ghana and the Ivory Coas t a s o r d e r s c o m e in . While smoked f i sh i s r e l a t i v e -ly l i t t l e i n f e c t e d by D e r m e s t e s on a r r i v i n g a t Mopti , b e c a u s e t h e f i s h e r m e n t r y t o s e l l i t i m m e d i a t e l y a f t e r s m o k i n g , d r i e d f i s h , w h i c h h a s r e m a i n e d l o n g e r i n t h e f i s h i n g c a m p s , i s n o r m a l l y a l r e a d y h e a v i l y i n f e c t e d . In t h e s h o p s of Mopti , which a r e f u l l t h roughou t the y e a r , D e r m e s t e s and Nec rob i a f ind o p t i m u m c o n d i t i o n s f o r d e v e l o p m e n t : s h a d e , l o w e r t e m p e r a t u r e t h a n in b r o a d dayl ight , g r e a t e r humidi ty du r ing the hot p a r t of the day and abundant food . E x t e r n a l t r e a t m e n t of the bund le s of d r i e d o r smoked f i s h by s p r a y i n g t h e m wi th i n s e c t i c i d e i s of no u s e if i n s i d e t h e r e a r e s u f f i c i e n t D e r m e s t e s t o c o n s u m e t h e whole of t h e i r c o n t e n t s . D i s i n s e c t i z a t i o n of a b a t c h of f i s h i s a w a s t e of t i m e and m o n e y i f , a f t e r t r e a t m e n t , i t h a s t o be put b a c k i n a p l a c e s w a r m i n g w i t h l a r v a e and f u l l - g r o w n i n s e c t s .

T e s t s on t r e a t m e n t w i th m e t h y l b r o m i d e in an a u t o c l a v e u n d e r v a c u u m w e r e m a d e a t Mopt i in 1954. T h i s p r o c e s s i s e f f e c t i v e and quick , but i t s w i d e -s p r e a d u s e would r e q u i r e t h e i n s t a l l a t i o n of l a r g e - c a p a c i t y a u t o c l a v e s , a t c o n s i d e r a b l e c a p i t a l o u t l a y . A l so , m e t h y l b r o m i d e i s a v e r y tox i c p r o d u c t which could be d a n g e r o u s in the hands of i n e x p e r i e n c e d p e r s o n n e l . A f u r t h e r d i s a d v a n t a g e i s t h a t t h e i n s e c t i c i d e e f f e c t i s no t p e r m a n e n t ; f i s h w h i c h i s c o m p l e t e l y f r e e f r o m i n s e c t s on leaving the au toc lave i s not p ro tec t ed agains t s u b s e q u e n t r e i n f e c t i o n . It would h a v e t o be p l a c e d in h e r m e t i c a l l y s e a l e d p a c k s i m m e d i a t e l y on l e a v i n g t h e a u t o c l a v e , o r e l s e w r a p p e d i n m a t e r i a l t r e a t e d e x t e r n a l l y w i t h a n i n s e c t i c i d e h a v i n g a s t r o n g r e s i d u a l e f f e c t , a s in t h e t e c h n i q u e u s e d in t h e R e p u b l i c of Chad w h i c h h a s a l r e a d y b e e n d e s -c r i b e d . A s t h i s point h a s not b e e n s tud ied , t h e 1954 t e s t s in Mopti have not been fo l lowed up. In D a k a r , h o w e v e r , low t o n n a g e s of d r i e d o r smoked f i sh


a r e t r e a t e d e v e r y y e a r w i th m e t h y l b r o m i d e , w h i c h i s a l s o c u r r e n t l y u s e d f o r r e m o v i n g i n s e c t s f r o m o t h e r f o o d s t u f f s .

T h e s e f ew r e f l e c t i o n s on the r e m o v a l of i n s e c t s f r o m d r i e d o r s m o k e d f i s h i n A f r i c a a r e in no way in t ended t o be a c o m p l e t e and e x h a u s t i v e r e v i e w of t h e d i f f e r e n t a s p e c t s of t he p r o b l e m . A s o l u t i o n c a p a b l e of g iv ing s a t i s -f a c t o r y r e s u l t s in one r e g i o n m i g h t t u r n out to be i n a p p l i c a b l e o r i n e f f e c t i v e in a n o t h e r r e g i o n . E a c h c a s e s h o u l d t h e r e f o r e be s t u d i e d i nd iv idua l l y bo th a s r e g a r d s the t h e o r e t i c a l and t e c h n i c a l a s p e c t s of i n s e c t r e m o v a l , and with r e f e r e n c e t o t h e e c o n o m i c and s o c i o l o g i c a l a s p e c t s of t h e f i s h i n g i n d u s t r y and t h e u t i l i z a t i o n of i t s p r o d u c t s . T h i s p o i n t h a v i n g b e e n m a d e , t h e u s e of r a d i o a c t i v e m a t e r i a l s s e e m s a m o n g t h e m o s t a t t r a c t i v e of t h e m e t h o d s a v a i l a b l e f o r d e s t r o y i n g i n s e c t s h a r m f u l t o f o o d s t u f f s , a s t h e s e m a t e r i a l s have m o r e e x t e n s i v e p o s s i b i l i t i e s t han o t h e r i n s e c t i c i d e s . Depending-on the d o s e s used , the i n s e c t s a r e m o r e o r l e s s r a p i d l y ki l led, the adu l t s a r e s t e r i -l i zed , o r t he l a r v a e a r e p r e v e n t e d f r o m a c h i e v i n g n y m p h o s i s , and t h e r e i s no d a n g e r of r e s i s t a n t s t r a i n s a p p e a r i n g . T h e i n s e c t i c i d e p r o p e r t i e s a f f e c t the bulk of the p r o d u c t t r e a t e d , even if it i s h e r m e t i c a l l y packed , and t h e r e i s no con tac t with b o d i e s h a r m f u l to human h e a l t h . However , a t the p r e s e n t t i m e t h e d e v e l o p m e n t of an i n s t a l l a t i o n f o r r e m o v i n g i n s e c t s by m e a n s of g a m m a r a y s i s of i n t e r e s t p r i n c i p a l l y to the i n d u s t r i a l i z e d c o u n t r i e s seek ing t o d e v e l o p a l l t h e p o s s i b l e u s e s of t h e r a d i o a c t i v e i s o t o p e s t h e y p r o d u c e . T h e d e v e l o p i n g A f r i c a n c o u n t r i e s a w a i t i n f o r m a t i o n a s to t h e p r a c t i c a l a d -v a n t a g e s and a b o v e a l l t he c o s t of s u c h an i n s t a l l a t i o n b e f o r e t a k i n g up any p o s i t i o n .

I s h o u l d l i k e t o c l o s e t h i s d i s c u s s i o n by a d o p t i n g t h e p o i n t of v i e w of t h e S o c i é t é C e n t r a l e p o u r l ' E q u i p e m e n t du T e r r i t o i r e (SCET) and of the So-c i é t é C e n t r a l e p o u r le D é v e l o p p e m e n t E c o n o m i q u e et S o c i a l (SEDES) wi th r e f e r e n c e to the t i m e l i n e s s of p r o p o s i n g to an A f r i c a n g o v e r n m e n t t h e r e -m o v a l of i n s e c t s by i r r a d i a t i o n i n p r e f e r e n c e t o m o r e c o n v e n t i o n a l p r o c e -d u r e s : " W e c o n s i d e r t h a t w o r k on t h e d i s i n s e c t i z a t i o n of f i s h by m e a n s of g a m m a r a y s i s a t t oo e a r l y a s t a g e of d e v e l o p m e n t f o r t h i s t e c h n i q u e to be r e c o m m e n d e d f o r a d o p t i o n at p r e s e n t . We do c o n s i d e r , h o w e v e r , tha t t h e m e t h o d m a y be a v e r y p r o m i s i n g one; f o r t h i s r e a s o n we t h i n k it d e s i r a b l e to e n c o u r a g e r e s e a r c h on the s u b j e c t of r a d i a t i o n e f f e c t s which would be d i -r e c t e d t o w a r d s the d i s i n s e c t i z a t i o n of a n i m a l f o o d s t u f f s . "

DISINSEC TI ZA TION OF AFRICAN DRIED AND SMOKED FISH BY MEANS OF IRRADIATION

M . H . BOISOT AND M. GAUZIT ASSOCIATION FOR THE DEVELOPMENT OF

INDUSTRIAL APPLICATIONS OF RADIATION, PARIS, FRANCE


DISINSECTIZATION OF AFRICAN DRIED AND SMOKED FISH BY MEANS OF IRRADIATION. 1. The problem of conserving dried and smoked fish

Fresh water fisheries are one of the major sources of protein in Africa. More than 100 000 t of fish are believed t o be caught commerc ia l ly in the Niger basin and 150 000 t in that of the Chad. These dried or smoked fish are then exported throughout Black Africa. Through attack by parasitic insects more than 30 wt.% of the fish are destroyed. None of the conventional methods of combating these insects has so far produced any pract ical results. 2 . Radiation experiments carried out to da te

A series of irradiation experiments has been carried out in France with doses of 20 000,100 000,500 000 rad. The order of magnitude of lethal and sterilizing doses has been determined without any organoleptic change being observed at 500 000 rad. 3. Studies which are still necessary

The^e comprise entomological studies, determination of pract ical dose, studies on nutritional value, research into packaging techniques, and economic analysis. These studies are not extensive if one leaves aside the problems of wholesomeness and edibility (for which, incidentally, very favourable results have a l -ready been obtained with fish subjected to doses well above the 15 000 to 40 000 rad which would probably i be necessary in this case). 4 . Proposals for organizing research

(a) Preliminary studies which might be carried out ei ther in Africa or Europe. (b) Technical development which would certainly necessitate the construction of a pilot plant in Africa.

5. Conclusion An economic study shows that for an increase of the order of 1% in the pr ice of the product one can

expect to e l im ina t e losses amounting to several tens of per cen t .

DES INSECTION AU MOYEN DES RAYONNEMENTS DU POISSON SECHE ET FUME EN AFRIQUE. 1. Le p rob lème d e la conservation des poissons séchés et fumés

La pêche en eau douce est une des sources les plus importantes de protéines en Afrique. Plus de 100 000 t

de poissons seraient commercial isées dans le bassin du Niger et 150 000 dans celui du Tchad. Ces poissons

séchés ou fumés sont ensuite exportés dans toute l 'Afrique Noire. Ils sont attaqués par des insectes parasites

qui en détruisent plus de 30% en poids. Aucun moyen de lut te « classique » n ' a encore donné de résultat

pratique.

2 . Expériences par irradiation e f fec tuées jusqu'à présent

Une série d'irradiation a é té effectuée en France à 20 000, 100 000 et 500 000 rad. Un ordre de grandeur

des doses lé ta les e t stéril isantes a é t é dé te rminé , sans qu ' aucune modi f ica t ion organolept ique a i t pu Être

déce l ée à 500 000 rad.

3 . Inventaire des études encore nécessaires

Elles porteraient sut l 'entomologie, la détermination de la dose pratique, le pouvoir nutritif, les embal-

lagese t l ' analyse économique. Leur volume n'est pas important, si l 'on excepte toutefois les problèmes de

salubrité et de comestibili té (pour lesquels des résultats très favorables ont déjà é t é obtenus, par ailleurs, sur

des poissons à des doses très supérieures aux 15 0.00 à 40 000 rad qui seraient probablement nécessaires dans ce

cas).

85

86 BOISOT and GAUZIT

4 . Proposition d'organisation des recherches

a) Etudes préliminaires qui pourraient être faites en Afrique ou Europe.

b) Mise au point technique qui nécessiterait obligatoirement la construction d'une unité pilote en Afrique.

5. Conclusion

Une étude économique montre que, pour une augmentation du prix du produit de l'ordre de 1 % on peut

ainsi espérer éliminer des pertes qui s 'élèvent à plusieurs dizaines de pour cent.

Д Е З И Н С Е К Ц И Я А Ф Р И К А Н С К О Й СУШЕНОЙ И КОПЧЕНОЙ Р Ы Б Ы С Р Е Д С Т В А М И О Б -Л У Ч Е Н И Я . 1 . П р о б л е м а с о х р а н е н и я вяленой и копченой рыбы

Р ы б н а я л о в л я в п р е с н ы х в о д а х я в л я е т с я с а м ы м в а ж н ы м источником получения про -т е и н о в в А ф р и к е . Свыше 100 000 т рыбы м о ж н о в ы л о в и т ь и продать в б а с с е й н е Н и г е р а и 150 000 т - в б а с с е й н е Ч а д а . Н а к о н е ц , в я л е н а я и к о п ч е н а я р ы б а в ы в о з и т с я в о в с е с т р а н ы Ч е р н о й А ф р и к и . В р е д н ы е н а с е к о м ы е у н и ч т о ж а ю т с в ы ш е 30% э т о й р ы б ы в е е в е с о в о м в ы р а ж е н и и . Никакой "обычный" м е т о д борьбы не дал еще практического р е з у л ь т а т а . 2 . Проведенные опыты

Во Франции была проведена с е р и я облучений д о з а м и 20 000 , 100 000 и 5 lUOOO р а д . Ь ы л у с т а н о в л е н порядок величин л е т а л ь н ы х и с т е р и л и з у ю щ и х д о з , и при э т о м не наблюдалось к а -к и х - л и б о о р г а н о л е п т и ч е с к и х и з м е н е н и й при 500 000 р а д . 3 . П е р е ч е н ь еще н е о б х о д и м ы х и с с л е д о в а н и й

Они коснулись бы э н т о м о л о г и и , определения практической д о з ы , питательности , у п а к о в -ки и э к о н о м и ч е с к о г о а н а л и з а . Вопрос об их о б ъ е м е не п р е д с т а й л я е т с я с у щ е с т в е н н ы м , е с л и , о д н а к о , при э т о м будут и с к л ю ч е н ы п р о б л е м ы п о л е з н ы х с в о й с т в и с ъ е д о б н о с т и (в отношении к о т о р ы х у ж е получены в е с ь м а п о л о ж и т е л ь н ы е р е з у л ь т а т ы , в ч а с т н о с т и , в отношении р ы б ы , облученной д о з а м и , з н а ч и т е л ь н о превышающими 15 0 0 0 - 4 0 000 рад , к о т о р ы е , в е р о я т н о , были бы н е о б х о д и м ы м и в данном с л у ч а е ) . 4 . Предложение в отношении проведения исследований

- П р е д в а р и т е л ь н ы е и с с л е д о в а н и я , к о т о р ы е м о г л и бы б ы т ь п р о в е д е н ы в А ф р и к е или Е в р о п е .

- Т е х н и ч е с к а я р а з р а б о т к а , к о т о р а я о б я з а т е л ь н о п о в л е к л а бы з а собой с т р о и т е л ь с т в о опытной у с т а н о в к и в А ф р и к е .

5 . З а к л ю ч е н и е Экономическое изучение п о к а з ы в а е т , что при увеличении стоимости продукта приблизи-

т е л ь н о на 1% м о ж н о н а д е я т ь с я на у с т р а н е н и е п о т е р ь , к о т о р ы е в ы р а ж а ю т с я н е с к о л ь к и м и д е -с я т к а м и п р о ц е н т о в . '

EXPERIENCES PRELIMINARES SOBRE LA RADIODESINSECTACION DE PESCADOS SECOS Y AHUMADOS EN AFRICA. 1. El problema de la conservaciôn de los pescados secos y ahumados

La pesca de agua dulce es una de las fuentes m äs importantes de proternas en Afr ica . En la cuencai d e l Niger se comercia l izan mâs de 100 000 t de pescado y mâs de 150 000 t en la del Tchad. Estos pescados se secan о ahûman y se exportan seguidamente a toda el Africa negra, pero son atacados por insectos parâsitos

que destruyen mâs de l 30% en peso. Hasta ahora no ha dado resultados ningûn medio de lucha « clâsico » .

2 . Experiencias de irradiaciones efectuadas

En Francia se ha Uevado a cabo una serie de irradiaciones con dosis de 20000, 100 000 y 500 000 rad.

Se ha determinado el orden de magnitud de las dosis letales y esterilizantes, y no se ha observado modificàciôn

organoléptica alguna a 500 000 rad.

3. Relaciôn de los estudios aun necesarios.

Afin quedan por hacer estudios sobre entomologîa, determinaciân de la dosis prâctica, poder nutritivo,

embalajes y anâlisis econômico; su amplitud no es importante, si se exceptûan los que se refieren a problemas

de salubridad y de comestibilidad (para los que, por otra parte, se han obtenido ya resultados muy favorables

con pescados sometidos a dosis muy superiores a las de 15 000 a 40 000 rad que serîan probablemente nece-

sarias en este caso).

4. Propuesta de organizaciôn de las investigaciones

a ) Estudios preliminares que podrîan realizarse en Africa о en Europa. b) Perfeccionamiento técnico que exigiria la construcciôn de una planta piloto en Africa.

DISINSECTIZATION OF AFRICAN DRIED AND SMOKED FISH 87

5. Conclusi6n Un estudio econdmico muestra que con un aumento del precio del producto del orden del 1% se podrîan

él iminai pérdidas que pueden llegai a set de mâs del 30%.

I . THE P R O B L E M O F CONSERVING DRIED AND SMOKED FISH

Marketable quantities

U n d e r e x i s t i n g a r r a n g e m e n t s , i t i s d i f f i c u l t t o m a k e a n y e s t i m a t e of p r o d u c t i o n . P r e s e n t output i s p laced at about 100 000 t of f r e s h f i sh fo r Mali , and a t m o r e t h a n 150 000 t f o r C h a d . D r y i n g o r s m o k i n g r e d u c e s the weight of t he f i s h by about one q u a r t e r . The quan t i ty put on the m a r k e t i s a l so d i f -f i cu l t to e s t i m a t e , s i n c e the e x t r e m e l y compl i ca t ed and s c a t t e r e d d i s t r ibu t ion n e t w o r k m a k e s it v e r y d i f f i c u l t to c o m p i l e s t a t i s t i c s . F o r e x a m p l e , n e a r l y 20 000 t f r o m Chad a r e sa id to be m a r k e t e d in N i g e r i a , the C e n t r a l A f r i c a n R e p u b l i c and C a m e r o o n .

E x p o r t s f r o m Mal i a r e m a i n l y to Ghana and the I v o r y Coas t ; the quan t i -t i e s m a r k e t e d a r e s u p p o s e d to e x c e e d 15 000 t f o r a p r o d u c t w h o s e i n i t i a l p r i c e v a r i e s , d e p e n d i n g on the s p e c i e s , b e t w e e n 1 and 3 F r e n c h f r a n c s p e r k i l o g r a m . 1960 s t a t i s t i c s ind ica te an expor t t r a d e f i g u r e of 30 mi l l ion f r a n c s .

T h e s t a t i o n a t Mop t i in M a l i m a r k e t s about 12 0 0 0 - 1 5 000 t of d r i e d o r s m o k e d f i s h , and c u r r e n t e s t i m a t e s po in t t o the p r o c e s s i n g of 70 t / d in the n e a r f u t u r e . T h i s p r o d u c t i o n of f i sh , a s b a s i c to the food n e e d s of the popu-l a t i o n a s m e a t , h a s the a d v a n t a g e of invo lv ing n e i t h e r d a m a g e to vege t a t i on n o r l o s s of so i l f e r t i l i t y . N u m e r o u s e f f o r t s a r e now being made to develop i t .

Damage occurring

At p r e s e n t only d r i e d o r s m o k e d f i s h can be m a r k e t e d . The i m p e r f e c t d e v e l o p m e n t of p a c k a g i n g and the p o o r q u a l i t y of c o n s e r v a t i o n f r o m i n s e c t d a m a g e a r e v e r y h a r m f u l to t h i s t r a d e ; t he h i g h - q u a l i t y p r o d u c t i s a l m o s t i n v a r i a b l y a t t a c k e d by h a r m f u l i n s e c t s wh ich c a u s e l o s s e s , s o m e t i m e s v e r y c o n s i d e r a b l e , d u r i n g t r a n s p o r t and s t o r i n g and b e f o r e c o n s u m p t i o n . Aga in v e r y f ew s t a t i s t i c s a r e a v a i l a b l e , bu t we c a n e s t i m a t e t h e l o s s a s a t l e a s t 2 5 - 3 0 % b y w e i g h t , a n a l a r m i n g f i g u r e c o n s i d e r i n g t h a t n e i t h e r t h e b o n e s n o r the skin a r e a f f e c t e d . L o s s of n u t r i t i v e value i s t h e r e f o r e 1 . 2 - 1 . 5 t i m e s t h i s f i g u r e . I t shou ld be p o i n t e d out t h a t t he M a l i a u t h o r i t i e s e s t i m a t e the t o t a l w e i g h t l o s s a s . b e t w e e n 40 - 50%.

V a r i o u s m e t h o d s have been t r i e d in the pa s t to comba t this p rob lem, with no p r a c t i c a l r e s u l t f r o m t h e i r u s e :

(a) B e t t e r d r y i n g (use of an i n f r a - r e d tunnel) (b) Act ion of hea t (50-60°C) (c) F u m i g a t i o n u n d e r v a c u u m w i t h m e t h y l b r o m i d e o r e t h y l e n e ox ide (d) A p p l i c a t i o n of i n s e c t i c i d e s d i r e c t t o t h e f i s h . In any c a s e , the f i s h cannot r e m a i n in tac t fo r s e v e r a l months a f t e r t r e a t -

m e n t u n l e s s , of c o u r s e , i t i s p r o t e c t e d f r o m f r e s h in fe s t a t i on .


II . RADIATION E X P E R I M E N T S CARRIED OUT TO DATE

Organization of the tests

T h e f i r s t s e r i e s of s t u d i e s w a s m a d e a l i t t l e o v e r a y e a r a g o . It w a s a i m e d a t c o n f i r m i n g the a d v a n t a g e s of the r a d i a t i o n p r o c e s s and a t d e m o n -s t r a t i n g t h a t i n d o s e s l i k e l y to b e u s e d in d i s i n s e c t i z a t i o n , i r r a d i a t i o n i n -v o l v e d no c h a n g e in the o d o u r and f l a v o u r of t h e p r o d u c t .

A b o u t 10 kg of f i s h , i . e . s o m e 50 d r i e d and s m o k e d f i s h of f i v e d i f -f e r e n t s p e c i e s found on the m a r k e t in Mopti , sub jec t to m o r e o r l e s s s e r i o u s i n s e c t a t t a c k s of D e r m e s t e s and N e c r o b i a , w e r e sent to F r a n c e by the Mopti Hydrob io logy L a b o r a t o r y , t hanks to the good o f f i c e s of D r . Daget . The c o n -s ignmen t , which went by a i r , cons i s t ed of the fol lowing s p e c i e s :

(a) M o r m y r i d a e , d r i e d (b) T i l ap ia , d r i e d (c) L a r g e L a t e s (g ros l a t e s ) , d r i e d (d) L a b e o * and l a r g e L a t e s , smoked (e) C l a r i a s , s m o k e d . F o r r e a s o n s of conven ience in handl ing du r ing i r r a d i a t i o n , each f i sh was

p l a c e d in a s m a l l p o l y e t h y l e n e b a g s e a l e d a t bo th ends ; e a c h b a g c o n t a i n e d e i t h e r a whole m e d i u m - s i z e d f i s h (with i t s head and t a i l cut off if n e c e s s a r y ) o r a p i ece of a l a r g e f i s h . P o l y e t h y l e n e w a s chosen a s being both a s t anda rd packag ing m a t e r i a l f o r f o o d s t u f f s and one which r e s i s t s h igh r a d i a t i o n d o s e s r e l a t i v e l y w e l l .

T h r e e b a g s conta in ing two d r i e d M o r m y r i d a e and one d r i ed T i l ap i a w e r e k e p t a s c o n t r o l s . A l l t h e o t h e r b a g s w e r e d iv ided in to t h r e e b a t c h e s , e a c h con ta in ing a l l t he f ive s p e c i e s l i s t e d . T h e s e w e r e i r r a d i a t e d in the sh i e lded g a m m a c h a m b e r f o r f u e l e l e m e n t s of t he E L - 3 r e a c t o r of the C o m m i s s a r i a t à l ' é n e r g i e a t o m i q u e . T h r e e e x p o s u r e d o s e s w e r e used : 20 000, 100 000 and 500 000 r a d . Owing to v a r i o u s c a u s e s of e r r o r , t he a c c u r a c y of t h e s e v a l u e s can be g u a r a n t e e d to w i th in only about 15%, which w a s adequa te f o r the p u r p o s e .

T h e f i s h w e r e t h e n f l own b a c k to M o p t i . M o s t of t h e m r e m a i n e d in the unopened p l a s t i c p a c k s ; s o m e of the b a g s , h o w e v e r , had b e e n opened , and the f i s h r e m o v e d and p l a c e d in k r a f t p a p e r e n v e l o p e s . The p u r p o s e of t h i s w a s to r e v e a l the s o u r c e of a n y c h a n g e s in odour which a r o s e e i t h e r th rough p u t r e f a c t i o n o r m o u l d i n e s s of f i s h which had not b e e n c o m p l e t e l y d e h y d r a t e d , p r by d e c o m p o s i t i o n of the p l a s t i c u n d e r the h i g h e s t r a d i a t i o n d o s e s .

W h e n the f i s h a r r i v e d a t Mop t i , 15 d a f t e r i r r a d i a t i o n , t h e y w e r e i m -m e d i a t e l y e x a m i n e d and s u b j e c t e d to an o r g a n o l e p t i c c h e c k . The f u l l - g r o w n i n s e c t s and l a r v a e which w e r e s t i l l a l i ve w e r e s y s t e m a t i c a l l y sought out and r e a r e d .

Organoleptic results

The e x p o s u r e of food t o h igh d o s e s of i on iz ing r a d i a t i o n t e n d s to c a u s e o r g a n o l e p t i c c h a n g e s which b e c o m e m o r e p r o n o u n c e d a s the d o s e i s i n c r e a s e d , and which v a r y a c c o r d i n g t o the type of p r o d u c t .

* Fish of the family Cyprinidae


N u m e r o u s t e s t s h a v e b e e n m a d e in r e c e n t y e a r s on v a r i o u s f o o d s t u f f s ; p a r t i c u l a r m e n t i o n i s m a d e of the c a s e of f r e s h f i s h , a p r o d u c t which i s e s -p e c i a l l y s e n s i t i v e f r o m the o r g a n o l e p t i c point of v i e w . T h e d o s e s f o r which no change i s o b s e r v e d v a r y , depend ing on the s p e c i e s , b e t w e e n 100 000 and 800 000 r a d .

T a s t i n g t e s t s c a r r i e d out at Mopti to c o m p a r e the v a r i o u s f i sh which had b e e n t r e a t e d o r not t r e a t e d , and kept in po lye thy lene b a g s o r r e m o v e d f r o m t h e m , showed tha t t h e r e w a s no d e t e c t a b l e o r g a n o l e p t i c change f o r the f i v e s p e c i e s s tud ied , e v e n f o r a d o s e of 500 000 r a d , which i s a t l e a s t t en t i m e s h i g h e r than any which could be e n v i s a g e d f o r p r a c t i c a l u s e .

T h e t e s t e r s found no c h a n g e in t h e d r i e d M o r m y r i d a e and T i l a p i a , o r t he s m o k e d C l a r i a s , L a b e o and L a t e s ; wi th the d r i e d L a t e s the c o n c l u s i o n s w e r e l e s s c l e a r l y de f ined b e c a u s e of the uneven in i t i a l qua l i ty of the p r o d u c t . C l a s s i f i c a t i o n of qual i ty , in d e c r e a s i n g o r d e r , was a s fo l lows :

No. 41 - s u b j e c t e d to 100 000 r a d and r e m o v e d f r o m the bag No. 42 - s u b j e c t e d to 100 000 r a d and l e f t in the bag No . 43 - sub j ec t ed to 500 000 r a d and r e m o v e d f r o m the bag No. 40 - s u b j e c t e d to 20 000 r a d and l e f t in the bag No . 44 - s u b j e c t e d to 500 000 r a d and le f t in the bag . T h e s e d i f f e r e n c e s in t a s t e m u s t b e a t t r i b u t e d to t h e m e t h o d by w h i c h

d r y i n g w a s c a r r i e d out ; t h e y a r e n o r m a l to a l l t h e b a t c h e s of d r i e d " g r o s l a t e s " now on t h e m a r k e t in Mopt i , and t h e r e i s no r e a s o n to s u p p o s e t h a t i r r a d i a t i o n c h a n g e d a n y t h i n g at a l l .

Entomological results

N u m e r o u s ' tes ts m a d e in r e c e n t y e a r s on v a r i o u s i n s e c t s have shown tha t the d o s e s v a r y o v e r a wide r a n g e depend ing on the s p e c i e s , and a l so on w h e t h e r one i s i n v e s t i g a t i n g inh ib i t ion of the r e p r o d u c t i v e c a p a c i t y o r d e a t h in a g iven pe r iod a f t e r the t r e a t m e n t . In the c a s e of i n s e c t s which a r e c e r e a l p a r a s i t e s , s o m e s p e c i e s a r e c o m p l e t e l y s t e r i l i z e d by 5000 r a d , wh i l e t h e 17 s p e c i e s g e n e r a l l y e n c o u n t e r e d a r e a l l s t e r i l i z e d a t 17 000 o r 20 000 r a d , with an e f f i c i e n c y of c l o s e to 100%.

I m m e d i a t e l y a f t e r i r r a d i a t i o n , n o t h i n g w a s l e f t a l i v e a f t e r t r e a t m e n t a t 500 000 r a d . T h e i n s e c t s s u b j e c t e d t o 100 000 r a d w e r e d e a d o r dy ing ; t h o s e e x p o s e d to 20 000 r a d , h o w e v e r , w e r e s t i l l a l i v e , and on ly s i m i l a r s t u d i e s c a r r i e d out p r e v i o u s l y j u s t i fy the a s s u m p t i o n tha t the adul t s had been s t e r i l i z e d o r the l a r v a e r e n d e r e d i ncapab l e of ach iev ing n y m p h o s i s .

A f t e r t h e b a t c h w a s r e t u r n e d to Mopt i 15 d l a t e r , c a r e f u l s tudy showed t h a t t h e only s u r v i v o r s of t he b a t c h wh ich had b e e n s u b j e c t e d to 100 000 r a d w e r e one D e r m e s t e s a d u l t , one D e r m e s t e s l a r v a and one N e c r o b i a l a r v a . A l a r g e r n u m b e r of l i v e a d u l t s and l a r v a e w e r e found on o p e n i n g s o m e of the b a g s exposed to 20 000 r a d , a l though in o t h e r s t h e r e w e r e no s u r v i v o r s .

T h e i n s e c t s found a l i v e w e r e r e a r e d in the l a b o r a t o r y . The two l a r v a e and t h e adu l t which had r e c e i v e d 100 000 r a d d ied qu i te soon . T h o s e wh ich h a d r e c e i v e d 20 000 r a d r e m a i n e d a l i v e f o r p e r i o d s of v a r y i n g l e n g t h , bu t t h e r e w a s no i n d i c a t i o n of e g g - l a y i n g o r of d e v e l o p m e n t of the l a r v a e . The u n i r r a d i a t e d c o n t r o l s had b e e n d iv ided in to two b a t c h e s f o r r e a r i n g ; one did not d e v e l o p f o r an unknown r e a s o n , whi l e the o t h e r p r o l i f e r a t e d r ap id ly and


w a s in no d a n g e r u n t i l a l l the ed ib le p a r t s of t he f i s h which had b e e n p l aced in t h e r e a r i n g b o t t l e w e r e g o n e .

I I I . STUDIES WHICH ARE S T I L L NECESSARY

B e l o w i s g i v e n a l i s t of t h e m a i n s u b j e c t s on w h i c h s t u d i e s s h o u l d b e u n d e r t a k e n with a view to def in ing m o r e a c c u r a t e l y the condi t ions under which the i r r a d i a t i o n p r o c e s s c an be u s e d f o r p r a c t i c a l p u r p o s e s and in i n d u s t r i a l o p e r a t i o n s . W e h o p e t h i s l i s t i s a s c o m p l e t e a s p o s s i b l e , bu t i t m u s t b e p o i n t e d out t h a t i t h a s not y e t b e e n s u b j e c t e d to a n y d i s c u s s i o n o r c r i t i c a l s tudy by s p e c i a l i s t s in A f r i c a n p r o b l e m s of r a d i a t i o n t echn ique o r e n t o m o l o g i s t s .

E f f e c t of irradiation on insect parasites

T h e p r o b l e m i s to d e t e r m i n e t h e v a r i o u s l e t h a l d o s e s f o r i n s e c t p a r a -s i t e s at t he d i f f e r e n t s t a g e s of t h e i r d e v e l o p m e n t : egg, l a r v a , nymph, adu l t . A s i m i l a r s tudy should be c a r r i e d out with r e s p e c t to s t e r i l i t y .

A s in the c a s e of c e r e a l p a r a s i t e s , t h e r e s e e m s l i t t l e po in t in k i l l i n g a l l the i n s e c t s at once; p r even t i ng t h e i r nymphos i s o r s t e r i l i z i n g t hem should be su f f i c i en t to p r e v e n t m o s t if not a l l of the d a m a g e .

Assessment of the practical dose

F u r t h e r r e s e a r c h would m a k e it p o s s i b l e t o s p e c i f y t h e e x a c t v a l u e of t he d o s e to be app l ied f o r s t e r i l i z a t i o n ; t h i s can f o r the p r e s e n t be e s t i m a t e d a t b e t w e e n 15 000 and 30 000 r a d . Such a s t u d y m i g h t b e c o n d u c t e d in t w o s t a g e s :

(1) D e t e r m i n a t i o n of the c o n d i t i o n s i n which f i s h a r e c o n t a m i n a t e d by i n s e c t s ; d u r a t i o n of s t o r a g e r e q u i r e d ; n u m b e r of g e n e r a t i o n s and t h e i r o v e r l a p ; t i m e at which the t r e a t m e n t should t ake p l a c e ( e i the r in a g iven s e a s o n , o r at the t i m e , f o r e x a m p l e , of en t ry into s t o r a g e o r of d i s p a t c h ) .

(2) A f t e r t h i s s tudy of the " a b s o l u t e " o p e r a t i n g cond i t i ons , i t would be u s e f u l t o d e t e r m i n e , by m e a n s of a p i lo t i n s t a l l a t i o n u s i n g s e m i -i n d u s t r i a l q u a n t i t i e s , t h e e x a c t o p e r a t i n g c o n d i t i o n s u n d e r w h i c h the l o s s e s c a u s e d by i n s e c t s could be a v o i d e d . B a t c h e s of f i s h of d i v e r s e o r ig in , t r e a t e d at d i f f e r e n t t i m e s , could be s tudied in c l ea r ly d e f i n ed c o n d i t i o n s with a v iew to c o m p a r i n g the e f f e c t o b s e r v e d f o r a l l t he p a r a m e t e r s i nvo lved .

Organoleptic studies

The p r e l i m i n a r y s t u d i e s which have a l r e a d y b e e n m a d e s e e m to d e m o n -s t r a t e t h a t t h e r e i s p r a c t i c a l l y no p r o b l e m a s f a r a s c h a n g e i n t a s t e and f l a v o u r i s c o n c e r n e d .


Study of the nutritional value

It i s h ighly i m p r o b a b l e , f o r the d o s e s which can be env i saged a p r i o r i (15 000 to 30 000 rad) , tha t any e f f ec t wi l l be o b s e r v e d , a s p r o t e i n s in p a r -t i c u l a r a r e r e l a t i v e l y r e s i s t a n t to i r r a d i a t i o n . C e r t a i n s t u d i e s m i g h t , if n e c e s s a r y , be conducted to d e t e r m i n e the magni tude of the e f f ec t s obse rved .

Wholesomeness and edibility

T h i s i s an i m p o r t a n t p r o b l e m which, if i n v e s t i g a t e d fu l ly , would l ead to v e r y ex tens ive work and r e s e a r c h . As we a r e not spec i a l i s t s in th is field we should l ike s imply to make the two following r e m a r k s :

(1) The d o s e s would be r e l a t i v e l y low, about t en t i m e s l e s s than those c o n t e m p l a t e d f o r p a s t e u r i z i n g f r e s h f i s h ; n u m e r o u s t e s t s on t h e ed ib i l i ty of i r r a d i a t e d f i sh a r e now in p r o g r e s s in many c o u n t r i e s , in p a r t i c u l a r in the Uni ted S t a t e s of A m e r i c a ; the d o s e s u s e d a r e of the o r d e r of 250 000 to 500 000 r a d ; t h u s f a r no p r o b l e m s have been encoun te red and the United S ta tes Atomic E n e r g y C o m m i s s i o n in tends to r e q u e s t the au tho r i za t i on of the Food and D r u g s A d m i n i -s t r a t i o n f o r m a r k e t i n g c e r t a i n t y p e s of f i s h a f t e r t r e a t m e n t with t h e s e m u c h h i g h e r d o s e s .

(2) It i s highly poss ib le that dr ied and smoked f ish would in their p resen t s t a t e not even be c o n s i d e r e d a s edib le , judged by W e s t e r n t a s t e s , but t h i s i s qui te a d i f f e r e n t p r o b l e m .

Study of packaging

T h e r e would be no point in de s t roy ing the i n s e c t s if subsequent r e -c o n t a m i n a t i o n w a s not a l s o p r e v e n t e d . The u s e of s e a l e d p a c k a g i n g d o e s not s e e m d e s i r a b l e , and c e r t a i n t e s t s wil l have to be m a d e on a s e m i -i n d u s t r i a l s c a l e so t h a t t he e n t i r e p r o c e s s m a y be m a d e p r a c t i c a b l e ( fo r example , s p r a y i n g in sec t i c ide into the mat t ing used at p r e s e n t , use of s u i t -ably d i s in f ec t ed w a r e h o u s e s , e t c ) .

Economic analysis

P a r a l l e l to the p r e c e d i n g s t ud i e s and a s soon a s the dose to be appl ied h a s b e e n d e t e r m i n e d , a p r e l i m i n a r y p lan and then a cos t ing p r o j e c t f o r i n -d u s t r i a l ins ta l la t ion will be d rawn up, so a s to p e r m i t a s s e s s m e n t of the cost of the t r e a t m e n t and ana ly s i s of i t s economic des i r ab i l i t y , with an indication of the changes in p r e s e n t c o m m e r c i a l p r a c t i c e which it wil l involve.

We should indica te , however , that , a s shown by the Annex to this paper , t he p r e l i m i n a r y a s s e s s m e n t s which can now be m a d e show the a d v a n t a g e s of t h i s t y p e of t r e a t m e n t . F o r a p r o d u c t p r i c e - i n c r e a s e of l e s s t h a n 1%, t h e r e i s r e a s o n to hope tha t l o s s e s which a r e f r e q u e n t l y in e x c e s s of 10% can be e l i m i n a t e d . A sol id b a s i s shou ld be p r o v i d e d f o r such a t e s t of the e c o n o m i c s of the p r o c e d u r e .


I V . P R O P O S A L S F O R ORGANIZING R E S E A R C H

With the s u b m i s s i o n of a p r o v i s i o n a l l i s t of r e s e a r c h p r o j e c t s to be u n d e r t a k e n , the ques t ion a r i s e s of how it should be o r g a n i z e d . The preced ing e n u m e r a t i o n shows that two s t a g e s can be d i s t i ngu i shed .

Preliminary studies

T h e s e would involve the t r e a t m e n t of s m a l l a m o u n t s and p e r m i t a s s e s s -m e n t of r e s u l t s now b e i n g o b t a i n e d . T h e s e s t u d i e s and the i r r a d i a t i o n i n -v o l v e d cou ld b e c a r r i e d out i n a E u r o p e a n c o u n t r y o r , p e r h a p s p r e f e r a b l y , in an i n s t i t u t e s i t ua t ed in A f r i c a , even if i t s equ ipment w e r e v e r y r u d i m e n t a r y ( s i m p l i f i e d g a m m a ce l l , f o r e x a m p l e ) .

Technical development

T h i s i s t h e s e c o n d s t a g e of the r e s e a r c h , t he m o s t c o s t l y and the only o n e i n w h i c h t e c h n o l o g i c a l d i f f i c u l t i e s w o u l d b e l i k e l y t o a r i s e , s i n c e t h e u s e of i r r a d i a t i o n f o r t he d i s i n s e c t i z a t i o n of f i s h g ives r i s e to c e r t a i n p r a c -t i c a l p r o b l e m s , in p a r t i c u l a r t h a t of p a c k a g i n g , which c a n only be r e s o l v e d by the c o n s t r u c t i o n of a p i lo t p l an t . With s u c h a p lan t e x p e r i m e n t s could be c a r r i e d out to d e t e r m i n e i r r a d i a t i o n p r o c e d u r e s and the b e s t way of handl ing and cond i t ion ing the p r o d u c t s .

If p a r a l l e l s t u d i e s could be conduc ted on p r o d u c t s o t h e r t h a n d r i e d and s m o k e d f i s h ( f r u i t , f r e s h f i s h , e t c . ) , t h i s p i lo t i n s t a l l a t i o n cou ld a l s o b e u s e d f o r t h o s e p r o d u c t s w h i c h a p p e a r e d m o s t p r o m i s i n g .

L a s t l y , a c o m p r e h e n s i v e e c o n o m i c s t u d y could be m a d e to d e f i n e p r e -c i s e l y the o v e r a l l a d v a n t a g e s of applying t h i s new p r o c e s s to the c o n s e r v a t i o n of f i s h .

V . CONCLUSION

T h i s p a p e r h a s d e s c r i b e d t h e r e s u l t s o b t a i n e d in a p r e l i m i n a r y s e r i e s of t e s t s on t h e d i s i n s e c t i z a t i o n of A f r i c a n d r i e d and s m o k e d f i s h by m e a n s of t r e a t m e n t wi th i o n i z i n g r a d i a t i o n . T h e p r o m i s i n g e n t o m o l o g i c a l and o r -g a n o l e p t i c r e s u l t s o b t a i n e d show tha t t h i s i s v e r y p r o b a b l y a v a l u a b l e t e c h -n i q u e . The s t u d i e s , which have h i t h e r t o b e e n m a d e on a v e r y m o d e s t budget , s h o u l d b e c o n t i n u e d and f o r m p a r t of a c o n c e r t e d p l a n of a c t i o n . T o t h i s e n d i t i s e s s e n t i a l t h a t t h e d e v e l o p i n g c o u n t r i e s s h o w a n a w a r e n e s s of t h e o p p o r t u n i t i e s f o r . t h e i r r e s p e c t i v e e c o n o m i e s t o t a k e a d v a n t a g e of c e r t a i n o p e r a t i o n s involv ing a t o m i c e n e r g y which a r e not i n c o m m e n s u r a t e with t h e i r m e a n s .


ANNEX

SCALE O F COSTS FOR IRRADIATION T R E A T M E N T

This discussion is based on the assumption of an industrial installation meet ing the following require-ments, which may be regarded as representing a reasonable order of magnitude and as taking into account the present level of developments in technology:

1 Quantity to be treated: we assumed the t reatment of 25 000 t /y r (or 3 t / h ), with the plant operating 24 h a day, 7 d a week and 50 weeks a year. This quantity corresponds to an amount which could conceivably be treated at Mopti in the near future. As a variant on this, a capacity of 14 000 t/уг has also been considered; this is the amount treated at present.

Dose applied: two values were considered; first, that of 30 000 rad which is probably an unfavourable hypothesis, and secondly, that of 17 000 rad, which is similar to that proposed for removing insects from cereals.

Radiation yield: we assumed that a yield of 20% could be obtained if cobalt were used, given the geo-metric shape of the packets of fish to be treated; we also considered a yield of 15%, which should represent a min imum.

Cost of cobalt: this was assumed as Ffr. 5 per curie (US $1 per curie) including delivery. Maintenance: the annual plant main tenance costs (not including the cobalt) were estimated as 2% of

the init ial investment.

1. UNFAVOURABLE ASSUMPTION

14 000 t /yr; 30 000 rad; yield 15%

Investment (all amounts in French francs)

Buildings and indoor installations 800 000 Cobalt source (62 000 Ci) 310 000

fr. 1110 000

Annual opera ring cost

Depreciation (over 10 yr) I l l 000 Interest (4% per annum) 25 000 Consumable materials, e lectr ici ty 10 000 Maintenance 11000 Personnel (handling) 10 000 Management (par t - t ime) 25 000 Replacement of cobalt (15% per annum) 47 000 Additional for packaging 20 000

fr. 259 000

i. e . a t reatment cost of fr. 18 per ton.

2. FAVOURABLE ASSUMPTION

25 000 t /yr ; 17 000 rad; yield 20%

Investment

Buildings and installations 800 000 Cobalt source (48 000 Ci) 240 000

fr . 1040 000


Operating cost

A similar calculat ion gives fr. 215 000

i . e . a treatment cost of fr. 9 per ton.

3. COMPARISON WITH THE PRICE OF FISH

The two figures quoted above for the cost of treatment must be compared with the price of the fish at the different stages of marketing (see Table below).

TABLE

P R I C E O F F O U R T Y P E S O F F I S H A T D I F F E R E N T M A R K E T I N G S T A G E S

Price (Ffr. ) of fish:

Dried Dried Smoked Smoked Mormyr idae Ti lap ia Clar ias Capi ta ines

Purchase p r i ce f rom t h e f ishermen in the compounds 400-800 400-1000 1200-1600 800-1800

Purchase p r ice at t he shop in Mopti 1300 800-1600 1000-2600 2600

Sa le pr ice to the cus tomer on the Ivory Coast 3000-5000 6000 4800 6000

CLOSTRIDIUM BOTULINUM, TYPE E, IN RELATION TO IRRADIATION TREATMENT OF FRESH FISH, WITH SPECIAL REFERENCE

TO TROPICAL CONDITIONS

K. ABRAHAMSSON AND N. MOLIN

SWEDISH INSTITUTE OF FOOD PRESERVATION RESEARCH

GÔTEBORG, SWEDEN

AND

N . N . DE SILVA

THE FISHERIES RESEARCH STATION, COLOMBO, CEYLON


CLOSTRIDIUM BOTULINUM, TYPE E, IN RELATION TO IRRADIATION TREATMENT OF FRESH FISH, WITH SPECIAL REFERENCE TO TROPICAL CONDITIONS. The work reported concerns a study of the effect of radiation treatment on fresh fish packed in polythene, with and without vacuum, in relation to the normal spoilage.flora. The experiments performed, the methods used and the results obtained are presented. The results show that vacuum packing of fish inoculated with CI. botulinum increased the strength of the toxin formed in the initial stage of storage. However, upon prolonged storage at 20° С about the same amount of toxin was found in samples packed in air, indicating little advantage to vacuum packing of fish. Results at various'irradiation dose levels are given in a table.

TRAITEMENT PAR IRRADIATION DU POISSON FRAIS, EN CE QUI CONCERNE CLOSTRIDIUM BOTULINUM E, EN PARTICULIER DANS DES CONDITIONS TROPICALES. Le mémoire décrit des études sur l 'effet de l'irradiation sur du poisson frais enveloppé de polythÈne, sous vide ou non, notamment en ce qui concerne la flore microbienne qui provoque habituellement son altération. L'auteur expose les expériences faites, les méthodes appliquées et les résultats obtenus. Ces résultats montrent que l'emballage sous vide de poisson infesté par Cl. botulinum E a pour effet d'augmenter la nocivité de la toxine formée au stade initial du stockage. Cependant, après un long stockage à 20°C environ, on a trouvé la même quantité de toxine dans les échantillons emballés sous air, ce qui indique que l'emballage du poisson sous vide n'offre que peu d'avantages. Ún tableau donne les résultats obtenus pour différentes doses d'irradiation.

CLOSTRIDIUM BOTULINUM, ТИП E , И ЕГО РОЛЬ В ОБРАБОТКЕ СВЕЖЕЙ РЫБЫ О Б -ЛУЧЕНИЕМ С АКЦЕНТИРОВАНИЕМ ОСОБОГО ВНИМАНИЯ НА ТРОПИЧЕСКИХ УСЛОВИЯХ. Освещаются вопросы изучения воздействия радиационной обработки свежей рыбы, упакованной в политен, с вакуумом и без него, в связи с обычной неблагоприятной флорой. Приводятся сведения о проведенных экспериментах, использованных методах и о полученных рёзультатах. Результаты показывают, что вакуумная упаковка рыбы с добавлением .Cl, botulinum увели-чивает силу токсина, образовавшегося в первоначальной стадии хранения, однако при длитель-ном хранении при температуре в 20°С в образцах, упакованных с воздухом, было обнару-жено то же самое количество токсина, что указывает лишь на небольшие преимущества ва-куумной упаковки рыбы. В таблице приводятся результаты различных уровней дозы облучения.

CLOSTRIDIUM BOTULINUM. DEL TIPO E, EN RELACION CON EL TRATAMIENTO TOR IRRADIACION DE PESCADO FRESCO, ESPECIALMENTE ËN CLIMAS TROPICALES. El autor describe los trabajos realizados para estudiar los efectos de la irradiación sobre el pescado fresco empaquetado en bolsas de polietileno al vacío o no, en relación con la flora destructiva corriente. La memoria explica los experimentos hechos, los métodos seguidos y los resultados finales; estos últimos muestran que si se embala pescado al vacío después de inocu-larle Cl. botulinum, aumenta la potencia de la toxina formada en la fase inicial del almacenamiento. Sin embargo, después de un período prolongado de almacenamiento a 20"C se encontró aproximadamente la misma cantidad de toxina en las muestras embaladas sin hacer el vacío, lo que indica que prácticamente no vale la

95

96 ABRAHAMSSON et al .

репа de recurrir al sistema de empaquetado al vacxo. Los resultados obtenidos a diversos nivelés de irradiacidn figuran en un cuadro.,

I N T R O D U C T I O N

T h e n e e d to i n t r o d u c e new m e t h o d s of food p r e s e r v a t i o n t echno logy into deve lop ing c o u n t r i e s wi th in the t r o p i c a l be l t a r i s e s f r o m the rap id ly changing p a t t e r n of s o c i a l and e c o n o m i c c o n d i t i o n s in t h e s e c o u n t r i e s . It i s a l s o f u r t h e r e m p h a s i z e d b y t h e f a c t t h a t s o m e t i m e s t r a d i t i o n a l m e t h o d s of food h a n d l i n g a r e , in t h i s r e g i o n , not e a s y t o a p p l y .

I r r a d i a t i o n a s a m e a n s of p r e s e r v i n g p e r i s h a b l e f o o d s h a s , h o w e v e r , c e r t a i n a d v a n t a g e s w h i c h m i g h t m a k e t h i s p r e s e r v a t i o n t e c h n i q u e u s e f u l in t h e t r o p i c s .

T h e p r o m i s i n g r e s u l t s r e p o r t e d by R h o d e s [1] f r o m f e a s i b i l i t y s t u d i e s of p a s t e u r i z a t i o n of f i s h b y i o n i z i n g r a d i a t i o n u n d e r m a r k e t i n g c o n d i t i o n s in the United Kingdom a r e i n t e r e s t i n g in t h i s connect ion , a s ra t iona l handling a n d p r e s e r v a t i o n of f r e s h f i s h a r e of v i t a l i m p o r t a n c e f o r m a n y of t h e d e -ve lop ing c o u n t r i e s . H o w e v e r , t he i n t roduc t i on of packing in connect ion with i r r a d i a t i o n t r e a t m e n t n e c e s s a r i l y i n t r o d u c e s a s e t of s p e c i a l c i r c u m s t a n c e s , e s p e c i a l l y f o r g r o w t h of C l o s t r i d i a , which i s f o r t he p r e s e n t t i m e not v e r y w e l l u n d e r s t o o d . T h i s i m p l i c a t i o n shou ld b e e v a l u a t e d a l s o in v i e w of t h e f a c t t h a t a d e q u a t e c o n t r o l of t e m p e r a t u r e d u r i n g s t o r a g e m i g h t be m o r e d i f -f i c u l t t o a c h i e v e i n t h e t r o p i c s t h a n in t e m p e r a t e a r e a s . In a ho t c l i m a t e with d i f f e r e n t r aw m a t e r i a l s t he e f f e c t of s ea l i ng and eventua l ly vacuum pack-i n g in c o m b i n a t i o n wi th i r r a d i a t i o n m i g h t a l s o g ive r i s e to m i c r o b i o l o g i c a l c h a n g e s w h i c h a r e d i f f e r e n t to t h o s e o b s e r v e d in t e m p e r a t e a r e a s .

T h e w o r k r e p o r t e d h e r e i s a n a t t e m p t t o s t u d y t o x i n p r o d u c t i o n by C l o s t r i d i u m b o tu l i num, type E , in f i s h packed in po ly thene , with and without v a c u u m , in r e l a t i o n to the n o r m a l spo i l age f l o r a and the e f f e c t of i r r a d i a t i o n in c o n t r o l l i n g i t .

METHODS

1. Toxin production in fish fillets

C l o s t r i d i u m b o t u l i n u m , t y p e E ( s t r a i n 1537 o b t a i n e d f r o m D r . A . J o h a n n s e n , P u b l i c H e a l t h A u t h o r i t y L a b o r a t o r y , Lund , Sweden) , w a s u s e d a s t h e i n o c u l u m . A s p o r e s u s p e n s i o n of t h i s o r g a n i s m i n a c o n c e n t r a t i o n of 10®/ml in a 0 . 8 % s o l u t i o n of s o d i u m c h l o r i d e w a s p r e p a r e d and u s e d t o i n o c u l a t e t h a w e d h e r r i n g f i l l e t s o b t a i n e d f r o m c o m m e r c i a l l y f r o z e n p a c k s . T h e f i l l e t s w e r e put in l a m i n a t e d p o l y t h e n e b a g s . E a c h f i l l e t w e i g h i n g a p -p r o x i m a t e l y 30 g r e c e i v e d 1 m l of t h e s p o r e s u s p e n s i o n . Two i n o c u l a t e d f i l l e t s w e r e p a c k e d in e a c h b a g , t h e i n o c u l a t e d i n s i d e f a c i n g e a c h o t h e r . T h r e e s e t s of p a c k e t s c o n t a i n i n g i n o c u l a t e d f i s h f i l l e t s w e r e p r e p a r e d , n a m e l y i n o c u l a t e d - v a c u u m p a c k e d , i n o c u l a t e d and p a c k e d w i thou t v a c u u m , and i n o c u l a t e d and p a c k e d w i thou t s e a l i n g . In ad d i t i o n c o n t r o l p a c k s w e r e p r e p a r e d , o n e s e t v a c u u m p a c k e d a n d t h e o t h e r p a c k e d w i t h o u t v a c u u m .

CL. BOTULINUM AND IRRADIATION TREATMENT 97

All the packs w e r e incubated a t 20°C and sampl ing was done on a l l types of t r e a t m e n t a f t e r 24, 48 and 72 h incubat ion a t 20°C.

2. Toxin assay

Toxin product ion in f i sh m u s c l e was t e s t ed f r o m an ex t r ac t of the m u s c l e by b lending the con ten t s of e a c h packe t with 60 m l of a 0 .8% NaCl .solut ion. T h e b l ended s a m p l e s w e r e he ld a t +4°C f o r 4 h . L a t e r 10 m l of t he N a C l so lu t ion w e r e added and t h e s a m p l e s c e n t r i f u g e d t w i c e a t 4500 r p m .

T o x i c i t y of t he m u s c l e e x t r a c t s w a s d e t e r m i n e d by i t s e f f e c t on m i c e a f t e r i n t r a p e r i t o n e a l i n j e c t i o n . E a c h m o u s e (16-18 g) r e c e i v e d 0 . 5 m l of t he e x t r a c t , t h r e e m i c e be ing i n o c u l a t e d wi th e a c h s a m p l e . A f t e r i n o c u -l a t i o n t h e m i c e w e r e o b s e r v e d o v e r 48 h .

The m e a n le tha l dose (MLD) was calculated f r o m a s tandard curve prev i -o u s l y ob ta ined showing the r e l a t i o n s h i p be tween tox in c o n c e n t r a t i o n and s u r v i v a l t i m e of m i c e a f t e r inocu la t ion with d i lu t ions of the toxin p r o d u c e d by the p a r t i c u l a r type E s t r a i n u s e d in the e x p e r i m e n t ( s e e F i g . 1).

In v i t r o tox in n e u t r a l i z a t i o n u s ing equa l v o l u m e s of f i sh e x t r a c t and type E a n t i - s e r u m di luted 1 : 10 with phys io logica l sa l ine and inoculated into m i c e ac ted a s c o n t r o l s .

MEAN LETHAL DOSE (MLD)

FIG. 1. Survival time for mice after intraperitoneal injection with dilutions of Clostridium botulinum, type E, toxin

3. Irradiation experiments

Two s e t s of f i l l e t s one of which was inoculated with the spore suspension a t a l e v e l of 2 X 10® p e r 60 g of m u s c l e , w e r e v a c u u m p a c k e d in po ly thene bags a s p r e v i o u s l y d e s c r i b e d and i r r a d i a t e d with a d o s e of 0 . 1 , 0 . 3 and 0 . 6 M r a d f r o m a 60Co s o u r c e ( G a m m a c e l l - 2 2 0 , A t o m i c E n e r g y of Canada L t d . ) . T o g e t h e r with c o n t r o l p a c k s which w e r e not i r r a d i a t e d , t hey w e r e i n c u b a t e d a t 20°C and e x a m i n e d f o r tox in p r o d u c t i o n a f t e r 40 h .

4. Bacteriology

B a c t e r i a l counts w e r e done on r e p r e s e n t a t i v e packs of a l l types of t r e a t -m e n t u s i n g Di fco n u t r i e n t a g a r in p o u r - p l a t e s . The p l a t e s w e r e incuba ted a e r o b i c a l l y a t 20°C and colonies w e r e counted a f t e r five d a y s . To d e t e r m i n e

98 ABRAHAMSSON et al .

t h e d i f f e r e n c e s i n t h e b a c t e r i a l f l o r a , c o l o n i e s w e r e p i c k e d u p a t r a n d o m f r o m e a c h s e t of c o u n t s f r o m t h e d i f f e r e n t t y p e s of t r e a t m e n t . T h e y w e r e c l a s s i f i e d u s i n g t h e c r i t e r i a d e f i n e d b y S h e w a n , H o b b s and H o d g k i s s [2] .

R E S U L T S

1. Toxin production experiments

In a l l i nocu l a t ed s a m p l e s toxin w a s p r o d u c e d be tween 24- and 48-h incu-b a t i o n a t 20°C. In v a c u u m - p a c k e d f i l l e t s which w e r e i n o c u l a t e d , m a x i m u m l e v e l s of t o x i n w e r e f o r m e d a f t e r 48 h , b u t t h e l e v e l s d e c r e a s e d s l i g h t l y a f t e r 72 h . In f i l l e t s p a c k e d without v a c u u m , tox in a p p e a r e d to be p roduced m o r e s l o w l y and t h e t o x i n l e v e l o b t a i n e d a f t e r 72 h w a s no t v e r y d i f f e r e n t f r o m tha t o b t a i n e d a f t e r 48 h . In i nocu l a t ed f i l l e t s packed in po ly thene bags wi thout s e a l i n g , t h e l e v e l of tox in a f t e r 48 h w a s abou t 50% of t ha t in s ea l ed b a g s . But a f t e r 72 h the tox in s t r e n g t h equa l l ed tha t in the s ea l ed b a g s , p a c k e d wi th o r wi thou t v a c u u m . None of t h e u n i n o c u l a t e d c o n t r o l p a c k s showed a n y t o x i c i t y ( F i g . 2).

О 2A 48 7 2

TIME ( h )

FIG. 2. Development of toxin by Clostridium botulinum, type E, on herring fillets at 20°C under different conditions of packing

1. О Inoculated, packed with vacuum 2. • Inoculated, packed without vacuum 3. A Inoculated, open 4. A Uninoculated, packed with vacuum 5. • Uninoculated, packed without vacuum

In a l l c a s e s of t ox in p r o d u c t i o n t ox in n e u t r a l i z a t i o n t e s t s m a d e a s c o n -t r o l s i nd i ca t ed t ha t the dea th of m i c e was s p e c i f i c a l l y caused by type E botu-l i n u m tox in .

E x a m i n a t i o n of t h e f i l l e t s a f t e r 48 h of i n c u b a t i o n a t 20"C ind ica ted tha t t h e f i l l e t s w e r e u n a c c e p t a b l e a s food owing to o b j e c t i o n a b l e o d o u r s .


2. Irradiation experiments

I r r a d i a t i o n w i t h 0 . 3 and 0 . 6 M r a d p r e v e n t e d t o x i n p r o d u c t i o n a s w e l l a s t h e m o r e o b v i o u s t y p e of s p o i l a g e c h a n g e s w h e n t e s t e d a f t e r 4 0 - h i n c u -ba t ion a t 20°C. At p ro longed s t o r a g e (64 h), h o w e v e r , the s a m p l e s r ece iv ing 0 . 3 M r a d b e c o m e t o x i c . In the u n i r r a d i a t e d p a c k s and in the i r r a d i a t e d packs r e c e i v i n g t h e l o w e s t d o s e ( 0 . 1 M r a d ) , t h e r e w a s a l s o in t h i s e x p e r i m e n t a s i g n i f i c a n t l y h i g h e r tox in s t r e n g t h in the vacuum-packed s a m p l e s c o m p a r e d with s a m p l e s which w e r e not v a c u u m packed (Tab le I) .

TABLE I

D E V E L O P M E N T O F T O X I N B Y C L O S T R I D I U M B O T U L I N U M , T Y P E E, O N H E R R I N G F I L L E T S A T 20°C,

I R R A D I A T E D A N D N O N - I R R A D I A T E D

T r e a t m e n t Toxin strength in MLD af ter 40 h

Vacuum 800 Unirradiated controls

No vacuum 80

Vacuum 350 Irradiat ion dose 0 . 1 Mrad

No vacuum 55

Vacuum 0 a

Irradiat ion dose 0 . 3 Mrad No vacuum 0 a

Vacuum 0 Irradiation dose 0 . 6 Mrad

No vacuum 0

a Toxin was, however , found in samples incubated in 64 h at 20°C.

3. Bacteriological studies

D i f f e r e n c e s i n l e v e l s of b a c t e r i a l coun t s ( a e r o b i c ) p e r g r a m of f i s h did not a p p e a r to be s i g n i f i c a n t u n d e r the c o n d i t i o n s of t h e e x p e r i m e n t w h e t h e r t h e f i l l e t s w e r e p a c k e d in po ly thene with o r wi thout v a c u u m o r l e f t u n s e a l e d ( F i g . 3) . I r r a d i a t i o n wi th 0 . 6 M r a d e f f e c t i v e l y l o w e r e d t h e b a c t e r i a l l o a d and, a f t e r 48-h incuba t ion , b a c t e r i a l load was only 0.1% of tha t of the u n i r r a d i -a t ed co n t ro l p a c k s .

QUALITATIVE BACTERIAL TESTS

Q u a l i t a t i v e l y , t h e i n i t i a l flora of t he f r o z e n h e r r i n g f i l l e t s r e s e m b l e d c l o s e l y t h a t d e s c r i b e d by e a r l i e r w o r k e r s . T h e m a j o r p o r t i o n of t h e flora

100 ABRAHAMSSON et a l .

9 л о

2

3

0 48

TIME ( h )

72

FIG. 3. Total bacterial counts (aerobic) on fish fillets during storage at 20°C

1. • Packed without vacuum 2. Д Packs kept open 3. A Packed with vacuum

c o n s i s t e d of p igmented m i c r o c o c c i (35%), f l a v o b a c t e r i a (30%) and a c h r o m o -b a c t e r s (17.5%).

A f t e r s t o r a g e f o r 48 h in v a c u u m - p a c k e d po ly thene b a g s t h e r e w a s a s ign i f ican t change of the f l o r a . The c o l i f o r m s which compr i sed an ins ignif i -cant g roup in the c o n t r o l s b e c a m e a m a j o r component of the spo i lage f l o r a , const i tu t ing n e a r l y 40% of the to ta l viable count . S imi lar ly , the pseudomonads i n c r e a s e d in p r o p o r t i o n to 27.5%. T h e r e was a l so an i n c r e a s e , though l e s s s i gn i f i c an t , of t he a c h r o m o b a c t e r s . The m i c r o c o c c i and the f l a v o b a c t e r i a , on the o t h e r hand, w e r e n e a r l y comple t e ly s u p p r e s s e d . The spo i lage f l o r a a t 20°C r e m a i n e d c lo se ly s i m i l a r whe the r the polythene bags w e r e v a c u u m -packed o r no t .

I r r a d i a t i o n with 0 . 6 M r a d had a r e m a r k a b l e e f f e c t on the flora. The e n t i r e s p o i l a g e f l o r a w a s s u p p r e s s e d wi th t h e e x c e p t i o n of t h e wh i t e p i g -m e n t e d m i c r o c o c c i which w e r e the sole s u r v i v o r s of the i r r a d i a t i o n p r o c e s s (Table II).

DISCUSSION

C o n t r a r y to p r e v i o u s op in ions i t now a p p e a r s tha t CI. botu l inum i s w o r l d - w i d e in i t s d i s t r i b u t i o n ( M e y e r [3 ] ) . A high d e g r e e of i n c i d e n c e of CI . bo tu l inum, e s p e c i a l l y t y p e s A and B, h a s a l s o been r e p o r t e d u n d e r t r o p i c a l cond i t ions (Wi jewanta [4] ). Type E a l s o a p p e a r s to be p r e s e n t in t r o p i c a l f r e s h - w a t e r h a b i t a n t s IDe S i lva , N . N . , u n p u b l i s h e d ] . U n d e r t r o p i c a l cond i t ions , w h e r e condi t ions of hygiene in the food i n d u s t r y a l s o l e a v e m u c h to be d e s i r e d , the r i s k s of bo tu l i sm f r o m i r r a d i a t e d foods such a s f i sh appea r to be p a r t i c u l a r l y high. Since i r r ad i a t ed f ish have n e c e s s a r i l y to be wrapped in sea led con ta ine r s , such a s polythene envelopes, the chances f o r a s e l e c t i o n of s p o r e s of CI. botu l inum a p p e a r p a r t i c u l a r l y m a r k e d . A v a i l a b l e ev idence a l s o i n d i c a t e s tha t t h e s e s p o r e s a r e f a i r l y r e s i s t a n t to


TABLE II

E F F E C T O F I R R A D I A T I O N O N T H E B A C T E R I A L F L O R A O F P O L Y T H E N E - P A C K E D H E R R I N G F I L L E T S

Ini t ia l control

№ )

Storage for A 8 h at 20"C

Bacter ial groups Ini t ia l

control № )

Vacuum packed , unirradiated

(%)

Vacuum packed , irradiated

(%)

Achromobacter 1 7 . 5 2 2 . 5 _ Pseudomonads 5 . 0 2 7 . 5 -

Flavobacter ia 3 0 . 0 - -

Coliforms 5 . 0 4 0 . 0 -

Pigmented Micrococc i White Yel low ^ Orange J

3 5 . 0 5 . 0 100

Coryneforms 7 . 5 -

Bacilli - -

ionizing r ad ia t ion (Schmidt , Nank and Lechowich [5] and Rieman [6]) . The work d e s c r i b e d by us in the p r e s e n t contr ibut ion b e a r s some re la t ion to the a s s e s s m e n t of th i s r i s k .

CI. bo tu l inum, type E of t he s t r a i n u s e d , i s ab l e to g row and p r o d u c e toxin on a f i s h - j u i c e med ia a t t e m p e r a t u r e s between 3and 30°C [Abrahamsson, K . , unpub l i shed] . In the p r e s e n t i n v e s t i g a t i o n a n incuba t ion t e m p e r a t u r e of 20°C w a s u s e d . T h i s could r e s e m b l e c a s e s u n d e r p r a c t i c a l cond i t i ons w h e r e the i r r a d i a t e d food, c o n t r a r y to the r e c o m m e n d a t i o n s , might be kept a t r oom t e m p e r a t u r e f o r a c e r t a i n pe r iod of t i m e .

Among the f a c t o r s tha t migh t have an in f luence on toxin f o r m a t i o n , the me thod of pack ing a p p e a r e d to have s ign i f i can t i m p o r t a n c e . T h i s h a s been d i s c u s s e d in s o m e d e t a i l s by J o h a n n s e n [7] who s tud ied toxin f o r m a t i o n in inocu la t ed v a c u u m - p a c k e d f r e s h and c u r e d h e r r i n g . He found tha t v a c u u m packing had no spec i a l inf luence on toxin f o r m a t i o n and s ta ted that the cause of tox in f o r m a t i o n m a i n l y d e p e n d s on the qua l i ty of t he f i s h p r o d u c t i t s e l f . H o w e v e r , h i s r e s u l t s w e r e b a s e d on toxin t e s t s a f t e r an incuba t ion p e r i o d of f o u r d a y s a t 22°C.

O u r e x p e r i m e n t s ind ica t ed tha t tox in w a s a l s o f o r m e d on f i l l e t s i nocu -l a t ed and s t o r e d in open b a g s a s we l l a s in the v a c u u m - p a c k e d b a g s . The a e r o b i c s u r f a c e - s p o i l a g e f l o r a in the open b a g s m i g h t be c r i t i c a l f o r t h e g rowth of CI. bo tu l inum, i . e . a s pointed out by Watson [8 ] , by f o r m i n g an e f f e c t i v e oxygen b a r r i e r i m m e d i a t e l y be low i t . Q v o r t r u p and S u d h e i m e r [9] r epor t ed that the apparen t symbiot ic p roper ty of Pseudomonas was caused main ly by i t s oxygen consuming capaci ty . Mosse l and Ingram [10] expressed

102 ABRAHAMSSON et al.

t h e opinion tha t oxidat ion reduction potentials low enough fo r Clostridia to g row m a y be a t t a ined in compac t m a s s e s of food . A d rop in pH po ten t i a l s u f f i c i e n t to permit production of toxin by type E on spo i l ing f i s h m u s c l e h a s a l s o been reported by Ando and Inoue [11] .

Under these c i r cums tances vacuum packing is not essent ia l for toxin for-mat ion , an obse rva t ion a lso conf i rmed during ou r inves t igat ions . However, the r e s u l t s obtained by us a p p e a r to indica te tha t u n d e r a given se t of con-dit ions, vacuum packing might considerably favour toxin format ion. It might a l s o be noted tha t in o u r e x p e r i m e n t s the a e r o b i c b a c t e r i a l f l o r a r ema ined quant i ta t ive ly n e a r l y the s a m e whe the r the p l a s t i c bags were open, sea led without v a c u u m o r with v a c u u m . T h u s a v a i l a b l e oxygen s e e m s to be t h e ma in de te rmin ing f ac to r of toxin fo rma t ion . The combined effect of vacuum packing and oxygen exhaus t ion by the a s s o c i a t e d f l o r a m a y thus have been r e s p o n s i b l e f o r the f o r m a t i o n of high toxin l e v e l s in v a c u u m - p a c k e d f i s h . In the c a s e of f i sh packed without vacuum, a f t e r the exhaustion of avai lable oxygen inside the bag, toxin fo rma t ion p roceeded uninhibi ted.

The d e c r e a s e in toxin l eve l on prolonged incubation of vacuum-packed f i l l e t s i s not e a s y to exp la in . However , th i s d e c r e a s e might be r e l a t ed to the ef fec t on toxin s tabi l i ty of the changes in the physical and chemica l envi ronment brought about by a p r e f e r en t i a l l y selected f lo ra in the vacuum-packed s a m p l e s . Changes in pH and excre t ion of inhibi tory subs tances a r e a l so evident .

One of the conc lus ions tha t m a y be d r a w n f r o m o u r i n v e s t i g a t i o n s i s t ha t f o r i r r a d i a t i o n , vacuum packing o f f e r s l i t t le advantage o v e r o r d i n a r y sealed packing. If, as we have suggested, oxygen scavenging by the spoilage f l o r a a ids in botulinum toxin fo rmat ion ; the r e m o v a l of the f lo ra by i r r a d i -a t ion will to s o m e extent r e s t r i c t toxin f o r m a t i o n . Indeed it i s a l so l ike ly tha t the p r e s e n c e of oxygen within the pack d u r i n g i r r a d i a t i o n wi l l aid in b e t t e r s t e r i l i za t ion by the fo rma t ion of highly b a c t e r i c i d a l t r a n s i e n t - f r e e r a d i c a l s . Rhodes [1] h a s a l so r e p o r t e d acco rd ing to p r e l i m i n a r y inves t i -gations that s t o r age in the p r e s e n c e of oxygen was en t i re ly s a t i s f ac to ry dur ing a period up to ten days at 4.4UC. Under t rop ica l conditions in p a r -t i cu la r where the fat content of f ish is general ly low and the methods of cook-ing, f o r example with sp i ce s , m a s k t r a c e s of rancidi ty , these observa t ions b e a r a spec ia l r e l evance to the poss ib le d is t r ibut ion of polythene-packed f i sh f o r t r o p i c a l consumpt ion . The c r i t i c i s m m a y be jus t i f i ab ly m a d e tha t d i f -f e r e n c e s in the b a c t e r i a l f l o r a on the f i l l e t s e x a m i n e d du r ing the p r e s e n t s e r i e s of e x p e r i m e n t s a r e subs tan t ia l ly d i f fe ren t f r o m those obtained in the t r o p i c s . Recent work has , however, shown that the re appear to be two com-ponen t s of the b a c t e r i a l flora on t r o p i c a l f i s h - one growing p r e f e r e n t i a l l y at low t e m p e r a t u r e and ve ry s i m i l a r to the flora of f ish in t empera te waters , and the o the r an e s s e n t i a l l y m e s o p h i l i c component , m o s t l y g r a m - p o s i t i v e b a c t e r i a and y e a s t s (De Silva and Mendi s 112]). F u r t h e r , a f t e r f r e e z i n g , the emergent f lo ra of the f ish i s nea r ly the same as that reported for t ropical f i sh , namely that the g r a m - n e g a t i v e f l o r a tends to d e c r e a s e in number with the se lec t ion of the p redominan t ly g r a m - p o s i t i v e flora (De Silva [13]).

The choice of f rozen h e r r i n g f i l l e t s dur ing our exper iments , to some extent , t h e r e f o r e , p reven ted such wide v a r i a t i o n s in the composi t ion of the b a c t e r i a l f l o r a r e l a t i ve to t r o p i c a l condi t ions .


SUMMARY

T h a w e d h e r r i n g f i l l e t s w e r e i n o c u l a t e d wi th s p o r e s of C I . b o t u l i n u m , type E , and the tox in p r o d u c t i o n in f i l l e t s packed in l a m i n a t e d poly thene bags w e r e c o m p a r e d a t 20"C in s a m p l e s which w e r e v a c u u m packed , s e a l e d wi th-out v a c u u m , o r packed in open b a g s , r e s p e c t i v e l y .

T h e r e s u l t s s h o w t h a t v a c u u m p a c k i n g c o n s i d e r a b l y i n c r e a s e d t h e s t r e n g t h of toxin p r e s e n t a f t e r 48 h . Dur ing p ro longed s t o r a g e a t 20° C, how-e v e r , about the s a m e toxin s t r e n g t h w a s found in the t h r e e c a s e s .

T h e r e s u l t s a r e d i s c u s s e d in v i ew of t h e p o s s i b i l i t y t ha t i r r a d i a t e d f i s h m i g h t b e d i s t r i b u t e d in p o l y t h e n e b a g s u n d e r c o n d i t i o n s w h e r e t h e t e m p e r a -t u r e i s not p r o p e r l y c o n t r o l l e d .

R E F E R E N C E S

[1] RHODES, D . N . , Pasteurization of fish by ionizing radiation, Low Temperature Research Station, Cambridge Record Memorandum 395 (1963).

[2] SHEWAN, J. M . , HOBBS, G . , HODGKISS, W., A determinative scheme for the identification of certain genera of gram-negat ive bacteria with special reference to the Pseudomonadaceae, J. appl. Bacteriol. 23 (1960) 379-390.

[3] MEYER, K . F . , The status of botulism as a world health problem, Bull. World Health Organization lj> (1956) 281-298.

[4] WUEWANTA, E. A . , Toxigenic strains of Clostridium botulinum in soils of Ceylon, Ceylon J. Med. Sei. ( D ) ( 1 9 6 2 ) 59-67.

[5] SCHMIDT, C . F . , NANK, W.K. , LECHOWICH, R.V. , Radiation Sterilization of Food. II Some aspects of the growth, sporulation and radiation resistance of spores of Clostridium botulinum, type E, J. Food Sei. 27 (1962) 77-84.

[6] RIEMAN, H . , Germination of bacter ia l spores with chelators: Thesis, Copenhagen (1963). [7] JOHANNSEN, A . , Miljobetingelser for växt och toxinbildning av CI. botulinum meds'àrskild hänsyn

till förhallandena i vakumförpackade livsmedel, Svenska Institutet för Konserveringsforskning, Göteborg, SIK-Rpt 100(1961) 47-83.

[8] WATSON, D. W. Studies of Fish Spoilage. IV The bacterial reduction of trimethylamine oxide, J. Fish Res. Bd. Can. 4 (1939) 252-266.

[9] QVORTRUP, E. R. , SUD HE IM ER. R. L . , Some ecological relations of P. aeruginosa to CI. botul inum, type C, J. Bact. 45 (1943) 551-554.

[10] MOSSEL, D. A . A . , INGRAM, M . , The physiology of the microbia l spoilage of foods, J. appl . Bact. 18 (1955) 232-268.

[11] ANDO, Y . , 1NOUE, K . , Studies on growth and toxin production of CI. botulinum, type E, in fish products; I. On the growth in relation to the oxidation-reduction potential in the fish flesh, Bull. Jap. Soc. Sei. Fisheries 23 (1957) 458-462.

[12] De SILVA, N. N . , MEND IS, A. H. W . , Bacteriology of chil led water during thé preservation of fish, Bull. Fish. Res. Stn, Ceylon 16 1 (1963) 1 - 8 .

[13] De SILVA, N. N . , Marin Bacteria as indicators of upwelling in the sea, Bull. Fish. Res. Stn, Ceylon 16 2 (1963) 1 -10 .

PROSPECTS AND NEEDS FOR RADIATION DISINFESTATION OF

PACKED FRUITS AND VEGETABLES

A. S. TALHOUK

AMERICAN UNIVERSITY OF BEIRUT,

REPUBLIC OF LEBANON


PROSPECTS AND NEEDS FOR RADIATION DIS INFESTATION OF PACKED FRUITS AND VEGETABLES. In countries with adequate precipitation or irrigation water and high average yearly temperatures the growth of particular crops is favoured. The suitable climatic conditions, however, favour the multiplication of many pests in the stores. The problem of pests of packed fruits and vegetables, although cosmopolitan, presents a particular concern to the developing countries. The pests that are likely to be affected by irradiation and are less susceptible to the conventional methods of control are discussed, and recommendations made.

POSSIBILITE D'UTILISER LES RAYONNEMENTS POUR LA DESINSECTION DES FRUITS ET LEGUMES EMBALLES. Les pays où les précipitations et l'eau d'irrigation sont suffisamment abondantes et où les moyennes annuelles de températures sont élevées se prêtent particulièrement à la culture de certains fruits et légumes. Toutefois, ces conditions climatiques favorisent aussi la prolifération de nombreux parasites des produits stockés. Le problème des parasites des fruits et légumes emballés a un caractère international, mais il intéresse plus particulièrement les pays en voie de développement. L'auteur énumère les parasites sur lesquels les rayonne-ments auraient probablement plus d'effet que les méthodesde destruction, classiques et présente des recomman-dations au sujet de l'irradiation.

ПЕРСПЕКТИВЫ И НЕОБХОДИМОСТЬ ДЕЗИНСЕКЦИИ ОБЛУЧЕНИЕМ ФРУКТОВ И ОВОЩЕЙ В УПАКОВКЕ. В странах с достаточным количеством осадков или орошаемой воды и высокими среднегодовыми температурами имеются благоприятные условия для выра-щивания определенных культур. Благоприятные климатические условия, однако, способствуют размножению насекомых-вредителей в местах хранения этих культур. Хотя проблема борьбы с насекомыми-вредителями фруктов и овощей в упаковках является общей, она вызывает особую озабоченность в развивающихся странах. Сообщается о насекомых-вредителях, ко-торые, по-видимому, больше подвержены действию облучения и в меньшей степени поражают-ся при обычных методах борьбы с ними. Даются рекомендации.

PERSPECTIVAS Y NECESIDAD DE LA RADIODESINFESTACION DE FRUTAS Y VERDURAS EMPACADAS. Los países en que abundan las precipitaciones o el agua de riego y cuya temperatura media anual es elevada, son propicios para determinados cultivos; en cambio, estas condiciones climáticas favorecen la multiplicación de muchos parásitos en los almacenes. El problema que estos parásitos plantean en relación con las frutas y verduras empacadas es general pero afecta particularmente a los países en desarrollo. La memoria trata de los parásitos más sensibles a las radiaciones y menos vulnerables a los métodos clásicos de desinfestación, y formula recomendaciones.

Although the problem of insect infestation of s tored foods and food pro-ducts is of cosmopoli tan concern, i ts s ignif icance and acute sever i ty differ with the d i f ferent geographical and c l imatological regions of the world, as well as the na ture of the economy of the different count r ies .

An importing country is in a position to set i ts s tandards of insec t - f ree food p roduc t s , and usual ly , because of compet i t ion, m a n a g e s to get what it has reques ted . On the other hand, an agr icul tura l , exporting country is capable of exporting only a given proportion of its surplus produce originally

105

106 TALHOUK

des t ined f o r expo r t , b e c a u s e only a p a r t of th i s m e e t s in t e rna t iona l s t a n d a r d s as to qual i ty and p u r i t y .

A m o n g the f a c t o r s t h a t d e t e r m i n e t h e p r o p o r t i o n of e x p o r t a b l e p r o d u c e a r e the fo l lowing: (1) c l ima to log ie a l su i tab i l i ty f o r growing the c rop , (2) seed q u a l i t y and p u r i t y , (3) s t a t e of a d v a n c e of f a r m i n g m e t h o d s , and (4) p e s t c o n t r o l . T a k i n g f o r g r a n t e d tha t t h e c r o p s a r e g r o w n u n d e r s u i t a b l e c l i m a t i c c o n d i t i o n s and tha t t h e s e e d q u a l i t y and p u r i t y a r e s a t i s f a c t o r y , t h e t w o m a j o r d i f f i c u l t i e s t h a t c o n f r o n t e x p o r t a r e t h e p r o -d u c t i o n of h i g h g r a d e p r o d u c e b y m e a n s of p r o p e r , a d v a n c e d , s c i e n t i f i c m e t h o d s and the p r o t e c t i o n of t h i s p r o d u c e aga ins t p e s t s w h e t h e r in the f ie ld , in s t o r a g e , o r d u r i n g i t s c o n v e y a n c e t o t h e c o n s u m e r .

My e x p e r i e n c e i s l i m i t e d t o p a r t of t h e Midd le E a s t c o u n t r i e s , i nc lud -ing Lebanon , S y r i a , Saudi A r a b i a , J o r d a n , I r a q and to a s l ight ex ten t , I r a n ; In t h e s e c o u n t r i e s b e t w e e n 80 a n d 95% of t h e p o p u l a t i o n d r a w s i t s l i v i n g d i r e c t l y f r o m a g r i c u l t u r e , while a l a r g e p r o p o r t i o n of the r e m a i n i n g 5 to 20% e a r n t h e i r l iv ing by t r a d i n g m o s t l y with a g r i c u l t u r a l p r o d u c t s .

T h e c o u n t r i e s m e n t i o n e d a b o v e e n j o y c l i m a t e s t h a t r a n g e b e t w e e n t h e s u b t r o p i c a l and t h e t e m p e r a t e , a s w e l l a s t h e c o n t i n e n t a l . T h i s m a k e s it p o s s i b l e f o r t h e m t o g r o w p e r m a n e n t t r o p i c a l and s u b t r o p i c a l c u l t u r e s s u c h a s d a t e s and c i t r u s , o r t e m p e r a t e c l i m a t e t r e e s s u c h a s a p p l e s , o r t h e p i s t a c i o nut w h e r e c o n t i n e n t a l c l i m a t e s r e i g n . At t h e s a m e t i m e , t he extent of t h e g r o w i n g s e a s o n m a k e s it p o s s i b l e t o g r o w s e v e r a l v e g e t a b l e c r o p s th roughou t the e n t i r e y e a r . T h i s g r e a t advan tage i s at the s a m e t i m e a g r e a t d i s a d v a n t a g e when the p e s t p r o b l e m is c o n s i d e r e d . The high a v e r a g e y e a r l y t e m p e r a t u r e m a k e s it p o s s i b l e f o r a l a r g e n u m b e r of pe s t s p e c i e s to mul t ip ly wi thout i n t e r r u p t i o n o v e r t h e t w e l v e m o n t h s of t h e y e a r . A p e s t t h a t m i g h t h a v e two o r t h r e e g e n e r a t i o n s a y e a r in L i v e r p o o l o r V i e n n a w i l l h a v e t e n o r t w e l v e in D a m a s c u s o r D j e d d a h . T h e r e f o r e , a l t h o u g h p o t e n t i a l l y t h e c o u n t r i e s of t h e M i d d l e E a s t a r e c a p a b l e of p r o d u c i n g l a r g e q u a n t i t i e s of f o o d m a t e r i a l s w i t h t h e i r r a p i d l y i m p r o v i n g f a r m i n g m e t h o d s , t h e i r p e s t c o n t r o l p r o b l e m s a r e going to r e m a i n s e r i o u s , not only phys i ca l l y , but e c o -n o m i c a l l y a s we l l .

T a b l e s I - V show t h e y e a r l y a g r i c u l t u r a l e x p o r t s and i m p o r t s of the f ive c o u n t r i e s m e n t i o n e d a b o v e . It s h o u l d be b o r n e in m i n d tha t t he e x p o r t t o n -n a g e r e p r e s e n t s only a f r a c t i o n of the s u r p l u s p r o d u c t i o n tha t could be so ld f o r e x p o r t . T h i s i s e s p e c i a l l y t r u e f o r d a t e s in S a u d i A r a b i a , and t o a s l i g h t l y l e s s e r e x t e n t , I r a q . T h e v a s t o a s e s of A r a b i a a n d I r a q p r o d u c e s e v e r a l h u n d r e d t h o u s a n d t o n s of da te f r u i t , in s p i t e of t h e g r e a t t o l l t a k e n b y i n s e c t p e s t s and d i s e a s e s of t h e c r o p in t h e g r o v e s ( T a l h o u k [1]). S i m i -l a r l y , c i t r u s e x p o r t in L e b a n o n s u f f e r s g r e a t l y f r o m t h e " m e n a c e " of t h e M e d i t e r r a n e a n f r u i t f ly (Ta lhouk [2]), which r e d u c e s the e x p o r t of e a r l y and l a t e v a r i e t i e s of o r a n g e s of o t h e r w i s e e x c e l l e n t qua l i ty

The present status of dis infestation of packed foods

So f a r t h e c o n v e n t i o n a l m e t h o d s of i n d u s t r i a l d i s i n f e s t a t i o n of p a c k e d f o o d s c o n s i s t of one of t h r e e m e t h o d s o r a c o m b i n a t i o n of two of t h e m .

RADIATION DISINFESTA TION 107

TABLE 1

IRAQ

Expor t s and Imports of Some of the Agr icu l tura l P r o d u c t s

Product

Exports Imports

( t ) ( t )

1960 1961 1962 1960 1961 1962

Dates 2 5 0 6 0 1 187 090 228997 - - -

Wheat and mes l in - - 38 844 206 321 4 1 3 9 8 3 ?

Fresh fruits 6 526 5 7 7 1 ? 29 955 31349 34 891

Fresh vegetables - - - 50 977 45 285 59 238

Tomatoes - - - 19 770 18 622 24226

Onions, shallots and ga r l i c - - - 1013 1579 1886

Potatoes - - - 13 515 14399 16 993

Banana - - - 4 9 5 6 6 805 7 235

Citrus fruit , fresh and dried - - - 347 234 354

Pistacio (in the she l l ) - - - 234 163 46

Pistacio (shelled) - - - 10 30 243

Apple - - - 17 566 17 429 16 336

Cerea ls - - - 262021 483 755 69 175

Giant mi l l e t • - 992 - - - -

Barley 437 49 683 338 766 - 50 -

Rice, husked 103 15 52 867 69 683 69 155

Mi l l e t _ 332 2 _ _

Source: S ta t i s t ica l yearbook for fore ign t r ade 1960, 1961, and 1962, Iraqi Ministry of Economy, Baghdad.

T h e m e t h o d s a r e ma in ly the fol lowing:

(a) The u s e of contac t p o i s o n s of low m a m m a l i a n tox ic i ty

Such p o i s o n s a r e u s e d t o t r e a t the s u r f a c e of p a c k a g e s o r to i m p r e g n a t e sacks ; insec t ic ida lpowder is used to spr inkle on the packages when stacking them in the s t o r e s . Th i s method p r e v e n t s the e n t r a n c e o r e s t ab l i shmen t of a pes t , in c a s e the commodi ty w a s in i t i a l ly f r e e f r o m the p e s t in ques t ion . It a l so checks those i n sec t s at the s tage when they leave the commodity, e i ther as l a rvae ready t o pupa te ( e . g . E p h e s t i a spp . P l o d i a , e t c . ), o r a s adu l t s when condi t ions b e c o m e i n t o l e r a b l e f o r t h e m to r e m a i n in the s e e d ( e . g . C a l a n d r a spp . J1.

1 C 0 2 or toxic products of metabol ism.

108 TALHOUK

TABLE II

J O R D A N

E x p o r t s a n d I m p o r t s of S o m e of t h e A g r i c u l t u r a l P r o d u c t s

Exports Imports

1960 1961 1962 1960 1961 1962

Onion and ga r l i c 571 874 849 4 205 4 4 3 6 6 646

Tomatoes 36 894 3 6 2 5 5 33 274 1661 1728 1756

Potatoes for food 1371 859 766 12 515 10 504 10 817

Lentils - 649 8 624 1651 1900 2 5 4 5

Beans, haricots and fresh

broad beans 10 416 11434 - - - -

Cucumber , gherkins,

marrows, e t c . 2077 2 394 3 753 - - -

Pistacio (in the shell) - - - 41 - 40

Banana 2 4 7 4 2220 2 9 7 7 - - -

Orange 590 322 623 6 541 ' 5 1 0 0 0 6 844

Lemon 436 634 1 0 1 4 2 3 4 6 1859 2 799

Grape 753 1137 1027 614 537 1.443

Almond (in the shel l ) 401 32 515 - 65 -

Apple 3 105 42 5 978 5 260 7 912

Pears - - 76 170 338 273

Apricot 122 80 93 - - -

Peaches 443 - 157 - 288 413

Plums - 678 1248 - - -

Watermelon 14735 30 029 31557 - - -

Wheat 423 501 3377 70 130 64360 12 145

Date - - - 2 574 2 732 2248

Source: S ta t i s t ica l Yearbook 1960, 1961, 1962, Jordanian Ministry of Nat ional Economy, Depar tmen t of Statistics, A m m a n .

On the u i n e r hand , when t h e i n f e s t a t i o n h a s a l r e a d y s t a r t e d in the commodi ty b e f o r e p a c k i n g , t h e c o m m o d i t y wi l l b e s p o i l e d i n s p i t e of t h e t r e a t m e n t of t h e c o n t a i n e r . M o r e o v e r , w h e n s a c k s c o n t a i n i n g o i ly s e e d s o r b e a n s a r e t r e a t e d wi th DDT, the s e e d s a b s o r b a p p r e c i a b l e q u a n t i t i e s of t he i n sec t i c i de , a t l e a s t t h e l a y e r s n e a r t o t h e s u r f a c e . O t h e r i n s t a n c e s of c o n t a m i n a t i o n c o u l d b e e n u m e r a t e d .


TABLE III

L E B A N O N

E x p o r t s and I m p o r t s of S o m e of t h e A g r i c u l t u r a l P r o d u c t s

Exports Imports

1960 1961 1962 1960 1961 1962

Onion ahd ga r l i c 7 869 5 1 5 5 12296 4 8 4 6 3 319 * 2 895

Tomatoes 8 751 6 280 7 700 12102 5 359 3 669

Potatoes 25 523 18 545 2 3 4 3 2 22 647 10 292 3 641

Other vegetables - 3 351 169 9 401 8 092 2 666

Dates - - - 1741 1734 1453

Grapes 502 484 880 4 2 3 6 2 307 2317

Watermelon - - - 17 054 24307 31006

Muskmelon - - 4 0 8 7 4 960 5112

Wheat 5410 935 1 4 2 5 156 299 128 745 176 949

Banana 15 322 16398 15 557 - - -

Orange and manda r ine 63 378 49 851 25 885 - - -

Lemon 17 736 18316 18392 ' - - -

Almond and walnuts 109 106 113 - - -

Apples, pears and quinces 42 754 47 535 52349 - - -

Source: Bulletin Stat is t ique Tr imes t r i e l 1960, 1961, 1962, Lebanese Ministry of P lanning, Beirut, Lebanon.

(b) T h e u s e of f u m i g a n t s

F u m i g a n t s a r e undoubtedly v e r y he lpfu l in d i s i n f e s t a t i o n , e s p e c i a l l y in c a s e s of l ight ly packed m a t e r i a l . I have in mind g r a i n s , t u b e r s , f r e s h f r u i t s and s i m i l a r c o m m o d i t i e s . But when t ightly packed m a t e r i a l s , such a s da tes , f i g s , r a i s i n s , o r t o b a c c o h o g s h e a d s , a r e f u m i g a t e d , even u n d e r p a r t i a l v a c u u m , g a s p e n e t r a t i o n b e c o m e s v e r y d i f f i cu l t , o r even i m p o s s i b l e . B e -s i d e s , t h e r e a r e c e r t a i n s t a g e s of the p e s t s tha t , owing to s l ower me tabo l i sm, e s c a p e t h e e f f e c t of t h e p o i s o n g a s . A l l e n t o m o l o g i s t s a r e f a m i l i a r with ' the f a c t that eggs , l a r v a e , pupae and adul t s of E p h e s t i a o r P lod ia a r e of ten found in t h e s a m e p a c k a g e at t he s a m e t i m e , h e n c e a r e a s o n f o r t h e i n -e f f i c i e n c y of t h e f u m i g a t i o n . M a t t e r s b e c o m e m o r e c o m p l i c a t e d when e x -p o s u r e t i m e s a r e i n c r e a s e d to e n s u r e a high a r i t h m e t i c a l p roduc t of concen-t r a t i o n and t i m e . T h e d i f f i c u l t y of knowing a c t u a l l y höw m u c h of t h e g a s i s ava i l ab le to the i n s e c t s and how m u c h i s s o r b e d , and the r o l e of m o i s t u r e not only in so rp t ion but in the pos s ib l e re ten t ion and r eac t i on with the poison g a s , m a k e s fumiga t ion a pos s ib l e s o u r c e of h a z a r d to c o n s u m e r s .

110 TALHOUK

TABLE IV

SAUDI A R A B I A

E x p o r t s a n d I m p o r t s of S o m e of t h e A g r i c u l t u r a l P r o d u c t s

Exports Imports Product Ш ( t )

1959-60 1960-61 1961-62 1959-60 . 1960-61 1961-62

Garl ic 384 372 301

Onion 10 257 8 801 9 051

Potatoes 5 2 4 1 6 0 0 4 6 1 3 6

Other vegetables 8 0 1 1 5 781 4 818

Lentils 938 1010 1780

Date 668 : 2317 2 529 7 439 5 084 4 268

Bananas 13 5 575 6 433 6 4 5 1

Orange and mandar ine 41 10 214 10 265

Lemon and sweet l i m e 594 599 798

Grape 704 724 1260

Walnut 67 41 32

Pistacio 27 36 49

Apples 5 526 5910 7 058

Pears 63 263 230

Peaches 237 72 239

Water and muskmelon 46 4 2 2 3 1 7 6 1 2889

Other fresh fruits 2 238 930 499

Wheat 40 566 38 660 30 786

Barley 13 045 38 584 16 057

Com 8 666 30 735 20 807

Rice 45 545 77 828 179 725

Source: Foreign c o m m e r c e statist ics 1959-1962, Ministry of Nat ional Economy and Finance, Riad.

(с) H e a t t r e a t m e n t

H e a t t r e a t m e n t i s a m e t h o d tha t i s h e l p f u l in t r e a t i n g d r y g r a i n , c o f f e e b e a n s and t o b a c c o l e a v e s , but not d r i e d f r u i t s o r n u t s b e c a u s e of t he p o s s i -b i l i t y of s p o i l a g e of t h e c o m m o d i t y . T h e d i s a d v a n t a g e of t h i s me thod i s tha t t h e r e i s a l w a y s l i ke ly t o b e an a p p r e c i a b l e d i f f e r e n c e be tween the t e m p e r a t u r e a t t h e s u r f a c e and t h e i n s i d e of t h e t r e a t e d p a c k a g e s s o t ha t when t h e i n s ide


TABLE V

SYRIA

E x p o r t s and I m p o r t s of S o m e of t h e A g r i c u l t u r a l P r o d u c t s

Exports Imports

Product ^ ( I )

1958 1959 1960 1958 1959 1960

Cucumber and pumpkins - - - 5 1 2 4 941 899

Dates - - - 45 776 29 644 30 212

Bananas - - - 9 542 7 668 8 296

Orange and t anger ine - - - 3 367 40 567 39 911

Lemons - - - 6 629 1 1 6 5 4 11635

Watermelon - - - 18137 7 745 5 0 7 1

Tomatoes 3 481 5120 2 523 10 864 9 433 13 833

Onion 9 210 8 287 657 - - -

Lentils 18 022 - 23 760 - - -

Grapes 1876 128 5 036 - -

Pistacio (in the she l l ) 27 218 198 - - -

Walnut (in the she l l ) 399 - 383 - - -

Watermelon 4 1 5 6 6 421 6080 - - -

Wheat 177 834 238 1 20 87 713 228036

Barley 89 560 0 - - - -

Millet 20 156 6 561 2 742 - - -

Potatoes - - - 18 014 19 221 27 717

Haricot beans and broad

beans - - - 2 1 0 4 1 5 1 3 1709

Source: Statist ics of foreign t r ade 1958, 1959, 1960, Syrian Ministry of Economy, Damascus.

t e m p e r a t u r e i s high enough to ki l l t he p e s t , t he ou t s ide t e m p e r a t u r e migh t be too high and migh t e f f e c t spo i l age .

T h i s sho r t in t roduc t ion i s m e a n t to d r a w a t ten t ion to the i m p e r f e c t i o n s of t he p r e s e n t o r convent ional me thods . If r ad ia t ion i s employed, and s ince n e i t h e r the ac t ive nor the r e s t i n g s t a g e s of the p e s t s a r e r e s i s t a n t to i t , the d a n g e r of f l a r i n g would b e c o m e n o n - e x i s t e n t . T h e only p o s s i b l e s o u r c e of r e - i n f e s t a t i o n wil l be f r o m without. The quest ion of toxic r e s i d u e s , whether of c o n t a c t i n s e c t i c i d e s u s e d in i m p r e g n a t i o n o r s u r f a c e t r e a t m e n t , o r of p o i s o n g a s e s , would be d i s m i s s e d a l t o g e t h e r . T h e d a n g e r of a t o m i c r a d i a t i o n c o n t a m i n a t i o n of t r e a t e d food p r o d u c t s s e e m s to be absen t at t he dosages employed (Brownel l and Yudelovitch I 3J). Not only does i r r ad ia t ion

112 TALHOUK

not r a i s e t h e t e m p e r a t u r e of c o m m o d i t i e s w h i c h m i g h t r e s u l t in b a c t e r i a l f e r m e n t a t i o n , bu t t h e t r e a t m e n t h a s an a n t i s e p t i c e f f e c t .

Specific instances where radiation infestation might be helpful

A m o n g s t t h e d i f f i c u l t p r o b l e m s of p a c k e d f r u i t s and n u t s a r e t h e d r i e d f r u i t m o t h s , E p h e s t i a c a u t e l l a , E . e l u t e l l a and t h e p o l y p h a g o u s P y r a l i s f a r i n a l i s and P l o d i a i n t e r p u n c t e l l a . The f ew v i ta l r e q u i r e m e n t s of the adu l t s s e e m to b e e n t i r e l y m e t in t h e w a r e h o u s e s , s t o r e s o r sh ip h u l l s , which f a c t c a u s e s t h e m to b e c o m e e x t r e m e l y i m p o r t a n t f r o m t h e p lant q u a r a n t i n e v i e w -p o i n t , a s we l l a s a v e r y s e r i o u s s t o r a g e p r o b l e m of g r e a t e c o n o m i c s i g n i f i -c a n c e f o r t h e p r o d u c i n g c o u n t r i e s . O w i n g t o t h e l a c k of f o r c e d d i a p a u s e d u r i n g t h e i r l i f e c y c l e , t h e s e p e s t s r e p r o d u c e u n i n t e r r u p t e d l y in t h e w a r e -h o u s e s and ship h u l l s , and o f t en r e n d e r t h e expens ive goods u t t e r l y unsa l ab le by t h e t i m e t h e c a r g o r e a c h e s t h e r e t a i l e r , o r e v e n t h e w h o l e s a l e r . T h e au thor h a s b r e d one o r m o r e of t h e s e s p e c i e s f r o m d r i e d f igs , da t e s , p i s t a c io s , d r i e d a p r i c o t s , a l m o n d s , walnut m e a t s , p ine seed and c o n f e c t i o n a r y .

B e s i d e t h e c a t e r p i l l a r s m e n t i o n e d a b o v e , t h e c o m m o d i t i e s u n d e r c o n -s i d e r a t i o n o f t e n c o n t a i n T r i b o l i u m c o n f u s u m , T . c a s t a n c u m a s w e l l a s a n u m b e r of C u c u j i d b e e t l e s of c o s m o p o l i t a n d i s t r i b u t i o n . T h e s e b e e t l e s , a s w e l l a s t h e C a l a n d r a g r a n a r i a and o r y z a e , s p e n d t h e i r e n t i r e l i f e in o r on t h e c o m m o d i t i e s , w h i c h f a c t m a k e s i r r a d i a t i o n m o r e a d v a n t a g e o u s t h a n t h e c o n v e n t i o n a l m e t h o d s of t r e a t m e n t .

A s e r i o u s p r o b l e m f o r e x p o r t of c i t r u s f r u i t s i s t he M e d i t e r r a n e a n f r u i t fly, C e r a t i t i s c a p i t a t a . T h i s f ly l a y s i t s eggs in the f r u i t r ind of many c i t r u s v a r i e t i e s , bu t i t s l a r v a e only o c c a s i o n a l l y s u c c e e d in p e n e t r a t i n g t h e r i n d , and c o n s e q u e n t l y in r e a c h i n g t h e f r u i t pulp (Delanoue and So r i a [ 4] ). N e v e r -t h e l e s s , t h i s h ighly po lyphagous fly i s c o n s i d e r e d r igh t ly o r wrongly , a g r e a t p o t e n t i a l d a n g e r t o d e c i d u o u s f r u i t s in m a n y fly-free, c i t r u s - i m p o r t i n g c o u n t r i e s . D i f f e r e n t c i t r u s v a r i e t i e s m a t u r e be tween N o v e m b e r (e.g. m a n d a -r i n e s ) and m i d - M a y ( V a l e n c i a s ) . The f r u i t fly i s capab le of ac t ive in fes ta t ion p r a c t i c a l l y t h r o u g h o u t t h e s a m e p e r i o d , wi th a c o m p a r a t i v e r e t a r d a t i o n in a c t i v i t y d u r i n g J a n u a r y and p a r t of F e b r u a r y , in e x c e p t i o n a l l y co ld y e a r s . I r r a d i a t i o n of c i t r u s b o x e s k i l l s t h e e g g s and a n y l a r v a e t h a t m i g h t h a v e h a t c h e d ( B r o w n e l l and Y u d e l o v i t c h [ 3] ) .

A n i m p o r t a n t s e t of p e s t s a r e t h e r e d s p i d e r s , M e t a t e t r a n y c h u s u l m i and T e t r a n y c h u s u r t i c a e . In a u t u m n when the apple f r u i t s m a t u r e , the s p i d e r s l ay t h e i r w i n t e r e g g s on t w i g s , and the ca lyx end of f r u i t s . The eggs r e m a i n u n h a t c h e d u n t i l M a r c h o r A p r i l of t h e f o l l o w i n g y e a r , and due t o t h e g r e a t n u m b e r of p o s s i b l e h o s t s , the s a id m i t e s a r e r igh t ly c o n s i d e r e d a s impor t an t and u n d e s i r a b l e p o t e n t i a l s o u r c e s of i n f e s t a t i o n . A l t h o u g h t h e s e s p e c i e s of m i t e s a r e found in the E u r o p e a n c u s t o m e r c o u n t r i e s , the p r e s e n c e of t h e i r l i v i n g e g g s on i m p o r t e d f r u i t c r e a t e s a p r o b l e m t o o u r e x p o r t t r a d e . T h e t r e a t m e n t of e x p o r t a p p l e s in c r a t e s by m e a n s of i r r a d i a t i o n t o ki l l t he eggs should b e i n v e s t i g a t e d .

T h e po ta to t u b e r mo th P h t h o r i m e a o p e r c u l e l l a i s a s e r i o u s pe s t of t u b e r s in s t o r a g e . In w a r m c l i m a t e s i t c a n p r o d u c e a b o u t t w e l v e g e n e r a t i o n s a y e a r . I had s ix s u c c e s s i v e g e n e r a t i o n s f r o m t h r e e t u b e r s , without any food f o r the a d u l t s e x c e p t what t h e y could ge t f r o m t h e t u b e r i t s e l f . T h i s i s e v i -


dence of the ve ry low food r e q u i r e m e n t s of the adult . Again, the i r r ad ia t ion t r e a t m e n t could be helpful in th i s c a s e as wel l .

Another s t o r a g e p r o b l e m i s c r e a t e d by the d i f f e ren t s p e c i e s of Bruchid bee t l e s that at tack mainly leguminous s eeds : Bruchus p i so rum.B . ru f imanus , B . e r v i . Al though t h e y s e e m to have only one g e n e r a t i o n p e r y e a r , t h e y can r u i n t h e c o m m o d i t i e s t o a g r e a t ex t en t .

In i ts e s s e n c e , ;the infes ta t ion of s tored foods by insect would be grea t ly min imized if enough c a r e w e r e taken to c lean the s to rage spaces by actual ly sweeping the r e s i d u e s and burning them, and then applying r e s i d u a l contact s p r a y s on the walls and ce i l ings . This will not, however , prevent outbreaks if the commodi ty i tse l f i s not i n sec t - f r ee 1 ' . G ra in i r r a d i a t i o n would be the ideal solut ion, a f t e r ensur ing the hygienic s t eps s ta ted above. Although not d i r ec t ly concerned with the topic of th i s pape r , the poss ib i l i ty of i r r ad i a t i on of f u r n i t u r e a t t a c k e d by t h e C e r a m b y c i d b e e t l e g e n e r a S t r o m a t i u m and Hesperophanus , whose l a r v a e cause the des t ruc t ion of f u r n i t u r e , p ianos and o the r va luab le wooden w o r k s , should be c o n s i d e r e d . Book w o r m s that a r e d i f f i cu l t t o k i l l e v e n by f u m i g a t i o n would p r o b a b l y be e a s y to k i l l by i r r a d i a t i o n .

R E F E R E N C E S

[1] TALHOUK, A.S. , Insect Pests and Diseases of Agricultural Crops in the Eastern Province of Saudi Arabia, Aramco Publication, Beirut (1957).

[2] TALHOUK, A . S . , Einige entomologische Probleme der Lebanesischen Landwirtschaft, Anzeiger f . Schädlingskunde XXXVI 6 (1963) 81-85.

[3] BROWNELL, L.E., YUDELOVITCH, M. , "Effect of radiation on Mexican frui t - f ly eggs and larvae in grapefruit", Radioisotopes and Radiation in Entomology, IAEA, Vienna (1962) 193-206.

[4] DELANOUE, P., SOR1A, F., Au sujet de l 'avortement de l'évolution de Ceratitis capitata Wied, Ann. Inst. Nat. Rech. Agron. de Tunisie 35 (1962) 75-95.

2 In storage the insects have an ideal environment that affords plenty of food, excellent shelter, and many mates.

RADIATION PRESERVATION OF SOME FRUITS AND VEGETABLES

S . D . DHARKAR BIOCHEMISTRY AND FOOD TECHNOLOGY DIVISION,

ATOMIC ENERGY ESTABLISHMENT TROMBAY, BOMBAY, INDIA


RADIATION PRESERVATION OF SOME FRUITS AND VEGETABLES. Shelf l ife extension and sterilization processing by irradiation of certain tropical fruits werfe studied in the laboratory. It was demonstrated that alfonso mangoes and sapota slices could be kept for one year by first inactivating the enzymes by mild heat treatment and then irradiating to a dose of 4X 10s rad. The irradiated products were equal in acceptance to thermally sterilized controls. Oxidative flavour changes in canned mangoes were minimized when the removal of oxygen by exhausting was eff icient . Vitamin losses in mangoes and sapotas were no more than in thermally sterilized controls. By using a combined t rea tment in sterilizing orange juice the radiation dose could be lowered from 800 to 400 krad by a post-heat t reatment of 15 min at 50°C. Better retention of ascorbic acid, th iamine and riboflavin were obtained. Peas in brine sterilized by irradiation at 850 krad were found to be superior in flavour, colour, texture, and overall quality to thermally processed controls. Shelf-life extension of mangoes by delaying the ripening with irradiation was found t o be e f fec t ive at doses between 1200 and 2500 rad. Such a treatment would be useful in regulating ripening of such fruit for canning factory purposes. No difference could be found between irradiated and non-irradiated canned mangoes. In studying the inhibition of the sprouting of potatoes and onions by irradiation it was found that different varieties required different doses and those products approaching the break in dormancy required higher dosés. Other work in radiation

preservation showed that certain microorganisms were more sensitive to radiation when previously subjected to ultra-

sonic t rea tment . With yeasts there seemed to be a different mode of action in killing the cells at high and

low frequencies. Research on combining radiation treatment with cold storage of fruits to extend shelf l i fe

shows promise. Work is also being done on the use of irradiation treatment to reduce microbial contamination in

freeze-dried products.

IRRADIATION DE FRUITS ET LEGUMES EN VUE DE LEUR CONSERVATION. L'auteur a étudié en labora-

toire la possibilité d 'ut i l iser les rayonnements pour augmenter la durée de conservation des fruits tropicaux

stockés et les stériliser. Il a constaté que les mangues et les tranches de sapote pouvaient se conserver pendant

un an si on inactivait tout d'abord les enzymes par un léger traitement thermique suivi d 'une exposition à une

dose d e 4;103 rad. La qua l i té des produits irradiés étai t comparable à ce l le de produits témoins stérilisés

par traitement thermique. Le goût d'oxyde des mangues en bottes de conserve a été atténué lorsqu'on a réussi

à en retirer tout l 'oxygène. La perte en vitamines dans les mangues et les sapotes n ' a pas é té supérieure à

ce l l e qui accompagne les procédés de stéril isation par t ra i tement thermique . Pour la stérilisation du jus

d'orange, i l a é té possible d'abaisser la dose de 800 à 400 krad, si l ' irradiation était suivie d 'un traitement

thermique â 50°C pendant 15 minutes. L'auteur a constaté une meilleure rétention de l 'ac ide ascorbique, de

la th iamine et de la riboflavine. Pour les pois en saumure, i l a constaté qu'en ce qui concerne le goût, la

couleur, la consistance et la quali té générale , ceux qui avaient é t é stérilisés par exposition à une dose de

850 krad étaient supérieurs à ceux qui avaient é t é soumis à un trai tement thermique. La durée de la conser-

vation de mangues stockées dont le mûrissement avai t é té retardé par exposition à des doses variant entre

1200 et 2500 rad a été eff icacement prolongée. Ce traitement serait utile pour régulariser la maturation des

mangues destinées aux conserveries. Il n 'a pas é té possible de déce ler de d i f férence entre les mangues en

bottes qui avaient é té irradiées et celles qui ne l 'avaient pas été. Les recherches sur l 'emploi des rayonnements

pour empêcher la formation des germes de pommes de terre et d'oignons ont révélé qu 'il fallait appliquer des

doses différentes selon les variétés et que les produits approchant de la germination devaient être soumis à des

doses les plus élevées. D'autres travaux sur la conservation au moyen des rayonnements ont montré que certains

micro-organismes étaient plus radiosensibles s 'ils avaient é té soumis au préalable à un trai tement par ul tra-

sons. Pour ce qui est des levures, il semble que le mode d ' ac t ion soit différent selon que les cellules sont

détmites à haute ou à basse fréquence. On attend des résultats intéressants des recherches sur le traitement par

115

116 DHARKAR

les rayonnements combiné à la réfrigération ou à la congélation pour augmenter la durée de conservation des fruits. Des travaux sont également en cours sur l 'emploi de l 'irradiation pour réduire la contamination micro-bienne des produits séchés et congelés.

С О Х Р А Н Е Н И Е Н Е К О Т О Р Ы Х Ф Р У К Т О В И О В О Щ Е Й С ПОМОЩЬЮ О Б Л У Ч Е Н И Я . В л а б о р а т о р н ы х у с л о в и я х и з у ч а л и с ь проблемы продления срока хранения и стерилизующей о б -работки с помощью облучения н е к о т о р ы х тропических ф р у к т о в . Б ы л о показано , что альфонсо м а н г о и л о м т и к и с а п о т о м о ж н о с о х р а н я т ь в т е ч е н и е г о д а в н а ч а л е п у т е м д е з а к т и в а ц и и ф е р -м е н т а в р е з у л ь т а т е о б р а б о т к и м я г к и м т е п л о м и з а т е м облучения дозой 4-10 5 р а д . О б л у ч е н -ные продукты в равной степени о т в е ч а л и требованиям контроля м е т о д а м и термической с т е р и -л и з а ц и и . П о я в л е н и е к и с л о г о п р и в к у с а в к о н с е р в и р о в а н н ы х м а н г о было с в е д е н о к м и н и м у м у при э ф ф е к т и в н о м у д а л е н и и к и с л о р о д а п у т е м о т к а ч к и . П о т е р и в и т а м и н о в в м а н г о и с а п о т о были не больше, ч е м у контрольных э к з е м п л я р о в , обработанных м е т о д а м и термической с т е р и -л и з а ц и и . При и с п о л ь з о в а н и и комбинированной о б р а б о т к и во в р е м я с т е р и л и з а ц и и а п е л ь с и н о -в о г о сока дозу облучения можно было уменьшить с 800 килорад до 400 килорад при последую-щей т е п л о в о й о б р а б о т к е в т е ч е н и е 15 м и н при 50 ° С . Б ы л о д о с т и г н у т о л у ч ш е е у д е р ж а н и е а с к о р б и н о в о й к и с л о т ы , т и а м и н а и р и б о ф л а в и н а . Б ы л о у с т а н о в л е н о , ч т о при с т е р и л и з а ц и и г о р о ш к а в с о к у о б л у ч е н и е м д о з о й 850 к и л о р а д , он по с в о е м у в к у с у , ц в е т у , с т р у к т у р е и по о б щ е м у к а ч е с т в у л у ч ш е , ч е м п о с л е т е р м и ч е с к о й о б р а б о т к и . Б ы л о н а й д е н о , ч т о у в е л и ч е н и е с р о к а х р а н е н и я м а н г о в р е з у л ь т а т е з а д е р ж к и с о з р е в а н и я с помощью облучения э ф ф е к т и в н о д о с т и г а е т с я при величине д о з 1 2 0 0 - 2 5 0 0 р а д . Т а к а я о б р а б о т к а о к а з а л а с ь бы полезной при регулировании с о з р е в а н и я э т о г о плода для иелей консервирования . Никакого различия нельзя б ы л о бы о б н а р у ж и т ь м е ж д у о б л у ч е н н ы м и и н е о б л у ч е н н ы м и к о с е р в и р о в а н н ы м и м а н г о . При изучении вопроса о предотвращении прорастания к а р т о ф е л я и лука с помощью облучения было у с т а н о в л е н о , ч т о для различных разновидностей нужны разные дозы , и для продуктов, прибли-жающихся к м о м е н т у прекрашения с о с т о я н и я п о к о я , т р е б у ю т с я более высокие д о з ы . Д р у г а я работа по сохранению продуктов с помощью облучения п о к а з а л а , что некоторые микроорганиз-м ы более ч у в с т в и т е л ь н ы к и з л у ч е н и я м , если они п р е д в а р и т е л ь н о подверглись ультразвуковой о б р а б о т к е . С доожжами . п о - в и д и м о м у , имеет м е с т о разная форма действия, когда к л е т к и у б и -в а ю т с я при в ы с о к и х и низких ч а с т о т а х . П е р с п е к т и в н ы м и я в л я ю т с я исследования при к о м б и -нированной радиационной о б р а б о т к е с хранением ф р у к т о в в холоде с целью продления срока х р а н е н и я . П р о в о д и т с я р а б о т а по и с п о л ь з о в а н и ю облучения для у м е н ь ш е н и я м и к р о б н о г о з а -г р я з н е н и я с у ш е н ы х з а м о р о ж е н н ы х п р о д у к т о в .

CONSERVACION DE ALGUNAS FRUTAS Y VERDURAS POR IRRADIACION. Se han estudiado en labora-torio los métodos seguidos para prolongar el perïodo de conservaciôn de determinadas frutas tropicales y para

esterilizarlas рог irradiaciôn. Se demostrô que las ruedas de mango y de zapote pueden conservarse durante un

ano inactivando primero las enzimas mediante un tratamiento térmico moderado y sometiendo luego las ruedas

a una dosis de 4 • 105 rad. Los productos irradiados tuvieron la misma aceptaciôn que los esterilizados térmica-

mente. El cambio de sabor de los mangos en conserva, debido a la oxidaciôn, se redujo al minimo en los casos

en que la supresiôn de oxigeno por agotamiento fue eficaz. Las pérdidas de vitaminas de los mangos y zapotes

no fueron mayores que en la esteril izaciön térmica . Utilizando un t ra tamiento combinado para esterilizar

zumo de naranja, pudo reducirse la dosis de irradiaci<5n de 800 krad a 400 krad mediante un tratamiento térmico

localizado de 15 min a 50°C. Se logrô una retenciôn mejor del âcido ascôrbico, la tiamina y la riboflavina.

Se comprobô que los guisantes en salmuera esterilizados por irradiaciôn a 850 krad eran superiores en cuanto a

sabor, color, contextura y cualidades generales a los tratados té rmicamente . Se comprobö que era posible

prolongar el a lmacenamiento de los mangos retrasando su maduraciön mediante un tratamiento de irradiaciôn

a dosis comprendidàs entre 1200 y 2500 rad. Este método sirve para regular la maduraciön de estos frutos

y, por lo tanto, es de gran utilidad para su envase en fâbr ica . No se encontrô diferencia alguna entre los

mangos en conserva irradiados y sin irradiar. Al estudiar la manera de inhibit la germinaciôn de patatas y

cebollas por irradiaciôn se comprobô que cada variedad éxigia una dosis diferente. A medida que el tubérculo

se aproxima al momento final del estado latente, la dosis necesaria es mâs elevada. El empleo de la irradia-

ciôn para fines de conservaciôn ha idemostrado también que determinados microorganismos son mâs sensibles

a las radiaciones cuando se les somete primero a un tratamiento ultrasônico. En el caso de las levaduras parece

ser que la acciôn exterminadora de las ondas se ejerce de forma diferente sobre las células segûn se empleen

frecuencias elevadas о bajas. Ofrecen buenas perspectivas las investigaciones en curso sobre la conveniencia de combinar la irradiaciôn con el almacenamiento en frio de frutas para prolongar el periodo de conservaciôn. También se trabaja sobre la posibilidad de emplear la irradiaciôn para reducir la contaminaciôn microbiana de los productos liofilizados.

FRUITS AND VEGETABLE PRESERVATION 117

India ,with i t s heavy population, s c a r c i t y of food m a t e r i a l and inadequate t r a n s p o r t f a c i l i t i e s , n e e d s t o p r o c e s s and p r e s e r v e m o r e f o o d s . It i s of u t m o s t i m p o r t a n c e to i t s people tha t the w a s t a g e of food be r e d u c e d to the b a r e m i n i m u m . T r a n s p o r t f a c i l i t i e s a r e i m p r o v i n g s t ead i l y u n d e r the d i f -f e r e n t f ive y e a r p l a n s u n d e r t a k e n by the G o v e r n m e n t of India , but s t i l l we f i nd s o m e f r u i t and v e g e t a b l e g r o w i n g a r e a s e x p e r i e n c i n g a g lut and t h e c i t i e s and n o n - g r o w i n g a r e a s s u f f e r i n g s c a r c i t y . U n d e r s u c h c o n d i t i o n s t h e r e i s g r e a t l o s s , d u r i n g t r a n s p o r t and s t o r a g e , of t he i m p o r t a n t food c o m m o d i t i e s in Ind i a . Much of t h i s heavy l o s s can be avo ided by adopt ing the l a t e s t t e c h n i q u e s in food p r e s e r v a t i o n .

With r e g a r d to the above cons ide ra t ions , r e s e a r c h work has been under -taken at the Atomic Energy Es tab l i shment Trombay, India, and a p rog ramme h a s been d r a w n up f o r t he p r e s e r v a t i o n , by i r r a d i a t i o n , of m a n y f r u i t s and v e g e t a b l e s of e c o n o m i c i m p o r t a n c e .

W o r k done in o u r l a b o r a t o r i e s on f r u i t and v e g e t a b l e i r r a d i a t i o n c a n be d iv ided in to t h r e e c a t e g o r i e s : (a) r a d i o s t e r i l i z a t i o n of f r u i t s and v e g e -t a b l e s , (b) r a d i o p a s t e u r i z a t i o n to i n c r e a s e t h e shelf l i f e and (c) de l ay in r i p e n i n g of f r u i t s and inh ib i t ion of s p r o u t i n g in t u b e r s .

(a) Radiosterilization

F o u r c o m m o d i t i e s a r e included in th i s s tudy: f ru i t ju ice , two f r u i t s and a c o m m o n v e g e t a b l e .

O r a n g e ju i ce

The p r inc ip l e tha t spoi lage m i c r o o r g a n i s m s a r e s ens i t i zed to suble thal t e m p e r a t u r e s by p r e - i r r a d i a t i o n w a s appl ied to the s t e r i l i z a t i o n of o r a n g e j u i c e . The s t e r i l i z a t i o n dose of 800 k rad could be brought down to 4 0 0 k r a d if combined with a p o s t - i r r a d i a t i o n hea t t r e a t m e n t of 15 min a t 50°C. Th is combina t ion t r e a t m e n t e n s u r e s b e t t e r r e t e n t i o n of a s c o r b i c ac id , t h i amine and r ibo f l av in a s c o m p a r e d with the rad ia t ion t r e a t m e n t above by the h igher dose . Colour c h a n g e s in the i r r a d i a t e d ju ice a r e min imized under n i t rogen a t m o s p h e r e (F igs 1, 2), while a t the s a m e t i m e t h e r e was no no t iceab le d i f -f e r e n c e between the s u r v i v a l of the spoi lage o r g a n i s m s when i r r ad i a t i on was c a r r i e d out u n d e r oxygen o r n i t r o g e n . The a b s e n c e of t h e "oxygen e f f e c t " m a y be a r e s u l t of the t o t a l combined e f f ec t of the p r e s e n c e of s m a l l quan-t i t i e s of occ luded a i r , f r e e r a d i c l e a c c e p t o r s , s u c h a s a s c o r b i c ac id , and r a d i a t i o n p r o t e c t i n g f a c t o r s , s u c h a s S - H a m i n o a c i d s , c a r o t e n o i d s , p r o -t e i n s , e t c .

M a n g o e s and s a p o t a

Alphonso mangoes and sapota (Achras sapota) s l i c e s in cans can be p r e -s e r v e d f o r a y e a r by f i r s t i n a c t i v a t i n g the r e s p i r a t o r y e n z y m e s by a m i l d heat t r e a t m e n t of about 70°C and subsequent ly i r r ad i a t i ng them by a radiat ion d o s e of 4 X 1 0 5 r a d . It i s e s s e n t i a l to i n a c t i v a t e the r e s p i r a t o r y e n z y m e s by a m i l d h e a t t r e a t m e n t t o a v o i d a n a e r o b i c r e s p i r a t i o n in t h e m a n g o e s , g iving r i s e to a h a r d sweU in the c a n s . F i g u r e 3 shows the o p t i m u m t e m -

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F I G . l . Colour changes in orange ju ice irradiated under nitrogen and oxygen.

FIG.2 . Colour changes in orange ju ice irradiated under nitrogen and oxygen.

p e r a t u r e f o r i n a c t i v a t i n g r e s p i r a t o r y e n z y m e s a s d e t e r m i n e d by the W a r b u r g a p p a r a t u s . P e e l e d m a n g o e s , t h e r e f o r e , w e r e s l i c e d a n d p o u r e d i n t o 3 0 1 X 2 0 6 c a n s w i t h 40% s u c r o s e s y r u p and s u b j e c t e d t o a t e m p e r a t u r e of 70°C f o r 10 m i n . T h e r e w a s e v i d e n c e t o show t h a t t h e e f f e c t i v e n e s s of the e x h a u s t i n g p r o c e s s h a d m u c h t o do w i t h t h e q u a l i t y of t h e r a d i o s t e r i l i z e d f i n a l p r o d u c t . It w a s t h e r e f o r e n e c e s s a r y to s u b j e c t t h e s e c a n s to a v a c u u m of about 28 in Hg f o r 5 m i n to r e m o v e m u c h of the occ luded a i r be fo re sea l ing t h e m . O x i d a t i v e f l a v o u r c h a n g e s w e r e m i n i m i z e d w h e n e x h a u s t i n g w a s e f f i c i e n t .

F o o d - s p o i l a g e o r g a n i s m s a r e s e n s i t i z e d t o s u b l e t h a l t e m p e r a t u r e s by p r e - i r r a d i a t i o n . F i g u r e 4 shows the e f f ec t of p o s t - i r r a d i a t i o n heat t r e a t m e n t of 50°C on t h e y e a s t S a c c h a r o m y c e s c e r e v e s i a e i n m a n g o j u i c e . F i g u r e 5 s h o w s t h a t B a c i l l u s s u b t i l i s s p o r e s in p h o s p h a t e b u f f e r d id not show h i g h e r s ens i t i v i t y to t e m p e r a t u r e s f r o m 50-60?C by p r e - i r r a d i a t i o n . F o r th is r e a s o n , i n t h e m a n g o p r o d u c t d e v e l o p e d b y t h i s m e t h o d , i t w a s f o u n d i m m a t e r i a l w h e t h e r the h e a t t r e a t m e n t p r e c e d e d o r f o l l o w e d i r r a d i a t i o n , s i n c e 90% of the y e a s t c e l l s w e r e k i l l e d by t h e h e a t t r e a t m e n t a l o n e , t h e r e m a i n i n g 10% be ing i n a c t i v a t e d by the r a d i a t i o n p r o c e s s .

FRUITS A N D VEGETABLE PRESERVATION 119

FIG.3 . Opt imum tempera tu re for inac t iva t ing respiratory enzymes in mangoes .

x 1 0 3 R A D

FIG.4 . Post- irradiat ion hea t sensi t izat ion of Saccharomyces ce reves iae in m a n g o ju ice .

Mangoes w e r e found to be v e r y s e n s i t i v e to r ad i a t i on , w h e r e a s s a p o t a s w e r e not a f f ec t ed even when i r r a d i a t e d to 1. 2X10 6 r a d . In mangoes , unlike

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FIG. 5. Post- irradiat ion hea t t rea tment of Bacillus spores in phosphate buffer .

t he s a p o t a s , e v e n s m a l l r e s i d u a l a m o u n t s of a i r could n u l l i f y f a c t o r s , such a s n i t r o g e n pack ing ,wh ich o t h e r w i s e i m p r o v e the f l a v o u r .

Organolep t ic t e s t s by a pane l of j u d g e s showed that the rad ia t ion s t e r i l -i zed mango and sapota s l i c e s w e r e a s accep tab le a s the t h e r m a l l y s t e r i l i z e d c o n t r o l s . Vi tamin l o s s e s in both of t hese i r r a d i a t e d p roduc t s were not m o r e than in the t h e r m a l l y s t e r i l i z e d con t ro l s .

P e a s

Radiat ion s te r i l i za t ion was a l so employed fo r p re se rva t ion of peas . After p e a s in b r ine w e r e exhaus ted at 80-85°C in 301X206 cans which were double seamed , they w e r e i r r a d i a t e d to 850 krad and heat shocked at 100°C for 5 min. T h e s e cans w e r e found to be s t e r i l e and w e r e t e s t ed organolept ica l ly and f o r v i t a m i n conten t , e t c . A t a s t e - s c o r e , b a s e d on a n ine -po in t s c a l e (1 r e p r e -sen t ing e x t r e m e d is l ike) , by a pane l of twelve t a s t e r s showed a p r e f e r e n c e -s c o r e of 4. 8 f o r t h e r m a l l y p r o c e s s e d p e a s and 6. 5 f o r i r r a d i a t e d p e a s . T h e r m a l l y p r o c e s s e d p e a s w e r e v e r y s o f t and y e l l o w in c o l o u r , w h e r e a s i r r a d i a t e d p e a s w e r e of good t e x t u r e and g r e e n in c o l o u r . The o v e r a l l q u a l i t y of t he i r r a d i a t e d p r o d u c t w a s found to be m u c h b e t t e r t h a n tha.t of t h e t h e r m a l l y p r o c e s s e d p e a s .

(b) Extension of storage life

Dif f e r en t d o s e s of r a d i a t i o n ranging f r o m 12 to 200 k r a d w e r e employed f o r de lay ing the r i p e n i n g of r a w a lphonso m a n g o e s . T h e o p t i m u m d o s e f o r

FRUITS AND VEGETABLE PRESERVATION 121

t h i s p u r p o s e s e e m s to be 25 000 r a d . Ripening could be de layed in th i s c a s e by about 5-6 d, with the m i n i m u m of rad ia t ion d a m a g e . The alphonso mango i s v e r y s e n s i t i v e t o r a d i a t i o n . T h e r e w a s c o n s i d e r a b l e d e l a y in r i p e n i n g of t h e f r u i t i r r a d i a t e d t o 25 000 r a d . It w a s a l s o n o t i c e d t h a t t h e r e w a s a p r o g r e s s i v e de t e r i o r a t i on of the quali ty of the f r u i t with i n c r e a s e in radia t ion d o s e , 200 k r a d g iv ing a c o m p l e t e l y d a r k e n e d p r o d u c t . T h e r e w a s a l s o a g r e a t e r n u m b e r of spo i l ed m a n g o e s in lo t s i r r a d i a t e d to 50 000 r a d and u p -w a r d s . However , i t i s w o r t h m e n t i o n i n g t h a t no d a r k e n i n g of the p r o d u c t w a s o b s e r v e d in m a n g o e s i n c a n s i r r a d i a t e d t o 400 000 r a d . T h i s s h o w s t h a t r e s p i r i n g m a n g o e s a r e m o r e a f f e c t e d by r a d i a t i o n .

C o n t r o l of r i pen ing o f f e r s a g r e a t advan tage dur ing t r a n s - s h i p m e n t a s we l l a s in canning p r a c t i c e . Canning f a c t o r i e s in India a r e not able s o m e -t i m e s to m a t c h t h e i r p roduc t ion wi th the r ipen ing r a t e of the mangoes , with c o n s e q u e n t w a s t a g e . T h i s l o s s can be a r r e s t e d by con t ro l l ing the r ipen ing of t h e m a n g o e s . F r u i t s r i p e n e d a f t e r a d m i n i s t e r i n g a r a d i a t i o n d o s e of 50 000 r a d (h ighes t d o s e t h a t c a n be employed) have a l s o b e e n canned and s t e r i l i z e d t h e r m a l l y u s i n g a p r o c e s s s i m i l a r to tha t u s e d by c o m m e r c i a l c a n n e r i e s . No d i f f e r e n c e o r g a n o l e p t i c a l l y o r in co lou r o r v i t a m i n conten t could be o b s e r v e d in i r r a d i a t e d and n o n - i r r a d i a t e d , t h e r m a l l y canned m a n -g o e s . So c o n t r o l of r i p e n i n g c a n be a good t oo l even f o r t h e c o n v e n t i o n a l p r o c e s s e r .

(с) Inhibition of sprouting in potatoes and onions

W o r k on Indian v a r i e t i e s of po ta toes and onions was unde r t aken to f ind the op t imum rad ia t ion dose fo r sprout inhibit ion. The s to rage life of Phulwa po t a toe s and Redglobe onions when i r r a d i a t e d to 6000 rad could be extended by l i m o n t h s f o r po t a toe s and 1 month f o r on ions at r o o m t e m p e r a t u r e (21-35°C) and by 6 l and 3 i mon ths , r e s p e c t i v e l y , in cold s t o r age (10-12°C), on a 10% w a s t a g e b a s i s . O t h e r v a r i e t i e s of p o t a t o e s (Up to Date and Gola) w e r e i r r a d i a t e d in a n o t h e r e x p e r i m e n t and a v a r i e t a l d i f f e r e n c e f o r d o s e r e q u i r e m e n t was e s t ab l i shed , the Up to Date v a r i e t y r equ i r i ng 9000 r a d f o r s p r o u t inh ib i t ion . The s t a g e of m a t u r i t y of po t a toe s a l s o a f f e c t e d the f ina l dose f o r s p r o u t inhibi t ion , t h o s e n e a r i n g the b r e a k in s p r o u t d o r m a n c y r e -q u i r i n g h ighe r d o s e s of a t l e a s t 12 000 r a d .

Other programmes on radiation preservation

Combina t ion of u l t r a s o n i c and r a d i a t i o n t r e a t m e n t s

To m i n i m i z e r ad ia t ion d a m a g e i t i s i m p o r t a n t to lower the e f fec t ive r a -d ia t ion d o s e . T h i s can be ach i eved by combina t ion t r e a t m e n t s , One such t r e a t m e n t developed in our l a b o r a t o r y i s the p r e v i o u s u l t r a s o n i c t r e a t m e n t of s u s p e n s i o n s of f o o d - s p o i l a g e m i c r o o r g a n i s m s to r a d i a t i o n . It w a s o b -s e r v e d tha t M i c r o c o c c u s r a d i o d u r a m s and S t r e p t o c o c c u s f a e c a l i s a r e both s e n s i t i z e d to g a m m a r a d i a t i o n by p r e v i o u s u l t r a s o n i c t r e a t m e n t . F i g u r e 6 shows th is e f fec t . It s e e m s that the D-value, that i s the 90% reduction value, f o r t he combina t ion t r e a t m e n t i s j u s t half of tha t of the r a d i a t i o n t r e a t m e n t a l o n e . Ca l cu l a t i on of the f i n a l s t e r i l i z i n g d o s e f o r foods c o n t a m i n a t e d by

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100 GAMMA-DOSE SURVIVAL

L CURVE FOR V t M. RADIOOURANS

GAMMA-OOSE SURVIVAL CURVE FOR S. FAECALIS

e 0.01 t

1 2 3 4 5 6 5 10 15 20 25 3 0

RADIATION D O S E ( h ) RADIATION DOSE ( m l n )

FIG.6 . Effect of combina t ion of ultrasonic and radiat ion t rea tments on food-spoi lage microorganisms.

t h e s e o r g a n i s m s wi l l t h e r e f o r e show a p p r e c i a b l e d e c r e a s e in the r e q u i r e d r a d i a t i o n t r e a t m e n t .

Ano the r s tudy with u l t r a s o n i c t r e a t m e n t of S a c c h a r o m y c e s c e r e v e s i a e a t d i f f e r en t f r e q u e n c i e s showed that h igher u l t r a son ic f r e q u e n c i e s (1500 kc/s) have a d i f f e r e n t mode of ac t ion in ki l l ing the y e a s t c e l l s than that a t l o w e r f r e q u e n c i e s (20 k c / s ) . In the l a t t e r c a s e th i s i s caused by disrupt ion of ce l l s , and a t the h i g h e r f r e q u e n c i e s i t i s p r e s u m a b l y a r e s u l t of the a b s o r p t i o n of ene rgy . No sens i t iza t ion of m i c r o b i a l c e l l s to gamma radiat ion i s observable by p r e v i o u s low f r e q u e n c y u l t r a s o n i c t r e a t m e n t a s opposed to tha t ob ta ined , a t h i g h e r f r e q u e n c y t r e a t m e n t (300 k c / s ) . T h i s a s p e c t of t he p r o b l e m i s v e r y i m p o r t a n t f r o m t h e po in t of v i ew of t h e c o m b i n a t i o n t r e a t m e n t .

P r o j e c t s to combine g a m m a r ad i a t i on with cold s t o r a g e of f r u i t s t o ex -t e n d r e f r i g e r a t e d she l f l i f e , and i r r a d i a t i o n of f r e e z e - d r i e d p r o d u c t s t o r e d u c e m i c r o b i o l o g i c a l c o n t a m i n a t i o n , have a l s o been u n d e r t a k e n . P r e -l i m i n a r y r e s u l t s show s o m e p r o m i s e .

M i c r o b i a l g rowth po ten t i a l of i r r a d i a t e d po ta toes i s a l s o being s tud ied . E x t r a c t s o b t a i n e d f r o m i r r a d i a t e d and n o n - i r r a d i a t e d p o t a t o e s w e r e h e a t s t e r i l i z e d and inocula ted with fou r d i f f e r e n t m i c r o o r g a n i s m s ; t h e i r growth w a s fo l l owed e i t h e r t u r b i d i m e t r i c a l l y o r by the p l a t e count m e t h o d . T h e s a m e e x p e r i m e n t was r e p e a t e d 24 and 48 h a f t e r i r r a d i a t i o n of the po ta toes . Inhib i t ion of m i c r o b i a l g r o w t h w a s o b s e r v e d i m m e d i a t e l y a f t e r i r r a d i a t i o n , but a f t e r 48 h of s t o r age t h e r e was no inhibition at al l ; on the cont rary , the re w a s i n c r e a s e d g r o w t h . T h e s e e x p e r i m e n t s would show tha t s o m e an t i -me tabo l i t e s , which become annealed dur ing s torage , a r e fo rmed immediate ly a f t e r i r r a d i a t i o n .

USE OF IONIZING RADIATIONS TO PROLONG THE STORAGE LIFE OF FRUIT AND BERRIES

(REVIEW OF WORK IN THE USSR)

V . I . ROGACHEV

ALL-UNION RESEARCH INSTITUTE FOR THE CONSERVATION INDUSTRY,

MOSCOW, USSR


USE OF IONIZING RADIATION TO PROLONG THE STORAGE UFE OF FRUIT AND BERRIES (REVIEW OF WORK IN THE USSR). The irradiation of fruit is considered as a factor influencing thé microflora of fruits and the physiological and biochemical processes occurring during the storage of fruit. Accordingly, the survey presents the results of experiments studying the effect of irradiation on: (a) Microorganisms which cause fruit and berries to spoil; (b) The spoiling of fruits caused by repeated infection by microflora; (c) The bio-chemical processes occurring in fruit while stored; (d) The ripening of fruit during storage; (e) The periods for which fruits of varying degrees of ripeness can be stored; (f) Opportunities for the industrial processing of fruit.

In conclusion, it gives the results of experiments on the storage of irradiated fruits and berries: straw-berries, raspberries, blackcurrants, cherries, apricots, peaches, tomatoes, grapes, mandarines and subtropical persimmons and figs. Recommendations are made as to optimum irradiation doses for prolonging the periods during which these fruits and berries can be stored.

UTILISATION DES RAYONNEMENTS IONISANTS TOUR PROLONGER LA DUREE DE CONSERVATION DES FRUITS (EXPOSE DES TRAVAUX EN UNION SOVIETIQUE). L'irradiation des fruits est étudiée en tant que facteur agissant sur la microflore des fruits et sur les processus physiologiques et biochimiques s'opérant dans les fruits stockés. A ce propos, l'auteur apporte des données expérimentales concernant l'influence que l'irradiation exerce: a) sur les micro-organismes provoquant une altération des fruits; b) sur l'altération des fruits lors d'une nouvelle infection par la microflore; c) sur les processus biochimiques dans les fruits stockés; d) sur la maturation des fruits stockés; e) sur la durée de conservation de fruits parvenus à des degrés de maturité différents; f) sur Ц possibilité d'une transformation industrielle des fruits.

En conclusion l'auteur indique les résultats des essais de conservation par irradiation dont ont fait l'objet les fruits ci-après: fraises, framboises, cassis, cerises, abricots, pêches, tomates, raisins, mandarines, kakis des régions subtropicales et figues. Il recommande des doses d'irradiation optimales pour prolonger leur duriée de conservation.

ИСПОЛЬЗОВАНИЕ ИОНИЗИРУЮЩЕГО ОБЛУЧЕНИЯ ДЛЯ ПРОДЛЕНИЯ СРОКОВ ХРА-НЕНИЯ ФРУКТОВ И ЯГОД (ОБЗОР Р А Б О Т Ы , ОСУЩЕСТВЛЕННОЙ В СССР) . Облучение плодов рассматривается как фактор, влияющий на микрофлору плодов и на физиолого-био-химические процессы в плодах при их хранении. В связи с этим приводятся результаты экспе-риментов по влиянию облучения: al на микроорганизмы, вызывающие порчу плодов и ягод; б) на порчу плодов при их повторном заражении микрофлорой; в) на биохимические процессы в плодах при их хранении: г) на созревание плодов во время хранения; д) на сроки хранения плодов различной степени зрелости; е) на возможность промышленной переработки плодов.

В заключение даются оезультаты опытов по хранению облученных плодов и ягод: земля-ники. малины, черной сморг дины, черешни, абрикосов, персиков, томатов, винограда, манда-ринов, субтропической хурмы и инжира. Рекомендуются оптимальные дозы облучения для продления сроков хранения этих плодов и ягод.

UTILIZACION DE LAS RADIACIONES IONIZANTES PARA PROLONGAR LA CONSERVACION DE FRUTAS Y BAYAS (ESTUDIO DE LA LABOR REALIZADA EN LA UNION SOVIETICA). En la memoria se examina la irradiación de frutas como factor que influye sobre su microflora y sobre los procesos fisiológicos y bioquí micos que se producen en la fruta almacenada. A este respecto, el autor cita resultados experimentales de la influen-cia que ejerce la irradiación: a) sobre los microorganismos causantes del deterioro de las frutas y de las bayas;

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124 ROGACHEV

b) sobre el deterioro de las frutas cuando la microflora provoca una nueva infección; c) sobre los procesos bio-químicos de las frutas durante su almacenamiento; d) sobre la maduración de las frutas almacenadas; e) sobre la duración de la conservación de frutas que han llegado a grados de madurez diferentes, y f) sobre las posibili-dades de transformación industrial de las frutas.

En conclusión, el autor indica los resultados obtenidos en los ensayos de conservación por irradiación de las siguientes frutas y bayas: fresas, frambuesas, grosellas negras, cerezas, albaricoques, melocotones, tomates, uva, mandarinas, caquis subtropicales e higos, y recomienda dosis óptimas de irradiación para pro-longar su conservación.

Ion i z ing r a d i a t i o n s a f f e c t f r e s h f r u i t and b e r r i e s in two w a y s : t h e y i n -h ib i t the g r o w t h of m i c r o o r g a n i s m s in the r a w f r u i t , t h u s p r e v e n t i n g m i c r o -b i o l o g i c a l s p o i l a g e ; and t h e y c a u s e p h y s i o l o g i c a l and b i o c h e m i c a l d a m a g e to f r u i t t i s s u e s , which i s l i ab l e to r e d u c e n a t u r a l i m m u n i t y and to a c c e l e r a t e s p o i l a g e , if m i c r o f l o r a a g a i n a t t a c k t h e f r u i t a f t e r i r r a d i a t i o n . Both t h e s e e f f e c t s h a v e t o be t a k e n in to a c c o u n t w h e n s tudy ing t h e r a d i a t i o n c o n d i t i o n s s u i t a b l e f o r p r o l o n g i n g the s t o r a g e l i f e of f r e s h f r u i t and b e r r i e s . T h e p r e s e n t p a p e r d e s c r i b e s t h e m a i n r e s u l t s of t h e w o r k c a r r i e d out on t h i s p r o b l e m i n r e c e n t y e a r s i n t h e USSR.

E F F E C T O F I R R A D I A T I O N ON M I C R O O R G A N I S M S

S tud ies have b e e n m a d e of t h e r a d i a t i o n r e s i s t a n c e of the t h i r t e e n t y p e s of m o u l d s and y e a s t s w h i c h m o s t f r e q u e n t l y g i v e r i s e t o s p o i l a g e in f r e s h f r u i t and v e g e t a b l e s . T h e m o s t r e s i s t a n t t y p e s w e r e R h i z o p u s n i g r i c a n s (1. 2 t o 1. 5 M r a d ) , R h i z o p u s s t o l o n i f e r (1. 0 to 1. 5 Mrad ) and B o t r y t i s c i n e r e a (1. 0 t o 1 . 5 M r a d ) .

W i t h a n u m b e r of m i c r o o r g a n i s m s t h e d e g r e e of r a d i a t i o n r e s i s t a n c e d e p e n d s on t h e a g e of t h e c u l t u r e s . T h e f o l l o w i n g d a t a h a v e b e e n o b t a i n e d f o r A l t e r n a r í a c i t r i : a 1 - d c u l t u r e died a t 0. 4 to 0. 6 M r a d , a 3 - to 5 - d c u l -t u r e a t 0. 6 to 0. 8 M r a d and an 8 - to 10 -d c u l t u r e a t 1. 0 M r a d . S p o r e s e x -h i b i t e d t h e g r e a t e s t r e s i s t a n c e . F o r s o m e t y p e s ( e . g . M o n i l i a f r u c t i g e n a , P e n i c i l l i u m i t a l i c u m , P e n i c i l l i u m d i g i t a t u m ) t h e a g e of t h e c u l t u r e w a s u n i m p o r t a n t .

It m a y be conc luded f r o m the da ta ob ta ined tha t d o s e s of up to 1 . 5 M r a d would be r e q u i r e d to s u p p r e s s c o m p l e t e l y the ac t iv i ty of the m i c r o f l o r a which g i v e s r i s e t o s p o i l a g e in f r e s h f r u i t and b e r r i e s . H o w e v e r , d o s e s of t h i s o r d e r c o n s i d e r a b l y i m p a i r t he o r g a n o l e p t i c p r o p e r t i e s of the f r u i t i r r a d i a t e d ; t he c o l o u r b e c o m e s f a i n t e r o r d a r k e r , the t i s s u e s g row sof t , j u i ce i s exuded, and b r o w n , g r e y i s h b r o w n o r b l a c k s p o t s a p p e a r on the s u r f a c e of the f r u i t . Such d o s e s c a n n o t t h e r e f o r e be u s e d .

T h e m a x i m u m d o s e w h i c h d o e s no t c a u s e d e t e r i o r a t i o n in q u a l i t y i s , d e p e n d i n g on t h e t y p e of f r u i t i r r a d i a t e d , 0. 4 t o 0. 6 M r a d . T h u s t h e d o s e r a n g e f o r i r r a d i a t i n g f r e s h f r u i t and b e r r i e s i s f r o m 0. 2 to 0. 4 - 0 . 6 M r a d .

E F F E C T O F R E P E A T E D M I C R O B I O L O G I C A L I N F E C T I O N ON T H E S T O R A G E O F I R R A D I A T E D F R U I T AND B E R R I E S

O v e r a c e r t a i n d o s e (0. 2 t o 0 . 4 M r a d , d e p e n d i n g o n t h e t y p e of f r u i t i r r a d i a t e d ) , i r r a d i a t i o n l e a d s to a c c e l e r a t e d spo i l age if t he f r u i t and b e r r i e s

STORAGE LIFE OF FRUIT AND BERRIES /

TABLE I

S T O R A G E L I F E O F C E R T A I N I R R A D I A T E D F R U I T

125

Irradiat ion dose Storage l i f e (d) before spoilage occurs for: be fore in fec t ion „ , . „ , „ , .

(Mrad) Strawberries Cherries Peaches Apricots Tomatoes Apples Tanger ines Grapes

Unirradiated control sample 3 9 6 3 3 5 5 6

0 . 1 3 9 6 3 3 5 5 6

0 .2 3 12 6 3 3 5 5 6

0 . 3 3 12 6 3 2 5 4 6

0 .4 3 12 4 2 2 2 3 6

0 .5 0 . 2 7 2 1 1 2 2 5

0 . 6 0 . 2 7 2 1 - 1 1 2 5

a r e aga in i n f ec t ed a f t e r i r r a d i a t i o n . Tab le I g i v e s d a t a on the s t o r a g e l i fe of v a r i o u s t y p e s of f r u i t and b e r r i e s i r r a d i a t e d wi th d i f f e r e n t d o s e s and t h e n a r t i f i c i a l l y i n f e c t e d wi th y e a s t s and m o u l d s .

In v iew of t he f a c t t h a t i r r a d i a t i o n r e d u c e s t h e i m m u n i t y of f r u i t , i r -r a d i a t e d f r u i t and b e r r i e s shou ld be kep t in c o n d i t i o n s w h e r e t h ë r i s k of f r e s h i n f e c t i o n i s r e d u c e d to a m i n i m u m . E v e n t h e s i m p l e s t m e t h o d s of p r e v e n t i n g d i r e c t c o n t a c t of m i c r o f l o r a wi th the i r r a d i a t e d f r u i t m a y be e f f e c t i v e . If t h i s i s done , r a d i a t i o n d o s e s c a n be s l i g h t l y i n c r e a s e d and s t o r a g e p e r i o d s t h u s p r o l o n g e d .

E F F E C T O F IRRADIATION ON T H E RIPENING O F STORED F R U I T

The p r o c e s s e s which o c c u r in s t o r e d f r u i t a r e c l o s e l y c o n n e c t e d wi th the d e g r e e of r i p e n e s s of the f r u i t . It i s imposs ib le to es tab l i sh the optimum c o n d i t i o n s of i r r a d i a t i o n and s u b s e q u e n t s t o r a g e wi thout f i r s t s tudy ing the r i p e n i n g p r o c e s s in f r u i t , b e r r i e s and v e g e t a b l e s a f t e r h a r v e s t i n g .

I n v e s t i g a t i o n s have shown that the d i f f e r e n t t y p e s of f r u i t d i f f e r widely in t h e i r r e s p o n s e to i r r a d i a t i o n . T h e i r r a d i a t i o n of a p r i c o t s and p e a c h e s h a s a c o n s i d e r a b l e e f f e c t on the o x i d a t i o n - r e d u c t i o n f e r m e n t a t i o n s y s t e m . A s a r e s u l t , t he a m o u n t s of oxygen a b s o r b e d and c a r b o n d iox ide g iven off by i r r a d i a t e d f r u i t d u r i n g s t o r a g e , and a l s o the q u a n t i t i e s of a l c o h o l and a c e t a l d e h y d e p r e s e n t in the t i s s u e s , a r e c o n s i d e r a b l y h i g h e r t h a n in the c a s e of u n i r r a d i a t e d p e a c h e s .

I r r a d i a t i o n g i v e s r i s e t o an i n c r e a s e in t h e c o n t e n t of s o l u b l e p e c t i n and to a c o r r e s p o n d i n g d e c r e a s e in the amount of p ro topec t in and of the pect in in the i n t e r m e d i a t e l a y e r s . These data a r e con f i rmed by h i s tochemica l inves t iga t ions .

The con ten t of s u g a r s and o r g a n i c a c i d s d r o p s i m m e d i a t e l y a f t e r i r -r a d i a t i o n , but a f t e r a s t o r a g e p e r i o d of s i x d a y s the v a l u e s f o r i r r a d i a t e d and u n i r r a d i a t e d f r u i t a r e a l m o s t i d e n t i c a l .

126 ROGACHEV

I r r ad ia t ion with a dose of 0. 3 Mrad was found to give r i s e to acce le ra ted c a r o t e n o i d f o r m a t i o n in u n r i p e y e l l o w - f l e s h e d p e a c h e s a s c o m p a r e d wi th t h e c o n t r o l f r u i t . H o w e v e r , i r r a d i a t i o n of r i p e p e a c h e s of t he s a m e type did not l ead to any d i f f e r e n c e f r o m u n i r r a d i a t e d s a m p l e s .

I r r a d i a t i o n w a s a l s o found to i n t e n s i f y an thocyanin f o r m a t i o n . The i n -c r e a s e d amount of an thocyanins in i r r a d i a t e d f r u i t can be explained in t e r m s of an i n t e n s i f i c a t i o n in the ox ida t ion p r o c e s s e s , in p a r t i c u l a r the oxidat ion of c o m p o u n d s in the t ann ic c o m p l e x .

T h e r i p e n i n g r a t e of i r r a d i a t e d p e a c h e s d u r i n g s t o r a g e i s g r e a t l y a f f ec t ed by v a r i o u s f a c t o r s , including the dura t ion of the s to rage per iod and the s t o r a g e t e m p e r a t u r e b e f o r e i r r a d i a t i o n . T h u s , in i r r a d i a t e d p e a c h e s p igment fo rma t ion i s a c c e l e r a t e d and th i s can be r e g a r d e d , f r o m an ex te rna l point of view, a s c o r r e s p o n d i n g to an a c c e l e r a t i o n of the r ipen ing p r o c e s s . On the o t h e r hand, t h i s p h e n o m e n o n i s a c c o m p a n i e d by s l o w e r c o n v e r s i o n of p e c t i n s u b s t a n c e s , which a f f e c t s t he c o n s i s t e n c y of the f r u i t .

The p r o c e s s e s o c c u r r i n g in i r r a d i a t e d a p r i c o t s a r e s i m i l a r to those d e s -c r i b e d a b o v e . A s a r e s u l t of c o n s i d e r a b l e a c c u m u l a t i o n of a c e t a l d e h y d e , e thano l and c a r b o n dioxide, a p r i c o t s b e c a m e u n s a t i s f a c t o r y in qual i ty a f t e r a s t o r a g e p e r i o d of s e v e n d a y s . H o w e v e r , f u r t h e r i n v e s t i g a t i o n s showed tha t the t rouble was not so much the amount of t hese subs tances a s the a l t e r -a t i o n s wh ich took p l a c e i n the t r e n d of t h e o x i d a t i o n - r e d u c t i o n p r o c e s s e s u n d e r the i n f l u e n c e of i r r a d i a t i o n . A s tudy of t h e r e s p i r a t o r y p r o c e s s showed that o v e r the f i r s t t h r e e days the i r r a d i a t e d f r u i t gave off m o r e c a r b o n dioxide (28. 5 m l / k g h) t han u n i r r a d i a t e d f r u i t (18 m l / k g h) and a b -s o r b e d m o r e oxygen (27 and 16 m l / k g h, r e s p e c t i v e l y ) . In the d a y s tha t followed, the i r r a d i a t e d f r u i t gave off v e r y l i t t le c a r b o n dioxide (7-8 m l / k g h) but b e g a n to a b s o r b a g r e a t d e a l of oxygen , i . e . t h e r e w a s c o n s i d e r a b l e i n t e n s i f i c a t i o n of the oxidat ion p r o c e s s e s . On f u r t h e r s t o r a g e , the amount of c a r b o n d ioxide g iven off by the i r r a d i a t e d f r u i t aga in i n c r e a s e d s h a r p l y and t h e r e was a d e c r e a s e in oxygen abso rp t ion . Consequent ly , at t h i s s tage a n a e r o b i c - r e s p i r a t i o n p r o c e s s e s w e r e p r e d o m i n a n t and a n u m b e r of c o m -pounds began to b r e a k down, in p a r t i c u l a r s u g a r s , whose content f e l l f r o m 9-7%. T h e s e s h a r p changes in the na tu re and r a t e of the oxidat ion-reduct ion p r o c e s s e s did not occur in the con t ro l s a m p l e s .

I r r a d i a t i o n h a s a d i f f e r e n t e f f e c t on s t r a w b e r r i e s , which exhibit delayed p i g m e n t f o r m a t i o n ( F i g . 1) and r e d u c e d b r e a k d o w n of p e c t i n s u b s t a n c e s .

T h e e f f e c t of i r r a d i a t i o n on the r i p e n i n g of t o m a t o e s a f t e r h a r v e s t i n g depends on the d e g r e e of r i p e n e s s of the f r u i t . In pink t o m a t o e s i r r a d i a t i o n i n c r e a s e d (in c o m p a r i s o n wi th t h e c o n t r o l s a m p l e s ) t he a m o u n t of c a r b o n d ioxide g iven off o v e r the f i r s t two d a y s (20-24 m l / k g h, a s opposed to 16-17 m l / k g h) and r e d u c e d t h e a b s o r p t i o n of oxygen (6 -10 m l / k g h, a s opposed to 17-20 m l / k g h) . The r e s p e c t i v e r e s p i r a t i o n c o e f f i c i e n t s w e r e 0. 83 to 0. 94 in the i r r a d i a t e d f r u i t and 1. 06 to 1. 30 in the con t ro l f r u i t . In subsequent days the r e s p i r a t i o n p r o c e s s of the i r r a d i a t e d f ru i t was r e s to r ed , and on the f o u r t h day it r e a c h e d the n o r m a l l e v e l . G r e e n f r u i t a f f e c t e d by i r r a d i a t i o n did not r e c o v e r even a f t e r a p e r i o d of two w e e k s .

I r r a d i a t i o n of pink t o m a t o e s c a u s e d a c o n s i d e r a b l e i n c r e a s e in the ca rbon-d iox ide content of the t i s s u e s , and a reduc t ion in the quantity of oxy-gen, in c o m p a r i s o n with u n i r r a d i a t e d f r u i t . A f t e r two days the composi t ion

STORAGE LIFE OF FRUIT AND BERRIES / 127

WAVE LENGTH (nm)

F I G . l . Optical density of extracts of pigments from strawberries after storage period of three days 1. Init ial raw product 2 . Control (unirradiated) 3 . Irradiated with a dose of 100 krad at a dose rate of 750 R/s 4 . Irradiated with a dose of 100 krad at a dose rate of 1100 R/s 5 . Irradiated with a dose of 300 krad at a dose rate of 750 R/s 6. Irradiated with a dose of 300 krad at a dose rate of 1100 R/s 7 . Irradiated with a dose of 600 krad at a dose rate of 750 R/s 8 . Irradiated with a dose of 600 krad at a dose rate of 1100 R/s

of the g a s e s in the t i s s u e s of i r r a d i a t e d and u n i r r a d i a t e d t o m a t o e s b e c a m e iden t i ca l . In g r e e n i r r a d i a t e d f r u i t , t h i s evening-out p r o c e s s did not occur , a s a r e su l t of the in tens i f i ca t ion in anaerobic r e s p i r a t i o n . This i s conf i rmed by data on the i n c r e a s e d content of aceta ldehyde and ethanol .

I r r a d i a t i o n only h a s a subs t an t i a l e f fec t on caro tenoid synthes i s in g reen f r u i t . A f t e r a p e r i o d of 10-14 d fo l lowing i r r a d i a t i o n , such f r u i t w a s found t o con t a in 2 . 5 t o 3 t i m e s l e s s c a r o t e n o i d s t h a n the c o n t r o l s a m p l e s . R e -t a r d e d s y n t h e s i s of c a r o t e n o i d s w a s even m o r e a p p a r e n t a t high i r r a d i a t i o n d o s e s . In the pink f r u i t , w h e r e the syn thes i s of c a r o t e n o i d s had begun be fo re i r r a d i a t i o n , t he l a t t e r had no e f f ec t on the deve lopment of the p r o c e s s .

Study of the l i g h t - a b s o r p t i o n s p e c t r a wi th hexane e x t r a c t s (F ig . 2) r e -vealed that not only a r e lycopene and ca ro tene (X= 400-520 nm) fo rmed during s to rage , but that t h e r e i s a l so a f u r t h e r accumulat ion of co lou r l e s s p r e c u r s o r compounds (X= 2 8 0 - 3 0 0 n m and X= 340nm) , in p a r t i c u l a r ß - c a r o t e n e , phyto-f l ueneandphy toene . At the s a m e t i m e even e a r l i e r p r e c u r s o r s (A= 260-280 nm), in p a r t i c u l a r t e t r a h y d r o p h y t o e n e , d i s a p p e a r e d . T h e s e c h a n g e s w e r e c h a r -a c t e r i s t i c s of both u n i r r a d i a t e d and i r r a d i a t e d f r u i t , but i n i r r a d i a t e d f r u i t c a r o t e n o i d s y n t h e s i s p r o c e e d e d m o r e s lowly . T h i s r e d u c t i o n in syn the t i c a c t i v i t y in t h e i r r a d i a t e d f r u i t i s c a u s e d by t h e e f f e c t of i r r a d i a t i o n on the e n e r g y p r o c e s s e s in t h e c e l l s .

128 ROGACHEV

2.25 2 "

.1.75

2.00

1.50

0.50:

0.75

0.00

1.00

0.25

ш о

2(0 M 300 20 40 «0 M 400 20 40 № Ю 300 20 40 60 «0 «00 20 40 60 M 700 790

WAVE LENGTH [ u m ]

FIG. 2. Carotenoid synthesis in tomatoes 1. Ini t ial raw product 1* Irradiated with a dose of 300 krad after storage period of 3 d 1" Irradiated with a dose of 300 krad after storage period of 13 d 2 ' Control (unirradiated) samples after storage period of 3 d 2* Control (unirradiated) af ter storage period of 13 d

I r r a d i a t i o n - i n d u c e d i n t e r f e r e n c e wi th o x i d a t i o n - r e d u c t i o n p r o c e s s e s in pink and g r e e n t o m a t o e s does not only a f fec t ca ro teno id syn thes i s . Func-t iona l physiological d i s t u r b a n c e s (the appea rance of da rk spots on the sur face of the f r u i t fo l lowed by a t t a c k s of mould in t h e s e p l aces ) a l s o o c c u r . P ink and r e d f r u i t p r o v e d to be m u c h l e s s s u b j e c t to phys io log i ca l d i s t u r b a n c e s a f t e r i r r a d i a t i o n , and in t h i s r e s p e c t w e r e no d i f f e r e n t f r o m u n i r r a d i a t e d t o m a t o e s . F r o m t h e po in t of v i e w of t h e c o n t e n t of b a s i c c h e m i c a l s u b -s t a n c e s , t h e i r r a d i a t e d g r e e n f r u i t w e r e h a r d l y a n y d i f f e r e n t f r o m u n i r -r a d i a t e d f r u i t .

It would s e e m , t h e r e f o r e , t h a t i r r a d i a t i o n shou ld only be c a r r i e d out w i th r e d t o m a t o e s . T h e i r r a d i a t i o n of g r e e n and p ink t o m a t o e s d o e s not y i e ld pos i t ive r e s u l t s . The s l o w e r r a t e of r i pen ing which r e s u l t s f r o m the s l o w e r a c c u m u l a t i o n of c a r o t e n o i d s i s not a c c o m p a n i e d by the r e t e n t i o n of s t r u c t u r a l f i r m n e s s in the t i s s u e s . F u r t h e r m o r e , i n t e r f e r e n c e wi th the o x i d a t i o n - r e d u c t i o n p r o c e s s e s l e a d s to a r e d u c t i o n in the i m m u n i t y of the f r u i t , the o c c u r r e n c e of func t iona l d i s o r d e r s in the t i s s u e s , and m o r e rapid in fec t ion of the t o m a t o e s with m i c r o o r g a n i s m s dur ing s t o r a g e .

To ob ta in i n f o r m a t i o n on the d i s t u r b a n c e s in the e n e r g y m e t a b o l i s m of f r u i t b r o u g h t abou t by i r r a d i a t i o n , a s tudy w a s m a d e of t he p r o c e s s of oxidative phosphoryla t ion and the dynamics of change in the phosphorus com-pounds of the a c i d - s o l u b l e f r a c t i o n , which conta ins compounds with m a c r o -e n e r g e t i c bonds p l ay ing the p a r t of e n e r g y d o n o r s . T h e s e i n v e s t i g a t i o n s w e r e c a r r i e d out w i th t o m a t o e s , p e a c h e s , a p r i c o t s and a p p l e s .


FIG.3. Effect of irradiation on the phosphorylation capaci ty of fruit tissues • absorption of 0 2 ( m l / g of tissue in 1 hour) • absorption of P ( m g / g of tissue in 1 hour) ' Green tomatoes 1. Control (unirradiated) 2 . Irradiated at a dose of 300 000 rad at a dose ra te of 28 R/s 3 . Irradiated at a dose of 300 000 rad at a dose ra te of 1100 R/s Red tomatoes 1 ' Control (unirradiated) 2 ' Irradiated at a dose of 300 000 rad at a dose ra te of 28 R/s

Studies of the r a t e of ox ida t ive phosphory l a t i on in i r r a d i a t e d t o m a t o e s r evea led a cons ide rab le reduct ion in the oxidation and espec ia l ly in the phos-phorylat ion capaci ty of t i s s u e s ( subs t ra te - succ ina te ) a f t e r i r rad ia t ion (Fig.3) .

T h e a m o u n t of p h o s p h o r u s i n t h e a c i d - s o l u b l e f r a c t i o n in i r r a d i a t e d s a m p l e s w a s l i t t l e d i f f e r e n t f r o m t h a t in t h e c o n t r o l s a m p l e s . H o w e v e r , whi le t he a m o u n t of i n o r g a n i c p h o s p h o r u s w a s a l w a y s h i g h e r , t he a m o u n t of phosphorus p r e s e n t following a 7 - m i n hydro lys i s in a n o r m a l HCl solution (i. e . p h o s p h o r u s of A T P - t y p e compounds ) was in a l l c a s e s a l m o s t half the c o r r e s p o n d i n g a m o u n t in u n i r r a d i a t e d f r u i t . It c an t h e r e f o r e be a s s u m e d that the i r r ad i a t i on of t oma toes s lows down the p r o c e s s of adenine nucleotide f o r m a t i o n , and t h a t t h i s , t o g e t h e r wi th the d i s t u r b a n c e s of t h e o x i d a t i v e -p h o s p h o r y l i z a t i o n p r o c e s s e s , l e a d s t o a s h a r p r e d u c t i o n (but not to c o m -p l e t e c e s s a t i o n ) of e n e r g y m e t a b o l i s m in u n r i p e f r u i t .

Studies of oxidat ive phosphoryla t ion at d i f f e r en t points in the r e s p i r a t i o n cha in (oxidat ive s u b s t r a t e s - a l p h a - k e t o g l u t a r a t e , s u c c i n a t e , py ruva te ) in p é a c h e s and a p r i c o t s r e v e a l e d d e c r e a s e d p h o s p h o r y l a t i o n and oxida t ion s l igh t ly d i f f e r e n t f r o m , o r i d e n t i c a l with, t ha t of the c o n t r o l s (Fig . 4). O x i d a t i v e - p h o s p h o r y l a t i o n d i s t u r b a n c e s w e r e found to be m o r e p ronounced the h i g h e r the i r r a d i a t i o n d o s e s and the longe r the s t o r a g e p e r i o d s . T h e r e was a p a r t i c u l a r l y s h a r p d r o p in phosphory l a t i on capac i t y in the r i p e f r u i t .

However , because of the absence in such f r u i t of any need fo r the energy r e s e r v e s n e c e s s a r y f o r t h e r i p e n i n g p r o c e s s , t h e i n h i b i t i n g a c t i o n of i r -r a d i a t i o n on the p r o c e s s of oxidat ive phosphory la t ion had l e s s e f fec t on r ipe f r u i t than on g r e e n f r u i t .

Thus , e x p e r i m e n t a l da ta show tha t ioniz ing r a d i a t i o n s have a c o n s i d e r -ab le e f f e c t on the r i pen ing of f r e s h f ru i t , b e r r i e s and v e g e t a b l e s a f t e r h a r -v e s t i n g . T h i s e f f e c t m a n i f e s t s i t s e l f m a i n l y i n t h e p r o c e s s e s c o n n e c t e d

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FIG.4 . Effect of irradiation on oxidative phosphorylation in the respiration chain in peaches and apricots • absorption of Ог ( m l / g of tissue in 1 h) • absorption of P ( m g / g of tissue in 1 h) 1. Control ( unirrad ia ted ) 2 . Irradiated at 200 000 rad 3 . Irradiated at 300 000 rad 4 . Irradiated at 400 000 rad

with the t r a n s f o r m a t i o n of the p e c t i n c o m p l e x , t h e f o r m a t i o n of p i g m e n t s , and a l s o wi th c h a n g e s i n con ten t of s u g a r s and o r g a n i c a c i d s .

T h e u s e of i r r a d i a t i o n , w h i l e p e r f e c t l y f e a s i b l e a s a m e a n s of p r e -vent ing o v e r - r i p e n i n g in peaches , a p r i c o t s and s t r a w b e r r i e s during s torage , cannot be r e c o m m e n d e d fo r g r e e n t o m a t o e s .

E F F E C T OF RIPENESS ON THE STORAGE OF FRUIT AND BERRIES A F T E R IRRADIATION

The r e s u l t s of t e s t s on the i r r a d i a t i o n of f r u i t and b e r r i e s at d i f f e r e n t s t a g e s of r i p e n e s s a r e g iven in Tab le II.

E F F E C T OF IRRADIATION ON STORAGE L I F E O F F R U I T AND BERRIES

Irradiation of strawberries

F o l l o w i n g e x p o s u r e to 0 . 3 - 0 . 4 M r a d , the m o s t e f f e c t i v e d o s e s , h igh-qua l i t y b e r r i e s c a n be s t o r e d a t 20-25°C f o r 7 - 8 d a s aga in s t 2 - 3 d f o r un -i r r a d i a t e d s t r a w b e r r i e s (F ig . 5). I r r a d i a t i o n wi th d o s e s of 0. 5 - 0 . 6 M r a d l e a d s to b r e a k d o w n of the p e c t i n s u b s t a n c e s and to an i n c r e a s e in c e l l p e r -meabi l i ty in the t i s s u e s ; a s a r e su l t , ju ice i s exuded f r o m the b e r r i e s , which b e c o m e v e r y suscep t ib l e to r e p e a t e d infec t ion with moulds (mainly Rhizopus n i g r i c a n s ) and to spo i lage .

S t o r a g e of i r r a d i a t e d b e r r i e s a t a t e m p e r a t u r e of about 5°C m a k e s it p o s s i b l e t o p r o l o n g the s t o r a g e p e r i o d a s shown in T a b l e III.

STORAGE LIFE OF FRUIT AND BERRIES / 1 3 1

TABLE II

E F F E C T O F R I P E N E S S ON S T O R A G E O F I R R A D I A T E D F R U I T

Day on which mic rob io log ica l spoi lage began for: Ripeness Unirradiated Irradiated with a dose

(controls) of 0 . 3 Mrad

Strawberries Fully ripe 1 - 2 4 - 5

Techn ica l ly r ipe 2 - 3 7 - 9

Apricots Fully ripe 2 - 3 5 - 6

Techn ica l ly ripe 3 - 4 7 - 8

Peaches Fully ripe 3 - 5 8 -10

Techn ica l ly r ipe 5 -7 12-15

Tomatoes Fully r ipe 3 - 7 20 -30

Green 7 - 9 5 - 6

FIG.5. Storage of unirradiated (control) and irradiated fruit peaches

— apricots - ! - strawberries

TABLE III

S T O R A G E P E R I O D F O R I R R A D I A T E D S T R A W B E R R I E S A T 5°C

I r radiat ion (Mrad) Without i r radiat ion

(controls) 0 . 2 0 . 4 0 . 6

Storage period (d) 15 20 26 26

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TABLE IV

C O M P A R I S O N O F Q U A L I T A T I V E C H A N G E S IN C O N T R O L S A M P L E S O F S T R A W B E R R I E S AND

S T R A W B E R R I E S I R R A D I A T E D A T 0 . 6 M r a d

Storage period

(d)

Content of dry substances

(%)

Irradiated Control

T o t a l amount of sugars

№ )

Irradiated Control

To ta l amoun t of organic acids

07°) Irradiated Control

Ascorbic acid (mg %)

Irradiated Control

Pigments X= 510 nm d = 20 m m

Irradiated Control

0 9 . 5 10.0 5 . 7 6 . 0 0 . 7 8 0 . 8 2 50 54 1 . 1 0 1 .40

1 9 . 6 9 . 7 6 . 0 6 . 2 0 . 7 8 0 . 8 2 51 51 1 . 2 0 1 .67

2 9 . 8 9 . 6 6 . 2 5 . 6 0 . 7 6 0 . 8 0 51 50 1 . 3 0 1 . 8 2

3 9 . 8 9 . 2 6 . 2 5 . 4 0 . 7 6 0 . 8 0 52 48 1 . 4 0 1 . 8 0

4 1 0 . 0 a 6 . 4 a 0 . 7 4 a 52 a 1 . 4 5 a

3 Sample comple te ly a f fec ted by mould and not analysed.

T a b l e IV g ives da t a on the c h a n g e s in qual i ty o c c u r r i n g du r ing s t o r a g e (at 25°C) in the c a s e of s t r a w b e r r i e s i r r a d i a t e d with a dose of 0. 6 Mrad and a l s o of u n i r r a d i a t e d (control) s a m p l e s .

P i g m e n t i n v e s t i g a t i o n s showed an i n c r e a s e in pe la rgonin and in cyanin in the c a s e of s t o r e d u n i r r a d i a t e d b e r r i e s . In i r r a d i a t e d b e r r i e s , however , t h e r e was p r a c t i c a l l y no s y n t h e s i s of cyanin and only pe largonin-anthocyanin was f o r m e d ; t h i s p r edomina t ed quant i ta t ively .

When pos i t ive r e s u l t s had been obtained in l a b o r a t o r y t e s t s , ba tches of b e r r i e s w e r e i r r a d i a t e d u n d e r condi t ions app rox ima t ing those ac tua l ly used in the t r a d e . The s t r a w b e r r i e s , placed in s i eves , were i r r a d i a t e d with doses of 0. 1 - 0 . 4 M r a d at a d o s e r a t e of 150 R / s , and s t o r e d in u n c o o l e d w a r e -h o u s e s a t an a i r t e m p e r a t u r e of 25-28°C.

A f t e r the f i r s t day the con t ro l s a m p l e s w e r e a t tacked a l l ove r by mould; t he b e r r i e s exuded a l a r g e a m o u n t of j u i c e and began to f e r m e n t , and the weight was a l m o s t ha lved. B e r r i e s i r r a d i a t e d with a dose of 0. 1 Mrad were only a f f e c t e d to 10-20% by mou ld o v e r t h i s p e r i o d , whi le t h o s e i r r a d i a t e d with h ighe r doses had n o r m a l appea rance and were not spoiled at a l l . B e r r i e s i r r a d i a t e d a t 0. 2 M r a d kep t without spo i l i ng f o r two days , whi le t h o s e i r -r a d i a t e d with d o s e s of 0. 3 - 0 . 4 M r a d began to spo i l only on the f o u r t h day . Throughou t t h i s t i m e the weight of the b e r r i e s r e m a i n e d a l m o s t unchanged; t h e y w e r e d r y , f i r m and s u i t a b l e f o r u s e bo th in t h e i r f r e s h s t a t e and f o r i n d u s t r i a l p r o c e s s i n g .

Irradiation of raspberries

G e n e r a l l y speak ing , i r r a d i a t i o n h a s the s a m e e f f ec t on r a s p b e r r i e s a s on s t r a w b e r r i e s . B e r r i e s i r r a d i a t e d wi th d o s e s of 0 . 1 and 0. 2 M r a d w e r e a f f e c t e d wi th m o u l d on t h e t h i r d day when kep t a t 25°C. I r r a d i a t i o n with


d o s e s of 0. 3 and 0. 4 M r a d p r e v e n t e d a t t a c k s by m o u l d f o r 5 d, but a f t e r 4 d t h e r e was cons ide rab le development of y e a s t s on the b e r r i e s . The contro l ( u n i r r a d i a t e d ) s a m p l e s w e r e a f f e c t e d by m o u l d to an ex t en t of 30% on t h e f i r s t day of s t o r a g e and on t h e s e c o n d day w e r e c o m p l e t e l y i n f e c t e d wi th B o t r y t i s c i n e r e a .

T h u s i r r a d i a t i o n with d o s e s of 0. 3 - 0 . 4 M r a d m a k e s i t p o s s i b l e to i n -c r e a s e the s t o r a g e l i f e of r a s p b e r r i e s a t 20-25°C by 3 - 4 d in c o m p a r i s o n wi th u n i r r a d i a t e d b e r r i e s .

Irradiation of blackcurrants

T e s t s showed i r r a d i a t i o n to be e f f e c t i v e a s a m e a n s of p ro long ing the s t o r a g e l i fe of b l a c k c u r r a n t s only when the s t o r a g e t e m p e r a t u r e w a s low. F o r example , at 7-8°C the s t o r a g e l i fe was i n c r e a s e d f r o m 5 d (unir radia ted b e r r i e s ) to 17 d ( b e r r i e s i r r a d i a t e d with doses of 0. 2-0 . 6 Mrad). At 20-25°C, however , t h e r e was no d i f f e r ence in the per iod a f t e r which un i r rad ia ted s am-p l e s and t h o s e i r r a d i a t e d wi th d o s e s of 0. 1 - 0 . 3 M r a d w e r e s p o i l e d (5 d). Al though i r r a d i a t i o n with d o s e s of 0. 4 - 0 . 6 M r a d led to a c e r t a i n i n c r e a s e i n the s t o r a g e l i f e , t h e q u a l i t y of t h e b e r r i e s d e t e r i o r a t e d c o n s i d e r a b l y .

Irradiation of cherries

The bes t r e s u l t s w e r e obta ined with d o s e s 0. 2 - 0 . 4 Mrad . At 20-25°C t h e s e s a m p l e s could be kept without spoi lage f o r m o r e than 30 d, i . e . m o r e than fou r t i m e s a s long a s the c o n t r o l s a m p l e s . The f r u i t was in good con-di t ion even a f t e r one m o n t h ' s s t o r a g e , e s p e c i a l l y when a d o s e of 0. 2 Mrad was used . It i s not adv i sab le to u se d o s e s h igher than 0. 4 Mrad s ince func-t iona l d i s o r d e r s o c c u r in the f r u i t , which a s a r e s u l t b e c o m e s brown, sof t and wr ink l ed .

Irradiation of apricots and peaches

Doses of 0. 2 -0 . 3 Mrad w e r e the mos t e f fec t ive (Fig. 6). At these doses the s t o r a g e l i f e at 20-25°C i n c r e a s e s f o r a p r i c o t s f r o m 3 to 6 - 7 d and f o r p e a c h e s f r o m 5 to 9 - 1 2 d.

I n c r e a s i n g t h e i r r a d i a t i o n d o s e r e d u c e d the s t o r a g e l i f e ; a t d o s e s of 0. 5 - 0 . 6 Mrad the s t o r a g e l i fe of i r r a d i a t e d and c o n t r o l f r u i t was the s a m e . T h i s i s a r e s u l t of r educ t ion of the n a t u r a l r e s i s t a n c e of the f r u i t to m i c r o -b i o l o g i c a l s p o i l a g e a t d o s e s above 0. 3 - 0 . 4 M r a d . It should a l s o be noted tha t i r r a d i a t i o n with d o s e s above 0 . 4 M r a d c a u s e s f u n c t i o n a l d i s t u r b a n c e s in the t i s s u e s . T h i s l e a d s t o the f o r m a t i o n of b r o w n c o n c r e t i o n s a r o u n d the s t a lk . Wrinkl ing of the skin and sof tening of the f r u i t t i s s u e s a l so occur , and the m a r k e t i n g qua l i t i e s of the f r u i t d e t e r i o r a t e cons iderab ly .

L a r g e b a t c h e s of r i p e and g r e e n p e a c h e s in d i f f e r e n t b o x e s w e r e i r -r a d i a t e d wi th d o s e s of 0. 3 and 0. 4 M r a d at a d o s e r a t e of 150 R / s . The f r u i t w a s s t o r e d in a w a r e h o u s e at 22-25°C and a h u m i d i t y of 85%. A f t e r 3 d, 20-30% of the u n i r r a d i a t e d r ipe and g r e e n f ru i t was spoi led. T h e r e was no damage a f t e r th i s s a m e pe r iod in the boxes containing the i r r a d i a t e d f ru i t . A f t e r 4 d, 70-80% of the r i p e and 30-3 5% of the g r e e n con t ro l (un i r rad ia ted) s a m p l e s w e r e s p o i l e d . T h e i r r a d i a t e d f r u i t w a s i n good c o n d i t i o n . T h e

134 ROGACHEV

FIG.6. Ripe peaches stored for 4 d

f i r s t s i g n s of d a m a g e in the b o x e s con ta in ing the i r r a d i a t e d f r u i t a p p e a r e d a f t e r 10 d, and c o n s i d e r a b l e d e t e r i o r a t i o n ensued a f t e r 15 d (F ig . 6).

Irradiation of grapes

I r r a d i a t i o n with d o s e s of 0. 4 - 0 . 6 Mrad m a k e s it poss ib le to a r r e s t the g r o w t h of the m i c r o o r g a n i s m s wh ich c a u s e d a m a g e to f r e s h g r a p e s , and t h e r e f o r e to i n c r e a s e the s t o r a g e pe r iod by 10-15 d at 20-25°C. However , the use of d o s e s above 0. 4 Mrad p r o d u c e s yellowing in some types of g rape (White Muscat , Chasse l a s ) , and a l so r e d u c e s t he i r immuni ty to repea ted in fec-t ion with m i c r o f l o r a . It i s t h e r e f o r e advisable to use doses of 0. 2 -0 . 3 Mrad, which m a k e s i t p o s s i b l e to s t o r e the g r a p e s at 25°C fo r 15-30 d. The con-t r o l ( un i r r ad i a t ed ) s a m p l e s kept f o r 4 -7 d (Fig . 7).


(2)

FIG.7. Grapes stored for 10 d at 2 2 - 2 5 ' C (1) Controls (2) Irradiated at 300 krad

Irradiation of tomatoes

I r r ad i a t i on has d i f f e r en t e f f e c t s on t oma toes at va r ious s t ages of r i pen -ing. Unr ipe f r u i t k e e p s l e s s wel l a f t e r i r r a d i a t i o n than n o n - i r r a d i a t e d f r u i t . As f o r r ipe f ru i t , i r r a d i a t i o n m a k e s it poss ib le to prolong the s to rage per iod by t h r e e to fou r t i m e s in c o m p a r i s o n with the con t ro l s a m p l e s . I r r ad i a t i on with a dose of 0. 1 - 0 . 2 Mrad h a r d l y r e d u c e s the d e g r e e of m i c r o b i o l o g i c a l infec t ion in t o m a t o e s ; a dose of 0 . 3 Mrad c o n s i d e r a b l y r e d u c e s the n u m b e r of m i c r o o r g a n i s m s ; and 0 . 4 - 0 . 5 M r a d a l m o s t c o m p l e t e l y a r r e s t s the de-v e l o p m e n t of m i c r o f l o r a .

To c h e c k the r e s u l t s of the l a b o r a t o r y t e s t s , l a r g e b a t c h e s of r i p e t o -m a t o e s w e r e i r r a d i à t e d with d o s e s of 0 . 3 - 0 . 4 M r a d . Dur ing s t o r a g e , the

136 ROGACHEV

s u p e r i o r i t y of i r r a d i a t e d o v e r u n i r r a d i a t e d f r u i t w a s f u l l y c o n f i r m e d ; i r -r a d i a t i o n w a s p a r t i c u l a r l y e f f e c t i v e f o r t h o s e b a t c h e s in which the t o m a t o e s had i n i t i a l l y c o n t a i n e d a l a r g e n u m b e r of m i c r o o r g a n i s m s . E v e n a t a t e m -p e r a t u r e of 2 2 - 2 5 ° C and i n c o n d i t i o n s of r e p e a t e d i n f e c t i o n by m i c r o f l o r a , s u c h f r u i t c o u l d be s t o r e d wi thou t s p o i l i n g f o r 6 d; t h e c o n t r o l b o x e s c o n -t a i n e d abou t 20% of s p o i l e d f r u i t . Wi th n o r m a l i n i t i a l m i c r o b i o l o g i c a l i n -f e c t i o n , i r r a d i a t e d r i p e f r u i t c o u l d be k e p t wi thou t s p o i l a g e f o r up to 30 d.

Irradiation of tangerines

T h e m a i n c a u s e s of spo i l age in t a n g e r i n e s a r e P é n i c i l l i u m i t a l i c u m and P é n i c i l l i u m d i g i t a t u m , w h o s e r e s i s t a n c e to r a d i o a c t i v i t y i s r e l a t i v e l y low. H o w e v e r , in a n u m b e r of c a s e s t a n g e r i n e s c o n t a i n A l t e r n a r i a c i t r i , w h o s e r a d i o - r e s i s t a n c e i s t h r e e t o f o u r t i m e s h i g h e r .

In the a b s e n c e of A l t e r n a r i a c i t r i , i r r a d i a t i o n with d o s e s of 0. 1 - 0 . 2 Mrad i s a v e r y e f f e c t i v e me thod of p ro long ing the s t o r a g e l i fe of t a n g e r i n e s . When t h i s m o u l d i s p r e s e n t , h o w e v e r , e v e n d o s e s of up to 0. 75 M r a d h a v e l i t t l e a d v e r s e e f f e c t on i t s d e v e l o p m e n t .

It s h o u l d a l s o be p o i n t e d out t h a t d o s e s of 0 . 3 - 0 . 4 M r a d and a b o v e c a u s e d f u n c t i o n a l d i s t u r b a n c e s in t a n g e r i n e s , which m a n i f e s t e d t h e m s e l v e s in the a p p e a r a n c e of b rown spo t s on the sk in of the f r u i t . Although browning of the s k i n had no. e f f e c t on the q u a l i t y of t he e d i b l e p a r t of t h e f r u i t , t h e y w e r e c o n s i d e r a b l y d i f f e r e n t in o u t w a r d a p p e a r a n c e f r o m n o r m a l f r u i t , and c o u l d no t b e a c c e p t e d a s s a t i s f a c t o r y by n o r m a l t r a d e a n d c o n s u m e r s t a n d a r d s .

FIG. 8. Tangerines stored for 15 d at 22-25*C; controls

F i g u r e s 8 - 1 0 show the ou tward a p p e a r a n c e of t a n g e r i n e s i r r a d i a t e d with d o s e s of 0. 2 and 0. 4 M r a d c o m p a r e d w i t h c o n t r o l s a m p l e s ( u n i r r a d i a t e d f r u i t ) . It m a y t h e r e f o r e be c o n c l u d e d t h a t d o s e s of about 0. 2 Mrad a r e a d -equa te f o r t he p u r p o s e of p r e v e n t i n g the deve lopmen t of P é n i c i l l i u m i t a l i cum and P é n i c i l l i u m d i g i t a t u m , and m a k e it p o s s i b l e to i n c r e a s e c o n s i d e r a b l y t h e s t o r a g e l i f e of t a n g e r i n e s . W h e n the f r u i t a r e a t t a c k e d by A l t e r n a r i a c i t r i , h o w e v e r , t h e i r r a d i a t i o n of t a n g e r i n e s i s no t a d v i s a b l e .


FIG. 9. Tangerines stored for 15 d at 2 2 - 2 5 ' C ; irradiated at 200 krad

FIG. 10. Tangerines stored for 15 d at 2 2 - 2 5 ' C ; irradiated at 400 krad

Irradiation of subtropical persimmons

T h e s t o r a g e l i f e of s u b t r o p i c a l p e r s i m m o n s i s v e r y s h o r t and the r i p e f r u i t i s q u i t e u n s u i t a b l e f o r t r a n s p o r t i n g . T h e p o s s i b i l i t i e s of i n d u s t r i a l p r o c e s s i n g a r e a l s o l i m i t e d with t h i s f r u i t . The t a s t e and the nu t r i t i ve qua l -i t i e s of s u b t r o p i c a l p e r s i m m o n s a r e e x c e l l e n t .

T e s t s h a v e s h o w n t h a t i r r a d i a t i o n c a n be u s e d t o p r o l o n g the s t o r a g e l i f e of p e r s i m m o n s . F o r t h i s p u r p o s e g r e e n u n r i p e f r u i t wi th j u s t a s l i gh t t inge of yel low m u s t be u sed . At t h i s s t age of r i p e n e s s the f ru i t i s not edible;

138 ROGACHEV

i t i s no t ju i cy , t he c o l o u r of t he f l e s h i s w h i t i s h wi th ye l low p a t c h e s , and i t i s h a r d and b i t t e r .

A f t e r h e r m e t i c p a c k a g i n g and i r r a d i a t i o n of t h i s f r u i t wi th a d o s e of 1. 2 M r a d a t a d o s e r a t e of 8500 R / h , i t r i p e n e d on the s e v e n t h day , wi th a good f l a v o u r , and r e m a i n e d in t h i s s t a t e f o r m o r e than 150 d. The con -t r o l f r u i t r e m a i n e d g r e e n , g r a d u a l l y faded , and was a t t a c k e d by mould on t h e 22nd day . It i s t h u s p o s s i b l e to ob ta in f r o m s u b t r o p i c a l p e r s i m m o n s a new type of p r e s e r v e d f r u i t cons i s t ing of whole f r e s h f r u i t in h e r m e t i c a l l y s e a l e d pack ing i r r a d i a t e d wi th a d o s e of 1. 2 M r a d . Hea t s t e r i l i z a t i o n i s inappl icab le to the p r e p a r a t i o n of such c o n s e r v e s , s ince on heat ing the f ru i t a c q u i r e s a b i t t e r , a s t r i n g e n t f l avour .

Irradiation of figs

F r e s h f i g s keep l e s s we l l and a r e l e s s t r a n s p o r t a b l e than p e r s i m m o n s . T e s t s show tha t i r r a d i a t i o n m a k e s it p o s s i b l e to p r e s e r v e the f r u i t in h e r -m e t i c packag ing by a me thod s i m i l a r to that d e s c r i b e d above. T h e s e t e s t s a l s o showed t h a t d o s e s u p to 0. 8 M r a d have no e f f e c t on the qua l i ty of t he f r u i t , d o s e s of 0. 8 - 1 . 2 M r a d c a u s e s o m e so f t en ing a s a r e s u l t of the c o m -m e n c e m e n t of b reakdown of the pro topec t in , and a dose of 1. 2 Mrad c a u s e s t h e s k i n of b l a c k f i g s t o l o s e i t s c o l o u r . If t he c h a n g e in c o l o u r cou ld be d i s r e g a r d e d , the bes t c o u r s e would be to i r r a d i a t e h e r m e t i c a l l y packed f igs with a dose of 1. 7 Mrad . If th i s i s done, the f ru i t keeps well for two months a t a t e m p e r a t u r e of 25°C. I r r a d i a t i o n i n c r e a s e s t h e s w e e t f l a v o u r of t he f r u i t a s a r e s u l t of i n v e r s i o n of p a r t of t he s u g a r .

POSSIBILITY O F USING IRRADIATED F R U I T AND B E R R I E S F O R T H E P R E P A R A T I O N O F J U I C E

T e s t s have shown tha t it i s pos s ib l e to u s e i r r a d i a t e d f r u i t and b e r r i e s not only in t h e i r f r e s h s t a t e , but a l so fo r the p r e p a r a t i o n of j u i c e . The use of i r r a d i a t e d r a w p r o d u c t s in j u i c e p roduc t ion i s e f f ec t ive not only because of the i n c r e a s e in the s t o r a g e l i f e and the r e d u c t i o n of l o s s e s , but a l s o a s a r e s u l t of the 7 -10% i n c r e a s e in j u i c e y ie ld on p r e s s i n g .

T h i s i n c r e a s e can be a t t r i bu t ed to the fol lowing c a u s e s : (1) i n c r e a s e in p e r m e a b i l i t y of the c e l l w a l l s , (2) weaken ing of skin, (3) b reakdown of the p r o t o p e c t i n and pec t in of t he i n t e r m e d i a t e l a y e r s , which weakens the bonds b e t w e e n the c e l l s ; in p a r t i c u l a r the bond s t r e n g t h be tween the sk in and the p a r e n c h y m a t o u s c e l l s and be tween the c e l l s of the f l e s h i s r e d u c e d .

In j u i c e obta ined f r o m i r r a d i a t e d b lack g r a p e s , the p igment content i s a l w a y s h i g h e r t han in the j u i c e of u n i r r a d i a t e d f r u i t . T h i s i s owing to the f o r m a t i o n u n d e r the e f f e c t of r a d i a t i o n of de lph in in and cyan in a s a r e s u l t of the oxidat ion of ha loca t éch in and d - c a t e c h i n . I r r a d i a t i o n a l so c a u s e s the oxidat ion of s o m e of the tannic s u b s t a n c e s into f l avones .

A f t e r a two-mon th s t o r a g e per iod, the ju ice of some kinds of i r r a d i a t e d g r a p e s b e c a m e d a r k e r and acqu i r ed a b rownish t inge, a s a r e s u l t of the f o r -m a t i o n of qu inones and o t h e r p r o d u c t s of the oxida t ion and condensa t i on of tannic s u b s t a n c e s unde r the ac t ion of polyphenoloxidase, which i n c r e a s e s i t s


act ivi ty under i r rad ia t ion , reaching a maximum at about 0. 5 Mrad. However, polyphenoloxidase did not have the s a m e act ivi ty in a l l types of g r ape . F o r t h i s r e a s o n , t h o s e t y p e s of g r a p e which conta in highly ac t ive po lypheno l -o x i d a s e should be s u b j e c t e d to s h o r t h e a t t r e a t m e n t s to d e - a c t i v a t e the e n z y m e s .

Good-quality j u i ce s w e r e obtained f r o m such i r r a d i a t e d f ru i t a s apples , tomatoes and g rapes . A combined t r ea tmen t with i r rad ia t ion and sorbic acid p r o v e d to be e f f e c t i v e f o r p r o c e s s i n g j u i c e s . By u s i n g t h i s me thod it i s pos s ib l e to r e d u c e the i r r a d i a t i o n dose and a l s o the amount of s o r b i c acid added , in c o m p a r i s o n with the q u a n t i t i e s c o r r e s p o n d i n g to the ind iv idua l e f f e c t of e a c h of t h e s e two m e a n s of p r e s e r v a t i o n .

The s t o r a g e l i fe of j u i c e t r e a t e d with s o r b i c ac id (40-50 mg/1) and by i r r a d i a t i o n (0. 5 Mrad) i s long enough (about a y e a r ) f o r the me thod to be u s e d i n d u s t r i a l l y .

CONCLUSIONS

(1) E x p e r i m e n t a l s t u d i e s w e r e m a d e of the e f f ec t of g a m m a r ad i a t i on on f r e s h f ru i t and b e r r i e s . These es tab l i shed that i r r ad ia t ion helps to prolong s to rage pe r iods f o r the following types of f r u i t : s t r a w b e r r i e s , r a s p b e r r i e s , c h e r r i e s , a p r i c o t s , peaches , t a n g e r i n e s , g r a p e s , t o m a t o e s , sub t rop i ca l p e r s i m m o n s and f igs . F o r f r u i t such a s apples and p e a r s the data a r e con-t r a d i c t o r y and ind ica te the i m p o r t a n c e of v a r i o u s f a c t o r s such a s va r i e ty , da te of picking, e t c . ; t h i s r e q u i r e s f u r t h e r s tudy.

(2) The se lec t ion of i r r a d i a t i o n d o s e s f o r f r e s h f r u i t and b e r r i e s mus t be ba sed on two c o n s i d e r a t i o n s ; on the one hand, the g rowth of the m i c r o f l o r a caus ing spoi lage mus t be s u p p r e s s e d a s much a s poss ib le , and d o s e s le tha l to th i s m i c r o f l o r a m u s t be u s e d ; on the o t h e r , the lowes t p o s s i b l e d o s e s mus t be used, so a s not to weaken the n a t u r a l immuni ty of the f ru i t against m ic rob io log i ca l infec t ion and not to c a u s e funct ional phys io logica l and bio-c h e m i c a l d i s o r d e r s .

(3) The e f f ec t of i r r a d i a t i o n on r i p e n i n g a f t e r h a r v e s t i n g should a l s o be t aken into account . In t h i s r e s p e c t , t he v a r i o u s types of f r u i t d i f f e r f r o m each other . I r r ad ia t ion can be used with peaches , s t r a w b e r r i e s and apr ico t s a s a means of slowing down r ipening dur ing s to rage , but it i s not advisable f o r use with g r e e n t o m a t o e s .

(4) Since i r r ad i a t ion in the m a j o r i t y of c a s e s r educes the na tu ra l immunity of the f ru i t , an a t tempt should be made to reduce to the min imum the poss i -bi l i ty of r e p e a t e d m i c r o b i o l o g i c a l i n f ec t ion du r ing s t o r a g e , by oppor tune d i s i n f ec t i on of the w a r e h o u s e s , keep ing in s e a l e d p a c k a g e s , e t c .

(5) Since i n c r e a s e s in the age of mould fungi and y e a s t s u sua l ly i n c r e a s e t h e i r r e s i s t a n c e to r a d i o a c t i v i t y , i t i s a d v i s a b l e to c a r r y out i r r a d i a t i o n a s soon a s p o s s i b l e a f t e r h a r v e s t i n g .

о TABLE V

S U G G E S T E D CONDITIONS F O R I N C R E A S I N G S T O R A G E L I F E O F C E R T A I N I R R A D I A T E D F R U I T S

Types of frui t Recommended stage Doses causing:

Recommended Storage l i f e (d) a t 25°C:

or of ripeness Reduction Functional radiat ion dose berries before harvesting of i m m u n i t y disorders (Mrad) Irradiated Unirradiated

(Mrad) • (Mrad)

Strawberries Normal 0 . 5 - 0 . 3 - 0 . 4 5 -7 1 - 2

Raspberries Normal 0 . 5 - 0 . 3 - 0 . 4 3 - 5 1

Cherries Normal 0 . 3 0 . 4 0 . 2 20-30 6 - 7

Apricots Normal and technica l 0 . 4 0 . 4 0 . 2 - 0 . 3 7 - 8 2 - 3

Peaches Normal and techn ica l 0 . 4 0 . 4 0 . 2 - 0 . 3 12-15 5 - 6

T k e m a l i Unripe - - 0 . 0 3 - 0 . 0 4 30 7 -10 (a kind of damson)

Grapes Normal 0 . 3 0 . 3 0 . 2 15-30 4 - 7

Red tomatoes Normal 0 . 2 - 0 . 3 0 . 4 0 . 2 - 0 . 3 20-30 3 - 7

' Green peas Unripe - - 0 . 1 - 0 . 2 1 . 5 - 2 0 . 1 - 1 (hulled and in pods)

Tangerines Normal 0 . 1 0 . 2 - 0 . 3 0 . 2 15-30 7 -10

Subtropical persimmons Unripe - - 1 . 2 - 1 . 3 150 3 - 5 (he rme t i ca l ly packed)

Figs Normal - - 1 . 3 - 1 . 5 60 1 - 2 (he rme t i ca l ly packed)


(6) I r r a d i a t e d r a w p r o d u c t s can be used not only in the f r e s h s ta te but a l so f o r i n d u s t r i a l p r o c e s s i n g ; on p r e s s i n g , they give a 5-10% higher ju ice yield of b e t t e r qual i ty .

(7) The f i g u r e s shown in T a b l e V, which a r e b a s e d on e x p e r i m e n t a l da ta , m a y s e r v e a s a guide f o r c h e c k i n g in s e m i - i n d u s t r i a l and s u b s e q u e n t l y in i n d u s t r i a l c o n d i t i o n s .

B I B L I O G R A P H Y

BREGVADZE, U . D . , "Udlinenie sroka hranenija jablocnogo soka vozdejstviem g a m m a - l u 6 e j i sorbinovoj

kisloty" (Prolongation of storage of apple juice by gamma-rays and sorbic acid) , Konservnaja i ovoscesusil'naja

promyslennost' No. 2 (1963) 9-11.

FRUMKIN, M . L . . KOVALSKAYA, L . P . , EGOROVA. K . V . . DOROFEEVA, E . V . . Vli janie ionizirujuscih

izlucenij na vyhod i kacestvo vinogradnogo soka (Effect of ionizing radiations on the yield and quality of grape

ju ice) , Konservnaja i ovoscesusll'naja promyslennost' No.7 (1961) 16-20.

KHATIASHVIL1. S h . M . , TSETSKHLADZE, T. V. , CHERKEZISHVILI, L . I . , Vli janie gamma- i z lucen i j a

na nekotorye vidy plodov i fruktovyh konservov (Effect of gamma-radia t ion on some types of fruit and fruit

conserves), Trudy Instituta fiziki Akademii Nauk Gruzinskoj SSR VII (1960) 119-26. .

KOVALSKAYA, L . P . , "Faktory, v l i ja ju lc ih na sroki hranenija i kaêestvo sveiih plodov, jagod i ovoscej,

obrabotannyh gamma-lucami" (Factors affecting the storage and quality of gamma-irradiated fresh fruit, berries

and vegetables), Konservnaja i ovoscesus'il'naja promyslennost' No. 10 (1963) 22-26.

KOVALSKAYA, L . P . , DOROFEEVA, E . V . , PETRASH, I . P . , Deistvie gamma- luce j na skoiost' sozrevanija

i kacestvo tomatov (Effect of gamma rays on ripening rate and quality of tomatoes), Konservnaja i ovoscesu-

s'il'naja promyslennost' No. l l (1962) 20-23.

KOVALSKAYA, L . P . , SILAEVA, S . V . , Predvaritel 'naja issledovanija po izuêeniju dejstvija ionizirujusîih

izlucenij na sroki hranenija svezih mandatinov (Preliminary investigations on the effect of ionizing radiations

on the storage of fresh tangerines), Konservnaja i ovoscesusil 'naja promyslennost' No.9 (1963) 22.

KOVALSKAYA, L. P . . VASILEVA, K . V . , Deistvie gamma- luce j na sintez karotinoidov v tomatakh (Effect

of gamma rays on carotenoid synthesis in tomatoes), Konservnaja i ovoscesusil'naja promyslennost' No.7 (1963)

29-32.

KOVALSKAYA, L . P . , VASILEVA, K . V . , ZAKHAROVA, N . V . , PETRASH, I . P . , Deistvie ionizirujuscih

izlucenij na posleuborocnoe dozrevanie svezih plodov, jagod i ovoscej (Effect of ionizing radiations on ripening

after harvesting of fresh fruit , berries and vegetables) , Konservnaja i ovoscesusïl 'naja promyslennost' No. 12

(1963) 21.

METLITSKY, L . V . , MÜKHIN, E. N . , Deistvie ionizirujuscih izlucenij na sohranjaemost 'kartofel ja , ovoscej

i plodov (Effect of ionizing radiations on the storability of potatoes, vegetables and f r u i t ) . Konservnaja i

ovoscesusil 'naja promyslennost* No. 7 (1961) 2 2 - 2 5 . .

ROGACHEV, V . l . , Pr imenenie ionizirujuscih izlu£enij d l ja konservirovanija piscevyh produktov (Use of

ionizing radiations for preserving food products), Konservnaja i ovoscesusïl 'naja promyslennost' No. 1 (1959)

25-29j No.2 (1959) 6 -8 .

ROGACHEV, V . l . , FRUMKIN, M . L . , KOVALSKAYA. L . P . , DOROFEEVA, E . V . , " Izmeneni ja krasjas"cih

vesêestv svekly, sterilizovannoj ionizirujuscim izluïeniem i teplom" (Changes in the pigments of beet sterilized

with ionizing radiation and with h e a t ) , Konservnaja i ovoscesusil 'naja promyslennost N o . 2 (1960) 13-16.

142 ROGACHEV

ROGACHEV, V . l . , FRUMKIN, M . L . , KOVALSKAYA, L . P . , EGOROVA, K . V . , "Prevrascenija krasjasZih

vesïestv zelenogo goroska pri s tet i l izacii teplom i g a m m a - l u ê a m i " (Changes in the pigments of green peas

on sterilizing with heat and with gamma rays) , Konservnaja i ovosSesusil 'naja promyslennost* No. 9 ( i960)

19-24.

IRRADIATION STUDIES OF FRUIT AND VEGETABLES IN LATIN AMERICA

J. SANÍN-SÁDER

BOGOTA, COLOMBIA


IRRADIATION STUDIES OF FRUIT AND VEGETABLES IN LATIN AMERICA. A short discussion on the population ?nd food situation in Latin America is followed by the need for research on certain agricultural products for local use and on items for export upon which the economy of several countries depends. Radiation research on the sprout inhibition of potatoes indicates that between 8 and 10 krad are sufficient to delay sprou-ting for seven to eight months, which in many countries is sufficient to hold the product until the next harvest. The losses caused by ripening during the export shipment of bananas is about 25% and radiation studies to delay ripening show promise in reducing this loss. The same is true of the work on the papaya and there are indi-cations that it may be possible to ship this product for long distances after radiation treatment.

ETUDES SUR L'IRRADIATION DES FRUITS ET LEGUMES EN AMERIQUE LATINE. Après avoir exposé succinctement la situation démographique et âlimentaire en Amérique latine, l'auteur souligne la nécessité de procéder à des recherches sur certains produits agricoles destinés à la consommation locale ainsi que sur des articles dont l'exportation constitue la base de l'économie de plusieurs pays. D'après des recherches sur la possibilité d'utiliser les rayonnements pour prévenir la germination de la pomme de terre, une dose de 8 à 10 krad suffit, semble-t-il, à différer ce processus de sept à huit mois, ce qui dans de nombreux pays per-met de conserver les pommes de terre d'une récolte à l'autre. Pour les bananes, les pertes dues au mOrissement en cours de transport sont d'environ 25°io et d'après les études faites, l'irradiation permettrait également de retarder ce processus, et partant de réduire ces pertes. Les études faites sur la papaye aboutissent aux mêmes conclusions et il semble qu'après irradiation ce fruit puisse être expédié loin.

ИССЛЕДОВАНИЯ ПО ОБЛУЧЕНИЮ ФРУКТОВ И ОВОЩЕЙ В ЛАТИНСКОЙ АМЕРИКЕ. После краткого обсуждения проблем населения и положения с пищевыми продуктами в Латин-ской Америке говорится о необходимости проведения исследований по некоторым сельско-хозяйственным продуктам для местного потребления и предметом экспорта, от которых з а -висит экономика некоторых стран. Радиационные исследования по проблемам предотвращения прорастания картофеля свидетельствуют о том, что 8 — 10 килорад достаточно для предотвра-щения прорастания картофеля на 7 — 8 месяцев, что для многих стран достаточно для сохране-ния продукта до следующего урожая. Потери в связи с созреванием бананов во время экспор-та составляют приблизительно 25%, и радиационные исследования с целью предотвращения созревания оказались перспективными в деле уменьшения потерь. То же самое справедливо в отношении папайи, и имеются указания, что можно будет, вероятно, после радиационной обработки перевозить этот продукт на большие расстояния.

ESTUDIOS SOBRE IRRADIACION DE FRUTAS Y HORTALIZAS EN AMERICA LATINA. Se examina breve-mente la situación demográfica y alimentaria en América Latina, y se llega a la conclusión de que es necesario realizar investigaciones sobre determinados productos agrícolas para el consumo nacional y sobre algunos artículos de exportación de los que depende la economía de distintos países. Las investigaciones sobre la irra-diación como método para inhibir la germinación de la patata indican que bastan de 8 a 10 krad para retrasar la germinación por 7 u 8 meses, lo que en muchos países es suficiente para conservar el producto hasta la próxima cosecha. Las pérdidas de plátanos por maduración durante su transporte al extranjero son de un 25% aproximadamente, y los estudios sobre el empleo de las radiaciones para retrasar la maduración dejan entrever buenas perspectivas. Lo mismo cabe decir de las investigaciones sobre la papaya; parece ser que se podrá expedir este fruto a largas distancias después de irradiarlo.

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144 SANÎN-SADER

I w i sh to s p e a k b r i e f l y about t he i r r a d i a t i o n of f r u i t and v e g e t a b l e s in L a t i n A m e r i c a a n d to g ive you a s h o r t a c c o u n t of t h e p r e s e n t s i t u a t i o n in that a r e a as r e g a r d s the use of ionizing radia t ion in the p re se rva t ion of food-s tu f f s , emphas iz ing the poss ib i l i t i e s of using radia t ion to help solve the p rob -l e m s encoun te red by the La t in A m e r i c a n c o u n t r i e s in developing t h e i r a g r i -c u l t u r e . At t h e i r p r e s e n t s t a g e of d e v e l o p m e n t t h e s e c o u n t r i e s a r e f a c e d with the p r o b l e m of e x t r e m e l y r a p i d popula t ion g rowth , the a v e r a g e annual r a t e of which i s 2.5%, an e x t r e m e l y high f i g u r e by c o m p a r i s o n with that of o t h e r c o u n t r i e s of t he w o r l d . By the y e a r 2000 the needs of the popula t ion wi l l have i n c r e a s e d by 240% a s a r e s u l t of th i s r a p i d i n c r e a s e , and the p r e s e n t s t a t e of ma lnu t r i t ion in which mos t of the population of Lat in A m e r i c a l i v e s wi l l b e c o m e m o r e s e v e r e u n l e s s t h i s p r o b l e m i s t a ck l ed with the n e -c e s s a r y e n e r g y and s p e e d . T h e index of food p r o d u c t i o n p e r head of p o p u -l a t i o n in L a t i n A m e r i c a , which b e f o r e the w a r s tood a t 140, f e l l t o 102 in 1960: dur ing th i s p e r i o d the index fe l l f r o m 103 to 91 in Argent ina ; f r o m 101 to 98 in Colombia ; f r o m 105 to 96 in Chi le ; f r o m 104 to 96 in P e r u ; f r o m 98 to 71 in Uruguay: and f r o m 99 to 95 in Venezue la .

We a r e s eek ing a m e a n s of so lv ing t h i s p r o b l e m . In La t in A m e r i c a t h e r e f o r e , r e s e a r c h in the u s e of ion iz ing r a d i a t i o n f o r the p r e s e r v a t i o n of foods tu f f s i s n e c e s s a r i l y d i r e c t e d to the a r e a s of g r e a t e s t need, with a view to e l imina t ing the l a r g e l o s s e s of a g r i c u l t u r a l p r o d u c e caused , f o r example , by g e r m i n a t i o n , the p r e s e n c e of m i c r o o r g a n i s m s , r a p i d m a t u r a t i o n and the i n f e s t a t i o n of c e r e a l s .

A n u m b e r of L a t i n A m e r i c a n c o u n t r i e s a r e c a r r y i n g out p r o g r a m m e s of r e s e a r c h in the i r r ad i a t i on of foods tu f f s . F o r example , the Atomic Energy C o m m i s s i o n of A r g e n t i n a i s i n v e s t i g a t i n g the p o s s i b i l i t y of p r e v e n t i n g the ge rmina t ion of po ta toes and o ther c r o p s , while Braz i l has ca r r i ed out s imi l a r s t u d i e s at i t s N u c l e a r E n e r g y C e n t r e . In P u e r t o R ico the N u c l e a r E n e r g y C e n t r e i s a l s o s tudy ing w a y s of d e l a y i n g the r a p i d m a t u r a t i o n of b a n a n a s , and in V e n e z u e l a the In s t i t u t e of Sc i en t i f i c R e s e a r c h h a s done w o r k on the p r e s e r v a t i o n of p o t a t o e s , on ions and s t r a w b e r r i e s wi th good r e s u l t s . In Co lombia , the Ins t i tu te of N u c l e a r E n e r g y i s a l s o inves t iga t ing the p r e s e r -v a t i o n of p o t a t o e s u n d e r v a r i o u s s t o r a g e c o n d i t i o n s , a s we l l a s m e a n s of d e l a y i n g the m a t u r a t i o n of b a n a n a s and p a p a y a s .

T h e need f o r r e s e a r c h of t h i s s o r t in L a t i n A m e r i c a i s i l l u s t r a t e d by a s t u d y c a r r i e d out i n C o l o m b i a on the p r e s e r v a t i o n of p o t a t o e s . T h e p r o -duc t ion of p o t a t o e s in Co lombia i s f r a u g h t with n u m e r o u s r i s k s f o r the g r o w e r , p a r t i c u l a r l y with r e s p e c t t o the p r o b l e m of p r e s e r v i n g the pota toes f o r a s u f f i c i e n t p e r i o d be tween h a r v e s t s so a s to s a t i s f y the demand dur ing t h i s p e r i o d and to e n s u r e d i s t r i b u t i o n to v a r i o u s p a r t s of the coun t ry . The a n n u a l p r o d u c t i o n of p o t a t o e s in C o l o m b i a a m o u n t s to 700 000 t va lued a t app rox ima te ly US $40 mi l l ion . It i s e s t ima ted that l o s s e s due to germinat ion a m o u n t t o 20%, equ iva l en t t o 140 000 t / y r v a l u e d a t $8 m i l l i o n . P r i c e f l u c t u a t i o n s on t h e p o t a t o m a r k e t a r e s u c h t h a t d u r i n g the h a r v e s t p e r i o d s e l l i n g p r i c e s a r e l o w e r than the c o s t s of p roduc t ion , the g r o w e r having to b e a r the l o s s . Two m o n t h s l a t e r t he se l l ing p r i c e beg ins to r i s e , while by t h e end of t h e f i f t h m o n t h it h a s i n c r e a s e d f i v e - f o l d u n d e r the p r e s s u r e of demand o r ig ina t ing in the l a c k of adequate m e a n s of p r e s e r v a t i o n dur ing the s e v e n - m o n t h p e r i o d between h a r v e s t s .

IRRADIATION STUDIES IN LATIN AMERICA 145

Stud ies c a r r i e d out by t h e I n s t i t u t e of N u c l e a r E n e r g y i n d i c a t e t h a t a dose of be tween 8 and 10 k r a d i s suf f ic ien t to de lay ge rmina t ion f o r a pe r iod of s e v e n to e igh t m o n t h s in d i f f e r e n t v a r i e t i e s of p o t a t o and u n d e r v a r i o u s s t o r a g e cond i t i ons . S tudies on a l a r g e r s c a l e wil l p r o v i d e the b a s i s f o r an economic a s s e s s m e n t of th is method in r e l a t ion to o ther known methods . One of the p r o b l e m s u n d e r c o n s i d e r a t i o n i s the e a r l y m a t u r a t i o n of the b a n a n a . L o s s e s f r o m r a p i d m a t u r a t i o n dur ing the sh ipmen t of b a n a n a s to the United S t a t e s and E u r o p e a r e e s t i m a t e d a t 25%, in sp i t e of s p e c i a l t r a n s p o r t a r r a n g e m e n t s . F o r a coun t ry which i s e s s e n t i a l l y a g r i c u l t u r a l , l ike al l the L a t i n A m e r i c a n c o u n t r i e s , and which e x p o r t s m a i n l y a g r i c u l t u r a l p r o d u c e , t h i s p r o b l e m i s b e c o m i n g i n c r e a s i n g l y a c u t e . In the c a s e of C o l o m b i a bananas a r e , a f t e r cof fee , the m a i n expor t i t e m , amount ing to about 220 000 t va lued a t a p p r o x i m a t e l y $15 mi l l i on . The to ta l banana c rop amount s to 600 000 t and i t should be r e m e m b e r e d that the l o s s e s due to rap id matura t ion a r e e s t i m a t e d a t 25%. With t h i s s i t u a t i o n in mind the In s t i t u t e of N u c l e a r E n e r g y h a s c o n s i d e r e d it n e c e s s a r y to s tudy the p r o b l e m and, a l though we cannot yet give any r e s u l t s , i t i s expec ted that t h e s e will be s a t i s f a c t o r y , in sp i t e of the f a c t tha t the i r r a d i a t i o n i n s t a l l a t i o n s with which we a r e working a r e v e r y s m a l l and do not al low u s to t r e a t l a r g e quan t i t i e s of p r o d u c e in a r e l a t ive ly sho r t pe r iod , a s i s n e c e s s a r y in such c a s e s . The cobal t -60 source of 760 Ci which we a r e us ing belongs to the -Cancer Hospi ta l .

The p a p a y a a f f o r d s a n o t h e r e x a m p l e of t he u s e of ion iz ing r a d i a t i o n in delaying the r a p i d m a t u r a t i o n which p r e v e n t s t r a n s p o r t of the f r u i t ove r long d i s t a n c e s to a r e a s of consumpt ion .

S tud ies c a r r i e d out a t t he U n i v e r s i t y of C a l i f o r n i a u n d e r the d i r e c t i o n of D r . E . C . Maxie and D r . N . F . S o m m e r u n d e r con t rac t to the United States A t o m i c E n e r g y C o m m i s s i o n have shown that c e r t a i n t ypes of f r u i t not grown in that r eg ion , such a s the papaya, can be p r e s e r v e d with s a t i s f a c t o r y r e s u l t s a f t e r i r r a d i a t i o n . H o w e v e r , i t i s r e c o m m e n d e d t h a t f u r t h e r r e s e a r c h be c a r r i e d out c l o s e to t h e a r e a s of cu l t iva t ion t o p e r m i t e x a c t c o n t r o l of the t i m e of m a t u r a t i o n and o the r loca l f a c t o r s . Th i s r a i s e s the need f o r i r r a d i -a t ion f a c i l i t i e s in a n u m b e r of La t in A m e r i c a n coun t r i e s so that t h e s e p r o b -l e m s m a y be s tudied l oca l l y .

DATA ON RADIOSENSITIZATION OF FRUIT-SPOILAGE FUNGI BY

CHEMICAL SENSITIZERS

S.G. GEORGOPOULOS, E. GEORGIADOU AND B. MA CRIS GREEK ATOMIC ENERGY COMMISSION,

NUCLEAR RESEARCH CENTRE DEMOCRITUS, ATHENS, GREECE


DATA ON RADIOSENSITIZATION OF FRUIT-SPOILAGE FUNGI BY CHEMICAL SENSITIZERS. In con-tinuing studies on the possibilities of radiosensitizing spores of fungi important for fruit preservation by chemical means, mixtures of spore suspensions and solutions of the test compound are exposed t o sublethal doses of gamma radiation. The survival fraction is estimated by the viable cell count technique. Vitamin k5 is toxic to both Pénicillium italicum and Pullularia pullulans at room temperatures. A radiosensitizing effect has been

observed but its magnitude cannot be easily recognized because of the high toxicity. 1-naphthol.structurally

related to the v i tamin k5 compound, is not toxic to the fungi used. This substance-is a very good radio-

sensitizer for Candida tropicalis (a yeast) P.pullulans (a pseudosacharomycete) and probably Rhodotorula sp.

(another yeast) in air. In contrast, P. i talicum, Botrytis cinerea, and Aspergillus niger (all filamentous fungi)

could not be sensitized by 1-naphthol . For P. i tal icum experiments were conducted in both air and nitrogen

and the results were negat ive . Male ic acid does not seem to be of interest for the sensit ization of e i ther

P. i t a l i cum or P. pullulans.

DONNEES SUR LA RADIOSENSIBIUSATION, AU MOYEN DE SENSIBILISATEURS CHIMIQUES, DE

CHAMPIGNONS NUISIBLES AUX FRUITS. Dans le cadre de recherches approfondies sur la possibilité de

radiosensibiliser, par des procédés chimiques, les spores des champignons nuisibles aux fruits, on a exposé

des mélanges de solution du produit chimique testé et de spores en suspension à des doses sous-létales de rayons

g a m m a . Le pourcentage des spores ayant survécu a é té évaluée par la méthode de comptage des cellules

viables. A la température ambiante, la vitamine k5 a des effets toxiques tant sur Pénicillium italicum que sur

Pullularia pullulans. On a constaté un ef fe t de radiosensibilisation, mais il a é t é d i f f i c i l e d ' éva luer son

importance étant donné que la toxicité est élevée. Le 1-naphtol, composé dont la structure se rattache à celle

de la v i tamine k5 , n 'est pas toxique pour les champignons utilisés. Cette substance est un très bon agent de

radiosensibilisation pour Candida tropicalis (une levure), P. pullulans (un pseudosaccharomycète) e t proba-

blement Rhodotorula sp. (une autre levure)dans l 'a i r . Par contre, P. italicum, Botrytis cinerea et Aspergillus

niger (qui sont tous des champignons f i lamenteux) n'ont pu être sensibilisés par le 1-naphtol . Dans le cas de

P. i t a l icum, les expériences ont été faites à la fois dans un milieu aérobie et dans un milieu anaérobie et les

résultats ont é té négatifs. L'acide maléique ne semble pas avoir d'effets sensibilisateurs sur P. italicum ni sur

P. pullulans.

Д А Н Н Ы Е ПО С Е Н С И Б И Л И З А Ц И И К О Б Л У Ч Е Н И Ю Г Р И Б К О В , ВЫЗЫВАЮЩИХ П О Р Ч У П Л О Д О В , Х И М И Ч Е С К И М И С Е Н С И Б И Л И З А Т О Р А М И . В ходе н е п р е р ы в н ы х и с с л е д о в а н и й в о з м о ж н о с т и р а д и о а к т и в н о й с е н с и б и л и з а ц и и с п о р г р и б к о в , и м е ю щ и х в а ж н о е з н а ч е н и е д л я с о х р а н е н и я ф р у к т о в с помощью х и м и ч е с к и х м е т о д о в , с м е с и с у с п е н з и й спор и р а с т в о р ы и с -п ы т ы в а е м о г о соединения о б л у ч а л и с ь с у б л е т а л ь н ы м и д о з а м и г а м м а - и з л у ч е н и я . Доля в ы ж и -в а е м о с т и р а с с ч и т ы в а е т с я м е т о д о м с ч е т а 'жизнеспособных к л е т о к . При к о м н а т н ы х т е м п е р а -т у р а х витамин K s я в л я е т с я т о к с и ч н ы м в отношении как P é n i c i l l i u m i t a l i c u m , т а к H P u l l u l a r i a p u l l u l a n s . О т м е ч а л с я э ф ф е к т радиосенсибилизации , однако е г о величину н е л е г к о установить ввиду в ы с о к о й т о к с и ч н о с т и . 1 - н а ф т о л , с в я з а н н ы й в с т р у к т у р н о м отношении с с о е д и н е н и е м в и т а м и н а K s , не я в л я е т с я т о к с и ч н ы м в о т н о ш е н и и и с п о л ь з у е м ы х г р и б к о в . Э т о в е щ е с т в о я в л я е т с я очень хорошим р а д и о с е н с и б и л и з а т о р о м в в о з д у х е для C a n d i d a t r o p i c a l i s (дрожжи), Р. p u l l u l a n s ( п с е в д о с а х а р о м и ц е т ы ) и в е р о я т н о R h o d o t o r u l a s p . (другой вид дрожжей) . В про-т и в о п о л о ж н о с т ь э т о м у Р . i t a l i c u m , B o t r y t i s c i n e r e a и A c p e r g i l i u s m g e r (и т о , и д р у г о е —

147

148 GEORGOPOULOS e t a l .

волокнистые грибки) невозможно сенсибилизировать с помощью 1-нафтола . Эксперименты с P . i ta l icum проводились как в воздухе, так и в а з о т е , и результаты являются негативными. Малеиновая к и с л о т а , п о - в и д и м о м у , не п р е д с т а в л я е т и н т е р е с а при сенсибилизации как P . i t a l i c u m , так и P . p u l l u l a n s .

DATOS SOBRE RADIOSENSIBIUZACION DE LOS HONGOS QUE DETERIORAN LA FRUTA MEDIANTE EL EMPLEO DE SENSIBILIZADORES QUIMICOS. Continuando los estudios sobre la posibilidad de radiosensibilizar por medios químicos las esporas de los hongos que deterioran la fruta, se expusieron mezclas de suspensiones de esporas y soluciones de los compuestos de ensayo a dosis subletales de radiaciones gamma. Se calcula la fracción de supervivencia mediante la técnica de recuento de células viables. La vitamina k5 es tóxica tanto para el Pénicillium italicum como para la Pullularia pullulans a la temperatura ambiente. Se observó un efecto radiosensibilizador, pero no se pudo determinar fácilmente su magnitud a causa de la elevada toxicidad. El a-naftol , compuesto relacionado estructuralmente con la vitamina k5, no es tóxico para los hongos uti-lizados. Esta sustancia constituye im excelente radiosensibilizador para la Candida tropicalis(levadura), la P. pull«lans(seudosacatomíceto)yprobablementelaRhodotorulasp. (otra levadura) en el aire. En cambio, el P. italicum, la Botrytis cinérea y el Aspergillus niger (todos ellos hongos filamentosos) no se pudieron sensibili-zar con el a -naf to l . Con el P. italicum se realizaron experimentos en aire y en nitrógeno; los resultados fueron negativos. El ácido maleico no parece presentar interés para la sensibilización del P. italicum ni de la P. pullulans.

The radiation res is tance of most fruit-spoilage fungi var ies f rom 100 000 to 1 000 000 r ad . For many kinds of f r e s h f ru i t it has been found that doses above 200 000 rad cause undesirable changes in taste , texture or colour. It should be of interest , therefore , to know of conditions under which the fungal ce l l s may be sens i t i zed se lec t ive ly and which may p e r m i t p a s t e u r i z a t i o n at much lower dosages . Work in our Food Technology Labora to ry is sup-por ted in pa r t by a gran t f r o m the IAEA sind deals with the poss ib i l i t ies of sens i t iz ing fungi by chemica l means .

Ideally, a r ad iosens i t i ze r should be a compound that is non-toxic when used alone and which, if p resent during i r radiat ion, increases lethality. In prac t ice , many of the s ens i t i ze r s do have toxic effects if kept with the cells for prolonged per iods of t ime (e .g , v i tamin K5). Compounds of cons ider -able toxic i ty could not be t e s t e d because of the low d o s e - r a t e of our 6UCo source that makes it n e c e s s a r y for the ce l ls to r ema in under the action of the chemica l fo r 1 -2 h. F o r example , a l a rge number of t e s t s have been done with v i tamin К5 and we cannot be convinced that it i n c r e a s e s s e n s i -t iv i ty of our t e s t fungi. This is owing to i t s high toxici ty .

. Of the compounds r e l a t e d to v i tamin K5,. naphthalene compounds , L. naphthol and 1-naphthylamine, have been tes ted . The f o r m e r is pract ical ly non- toxic and a p p e a r s of i n t e r e s t . However, it s ens i t i zes ce l l s of some species but not of others (Table I). In contrast to L.naphthol, 1-naphthylamine seems not to be able to sensi t ize either P. italicum or P . pullulans.

Of the o ther r a d i o s e n s i t i z e r s r e p o r t e d in the l i t e r a tu r e , ma le ic acid, hydroquinone, and aminophenol have been tes ted on P. pullulans and P.italicum. Of t h e s e none has given p r o m i s i n g r e s u l t s , the s u r v i v a l f r a c t i o n s being about equal for populations i rradiated in the presence or in the absence of the chemica l . Hydroquinone usually caused m o r e killing in the non- i r rad ia ted samples , probably as a r e su l t of its radiat ion- induced oxidation.

These studies a re to be continued. There may be interesting differences d i scovered between bac t e r i a , yeas t s and moulds with r e spec t to the effect of r a d i o s e n s i t i z e r s .

RADIOSENSITIZATION OF FUNGI 149

TABLE I

SURVIVAL OF SOME FRUIT-SPOILAGE FUNGI AFTER IRRADIATION WITH AND WITHOUT L. NAPHTHOL

Species and dose Control

Unirradiated

L-naphthol 30 ppm

Irradiated

Control L-naphthol 30 p p m

Pullularia pul lulans

50 000 rad 100 7 9 - 1 0 1 5 9 . 0 - 1 0 0 0 - 2 . 5

Candida t ropical is

15 000 tad 100 6 8 - 1 0 9 1 8 . 0 - 5 0 . 0 0 - 2 . 3

Botrytis c inerea

25 000 rad 100 100 63.6 65.0

Geotr ichum sp.

, 20 000 rad 100 9 0 . 8 - 9 3 . 7 8 3 . 0 - 8 9 . 0 7 0 . 2 - 9 1 . 1

Pénic i l l ium i t a l i c u m

20 000 rad

(a) in air 100 9 8 . 0 - 106.5 4 2 . 5 - 5 0 . 0 5 0 . 0 - 5 4 . 5

( b ) i n anoxia 100 9 0 . 8 - 9 3 . 7 8 3 . 0 - 89.0 7 0 . 2 - 9 1 . 1

Aspergillus niger

30 000 rad 100 9.9.0 56.0 54.0

RADIOSENSITIVITY OF PURIFIED AND CRUDE PECTIC ENZYME PREPARATIONS

К. VAS AND G. PROSZT INSTITUTE OF FOOD TECHNOLOGY AND MICROBIOLOGY,

COLLEGE OF HORTICULTURE AND VITICULTURE. BUDAPEST, HUNGARY


RADIOSENSITIVITY OF PURIFIED AND CRUDE PECTIC ENZYME PREPARATIONS. Solid and liquid pre-parations containing pectic enzymes of fungal origin can successfully be sterilized by relatively high doses (around 1 Mrad) of ionizing radiations without appreciable damage to enzyme activity. In contrast, pectolytic enzymes in the purified state proved to be rather radiosensitive. Purification has been achieved by fractionation on Sephadex gel columns. Combining the "pure" enzyme solution with certain other fractions obtained by the gel filtration procedure, partially or completely restored the original radio-resistance of the enzymes as found in the crude preparation. Attempts were made to characterize the radio-protective substances, and it is prob-able that the most effective fraction contains purin and/or pyrimidin derivatives. A closer identification of these substances is under way. It is hoped that knowledge of these compounds will prove to be of value in re-gulating enzyme sensitivity in a positive or in a negative sense to suit the varying needs of the food technologist.

RADIOSENSIBILITE DE PREPARATIONS D'ENZYMES PECT1QUES A L'ETAT PURIFIE ET A L'ETAT BRUT. On peut arriver à stériliser des préparations solides et liquides d'enzymes pectiques provenant de champignons en les exposant à des doses relativement intenses (environ 1 Mrad) de rayonnements ionisants sans nuire de manière appréciable à l'activité des enzymes. En revanche, il s'est avéré que les enzymes pectiques à l'état purifié étaient assez radiosensibles. La purification a été effectuée par fractionnement sur colonnes à gel Sephadex. On a constaté que si la solution d'enzymes purs était mélangée à certaines autres fractions obtenues par filtration sur une colonne à gel, les enzymes retrouvaient partiellement ou complètement la radiorésistance première des préparations non purifiées. On s'est efforcé de définir les propriétés des substances radioprotectrices et il est probable que la fraction la plus efficace est celle qui contient des dérivés de la purine ou de la pyrimidine. Des travaux sont en cours en vue d'identifier ces substances avec plus de précision. On espère que la connais-sance de ces composés contribuera à régulariser la sensibilité des enzymes dans un sens positif ou négatif selon les besoins divers des industries alimentaires.

ЧУВСТВИТЕЛЬНОСТЬ К ОБЛУЧЕНИЮ ОЧИЩЕННЫХ И НЕОЧИЩЕННЫХ ПРЕПАРАТОВ ПЕКТИНОВОГО ФЕРМЕНТА. Твердые и жидкие препараты, содержащие пектиновые фермен-ты грибкового происхождения, можно успешно стерилизовать сравнительно высокими дозами (приблизительно 1 мрад) ионизирующих излучений без ощутимого ущерба для активности фер-мента . В противоположность этому пестолитические ферменты в очищенном состоянии оказа -лись довольно радиочувствительными. Очистка достигается перегонкой на колонках "Сефа-декс г е л ь " . Сочетание раствора " ч и с т о г о " фермента с некоторыми другими фракциями, полученными методами фильтрации г е л я , частично или полностью восстанавливало первона-чальную сопротивляемость ферментов к радиации, как это было установлено на сыром препа-р а т е . Предпринимались попытки дать характеристику радиозащитных веществ и, вероятно, в наиболее эффективной фракции содержатся производные пурина и/или пиримидина. Прово-дится более подробное изучение этих в е щ е с т в . В ы р а ж а е т с я надежда, что знания относи-тельно этих соединений окажутся полезными при регулировании чувствительности фермента в позитивном или негативном смысле для удовлетворения меняющихся потребностей техно-логии пищевой промышленности. '

RADIOSENSIBILIDAD DE LOS PREPARADOS DE ENZIMAS PECTICAS PURIFICADAS Y SIN PURIFICAR. Con dosis relativamente elevadas (alrededor de 1 Mrad) de radiaciones ionizantes es posible esterilizar satisfactoria-mente preparados sólidos y líquidos que contengan enzimas pécticas derivadas de hongos, sin perjuicio apreciable

151

152 VAS and PROSZT

para la actividad de las enzimas. En cambio, las enzimas pectoliticas en estado purificado resultaron bastante radiosensibles. La purificación se ha efectuado por fraccionamiento en columnas de gel Sephadex. Combinando la solución « pura » de enzimas con algunas otras fracciones obtenidas por filtración con gel se restauró parcial o completamente la radiorresistencia inicial que tenían las enzimas del preparado sin purificar. Se trató de identificar las sustancias radioprotectoras y es probable que la fracción más eficaz contenga derivados de la purina y de la pirimldina. Se está haciendo una identificación más rigurosa de estas sustancias. Se espera que el conocimiento de estos compuestos sea de utilidad para regular la sensibilidad de las enzimas en sentido positivo o negativo según necesiten los técnicos de la alimentación.

P e c t i c enzymes of fungal or igin a r e widely used in food technology to i n c r e a s e the yield in f ru i t juice production, as well as f o r the c lar i f ica t ion of the p r e s s e d juice. Raw enzyme prepara t ions a re usually highly contami-nated by moulds and bac ter ia which ser iously impair the preservat ive qual i-t i e s oi l iquid p r e p a r a t i o n s (mould b ran ex t rac t s ) and contaminate the f ru i t mash or f ru i t juice to which these, or the mould bran i tself , a re added. To be able to abandon the present -day use of chemical preservat ives and to d e s -t r o y the m i c r o f l o r a of such p repara t ions , one of us (K. Vas) proposed e x -p e r i m e n t s f o r c l a r i f i ca t ion of the quest ion of whether ionizing r ad i a t ions could be used to eradicate microbial contamination f rom these and other en-zyme p repa ra t ions (amylases , p ro t eases , e t c . ) . The idea was based upon the great dif ferences in radiosensitivity of enzymes and microbes as reported in the l i t e ra tu re .

In a s e r i e s of exper iments , this proposi t ion has been shown to work for c o m m e r c i a l pect ic enzyme p repa ra t ions . X - r a y doses (200 kV, dose ra te : 0.2 Mrad/h) of 0 .8-1.0 Mrad applied to liquid or solid products ef fect ively destroyed all microbia l contaminants without appreciably affecting enzymic activity.

In cont ras t to these crude enzyme prepara t ions , par t ia l ly purified poly-g a l a c t u r o n a s e s proved to be much m o r e sens i t ive to ioniz ing r a d i a t i o n s .

After var ious unsuccessful pre l iminary t r i a l s , purification was achieved by gel f i l t ra t ion on Séphadex columns applying S^rensen (phosphate) and Mcllvaine (phosphate-bei t räte) bu f fe r s o r dist i l led wa te r as eluting agents .

In a s e r i e s of experiments, 2 - or 5 -ml portions of a liquid pectic enzyme prepara t ion (Polizim) were applied to Sephadex G 50 (gel fil tration) and С 25 (cation exchange) columns, respect ively (diameter = 19 mm, height = 135 mm) and fract ions of 5 or 2 ml were collected t.nd examined for polygalacturonase activity (see F i g s . l and 2. D: percentage degradation of pectin by v i sco -s ime t r i c measurement , R: total r e f r ac tomet r i c solids content and E4 1 0 : opti-cal density at 470 nm,optical path length: 1 cm).

As can be seen f r o m F i g s . 1 and 2 t h r e e main bands developed. Tne f i r s t contained the pectic enzymes, the second the yellowish-brown pigments and the th i rd the bulk of the soluble sol ids content . The e f f ic iency of the sepa ra t ion was found not to depend upon the pH value of the buf fe r , not,at l eas t ,wi th Sephadex G 50 in the pH range f r o m 4.02 to 7.52 (Fig. 3) .

With Sephadex С 25 (Fig . 2) the enzymes and the p igments could not be s e p a r a t e d because the to ta l soluble sol ids t r ave l l ed downwa-rds at a much s l o w e r r a t e than in the above two groups of components .

Radiosensit ivi t ies of the fract ions were then examined separately. While the ac t iv i ty of the o r ig ina l enzyme complex did not s u f f e r s e r i o u s l y f r o m

PECTIC ENZYME PREPARATIONS 153

E F F L U E N T V O L U M E

FIG. 1. Fractionation of liquid pectic enzyme preparation Polizim on a Sephadex G 50 column with phosphate buffer pH 6.00.

0 (V . ) II. S E P H A D E X С 2 5

1 0 0 - 0 Л

R C/ . ) (! E 4 7 0 i R

0 .5 - 5 - 5 0 -f E

W

0 - 0 • 0 Н - Л -5 0 100 ( m l )

E F F L U E N T V O L U M E

FIG. 2. Fractionation of liquid pectic enzyme preparation Polizim on a Sephadex С 25 column with phosphate buffer pH 6.00. •

r a d i a t i o n d o s e s of the o r d e r of 1 M r a d , the f r a c t i o n conta ining the " c o l o u r -l e s s " , p u r e e n z y m e (I, f r o m a Sephadex G 50 column) l o s t about 96% of i t s a c t i v i t y d u r i n g t h i s t r e a t m e n t ( F i g . 4) . In t h e s e e x p e r i m e n t s , ac t iv i ty was m e a s u r e d in t e r m s of S t a n d a r d P e c t o l y t i c A c t i v i t y (SPA 7 5 ) i n d i c a t i n g t h e v o l u m e , in l i t r e s , of an 0.6% p e c t i n so lu t ion which can be d e g r a d e d to 25% of i ts o r ig ina l spec i f i c v i s c o s i t y in 60 min at 50°C by 1 kg of the enzyme p r e p a r a t i o n . The ye l lowish-brown band, obtained on Sephadex С 25 columns (II) and con t a in ing the e n z y m e s but not t he bu lk of t he so lub l e s o l i d s , w a s s o m e w h a t l e s s s e n s i t i v e to i r r a d i a t i o n . A l o s s of ac t iv i ty of about 74% o c c u r r e d .

As can be obse rved , the p igment showed s o m e r ad io -p ro t ec t ive influence on po lyga lac tu ronases , while in the p r e s e n c e of both the coloured components and the r e s t of the so lub le s o l i d s ( i . e . in t h e o r i g i n a l e n z y m e p r e p a r a t i o n ) i r r a d i a t i o n had no a p p r e c i a b l e e f f e c t on p o l y g a l a c t u r o n a s e a c t i v i t y .

In f u r t h e r e x p e r i m e n t s the r a d i o - p r o t e c t i v e e f f ec t of the f r a c t i o n s was examined by combining the l a t t e r with the s e n s i t i v e " p u r e " enzyme f r a c t i o n b e f o r e i r r a d i a t i o n . Isolat ion of the t h r e e ma in components , i . e . the pur i f ied

154 VAS and PROSZT

о 20

MclLVAINE BUFFERS ENZYME SOLN ! 2 ml FRACTIONS : 5 m l

S0RENSEN BUFFERS ENZYME S O L N i 5 ml FRACTIONS : 2 ml

SOLUBLE SOLIOS

8 COLOUR -О

i, 5 6 7 p H OF E L U A N T

FIG. 3. Effect of pH and type of eluting agent on the fractionation of Polizim on Sephadex G 50 columns.

100

50-

i a

POLIZIM I

гь • I I

FIG. 4. Inactivation of polygalacturonases in a complex mixture (Polizim), as well as in partially putified preparations; Fraction I, from Sephadex G 50, Fig. 1; Fraction II, from Sephadex С 25, Fig. 2.

e n z y m e (A), t h e s u b s t a n c e ( s ) r e s p o n s i b l e f o r t h e p e a k ' i n r e f r a c t o m e t r i c s o l i d s conten t (B) and the p i g m e n t (C), was a t t e m p t e d by p a s s i n g l a r g e r amount s (2 X 10 ml) of P o l i z i m f i r s t th rough a Sephadex С 25 column (29 m m X 160 m m ) and then one of t he f r a c t i o n s t h r o u g h a G 50 co lumn (29 m m X 160 m m ) , Deve lopmen t was c a r r i e d out with S ^ r e n s e n phospha te b u f f e r of pH 6 .0 , On the G 25 co lumn В could be s e p a r a t e d f r o m a m i x t u r e of A and C. T h i s m i x t u r e was then run th rough a G 50 column, the opera t ion r e s u l t i n g in a f a i r l y c l e a r - c u t s e p a r a t i o n of A and С (F ig . 5).

Note h e r e tha t a f o u r t h f r a c t i o n of o c h r a c e o u s co lour (D) could a l s o be i s o l a t e d on the Sephadex С 25 co lumn ( F i g . 2); i t s amount was , h o w e v e r , c o m p a r a t i v e l y s m a l l .

The above f r a c t i o n s w e r e combined in v a r i o u s ways and then i r r a d i a t e d wi th 0.5 and 1.0 M r a d , r e s p e c t i v e l y . C h a n g e s in e n z y m e ac t iv i ty w e r e fol lowed by d e t e r m i n i n g the SPAi& v a l u e s . The r e s u l t s a r e shown in F i g . 6 .

It can be s e e n that t he m a i n p ro t ec t i ve agent agains t i r r a d i a t i o n damage t o p e c t o l y t i c ac t iv i ty i s r e p r e s e n t e d by f r a c t i o n B . In a c c o r d a n c e with r e -s u l t s shown in F i g . 4 . , the ye l lowish -b rown p igmen t (C) a l s o e x e r t e d s o m e p r o t e c t i v e e f f e c t at t he l o w e r dose l eve l (0.5 M r a d ) , though, in c o n t r a s t to t he above , no s u c h e f f e c t could be d e t e c t e d a t 1 M r a d . T h i s d i s c r e p a n c y


STEP 1 STEP 2

S0RENSEN BUFFER pH = 6.0

SEPHADEX С 25

POIIZIM

А» С

А • С

SEPHADEX G 50

CONCENTRATION-

FIG. 5. Out l ine of t h e separa t ion p rocedure l e a d i n g t o pur i f ied po lyga lac turonases ( f r ac t ion A) and o ther substances.

bl Э < 100-> • _J < z 5 50-

c§ « u . C O 1Л j. 0

• Э

I s 50-0 z lu

t a <л < о к о. (г 0 х -О U. о О

О О

Q2 3.6 1.1 3.0 REFR. SOLIDS ('/ .)

О : 0.5 Mrad • : 1.5 Mrad

A : PURIFIED ENZYME В • SOLUBLE SOLIDS С : YELLOW PIGMENT W : WATER

FIG. 6. Radiosensitivity of purif ied polygalacturonases and their mixtures with other fractions obtained, from liquid enzyme preparation Pol izim, by column chromatography on Sephadex С 25 and G 50 columns.

might poss ib ly be expla ined by the d i f f e r ence in pec to ly t ic act ivi ty of the two solu t ions b e f o r e i r r a d i a t i o n (SPA75 = 803 and 188 1/kg, in the f i r s t and second expe r imen t , r e spec t ive ly ) .

To shed s o m e l ight on the c h e m i c a l n a t u r e of the f r a c t i o n s А, В, С and D, a s wel l a s the o r i g i n a l e n z y m e p r e p a r a t i o n (E), t h e i r v i s ib l e and u l t r a -v i o l e t s p e c t r a have b e e n d e t e r m i n e d . T h e s e a r e shown in F i g s . 7 and 8 .

The r a t h e r f l a t peak , at 280 n m , of the " p u r e " e n z y m e solut ion(A) s e e m s t o be r e l a t e d to i t s p r o t e i n n a t u r e , s p e c i f i c a l l y p e r h a p s to the p r e s e n c e of t y r o s i n e and t r y p t o p h a n e . F r a c t i o n B, wi th a p e a k at 265 n m , a p p e a r s t o con ta in p u r i n e and p y r i m i d i n e c o m p o u n d s . T h e r e l a t i v e p o s i t i o n of bands A and В i s c o m p a t i b l e wi th t h e a s s u m p t i o n t h a t В c o n t a i n s p y r i m i d i n e o r

156 VAS and PROSZT

FIG. 7. Spectra of fractions A to D in the visible region.

FIG. 8. Spectra of fractions A to D, as well as of the original liquid enzyme preparation (E) in the ultraviolet region.

p u r i n e b a s e s o r nuc leo t ides s ince the m o l e c u l a r weights of t hese compounds a r e s m a l l e r (110 - 400) than the m o l e c u l a r weight of p o l y g a l a c t u r o n a s e s (10 0 0 0 - 3 0 000), and so t hey move m u c h s lower on a m o l e c u l a r s i e v e than the e n z y m e s . The s a m e i s t r u e f o r s i m p l e c a r b o h y d r a t e s which a l so could be found in l a r g e a m o u n t s in f r a c t i o n В by t h e a n t h r o n e r e a g e n t . C o l o u r f r a c t i o n s С and D show s i m i l a r a b s o r p t i o n ( typ ica l f o r b r o w n i s h co lour) in t h e v i s i b l e r e g i o n , though С i s m o r e c o n c e n t r a t e d t h a n D. At t h e s a m e t i m e ; t h e i r u l t r a v i o l e t s p e c t r a s e e m to i nd i ca t e t h a t С w a s not c o m p l e t e l y f r e e f r o m A, n o r D f r o m B.


FIG. 9. Effect of ionizing radiations (1 Mrad) on the ultraviolet spectra of fractions A and B.

5 0 100 150 ( m l )

EFFLUENT VOLUME

FIG. 10. Elution pattern of an i r radiated (1 Mrad) liquid p e c t i c e n z y m e preparat ion on Sephadex G 100 column with Mcl lva ine buffer pH 4 .03 .

F u r t h e r , i t was found that i r r a d i a t i o n did not m a t e r i a l l y a l t e r the u l t r a -v io le t s p e c t r a of f r a c t i o n s A and В ( F i g . 9) . Note tha t when the o r i g i n a l e n z y m e p r e p a r a t i o n ( P o l i z i m ) was f i r s t i r r a d i a t e d and then s e p a r a t e d on a Sephadex G 100 co lumn ( M c l l v a i n e b u f f e r of pH 4 .03 ) , no appa ren t changes in t h e e lu t ion p a t t e r n o c c u r r e d ( F i g . 10) . E x p e r i m e n t s a r e in p r o g r e s s to i d e n t i f y the s u b s t a n c e ( s ) p r e s e n t in f r a c t i o n В by p a p e r c h r o m a t o g r a p h y and e l e c t r o p h o r e s i s , a s wel l a s by i n f r a - r e d s p e c t r o p h o t o m e t r y .

A knowledge of the n a t u r e of e n z y m e s m a y aid in t h e i r p r o t e c t i o n in c o m m e r c i a l p r e p a r a t i o n s and, on the o t h e r hand, m a y be used in i n c r e a s i n g t h e r a d i o s e n s i t i v i t y of t i s s u l a r e n z y m e s - an i m p o r t a n t a s p e c t of food i r -r ad i a t i on - by inac t iva t ing the p r o t e c t i v e subs t ances by chemica l o r phys ica l m e a n s .

158 VAS and PROSZT

I n s u m m a r y , i t m a y be sa id that though the ac t iv i ty of pec to ly t ic e n z y m e s in t h e n a t u r a l , c o m p l e x s t a t e i s riot a f f e c t e d by d o s e s up to 1 M r a d , t h e s e e n z y m e s p roved to be r a d i o s e n s i t i v e in p u r e so lu t ion p r e p a r e d by f r a c t i o n -at ion on Sephadex С 25 and G 50 gel f i l t r a t i o n c o l u m n s . Combining the p u r e enzyme solut ion with c e r t a i n o ther f r a c t i o n s , obtained by the above technique, p a r t i a l l y o r comple t e ly r e s t o r e d the originell r a d i o r e s i s t a n c e of the enzyme complex . A t t e m p t s w e r e m a d e to c h a r a c t e r i z e t h e s e r a d i o p r o t e c t o r s , and i t i s l i ke ly t h a t the m o s t e f f e c t i v e f r a c t i o n c o n t a i n s p u r i n e and p y r i m i d i n e d e r i v a t i v e s and s u g a r s , but t h e i r c l o s e r iden t i f i ca t ion r e m a i n s to be solved.

A C K N O W L E D G E M E N T S

We would l ike t o e x p r e s s o u r g ra t i t ude to the In t e rna t iona l A t o m i c E n e r g y Agency f o r s u p p o r t i n g t h i s w o r k by a r e s e a r c h c o n t r a c t , a s wel l a s to D r s . A. Hedbom (Biokemiska Inst i tut ionen, Uppsala) and В. Gelotte ( P h a r m a c i a , Uppsala) f p r the gene rous supply of Sephadex p r e p a r a t i o n s .

We a r e e s p e c i a l l y indebted to the l a t e D r . L . E . E r i c s o n (IAEA) f o r his h e l p in p r o v i d i n g t h e n e c e s s a r y ge l f i l t r a t i o n m a t e r i a l s and f o r t h e m o s t v a l u a b l e d i s c u s s i o n s we w e r e ab le to conduct with h i m . We shou ld l ike to t a k e t h i s o p p o r t u n i t y t o p a y a t r i b u t e t o h i s m e m o r y .

RADIATION INACTIVATION OF FOOT AND MOUTH DISEASE VIRUS I

D . MASSA

DEPARTMENT OF VETERINARY SERVICE,

MINISTRY OF HEALTH,

ROME, ITALY


RADIATION INACTIVATION OF FOOT AND MOUTH DISEASE VIRUS. This paper presents descriptions of several diseases of animals caused by viruses, the effects upon the animals by the disease, and the losses suffered in infected herds. The importance of the control of these viral diseases in international commerce by quarantine regulations on items, such as meat, milk, blood, hides, hair, wool, bone, animal feeds and packag-ing materials, is pointed out. Such information is followed by a detailed description of the experiments carried out to inactivate the Foot and Mouth Disease virus by heat and by irradiation, in both the liquid and dry states. It is indicated that the inactivation by irradiation requires 3 Mrad in the liquid state but that 4 Mrad are required if in the dry state. There is a short discussion on the need for similar researches with the other types of animal viruses and on some of the difficulties encountered in carrying out this type of work.

INACTIVATION PAR IRRADIATION DU VIRUS DE LA FIEVRE APHTEUSE. Le mémoire décrit plusieurs maladies virales répandues chez les animaux, les effets de ces maladies sur les animaux et les pertes subies par les troupeaux qui en sont atteints. Il montre combien il importe de lutter contre ces maladies virales en adoptant dans le commerce international des règlements de quarantaine à l'égard de produits tels que: viande, lait, sang, cuirs et peaux, poil, laine, os, aliments pour animaux et matériaux d'emballage d'origine animale. Le mémoire fournit ensuite une description détaillée des expériences d'inactivation du virus de la fièvre aph-teuse par traitement thermique et par irradiation, dans des liquides et dans des produits secs. D'après ces expériences, l'inactivation du virus dans des liquides exige une dose de 3 Mrad, mais pour inactiver le virus dans des produits secs, une dose de 4 Mrad est nécessaire. L'auteur discute brièvement la nécessité de procéder à des recherches semblables sur les autres types de virus de maladies des animaux et décrit certaines des diffi-cultés rencontrées dans l'exécution de travaux de cette nature.

ИНАКТИВАЦИЯ ВИРУСА ЯЩУРА ОБЛУЧЕНИЕМ. Описываются некоторые болезни животных, вызванные вирусами, действие этих болезний на животных и потери в поражен-ных стадах . Отмечается важность контроля этих опасных заболеваний в международной торговле с помощью правил карантина по таким видам продуктов как: мясо, молоко, кровь, шкуры, волос, шерсть, кости, фураж и упаковочные материалы. Такая информация сопро-вождается подробным описанием проведенных экспериментов с целью инактивации вируса ящура с помощью тепла и облучения как в жидком, так и в сухом состояниях. Указывается, что инактивация облучением требует дозы 3 мегарад в жидком состоянии, но в сухом со -стоянии требуется доза 4 мегарад. Кратко обсуждаются необходимость подобных исследова-ний с другими видами вирусов животных и некоторые трудности при выполнении работы .

INACTIVACION DEL VIRUS DE LA FIEBRE AFTOSA POR IRRADIACION. La memoria describe las diversas enfermedades animales causadas por los virus, los efectos que producen en los animales y las pérdidas sufridas en los rebaños infectados. Se destaca la importancia de luchar contra esas enfermedades en el comercio inter-nacional mediante reglamentaciones de cuarentena sobre productos tales como la carne, la leche, la sangre, las pieles, el pelo, la lana, los huesos, los piensos y los materiales de envase. Se describen luego detallada-mente los experimentos realizados para inactivar el virus de la fiebre aftosa mediante el calor y por irradiación, tanto en el estado líquido como en el estado seco. La inactivación por irradiación requiere 3 Mrad en el estado líquido y 4 en el estado seco. Se discute brevemente la necesidad de hacer investigaciones similares con los demás tipos de virus animales y se exponen algunas de las dificultades que presenta esta labor.

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160 MASSA

I N T R O D U C T I O N

T h i s p a p e r c o n c e r n s t h e e f f e c t s of i o n i z i n g e n e r g y on foo t and m o u t h d i s e a s e ( F M D ) v i r u s i n v i e w of s u g g e s t i n g a p o s s i b l e r a d i a t i o n s a n i t a t i o n t r e a t m e n t of a n i m a l p r o d u c t s , s u c h a s m e a t , h a i r , h i d e s , b o n e s , g l a n d s , e t c . , c o n t a m i n a t e d w i t h F M D v i r u s .

T h e e x p e r i m e n t s s o f a r c a r r i e d out a t t h e P e r u g i a V e t e r i n a r y R a d i o -b i o l o g i c a l G r o u p on t h e r a d i a t i o n i n a c t i v a t i o n of FMD v i r u s in the l iquid and d r y s t a t e [1] a r e d e s c r i b e d and m e n t i o n i s m a d e of the e x p e r i m e n t s in c o u r s e on the r a d i a t i o n inac t iva t ion of FMD v i r u s in s i tu , such a s in the blood, lymph g l a n d s and b o n e m a r r o w of t h e c a r c a s s e s of i n f e c t e d a n i m a l s [2]. F u r t h e r -m o r e an o u t l i n e i s g i v e n of t h e p o s s i b i l i t i e s of u s i n g i on i z ing r a d i a t i o n f o r t h e i n a c t i v a t i o n of o t h e r v i r u s e s w h i c h a r e t h e e t i o l o g i c a l a g e n t s of e x o t i c d i s e a s e s of g r e a t e c o n o m i c i m p o r t a n c e , s u c h a s r i n d e r p e s t ( R P ) , s w i n e f e v e r (SF) a n d A f r i c a n s w i n e f e v e r (ASF) .

B e f o r e c o n s i d e r i n g t h e p r o b l e m s c o n n e c t e d wi th t h e i r r a d i a t i o n of t h e F M D v i r u s , s o m e d a t a on t h e m o d e of t r a n s m i s s i o n of t h e v i r u s e s u n d e r d i s c u s s i o n , v i a i n f e c t e d p r o d u c t s , a r e b r i e f l y s u m m a r i z e d .

F O O T A N D M O U T H D I S E A S E

F o o t a n d m o u t h d i s e a s e i s a n a c u t e , f e b r i l e d i s e a s e of c a t t l e , s h e e p , g o a t s and p i g s , wh ich i s c h a r a c t e r i z e d by t h e f o r m a t i o n of v e s i c l e s in c o n -n e c t i o n wi th t h e m o u t h and f e e t , and s o m e t i m e s on t h e s k i n of t he u d d e r o r t e a t s of f e m a l e s . U n d e r c e r t a i n c o n d i t i o n s , h u m a n b e i n g s a r e s u s c e p t i b l e t o the d i s e a s e , bu t , e x c e p t in c h i l d r e n , t h e s y m p t o m s a r e m i l d . Hedgehogs m a y b e a f f e c t e d a n d m a y s p r e a d t h e d i s e a s e t o s t o c k n a t u r a l l y . I t h a s o c c u r r e d in a l m o s t e v e r y c o u n t r y in t h e ' w o r l d w h e r e c a t t l e a r e kep t , bu t i s v e r y m u c h m o r e c o m m o n in s o m e t h a n in o t h e r s . On the E u r o p e a n cont inent and in t h e c o u n t r i e s of South A m e r i c a t h e d i s e a s e i s a l m o s t c o n s t a n t l y p r e -s e n t . It i s a l s o ind igenous in m a n y p a r t s of A f r i c a and Asia , and s o m e t i m e s a s t r a i n of g r e a t l y i n c r e a s e d v i r u l e n c e c r o s s e s t h e M e d i t e r r a n e a n to invade Sou the rn E u r o p e and s w e e p ove r l a r g e a r e a s with e x t r e m e rap id i ty . A u s t r a l i a and New Z e a l a n d a r e f r e e f r o m F M D . T h e F M D a f f e c t s not only d o m e s t i -c a t e d a n i m a l s , bu t v e r y m a n y of t h e wi ld h e r b i v o r e s a s w e l l , hav ing b e e n s e e n in d e e r , a n t e l o p e , buf-falo, b i s o n , y a k s , e t c .

T h e F M D i s the t y p i c a l e x a m p l e of an in fec t ion c a u s e d by d i f f e ren t t ypes of v i r u s (О, A, C, SATj, SAT 2 , SAT3 , A s i a i) hav ing we l l d i s t i ngu i shed an t igen ic , b i o l o g i c a l a n d p h y s i c o - c h e m i c a l p r o p e r t i e s . T h e e x i s t e n c e , w i t h i n e a c h t ype , of a n u m b e r of s u b t y p e s o r v a r i a n t s m a k e s the p r o b l e m of F M D p r o p h i -l a x i s v e r y i n t r i c a t e . T h e m o s t d i f f u s e d FMD v i r u s in n a t u r e is that of type O.

T h e d i s e a s e i s not, a s a r u l e , an e x t r e m e l y f a t a l one in the adult an ima l , bu t when it a f f e c t s b r e e d i n g s t o c k a s m a n y a s 85% of the young a n i m a l s b o r n f r o m a f f e c t e d d a m s d i e . It c a u s e s g r e a t e c o n o m i c l o s s on a c c o u n t of t h e r e d u c t i o n in m i l k s e c r e t i o n in d a i r y h e r d s , s e v e r e l o s s of c o n d i t i o n in f a t s t o c k of a n y s p e c i e s , i n t e r f e r e n c e w i t h t r a d i n g i n l i v e s t o c k , a n d l o s s of c a l v e s , k i d s , l a m b s a n d p i g l e t s .

In c o u n t r i e s w h e r e t h e r e i s l e g i s l a t i o n a g a i n s t FMD, h e a v y e x p e n d i t u r e in c o m p e n s a t i o n t o o w n e r s and v a r i o u s q u a r a n t i n e and i s o l a t i o n m e a s u r e s

FOOT AND MOUTH DISEASE VIRUS 161

in t h e c l e a n s i n g and s t e r i l i z a t i o n of b u i l d i n g s , u t e n s i l s and p r o d u c t s a r e n e c e s s a r y . In the United Kingdom and North A m e r i c a , where s t r i c t m e a s u r e s of s laughter ing a f fec ted and in-contac t an imal s a r e in opera t ion. i t has caused l o s s e s amounting to many mi l l ions of pounds, paid as compensat ion to owners of a f fec ted a n i m a l s . In I taly, which is one of the coun t r i e s where the d i sease i s e n z o o t i c , the l o s s e s a m o u n t t o a p p r o x i m a t e l y 1 1 . 5 - 14.5 m i l l i o n pounds e v e r y y e a r .

T h e b e s t pH f o r F M D v i r u s i s 7.6. T h e s i z e of t he F M D v i r u s i s 10-12 n m F o r i s o l a t i o n and t i t r a t i o n of FMD v i r u s f r o m d i f f e r e n t m a t e r i a l s and p r o -duc t s , t he t e chn ique of t i s s u e c u l t u r e s in v i t r o (mono laye r t r y p s i n i z e d calf k idney c u l t u r e s ) can be s u c c e s s f u l l y e m p l o y e d .

The FMD v i r u s i s d i s s e m i n a t e d by in fec t ed a n i m a l s and t h e i r p r o d u c t s [3-101. The dange r of m e a t and m i l k d e r i v e d f r o m in fec ted a n i m a l s i s wel l p r o v e d . E x p e r i m e n t s have shown the s u r v i v a l of FMD v i r u s in c a r c a s s e s of s l a u g h t e r e d a n i m a l s which w e r e s u f f e r i n g f r o m FMD. Th i s i s an impor tan t m a t t e r in c o u n t r i e s w h e r e t h e d i s e a s e does not e x i s t , f o r m a n y o u t b r e a k s of the d i s ea se have been t r a c e d to ga rbage containing mea t t r i m m i n g s [11, 12].

The acidi ty which develops shor t ly a f t e r death in m u s c u l a r t i s sue usual ly d e s t r o y s the v i r u s within a few days u n d e r r e f r i g e r a t i o n . The FMD v i r u s , h o w e v e r , c an b e d e t e c t e d in the blood, l ymph g l a n d s , bone m a r r o w and fa t s t o r e d u n d e r r e f r i g e r a t i o n [13, 14]. T h e F M D v i r u s c a n be d e t e c t e d in a l l i n f e c t e d o r g a n s and t i s s u e s s t o r e d in t h e f r o z e n s t a t e f o r m o r e t h a n s i x m o n t h s [13, 14].

With r e g a r d to the c u r e d p r o d u c t s , the FMD v i r u s does not s u r v i v e in d ry s a u s a g e s and i ts inact iva t ion is caused by a quick es t ab l i shment of enzy-m a t i c and m i c r o b i o l o g i c a l p r o c e s s e s dur ing the s t a g e s of g r ind ing and p r o -c e s s i n g of m i x t u r e s [15-18] .

Even in p roduc t s such as the "capocol lo" and "b resao la" , made up chiefly of th ick m u s c u l a r po r t i ons , t he v i r u s inac t iva t ion i s advanced, being connec-ted with a r ap id lower ing of pH [15-18].

In h a m s t h e v i r u s s u r v i v a l l a s t s l o n g e r and it v a r i e s a c c o r d i n g to the d i f f e r en t p a r t s (musc l e , fa t , bone) that m a k e up the p roduc t . In the m u s c l e t h e v i r u s , w h e n it i s p r e s e n t , i s i n a c t i v a t e d d u r i n g the p r o c e s s i n g s t a g e and in any c a s e a lways dur ing the sa l t ing pe r iod . In fa t s and chief ly in bone t i s s u e it is able to surv ive fo r the whole pe r iod ranging f r o m curing to drying p r o c e s s e s , but d i s appea r s g radua l ly l a t e r ( f i r s t in fat and then in bone t i ssue) during the e a r l y r ipening p h a s e s [15-18].

The FMD v i r u s can e a s i l y r e t a i n i ts vi ta l i ty fo r v e r y cons iderab le lengths of t i m e in n a t u r e when it i s d r i ed , and owing to th is fac t the d i s ea se is sp r ead by a h o s t of i n t e r m e d i a t e o b j e c t s which have b e e n in con t ac t wi th a f f e c t e d a n i m a l s . The fol lowing p r o d u c t s can be r e s p o n s i b l e f o r the d i f fu s ion of t he d r i ed FMD v i r u s : h ides , h a i r , wool, hay, s t r aw , s acks and packing f ab r i c s . In one ca se , fo r ins tance , it was thought that the s t r a w in which f lower bulbs had been p a c k e d w a s r e s p o n s i b l e f o r t he d i f fu s ion of F M D v i r u s . A l i s t of the p r o d u c t s which can be r e s p o n s i b l e fo r the d i f fus ion of the FMD v i r u s has b e e n compi led by the О. I. R. S. A. [19].

T h e F M D v i r u s i s i n a c t i v a t e d by h e a t ; a t e m p e r a t u r e of 55°C f o r 10-14 min is suf f ic ien t to inact ivate it in the lymph; t e m p e r a t u r e s of60-70°C f o r 15 m i n and f o r 5 m i n a r e ab le t o i n a c t i v a t e F M D v i r u s , r e s p e c t i v e l y , in m i l k and in b lood .

162 MASSA

A s r e g a r d s t h e d i s i n f e c t a n t s , t h e F M D v i r u s i s d e s t r o y e d by s t r o n g a l k a l i e s and f o r m a l i n . In p r a c t i c a l d i s in fec t ion , a 2% c o m m e r c i a l lye (sodium h y d r o x i d e ) s o l u t i o n i s u s e d , b u t b e c a u s e of i t s c o r r o s i v e n a t u r e , s o m e w o r k e r s p r e f e r a 4% s o d i u m c a r b o n a t e s o l u t i o n wh ich i s b e l i e v e d t o be ju s t a s e f f e c t i v e .

R I N D E R P E S T

R i n d e r p e s t i s an acu t e , s p e c i f i c , inoculab le and f e b r i l e d i s e a s e of ca t t l e , c h a r a c t e r i z e d b y a n u l c e r a t i v e i n f l a m m a t i o n of m u c o u s m e m b r a n e s , e s p e c i a l l y t h o s e of t h e a l i m e n t a r y t r a c t .

R i n d e r p e s t i s not p r e s e n t in the E a s t e r n H e m i s p h e r e n o r W e s t e r n E u r o p e . D u r i n g m o s t of t h i s c e n t u r y it h a s b e e n p r e v a l e n t in A f r i c a and i s s t i l l e n z o o t i c in m o s t of e q u a t o r i a l and p a r t of n o r t h e r n A f r i c a , A s i a and the Middle E a s t . A u s t r a l i a , New Z e a l a n d , J a p a n and t h e P h i l i p p i n e s a r e f r e e of t h e d i s e a s e .

R i n d e r p e s t i s one of t h e m o s t s e r i o u s t h r e a t s t o w o r l d f o o d s u p p l i e s , a n d , l i k e F M D , i s c a u s e d by a v i r u s , bu t a f a r m o r e d e a d l y o n e . When R P s t r i k e s a h e r d , n ine out of t e n a n i m a l s m a y die , a c a t a s t r o p h e which i s not i n f r e q u e n t l y f o l l o w e d b y f a m i n e . C a t t l e a r e by f a r t h e m o s t s u s c e p t i b l e a n i m a l s . N a t u r a l o c c u r r e n c e i s r a r e in s h e e p and g o a t s . H o r s e , p i g s , Carnivora a r e i m m u n e .

T h e R P v i r u s i s e a s i l y d e s t r o y e d by hea t anil by o r d i n a r y d i s i n f e c t a n t s . If kept on ice in t h e d a r k , the v i r u s m a y r e t a i n i t s v i ru l ence f o r many weeks . T h e H P v i r u s w i l l r e m a i n i n f e c t i o u s f o r w e e k s in the cold and f o r m o n t h s in f r o z e n a n i m a l p r o d u c t s [ 2 0 , 2 1 ] . In I ta ly , f o r i n s t a n c e , the d i s e a s e obta ined a f o o t - h o l d in W o r l d W a r I due t o t h e i m p o r t a t i o n of i n f e c t e d f r o z e n b e e f ( K a r a V i c e n t i n o - B r e g a n z e 1918) [22] .

Ai c o r d i n g t o s o m e s o u r c e s , t h e R P v i r u s can a l s o be p r e s e n t in c u r e d m e a t , s k i n s and s a l t e d s k i n s [20]. T h e R P v i r u s can be p r o p a g a t e d in ch ick e m b r y o s and in t i s s u e c u l t u r e .

SWINE F E V E R

Swine f e v e r i s an a c u t e , h ighly i n f e c t i o u s v i r u s d i s e a s e of swine , c h a r a c -t e r i z e d b y s u d d e n o n s e t a n d h i g h m o r b i d i t y and m o r t a l i t y . D e s p i t e f a i r l y s a t i s f a c t o r y i m m u n i z a t i o n p r o c e d u r e s , it c o n t i n u e s t o c a u s e l a r g e l o s s e s in m a n y c o u n t r i e s of t h e w o r l d w h e r e s w i n e a r e r a i s e d .

T h e S F v i r u s i s not i n f e c t i o u s f o r amy known s p e c i e s of a n i m a l o the r than s w i n e . T h e S F v i r u s i s e a s i l y d e s t r o y e d by h e a t . It i s v e r y r e s i s t a n t in the d r y s t a t e and when it i s kept on i c e .

T h e S F v i r u s i s p r e s e n t in c o l d o r f r o z e n a n i m a l p r o d u c t s [23]. R a w g a r b a g e , con t a in ing p o r k s c r a p s f r o m i n f e c t e d p i g s , i s a c o m m u n a l s o u r c e of i n f e c t i o n . In I ta ly , f o r i n s t a n c e , t he S F s p r e a d at the end of Wor ld War II a s a r e s u l t of t h e i m p o r t a t i o n of i n f e c t e d p o r k m e a t f r o m i n f e c t e d c o u n t r i e s . T h e S F v i r u s i s a l s o p r e s e n t in c u r e d m e a t p r o d u c t s [23] . O u t b r e a k s o c -c u r r e d in P r u s s i a and i n Sweden f r o m the i m p o r t a t i o n of i n f ec t ed bacon f r o m A m e r i c a [23] . T h e S F v i r u s c a n a l s o b e p r e s e n t in s k i n s and in t h e b r i s t l e [23] . T h e s i z e of t h e S F v i r u s i s 3 0 - 35 n m . It c a n b e p r o p a g a t e d in t i s s u e


c u l t u r e , but t h e t e c h n i q u e i s not v e r y e f f e c t u a l . T h e S F v i r u s can be kep t at a pH of 5.5.

AFRICAN SWINE F E V E R

A f r i c a n swinè f e v e r i s a highly contagious v i r a l d i s e a s e of p o r c i n e ani -m a l s , un t i l r e c e n t l y conf ined to the A f r i c a n cont inent , but now a l so found in p a r t s of W e s t e r n E u r o p e (Por tuga l , Spain and F r a n c e ) . Although the symp-t o m s and l e s ions a r e in many r e s p e c t s s i m i l a r to those of swine fever , swine i m m u n e to S F a r e fu l ly s u s c e p t i b l e t o ASF. T h e m o r t a l i t y r a t e of A S F i s e x t r e m e l y h igh (95 to a 100 out of 100) among d o m e s t i c swine in newly in-f e c t e d a r e a s .

T h e A S F v i r u s c a n b e d e m o n s t r a t e d in b lood , a l l e x c r e t i o n s and s e -c r e t i o n s , t i s s u e f lu ids and i n t e r n a l o rgans of in fec ted p igs . It i s except ion-a l ly s t ab le ; r e p o r t s ind ica te that i t can s u r v i v e in blood s t o r e d in a co ld , da rk r o o m f o r a s long as 6 y r .

The ASF v i r u s i s p r e s e n t in cold o r in f r o z e n a n i m a l p r o d u c t s [24]. Raw g a r b a g e , conta in ing p o r k s c r a p s f r o m in fec ted p i g s , i s a c o m m u n a l s o u r c e of i n f e c t i o n . T h e A S F v i r u s i s a l s o p r e s e n t in c u r e d m e a t p r o d u c t s [24].

It h a s b e e n thought tha t the ASF o r i g i n a t e d in E u r o p e owing to the i m -por t a t ion of in fec ted p o r k m e a t f r o m Angola and Monzambico , (Lisbon, 1957) [23, 24, 25]. It ha s c aused and i s s t i l l caus ing d i s a s t e r s in the swine h e r d s . The ASF v i r u s can be p r o p a g a t e d in chick e m b r y o s .

RADIATION INACTIVATION O F T H E FOOT AND MOUTH DISEASE VIRUS IN THE LIQUID AND IN T H E DRY STATE.

R e s e a r c h into v i r u s inact iva t ion by i r r a d i a t i o n began a number of y e a r s ago; t h e f i r s t q u a n t i t a t i v e w o r k on the s u b j e c t d a t e s f r o m 1933 a n d s i n c e t h e n m a n y a u t h o r s , in p a r t i c u l a r Gowen, Ho lweek , L a c a s s a g n e , L u r i a , E x n e r and Lea , have been ac t ive in t h i s f ield; a l l have con t r ibu ted i n c r e a s -ingly u s e f u l i n f o r m a t i o n .

It w a s found f r o m t h e b e g i n n i n g t h a t v i r u s i n a c t i v a t i o n r e q u i r e s f a r s t r o n g e r r a d i a t i o n d o s e s t h a n the inac t iva t ion of b a c t e r i a and only r e c e n t l y the d e v e l o p m e n t of m o r e p o w e r f u l and p e n e t r a t i n g r a d i a t i o n s o u r c e s r e n -d e r e d p o s s i b l e m o r e t ho rough and quan t i t a t ive i nves t i ga t i ons into the e f f ec t of r a d i a t i o n on the d i f f e r e n t v i r u s e s .

The v i r u s e s m o s t t ho rough ly s tud i ed and m o s t f r e q u e n t l y m e n t i o n e d in t h e l i t e r a t u r e a r e : t o b a c c o m o s a i c v i r u s [ 2 6 - 2 8 ] , s m a l l p o x v i r u s [28], N e w c a s t l e d i s e a s e v i r u s [29] and b a c t e r i o p h a g e [30 ,31 ] . R e c e n t l y J o r d a n and K e m p e [32] h a v e s t u d i e d t h e e f f e c t of g a m m a r a y s on t h e v i r u s e s of p o l i o m y e l i t i s , S t . L o u i s e n c e p h a l i t i s . W e s t e r n e q u i n e e n c e p h a l o m y e l i t i s and cowpox, and they conclude that (1) g a m m a rad ia t ion is an eff ic ient m e a n s of inac t iva t ing t h e s e v i r u s e s , (2) the s m a l l e r v i r u s e s r e q u i r e h ighe r doses of r a d i a t i o n t o i n a c t i v a t e t h e m and (3) the r a t e of i n a c t i v a t i o n i s an e x p o -n e n t i a l f u n c t i o n of t h e r a d i a t i o n d o s e .

D a t a on t h e F M D v i r u s a r e f ew and s c a n t y [33] , h e n c e w e though t i t adv i sab l e to u n d e r t a k e quan t i t a t ive r e s e a r c h on the inac t iva t ion of cu l t u r ed

164 MASSA

F M D v i r u s [1] t y p e s О, A and С b y g a m m a r a d i a t i o n f r o m a 'Hot Spot Mk IV' ®Co s o u r c e [34].

In a i l c a s e s t h e v i r u s s u s p e n s i o n s e x p o s e d by u s w e r e in v i t r o c u l t u r e s of t r y p s i n - h y d r o l y s e d cal f k idney c e l l s , g r o w n in Roux f l a s k s wi th n u t r i t i v e m e d i u m (0.5% l a c t a l b u m i n h y d r o l y s a t e in E a r le b u f f e r so lu t i on with 2% calf s e r u m and an t ib io t i c s ) . In the c a s e of the FMD v i r u s type C, we a l so s tudied it i n t h e d r y s t a t e a f t e r l y o p h i l i z a t i o n of s m e a r s of c u l t u r e s o b t a i n e d a s d e s c r i b e d a b o v e .

M A T E R I A L AND T E C H N I Q U E S

Virus

T h e F M D v i r u s e s O, A and С f r o m our own s tock which w e r e s u i t a b l e f o r t i s s u e c u l t u r e s in v i t r o w e r e u s e d . E a c h t y p e w a s u s e d f o r i nocu la t ing 7 - d ca l f k idney c u l t u r e s in Roux f l a s k s , p r e p a r e d by o u r n o r m a l t e c h n i q u e [35].

When c y t o p a t h i c p h e n o m e n a b e c a m e e v i d e n t , in 15 to 18 h a f t e r inocu-l a t i o n , t h e f l u i d f r o m e a c h s t r a i n w a s c o l l e c t e d , c e n t r i f u g e d f o r 21) m i n at 5000 r p m and t h e s u p e r n a t a n t m a t e r i a l ( o r i g i n a l v i r u s s tock) d i s t r i b u t e d , in q u a n t i t i e s of 2 m l each , in to e igh t een s t e r i l e f l a s k s , n u m b e r e d r e s p e c t i v e l y , 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and ' c o n t r o l 1 and s t o r e d a t - 3 0 " C a w a i t i n g i r r a d i a t i o n .

Irradiation

Excep t f o r the two s a m p l e s No. 0 and ' c o n t r o l ' , a l l the v i r u s f l a s k s w e r e e x p o s e d ind iv idua l ly to e n s u r e t h e i r occupying the s a m e g e o m e t r i c a l pos i t ion in the i r r a d i a t i o n c h a m b e r ; s a m p l e No. 1 w a s e x p o s e d to 25 000 r a d ; t h e d o s e to o t h e r s a m p l e s w a s i n c r e a s e d p r o g r e s s i v e l y f r o m 250 000 to 4 000 000 r a d , which w a s r e c e i v e d by s a m p l e No. 16. Of the two u n e x p o s e d s a m p l e s , No. 0 w a s u s e d t o a s c e r t a i n t h e i n f e c t i v e t i t r e of t h e o r i g i n a l v i r u s s t o c k , w h i l e t h e c o n t r o l s a m p l e r e m a i n e d in s t o r a g e at t h e s a m e t e m p e r a t u r e and f o r t h e s a m e l e n g t h of t i m e a s s a m p l e No . 16 in o r d e r t o d e t e r m i n e w h e t h e r , i n d e p e n d e n t l y of r a d i a t i o n , t h e s e f a c t o r s cou ld p r o d u c e any c h a n g e s in t h e i n f e c t i v e n e s s of t h e v i r u s .

F o r a s c e r t a i n i n g the in fec t ive t i t r e of the v a r i o u s exposed and unexposed v i r u s s a m p l e s we u s e d 5 - t o 7 - d c u l t u r e s of t r y p s i n - h y d r o l y s e d ca l f k idney c e l l s ; e a c h s a m p l e w a s d i lu ted p r o g r e s s i v e l y by s t e p s of 0.1 with n u t r i t i v e m e d i u m , a dose, of 0.1 m l p e r indiv idual di lut ion being in t roduced into c o r r e s -ponding g r o u p s of f ive t e s t t u b e s e a c h . The t u b e s w e r e kept at 37°C and the c u l t u r e s e x a m i n e d m i c r o s c o p i c a l l y e v e r y 24 h d u r i n g t h r e e c o n s e c u t i v e days . The p r e s e n c e of the v i r u s w a s eva lua ted by the degree of i ts cytopathic e f f e c t , t he t i t r e be ing d e t e r m i n e d by the me thod of Reed and Muench [36] and e x p r e s s e d in cy topa thogen ic d o s e s (50 DCP50 / m l ) .

S t u d i e s of i n a c t i v a t i o n by g a m m a r a d i a t i o n w e r e e x t e n d e d t o t h e d r y v i r u s on ly in t h e c a s e of t y p e C. F o r t h i s p u r p o s e t h e c u l t u r e fluids ob -t a i n e d , a s a l r e a d y d e s c r i b e d , w e r e d i s t r i b u t e d i n q u a n t i t i e s of 4 m l i n to 12 s t e r i l i z e d f l a s k s m a r k e d r e s p e c t i v e l y No. 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and ' c o n t r o l ' and lyoph i l i zed in a v a c u u m at low t e m p e r a t u r e s . The s a m p l e s w e r e

FOOT AND M O U T H DISEASE VIRUS 165

i r r a d i a t e d , e x c e p t f o r No. 0 and ' c o n t r o l 1 ; s a m p l e No. 1 w a s e x p o s e d to 500 000 r a d and the s u c c e s s i v e s a m p l e s w e r e t r e a t e d with d o s e s which in-c r e a s e d p r o g r e s s i v e l y by 500 000 r a d each up to s a m p l e No. 10, which thus r e c e i v e d 5 000 000 r a d . Of the two unexposed s a m p l e s , No. 0 was used f o r a s c e r t a i n i n g the i n f e c t i v e t i t r e of t he l yoph i l i z ed v i r u s , wh i l e t h e c o n t r o l s ample r e m a i n e d in s to rage at the s a m e t e m p e r a t u r e and for the same length of t i m e a s s a m p l e No. 10. The lyophi l ized m a t e r i a l , d i lu ted and m a d e up to volume with nut r i t ive medium, was then subjec ted to the s a m e t e s t s as the cu l tu re f luids for de te rmina t ion of the infect ive t i t r e .

Inactivated virus

A f t e r the i n a c t i v a t i o n c u r v e s w e r e p lo t t ed f o r e a c h type of v i r u s , t h e v i r u s e s inac t iva ted by r ad ia t ion w e r e then sub jec t ed to f u r t h e r t e s t s in vivo to c o n f i r m r e m o v a l of the infect ive power , as wel l as in v i t ro to study the i r p r o p e r t i e s of i n t e r f e r e n c e and an t i gen c a p a c i t y of c o m p l e m e n t f ixa t ion in the p r e s e n c e of s p e c i f i c h y p e r i m m u n e an t i aph tha s e r u m .

T h r e e l i t t e r s of s u c k l i n g m i c e , 3 - 5 d old, w e r e u s e d f o r t h e t e s t s in vivo; the t h r e e g r o u p s of a n i m a l s w e r e t r e a t e d with FMD v i r u s inact iva ted by 3 M r a d of t ype A and, r e s p e c t i v e l y , o f t y p e s O a n d C, a d m i n i s t e r e d in -t r a p e r i t o n e a l l y in a s ing le dose of 0.1 m l .

R E S U L T S

T a b l e I s u m m a r i z e s t h e t i t r a t i o n r e s u l t s f o r t h e v a r i o u s F M D v i r u s s a m p l e s exposed to r ad i a t i on and the unexposed con t ro l s . The inact iva t ion c u r v e s plot ted f r o m t h e s e r e s u l t s fo r the t h r e e types of the FMD v i rus t es ted a r e shown in F igs . 1, 2 and 3.

In Table II the t i t r a t i on r e s u l t s fo r the v a r i o u s sample of the FMD v i r u s С i r r a d i a t e d in the d r y and t h e l iqu id s t a t e a r e g iven , and F i g . 4 shows t h e c o r r e s p o n d i n g inac t iva t ion c u r v e s .

The b io log ica l t e s t s with n e w - b o r n m i c e fu l ly c o n f i r m the r e s u l t s of the t e s t s in v i t r o ; a l l t he a n i m a l s i nocu la t ed p e r i t o n e a l l y wi th FMD v i r u s i r -r a d i a t e d with 3 M r a d s u r v i v e d wi thout m a n i f e s t i n g s y m p t o m s of any k ind . T h i s p r o v e s t h a t t h e i n f e c t i v e p o w e r of t he v i r u s h a s b e e n e l i m i n a t e d and c o n f i r m s once m o r e that calf kidney ce l l s in v i t r o a r e as sens i t ive to the FMD v i r u s as new-born m i c e .

T h e r e s u l t s ob ta ined i nd i ca t e in the f i r s t p l a c e tha t the t h r e e types» O, A and С of F M D v i r u s c u l t u r e r e a c t s i m i l a r l y to g a m m a r a d i a t i o n , in t h e l iqu id s t a t e . T h e i n a c t i v a t i o n c u r v e s a r e p r a c t i c a l l y i d e n t i c a l , and show that the f r a c t i o n of the v i r u s which su rv ive s i s an exponent ia l function of the g a m m a d o s e , w i th in the l i m i t s of e x p e r i m e n t a l e r r o r . Al l t h r e e t y p e s of v i r u s l o s e t h e i r i n f e c t i v e n e s s a f t e r i r r a d i a t i o n wi th 3 M r a d , i . e . a f t e r a v e r y high g a m m a dose . The r e s u l t s again con f i rm the r e m a r k a b l e r e s i s t ance of v i r u s e s in g e n e r a l and FMD v i r u s in p a r t i c u l a r to the e f fec t of rad ia t ion , c o n s i d e r i n g tha t an i n v e r s e r e l a t i o n i s known t o ex i s t b e t w e e n inac t iva t ion d o s e s and s i z e of v i r u s [37, 32].

As r e g a r d s the e f fec t of r ad i a t i on on dry FMD v i r u s , our t e s t s indicate that inact ivat ion was e f fec ted by t r e a t m e n t with 4 Mrad, so that 1 Mrad m o r e

166 MASSA

TABLE I

T I T R A T I O N R E S U L T S F O R T H E V A R I O U S F M D V I R U S S A M P L E S E X P O S E D T O R A D I A T I O N A N D T H E

U N E X P O S E D C O N T R O L S

Sample Dose Virus O a Virus A a Virus С a

No. (Mrad)

0 - 6.50 6.37 6.30

1 0.25 6.16 5.50 5.62

2 0.50 5.30 5.37 5.50

3 0 .75 4.67 4.62 4.83

4 1.0 4 .31 4.0 4.16

5 1.25 4.16 3.62 3.62

6 1.50 3.83 3.16 3.16

7 1.75 2.62 2.62 2.30

8 2.0 2.37 2.50 2.16

9 2 .25 2.0 2.16 1.83

10 2.50 1.50 1.32 1.30

11 2 .75 1.17 Traces Traces

12 3.0 Negat ive Negat ive Negative

13 3 .25 Negat ive Negat ive Negat ive


15 3 .75 Negat ive Negat ive Negat ive


Control Ь - 6.0 6.16 6.37

a DCP 5 0 /ml expressed by rec iproca l of nega t ive log. Ь Unexposed virus stored at the s a m e tempera tu re and for the s a m e length of t i m e as

sample No. 16. Data f rom Baldelli e t a l . [1]

p r o v e d n e c e s s a r y o v e r and a b o v e t h e q u a n t i t y r e q u i r e d f o r i n a c t i v a t i n g the s a m e v i r u s i n t h e l i q u i d s t a t e . T h i s i s in f u l l a g r e e m e n t w i t h t h e o b s e r -v a t i o n by L e a [28], a c c o r d i n g t o wh ich d r y v i r u s i s i n a c t i v a t e d by the d i r e c t e f f e c t of r a d i a t i o n a l o n e , w h e r e a s i n t h e c a s e of v i r u s in t h e l i q u i d s t a t e t h i s d i r e c t a c t i o n i s r e i n f o r c e d b y an i n d i r e c t a c t i o n c a u s e d b y i o n i z a t i o n of w a t e r m o l e c u l e s and c o n s e q u e n t f o r m a t i o n of f r e e r a d i c a l s w h i c h f a v o u r i n a c t i v a t i o n by ox ida t i on m e c h a n i s m s .

T h e Dio v a l u e f o r t h e l i qu id F M D v i r u s i s equ iva l en t t o 481 k r a d . T h e D i j v a l u e f o r t h e d r i e d F M D v i r u s i s e q u i v a l e n t t o 626 k r à d .

O t h e r e x p e r i m e n t s c a r r i e d out at the P e r u g i a V e t e r i n a r y Radiobio logica l G r o u p h a v e s h o w n t h a t : (1) F M D v i r u s i n a c t i v a t e d b y r a d i a t i o n d o e s no t i n t e r f e r e in v i t r o w i t h t h e s a m e t y p e of a c t i v e v i r u s [1] ; (2) F M D v i r u s

FOOT AND M O U T H DISEASE VIRUS 167

FIG. 1. Inactivation curve of the FMD virus, type 0 . Data from Baldelli et ai. [1]

FIG. 2. Inactivation curve of the FMD virus, type A. Data from Baldelli et al. [1]

i n a c t i v a t e d by r a d i a t i o n r e t a i n s i n t ac t i t s c a p a c i t y of f i xa t ion of t he c o m -p l e m e n t in t h e p r e s e n c e of s p e c i f i c h y p e r i m m u n e a n t i a p h t h a s e r u m [1].

T h e f i r s t poin t i s in f u l l a g r e e m e n t wi th t h e r e s u l t s of d ' A m o r e e t a l . [38] ob ta ined by i nac t i va t i ng F M D v i r u s type A e i t h e r with h e a t o r with f o r m a l i n , and thus s e e m s to c o n f i r m the v i e w s of t h o s e a u t h o r s , who con-s i d e r t h a t in the c a s e of t h e F M D v i r u s the c a p a c i t y t o i n t e r f e r e i s l i nked with the v i t a l i t y of t h e v i r u s .

The s e c o n d poin t i n d i c a t e s d i f f e r e n t b e h a v i o u r of t h e i r r a d i a t e d F M D v i r u s a s r e g a r d s i n f e c t i v e n e s s and an t igen ac t iv i ty of c o m p l e m e n t f ixa t ion and f u r t h e r c o n f i r m s the f ind ings of B r a d i s h et a l . [39], a cco rd ing to which the two p r o p e r t i e s a r e l inked to two d i f f e r e n t v i r u s componen t s .

168 MASSA

FIG.3. Inactivation curve of the FMD virus, type C. Data from Baldelli et al . [1]

D O S E ( M r a d )

FIG. 4 . Inactivacion curve of the FMD virus, type C, irradiated in the liquid and dry s ta te . Data f rom Baldelli et a l . [1]

Virus irradiated in the liquid s tate Virus irradiated in the dry s ta te ( lyophi l ized)

It i s w o r t h m e n t i o n i n g h e r e t h a t we h a v e a l s o e x p e r i m e n t s u n d e r w a y on s t r a i n s of the F M D v i r u s a t t enua ted by g a m m a r a d i a t i o n and by cont inuous p a s s a g e s in t i s s u e c u l t u r e to p r o d u c e l iv ing, a t t enua ted v a c c i n e s [40].

RADIATION INACTIVATION O F T H E F O O T AND M O U T H DISEASE VIRUS IN T H E B L O O D , L Y M P H G L A N D S AND B O N E M A R R O W O F T H E C A R -C A S S E S O F I N F E C T E D A N I M A L S

T h e s e e x p e r i m e n t s a r e b e i n g c o m p l e t e d and t h e r e s u l t s w i l l s o o n b e p u b l i s h e d [2] . T h e m a t e r i a l and t h e t e c h n i q u e a r e b r i e f l y d e s c r i b e d h e r e and s o m e p r e l i m i n a r y r e s u l t s a n t i c i p a t e d .


TABLE II

T I T R A T I O N R E S U L T S F O R T H E VARIOUS S A M P L E S O F T H E F M D VIRUS, T Y P E C, I R R A D I A T E D IN T H E D R Y AND IN T H E

LIQUID S T A T E

Virus С a Virus С a

Sample Dose liquid dry No. (Mrad) s tate ( lyophi l ized)

0 - 6.30 6.30

1 0 .5 5 . 5 0 5-37

2 1.0 4.16 4.50

3 1.5 3.16 3.67

4 2.0 2.16 3.50

5 2 .5 1.30 2.16

6 3.0 Negat ive 1.37

7 3 .5 Negat ive Traces

8 4 .0 Negat ive Negat ive

9 4 .5 Negat ive Negat ive

10 5.0 Negat ive Negat ive

Control b . 6.37 6.37

a D C P j 0 / m l expressed by rec iproca l of nega t ive log.

k Unexposed virus stored at the same t empera tu re and for the same length of t i m e as sample No. 10. Data f r o m Baldelli e t a l . [1]

P i g s a r e inocula ted with FMD v i r u s . The infec ted pigs a r e s l augh t e r ed wi th in 4 6 - 4 8 h, at t h e p e a k of e x p e r i m e n t a l i n f e c t i o n , d u r i n g t h e f e b r i l e p e r i o d and when t h e v e s i c l e s a p p e a r at t he poin t of i n o c u l a t i o n . T h e i s o -la t ion and the t i t r a t i on of t he FMD v i r u s is c a r r i e d out f r o m the blood, lymph g l a n d s and b o n e m a r r o w of the s l a u g h t e r e d a n i m a l s ; t h e n the s a m p l e s of b lood, lymph g l a n d s and bone m a r r o w a r e i r r a d i a t e d at r o o m t e m p e r a t u r e . F r o m t h e s e s a m p l e s and f r o m the c o n t r o l s , the FMD v i r u s i s i so l a t ed and t i t r a t e d , u s i n g the t e c h n i q u e of t i s s u e c u l t u r e in v i t r o , a s d e s c r i b e d by D u l b e c c o ( m o n o l a y e r t r y p s i n i z e d ca l f k idney c e l l s ) .

The e x a m i n e d t i s s u e r e v e a l e d quite a high v i r u s t i t r e , a s e x p r e s s e d in cy topha togen i c d o s e s (50 D C P 5 0 ) ; t h i s d a t a b e i n g in a c c o r d a n c e wi th o u r p r e v i o u s e x p e r i e n c e . T h e v i r u s t i t r e w a s , in e f f e c t , 4 . 2 4 / g i n t h e b o n e m a r r o w , 4 . 2 4 / g in t h e l y m p h g l a n d s and 5 . 7 4 / c m 3 in t h e b l o o d .

170 MASSA

F o r i n a c t i v a t i n g the v i r u s in the e x a m i n e d t i s s u e s , d o s e s of 2 M r a d f o r the blood and bone m a r r o w and of 1.5 M r a d f o r the l ymph glands w e r e n e c e s -s a r y .

RADIATION I N A C T I V A T I O N O F T H E R I N D E R P E S T , SWINE F E V E R AND A F R I C A N SWINE F E V E R VIRUSES.

No d a t a i s a v a i l a b l e a t t h e m o m e n t on t h e r a d i a t i o n i n a c t i v a t i o n of t h e R P , S F and A S F v i r u s e s . C o n s i d e r i n g t h a t an i n v e r s e r e l a t i o n i s known t o e x i s t b e t w e e n i n a c t i v a t i o n d o s e s and s i z e of v i r u s and tha t t h e F M D v i r u s i s one of t h e s m a l l e s t v i r u s e s known, we c a n f o r e s e e t h a t t he d o s e s n e c e s s a r y t o i n a c t i v a t e the R P , S F and A S F v i r u s e s , e i t h e r in the l iqu id and d r y s t a t e o r in t h e i n f e c t e d p r o d u c t s , a r e e x p e c t e d t o b e no g r e a t e r t h a n t h e d o s e s e m p l o y e d f o r t h e i n a c t i v a t i o n of t h e F M D v i r u s . T h i s s u p p o s i t i o n m u s t b e , h o w e v e r , c o n f i r m e d b y e x p e r i m e n t s w h i c h , due t o t h e s t r i c t q u a r a n t i n e m e a s u r e s , c a n on ly b e c a r r i e d out in t h e l a b o r a t o r i e s of t h e i n f e c t e d c o u n -t r i e s o r i n p a r t i c u l a r l y e q u i p p e d l a b o r a t o r i e s of t h e i m m u n e c o u n t r i e s .

C O N C L U D I N G R E M A R K S

F u r t h e r e x p e r i m e n t s a r e n e c e s s a r y to s tudy the e f f e c t s of ionizing ene rgy on t h e F M D v i r u s a n d o t h e r v i r u s e s s u c h a s R P , S F and A S F w h i c h a r e of i n t e r e s t t o t h e a n i m a l p r o d u c t i o n . In p a r t i c u l a r t h e i n f l u e n c e of a m b i e n t c o n d i t i o n s (oxygen , i n o r g a n i c s a l t s , t e m p e r a t u r e , e t c . ) d u r i n g i r r a d i a t i o n on v i r u s s u r v i v a l n e e d s t h o r o u g h i n v e s t i g a t i o n . O t h e r e x p e r i m e n t s a r e r e -q u i r e d t o s t udy t h e e f f e c t s of i o n i z i n g e n e r g y on v i r u s e s in s i t u . R a d i a t i o n m a y o f f e r a p o s s i b l e m e a n s of r e d u c i n g o r e l i m i n a t i n g t h e v i r u s t i t r e i n m a n y a n i m a l p r o d u c t s a n d t o s o l v e c o n s e q u e n t q u a r a n t i n e p r o b l e m s .

P r o d u c t s f r o m c o u n t r i e s i n f e c t e d w i t h s u c h d i s e a s e s a s F M D , R P and ASF r e p r e s e n t a c o n s t a n t d a n g e r f o r i m p o r t i n g c o u n t r i e s . Dis t inc t ive t r e a t -m e n t b a s e d on m e a t i n s p e c t i o n h a s not b e e n found to be su f f i c i en t l y r e l i a b l e . T h e c o m p l e t e e r a d i c a t i o n of t h e s e d i s e a s e s in t h e a n i m a l p o p u l a t i o n i s a long and e x p e n s i v e t a s k and it would be p r e f e r a b l e if a new techno logy could b e d e v e l o p e d t o t r e a t s u c h p r o d u c t s , i n c l u d i n g t h e p a c k i n g m a t e r i a l , i n a w a y t o m a k e t h e m s a f e t o t h e i m p o r t i n g c o u n t r i e s . T h e i n c r e a s e of p r o -duct ion which would fol low the abol i t ion of i m p o r t r e s t r i c t i o n s i s inca lcu lab le .

T h e a m o u n t a n d t h e v a l u e of i n f e c t e d p r o d u c t s , t h e i r t r e a t m e n t o r d i s -p o s a l u n d e r p r e s e n t c o n d i t i o n s , t h e a v a i l a b i l i t y of t h e t r a d i t i o n a l c h e m i c a l and p h y s i c a l m e t h o d s of s t e r i l i z a t i o n and t h e c o s t of s u c h t r e a t m e n t s m u s t b e i n v e s t i g a t e d and c o m p a r e d wi th the c o s t of the new i r r a d i a t i o n technology.

R E F E R E N C E S

[1] BALDELL1, В., BEGLIOMINI, A . , FRESCURA, T . , MASSA, D. , Inactivation of the aphthous virus by means of gamma radiation, Atomic Energy Research Establishment (translated by WHITSTON, O . S . ) trans. 1000, Harwell (1963).

[2] BALDELLI, В., BEGLIOMINI, A . , FRESCURA, T., MASSA, DL, Radiation inact ivat ion of the foot and mouth disease virus in blood, lymph glands and bone marrow of the carcasses of in fec ted pigs, in preparat ion.


[3] Ministry of Agriculture and Fisheries (Great Britain): Second Progress Report of the Foot and Mouth Disease Research Commi t t ee , His Majes ty ' s Stat ionary Off ice , London (1927) 1 - 4 1 7 .

[4] Minstry of Agriculture and Fisheries (Great Britain): Third Progress Report of the Foot and Mouth Disease Research Commit tee , His Majesty's Stationary Office, London (1928) 1-141.

[5] Ministry of Agriculture and Fisheries (Great Britain): Fourth Progress Report of the Foot and Mouth Disease Research Committee, His Majesty's Stationary Office, London (1931) 1-375.

[6] HENDERSON, W . M . , BROOKSBY, J .B. , J. Hyg. 46 (1948) 394. [7] WITTMANN, G. . Mh. Tierheilk. 9 (1957) 215. [8] WITTMANN, G. . Berl. Münch, t ierârztl . Wschr. 70 (1957) 321. [9] COTTRAL, G.E. , COX, B.F. , BALDWIN, P . E . , Amer.J . vet. Res.21 (1960) 288.

[10] СОХ, В.F. , COTTRAL, G.E., BALDWIN, D.E.. Amer. J. vet. Res.^22 (1961) 224. [11] MÖHLER, J.R., J. Amer. vet . med. Ass. (1929) 309. [12] ADEMOLLO, A. , Veterinaria Italiana 2 (1962) 768. [13] SA VI, P. , BALDELLI, В., MOROZZI, A. , Atti Soc. i tal . Sei. vet . 15 (1961) 736. [14] SAVI, P. . BALDELLI, В., MOROZZI, A . , Atti Soc. i ta l . Sei. vet. T | ( 1 9 6 1 ) 742. [15] SAVI, P. , BALDELLI, В., MOROZZI, A. , Atti Soc. i ta l . Sei. vet. 15 (1961) 745. [16] SAVI, P. , BALDELLI, В., MOROZZI, A. , FRESCURA, T . , Atti Soc. i ta l . Sei. vet. 15 (1961) 752. [17] SAVI, P. , BALDELLI, B., Bull. Off. int. Epiz. 57 (1962) 853. [18] SAVI, P. , BALDELLI, В., Bull. Off. int. Epiz. 57 (1962) 891. [19] O . I . R . S . A . , Organismo Internacional Regional de Sanidad Agropecuaria, Bull. Off. in t . Epiz. LIII

(1960)498. [20] STAZZI, P. , MIRRI, A. , Malatt ie infett ive degli animal i domestici . Istituto Zooprofilattico, Palermo

(1956). [21] CIL LI, V. , STICCO, E., Rev. Mili t . Med. Vet. _2 (1938) 3. [22] ADEMOLLO, A. , Veterinaria Italiana 9 (1958) 130. [23] PALTRINIERI, S . , FARINA, R., Aggiornamenti di malat t ie infettive, Lito-Offset Felici, S . , Pisa (1963). [24] BOTIJA, C. S. , ZooprofilassiJ^(1963) 587. [25] BOLDRINI, G. , Veterinaria Italiana 12 (1961) 44. [26] GOWEN, I . W . , Genetics 24 (1939) 72. [27] GOWEN, J .W. , PRICE, W.C . , Science 84 (1936) 536. [28] LEA, D.E. , Actions of radiations on Living Cells, 2nd e d . , University Press, Cambridge (1955). [29] WOESE, C . , POLLARD, E. , Arch. Biochem. Biophys. 50 (1954) 354. [30] US Army Quartermaster Corps, Radiation preservation of food (1957). [31] POLLARD, E . C . , GUILD, W . R . , Large Radiation Sources in Indus t ryJ I IAEA, Vienna (1960) 239. [32] JORDAN, R . T . , KEMPE, L . L . , Proc. S o c . e x p t l . Biol. Med. 91 (1956) 212. [33] LURIA, S . E . , Radiation biology U_(HOLLAENDER, A . , Ed. )McGraw-Hi l l , N. Y. (1955) 333. [34] BEGLIOMINI, A- , MASSA, D . , Minerva nuc l . 6 (1962) 343. [35] BALDELLI, B., TORLONE, V. , Annali della Facolfi di Medicina e Chirurgia délia Université degli Studi

di Perugia 50 (1959) 93. [36] REED, L., MUENCH, H . , Amer. J.Hyg. 27 (1938) 493. [37] DES ROSIER, N . W . , ROSENSTOCK, H. M . , Radiation technology in Food, Agriculture and Biology, Avi

Publ. Co., Westport (1960). [38] D'AMORE, A . , ORFEI, Z . , RAVAIOLI, L . . MAZZARACCHIO, V . . CASTAGNOLI, В., Rendiconti

Istituto Superiore di Sanità 21 (1958) 258. [39] BRA DIS H, C . J . , BROOKSBY, J .B . , DILLON, J. F. , NORAMBUENA, M., Proc. roy. Soc. В 140 (1952) 107. [40] BALDELLI, В., BEGLIOMINI, A . , FRESCURA, T . , MASSA, D . , At tenuated strains of t h e foot and

mouth disease by gamma radiation and by continuous passages in tissue culture, in preparation.

R E P O R T OF THE MEETING OF THE F AO / WHO / IAEA E X P E R T COMMITTEE

ON THE TECHNICAL BASIS FOR LEGISLATION ON THE WHOLESOMENESS AND MICROBIOLOGICAL

SAFETY OF IRRADIATED FOOD

H. E. GORES LINE ATOMIC ENERGY BRANCH,

FOOD AND AGRICULTURE ORGANIZATION, ROME, ITALY


REPORT OF THE MEETING OF THE FAO/WHO/IAEA EXPERT COMMITTEE ON THE TECHNICAL BASIS FOR LEGISLATION ON THE WHOLESOMENESS AND MICROBIOLOGICAL SAFETY OF IRRADIATED FOOD. Since the report of the subject meeting was not yet available to the panel a narrative description was presented on the: formation and composition of the Committee; the terms of reference; the general subjects of discussion; and a generalized list of the recommendations. This information was designed to be of assistance to the panel during certain portions of their discussions on the possible use of irradiation in the processing of food.

RAPPORT DE LA REUNION DU COMITE MIXTE D'EXPERTS FAO/OMS/AIEA, CHARGE D'ETUDIER LES BASES TECHNIQUES DE LA LEGISLATION SUR LA COMESTIBILITE ET LA SALUBRITE DES DENREES ALIMEN-TAIRES IRRADIEES. Etant donné que le compte rendu de la réunion du Comité mixte n'a pas encore été publie, l'auteur présente aux membres du Groupe d'étude un exposé sur les points suivants: formation et composition du Comité; mandat du Comité; principales questions étudiées; recommandations présentées. Ces renseignements avaient pour objet de faciliter l'examen par le Groupe d'étude de certains aspects de l'emploi éventuel de l'irradiation pour le traitement des denrées alimentaires.

ДОКЛАД СОВЕЩАНИЯ КОМИТЕТА ЭКСПЕРТОВ ФАО/ВОЗ/МАГАТЭ ПО ТЕХНИЧЕС-КИМ ОСНОВАНИЯМ ДЛЯ ЗАКОНОДАТЕЛЬСТВА, КАСАЮЩЕГОСЯ СОХРАНЕНИЯ КАЧЕСТ-ВА И МИКРОБИОЛОГИЧЕСКОЙ БЕЗОПАСНОСТИ ОБЛУЧЕННЫХ ПРОДУКТОВ ПИТАНИЯ. Поскольку у совещания экспертов еще нет доклада о заседании по данному вопросу, то дается общее описание: по вопросам создания и состава Комитета , е г о полномочий, общих т е м , представленных для обсуждения, и обобщенного перечня рекомендаций. Эта информация предназначена для использования на совещании экспертов во время обсуждения некоторых проблем относительно возможного использования облучения при обработке пищевых продуктов.

INFORME SOBRE LA REUNION DEL COMITE MIXTO DE EXPERTOS DE LA FAO, LA OMS Y EL OIEA ENCARGADO DE ESTUDIAR LAS BASES TECNICAS DE LA LEGISLACION SOBRE LA COMESTIBILIDAD Y LA SEGURIDAD MICROBIOLOGICAS DE LOS PRODUCTOS ALIMENTICIOS IRRADIADOS. Como no se pudo pre-sentar al Grupo el informe de la reunión, se describió el estado de las siguientes cuestiones: formación y composición del Comité; sus atribuciones; temas generales de studio, y lista general de recomendaciones. Esto se hizo para ayudar al Grupo de expertos en una parte de sus debates sobre el empleo de la irradiación para el tratamiento de productos alimenticios.

It is believed essent ia l that this panel should have before it information in the var ious f ie lds that may be n e c e s s a r y to cons ider be fore formula t ing recommendations for consideration by the International Atomic Energy Agency on how food i r rad ia t ion might be applied in developing countr ies . The sub-ject of wholesomeness of foods t rea ted by ionizing radiation is one on which extensive r e sea rch has been car r ied out in severa l countries. Such research has produced l a rge amounts of data indicating that food t r ea t ed by speci f ic

173

174 GORESLINE

r a d i a t i o n e n e r g i e s i s who le some and s a f e f o r consumpt ion . B e c a u s e of the impor t ance of the d i s cus s ions to be held by th i s panel , and in view of the fact t ha t t h e r e p o r t of t he m e e t i n g of e x p e r t s on t h e s u b j e c t of w h o l e s o m e n e s s i s not yet avai lable f o r d i s t r ibu t ion , i t i s m y p u r p o s e to de sc r ibe b r i e f ly the work of that group of e x p e r t s and p r e s e n t t h e i r r e c o m m e n d a t i o n s .

The mee t ing of a Joint FAO/WHO/IAEA Exper t Commit tee on the Technical B a s i s f o r L e g i s l a t i o n on I r r a d i a t e d Food m e t in Rome dur ing 21-28 Apr i l 1964. The m e e t i n g of th i s E x p e r t C o m m i t t e e was convened a s a r e s u l t of r e c o m -m e n d a t i o n s by an i n t e r n a t i o n a l mee t ing on the W h o l e s o m e n e s s of I r r a d i a t e d Foods held in B r u s s e l s in 1961. It was a p p a r e n t at that t i m e tha t t h e r e was need f o r d i s c u s s i o n s and p l a n s with a v iew t o m e e t i n g the r e q u i r e m e n t f o r s o m e m e a n s of r egu la t ing th i s new method of food p roces s ing a s it came into c o m m e r c i a l u s e . It was be l ieved highly d e s i r a b l e that f a i r l y u n i f o r m r e g u -l a t i o n s be adopted by the m a n y na t ions tha t would even tua l ly be c o n c e r n e d , in o r d e r to f ac i l i t a t e the exchange of i r r a d i a t e d food in in te rna t iona l c o m m e r c e . One of the p u r p o s e s of the E x p e r t C o m m i t t e e was to p r e p a r e i n f o r m a t i o n a l m a t e r i a l t ha t m i g h t be u s e f u l in guiding the p r e p a r a t i o n of na t iona l l e g i s -l a t i o n to r e g u l a t e i r r a d i a t e d f o o d s , and to do t h i s in advance of t he i n t r o -duc t ion of the p r o c e s s c o m m e r c i a l l y . It w a s be l i eved tha t t h i s l e g i s l a t i o n would p r o m o t e the a c c e p t a n c e of i r r a d i a t e d p r o d u c t s and r e m o v e m a n y p o s s i b i l i t i e s f o r c o n t r o v e r s y and m i s u n d e r s t a n d i n g , e s p e c i a l l y in such p r o -duc t s p a s s i n g in i n t e r n a t i o n a l c o m m e r c e .

T h e s i x t e e n p a r t i c i p a n t s w e r e s e l e c t e d f o r t h e i r knowledge in t h e d i f f e r e n t f i e ld s of food i r r a d i a t i o n and although they w e r e f r o m ten d i f fe ren t coun t r i e s they at tended only in t h e i r capac i t i e s as e x p e r t s . In addition the re w e r e s even a d v i s e r s and o b s e r v e r s who e n t e r e d into the work of the Commi t t ee and con t r ibu ted g r e a t l y t o the s u c c e s s of the m e e t i n g .

The C o m m i t t e e had b e f o r e it a working p a p e r that had been p r e p a r e d to point out v a r i o u s f i e ld s tha t needed a t tent ion and to p r e s e n t in fo rma t ion that m i g h t be of va lue t o the g r o u p . T h e r e w e r e a l s o d o c u m e n t s f o r r e f e r e n c e s u c h a s the P r o t o c o l f o r W h o l e s o m e n e s s Inves t iga t ions of R a d i a t i o n -P a s t e u r i z e d F o o d s , m a d e ava i l ab le by the United S ta tes A t o m i c E n e r g y C o m m i s s i o n , and the R e p o r t of the Work ing P a r t y on I r r a d i a t i o n of Food , of t h e Uni ted K i n g d o m M i n i s t r y of H e a l t h .

The t e r m s of r e f e r e n c e u n d e r which the Commi t t ee me t w e r e : "To c o n -s i d e r the avai lable evidence on the e f f ec t s on food of t r e a t m e n t with ionizing r a d i a t i o n and to m a k e r e c o m m e n d a t i o n s on (a) the g e n e r a l p r i n c i p l e s u n d e r which the p roduc t ion and u s e of i r r a d i a t e d food m a y be p e r m i t t e d and (b) the p r o c e d u r e s tha t should be adopted f o r the eva lua t ion of the w h o l e s o m e n e s s of i r r a d i a t e d f o o d " . In t h i s contex t w h o l e s o m e n e s s r e f e r r e d to s a f e t y f o r c p n s u m p t i o n of i r r a d i a t e d food , i n c l u d i n g n u t r i t i o n a l a s p e c t s .

F o r c e r t a i n s e s s i o n s the C o m m i t t e e was divided into t h r e e sec t ions f o r the p u r p o s e of c o n c e n t r a t i n g on c e r t a i n f i e l d s of i n t e r e s t and to develop m a t e r i a l f o r d i s c u s s i o n at s e s s i o n s of the Commi t t ee of the Whole. These s e c t i o n s w e r e G e n e r a l P r i n c i p l e s , W h o l e s o m e n e s s and Microb io logy . The eight days of de l i be ra t i on of t h i s Commi t t ee r e su l t ed in a r e p o r t of s ix ty - s ix p a g e s ent i t led "The T e c h n i c a l B a s i s f o r Leg i s l a t ion on I r r a d i a t e d Food" . It i s d iv ided in to s ix c h a p t e r s and nine a p p e n d i c e s . T h e s u b j e c t m a t t e r s e t s f o r t h i n f o r m a t i o n and r e c o m m e n d a t i o n s on the p r o b l e m s of i r r a d i a t e d food a r r i v e d a t by an i n t e r n a t i o n a l g r o u p and i n t e n d e d f o r v o l u n t a r y u s e by i n -

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t e r e s t e d na t ions in the p r e p a r a t i o n of any leg is la t ion f o r the control of m a n u -f a c t u r e , i m p o r t a t i o n , e x p o r t a t i o n o r d i s t r ibu t ion of i r r a d i a t e d food intended f o r publ ic consumpt ion .

T h e r e would be l i t t le va lue in rev iewing the v a r i o u s chap te r s and appen-d i c e s of t h i s documen t at t h i s t i m e . It would s e e m b e s t to p r e s e n t in a gene ra l way the r e c o m m e n d a t i o n s that were made , s ince it is in these t e r s e s t a t e m e n t s tha t the va lue of t he r e p o r t l i e s f o r a s s i s t i n g i n t e r e s t e d na t ions and f o r t he p r o m o t i o n of t h e hope f o r b e t t e r u n d e r s t a n d i n g in i n t e r n a t i o n a l t r a d e in i r r a d i a t e d food p r o d u c t s . In an abbrev ia ted f o r m these r e c o m m e n -dat ions a r e : (1) Tha t G o v e r n m e n t s should p roduce l e g i s l a t i o n to con t ro l i r r a d i a t e d food in tended f o r consumpt ion by the publ ic . (2) Tha t in so f a r a s p r a c t i c a b l e such l eg i s l a t i on should follow the m a t e r i a l s u g g e s t e d in t h e r e p o r t and t h u s m a k e a c o m m o n a p p r o a c h f o r l e g i s l a t i o n t h a t wi l l f a c i l i t a t e i n t e r n a t i o n a l t r a d e in i r r a d i a t e d food . (3) That d i s t r i bu t ion to the publ ic should be p e r m i t t e d only a f t e r accep tance by au thor ized o f f i c i a l s that the food i s sa fe f o r human consumpt ion . (4) Tha t l ega l con t ro l can bes t be accompl i shed by u s e of a l i s t of pe rmi t t ed foods . (5) Tha t i r r a d i a t e d f e e d s f o r c o n s u m p t i o n by a n i m a l s should be s u b j e c t to c o n t r o l ana logous to tha t f o r h u m a n food . (6) Tha t in t e rna t iona l c o - o p e r a t i o n through exchange of in format ion on animal f eed ing t e s t s and m i c r o b i o l o g i c a l s a f e t y of i r r a d i a t e d food would m i n i m i z e t h e need f o r s u c h t e s t i n g in e a c h c o u n t r y , t h u s r e d u c i n g c o s t s , and would e n c o u r a g e a c c e p t a n c e of e v i d e n c e f r o m o t h e r c o u n t r i e s . (7) T h a t t h e r e shou ld be i nd iv idua l o r c o l l e c t i v e d o s i m e t r y s t a n d a r d s e s t a b l i s h e d f o r d e t e r m i n i n g thé r a d i a t i o n dose , with an even tua l a i m of e s t a b l i s h i n g i n t e r n a t i o n a l d o s i m e t r y s t a n d a r d s . (8) Tha t t he m e t h o d s and s t a n d a r d s u s e d to e n s u r e m i c r o b i o l o g i c a l s a f e t y should be sub jec t to r e v i e w by compe ten t i n t e rna t i ona l b o d i e s in o r d e r that i n t e r n a t i o n a l l y a c c e p t e d m e t h o d s and s t a n d a r d s m a y be a g r e e d u p o n . (9) Tha t F A O / W H O / I A E A should cont inue t h e i r i n t e r e s t in the f ie ld of food i r r a d i a t i o n . T h e s e Agenc ies should encourage co-opera t ion between gove rn -men t s , c o n c e r n i n g m e t h o d s of c o n t r o l and u s e of i r r a d i a t e d food in v a r i o u s c o u n t r i e s and in t r a i n i n g of expe r t p e r s o n n e l f o r the appl ica t ion and con t ro l of the p r o c e s s .

T h e s e n ine r e c o m m e n d a t i o n s w e r e a r r i v e d at a f t e r long d e l i b e r a t i o n and s tudy . It i s be l ieved tha t in c a r r y i n g t h e m out many ways will be found to p r o m o t e i n t e rna t i ona l good wil l and unde r s t and ing and ways and m e a n s of p r o m o t i n g a g r e a t e r exchange of food i t e m s b e t w e e n the n a t i o n s . T h e d e l i b e r a t i o n s of t he pane l should r e s u l t in sugges t i ons tha t will be u s e f u l in a s s i s t i n g the deve lop ing c o u n t r i e s t o u t i l i z e r a d i a t i o n a s a food p r o c e s s i n g m e t h o d . T h i s can be r e c o m m e n d e d with conf idence and a s s u r a n c e that the food p r o d u c t s p r o d u c e d wi l l be w h o l e s o m e , n u t r i t i o u s and s a f e f o r h u m a n c o n s u m p t i o n .

PROBLEMS OF THE PASTEURIZATION OF FRUIT JUICES BY IRRADIATION

К. KAINDL, H. A L T M A N N , H. GAISCH, К. PROSENZ A N D G. STEHLIK

I N S T I T U T E OF BIOLOGY A N D AGRICULTURE, REACTOR CENTRE,

SEIBERSDORF, AUSTRIA


PROBLEMS OF THE PASTEURIZATION OF FRUIT JUICES BY IRRADIATION. This paper sets forth some of the problem areas involved in fruit juice preservation by irradiation and indicates some of the approaches that are being utilized in research to solve these problems by the group working at the Seibersdorf Laboratories.

PROBLEMES RELATIFS A LA PASTEURISATION DES JUS DE FRUITS PAR IRRADIATION. Le mémoire expose plusieurs des grands problèmes que pose la conservation des jus de fruits par irradiation; il indique un certain nombre de méthodes que l'équipe de chercheurs travaillant au Laboratoire de Seibersdorf applique pour résoudre ces problèmes.

ПРОБЛЕМА ПАСТЕРИЗАЦИИ ФРУКТОВЫХ СОКОВ ОБЛУЧЕНИЕМ. Излагаются не-которые из проблематичных областей, связанных с сохранением фруктовых соков с помощью облучения. Указываются некоторые подходы к проблеме, которые используются в исследова-ниях группой специалистов Зайберсдорфской лабораторией для решения этих проблем.

PROBLEMA QUE PLANTEA LA PASTEURIZACION DE LOS JUGOS FRUTALES POR IRRADIACION. La memoria expone algunos de los problemas que plantea la conservación de zumos de fruta por irradiación e indica los métodos que se están siguiendo en los laboratorios de Seibersdorf para tratar de resolverlos.

The a im of eve ry method f o r p r e s e r v a t i o n of foods should be to p r e -s e r v e the na tu ra l qual i t ies of the t r e a t e d foodstuff in the mos t economical m a n n e r . This m e a n s , fo r rad iopas teur iza t ion , the use of re la t ive ly low doses to prevent undesirable changes in f lavour, colour, odour, and texture. This implies r e s e a r c h on the radiosensi t ivi ty of microorganisms affecting the quality of p re se rva t ion of the foodstuff . The sens i t i za t ionmaybe possible by combined physical methods or by effecting biochemical p roce s se s , such as application of substances changing the metabolism of the microorganisms. The al terat ion of the different components of the foodstuff should be studied s imul taneously with the ver i f ica t ion of the wholesomeness of i r r ad i a t ed food by animal t e s t s . F ru i t juice has been selected as a model substance [1-3] for studies of yeas t behaviour against radiat ion.

TECHNOLOGICAL INVESTIGATIONS

For the pas teur iza t ion of f ru i t juices radiat ion doses between 0.2-2.0 Mrad a re nece s sa ry , depending on the m i c r o o r g a n i s m s p re sen t . Combined heat t reatment with i r radiat ion may lower the effective doses necessary for yeasts [4]. I r rad ia t ion t rea tment followed by slight heating (40-50°C) i s super ior to i r r ad i a t ion in the f rozen s ta te , f r o m an economical point of view. The data suggested that i r radia t ion causes cer ta in react ions in yeast which p e r -

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h a p s i n c r e a s e t h e r m a l e n e r g y , t h u s l e a d i n g t o r e a c t i o n s c a u s i n g d e a t h . It i s u n d e r s t o o d t h a t t h e s e e v e n t s t a k e p l a c e at t h e m o l e c u l a r l e v e l . F o r t h i s r e a s o n and f o r the p o s s i b l e dependence of the r a d i o r e s i s t a n c e on the gene t ic m a t e r i a l , r e s e a r c h in n u c l e i c a c i d s h a s been done .

RADIATION BIOLOGY O F YEASTS

An u n d e r s t a n d i n g of t h e y e a s t d o s e - s u r v i v a l s e e m s t o be a n e s s e n t i a l p r e r e q u i s i t e f o r s t u d y i n g s e n s i t i z i n g a g e n t s . In t h e c a s e of y e a s t s t h e r e e x i s t s t he p o s s i b i l i t y of d e t e r m i n i n g f e r m e n t a t i o n by u s i n g the W a r b u r g m e t h o d . T h e r e s u l t s [5] s h o w e d t h a t i r r a d i a t i o n p r o d u c e d a d e l a y in CO2 p roduc t ion fo l lowed by a r i s e tha t was dependent on the dose . The t ime delay p r e c e d i n g t h i s r i s e w a s found to be dependen t on t h e d o s e in such a way tha t t he h i g h e r the d o s e , the l o n g e r the d e l a y b e f o r e the r i s e .

T h e i n f l u e n c e of g a m m a i r r a d i a t i o n and of h e a t i n g on v a r i o u s y e a s t s t r a i n s h a s b e e n i n v e s t i g a t e d . It c an be s t a t e d t ha t t h e r e e x i s t s a p r i n c i p a l d i f f e r e n c e in the r e s p o n s e of y e a s t c e l l s t r e a t e d in t h e s e two ways . Although i n bo th c a s e s t h e s a m e f i n a l r e a c t i o n r e s u l t s ( r e d u c t i o n of n u m b e r of r e -p r o d u c t i v e ce l l s ) t he h e a t - d a m a g e d c e l l s l o s e t h e i r budding abi l i ty i m m e d i a t e l y , w h e r e a s the r a d i a t i o n - i n j u r e d c e l l s (50°C) l o s e t h e i r s a f t e r s e v e r a l g e n e r a t i o n c y c l e s [6]. F u r t h e r i n v e s t i g a t i o n a long t h e s e l i n e s i s n e c e s s a r y .

T h e b e h a v i o u r of a y e a s t s t r a i n wi th in a g i v e n t i m e in p r o p o r t i o n t o an a p p l i e d r a d i a t i o n d o s e can be a s c e r t a i n e d by t h e W a r b u r g m e t h o d .

Hav ing p e r f o r m e d c o m p a r a t i v e i n v e s t i g a t i o n s on the a v a i l a b l e m e t h o d s f o r d e t e r m i n i n g s u r v i v a l c u r v e s , a s u i t a b l e m e t h o d w a s deve loped [9]. T h i s m e t h o d i s c a p a b l e of e s t i m a t i n g :

(1) T h e i n c u b a t i o n t i m e ( s ix o r m o r e g e n e r a t i o n s ) which i s a c r i t e r i o n f o r t he s u r v i v a l a b i l i t y Of a c e l l

(2) T h e g e n e r a t i o n t i m e of i r r a d i a t e d and u n i r r a d i a t e d c e l l s (3) T h e p e r c e n t a g e of t h e s u r v i v i n g c e l l s p l o t t e d a g a i i i s t t h e d o s e . F u r t h e r m o r e , it i s p o s s i b l e to d i f f e r e n t i a t e be tween le tha l damaged ( l e s s

t h a n t w o g e n e r a t i o n s ) , d a m a g e d ( two t o s i x g e n e r a t i o n s ) and n o r m a l c e l l s . In the c o u r s e of t h i s r e s e a r c h w o r k , c e r t a i n t e c h n o l o g i c a l y e a s t c h a r a c t e r -i s t i c s c o m m o n t o t h e food i n d u s t r y h a v e b e e n s t u d i e d . T h u s a s t i m u l a t i n g e f f e c t on y e a s t , s u s p e n d e d in n u t r i e n t m e d i u m by 50 k r a d , could be e s t a b l i s h e d . T h i s t r e a t m e n t i n c r e a s e d the yie ld of y e a s t by 36% and the a lcohol product ion by 11%. A c c o r d i n g t o t h e s e h i g h e r y i e l d s t h e u t i l i z a t i o n of the n u t r i e n t m e d i u m could b e i m p r o v e d by 23% [10].

T h e f i r s t t r i a l s f o r d e t e c t i n g r a d i o s e n s i t i z i n g a g e n t s w e r e done wi th v i t a m i n K 5 w h i c h i s k n o w n t o s e n s i t i z e c e r t a i n m i c r o o r g a n i s m s [11] . In the c a s e of y e a s t t h e add i t i on of v i t a m i n K5 (1 m g %) i n h i b i t s f e r m e n t a t i o n , whi l e a d o s e of 100 k r a d ( p a s t e u r i z i n g dose ) i n f l u e n c e s m u l t i p l i c a t i o n . No o b s e r v a t i o n s w e r e m a d e c o n c e r n i n g the s ens i t i z i ng ac t ion of v i t amin K5 c o m -bined with i r r a d i a t i o n [12].

BIOCHEMISTRY O F YEAST

T h e r a d i o s e n s i t i v i t y of m i c r o o r g a n i s m s i s p o s s i b l y r e l a t e d to the c y t o -p l a s m i c , a s w e l l a s t h e g e n e t i c s t a t u s , of t h e s y s t e m . In a s m u c h a s t h e

PASTEURIZATION OF FRUIT JUICES 179

e n z y m e s y s t e m s of t h e c e l l d e p e n d on the g e n e s f o r t h e i r s y n t h e s i s , it i s l o g i c a l to inc lude r e s e a r c h on the r a d i a t i o n c h e m i s t r y of nuc le i c a c i d s * It i s known tha t t r a c e e l e m e n t s r e p r e s e n t r e s i s t a n c e f a c t o r s t o e x t e r n a l i n -f l u e n c e s and a r e a s s o c i a t e d wi th n u c l e i c a c i d s . T h e r e f o r e s t u d i e s on the t r a c e e l e m e n t con ten t of y e a s t n u c l e i c ac id by n e u t r o n a c t i v a t i o n a n a l y s i s have been done [13]. It was shown that i r r a d i a t i o n with coba l t -60 at low l e v e l s (up to 30 k r a d ) s p l i t s off t r a c e e l e m e n t s f r o m the n u c l e i c ac id [14]. I n s t a b i l i t y of r i b o n u c l e i c a c i d (RNA) i s i n d u c e d . It i s s u g g e s t e d tha t RNA is t h e r e f o r e made m o r e suscept ib le to degradat ion by RNase [15-17]. Deoxy-r ibonuc le i c ac id (DNA) shows an opposi te e f f e c t . The addit ion of me ta l ions (Cu)toDNA and RNA so lu t ions c a u s e s an inhibit ion of degrada t ion by nuc lease [17 ,19] . M o r e o v e r , evidence ex i s t s to indicate that a h igher content of meta l ions (Cu, Co) l eads to a r a d i o r e s i s t a n c e of RNA [15 ,17 ,18 ] .

T h e p o s s i b i l i t y of t r a n s i t i o n f r o m r a d i o r e s i s t a n c e of nuc l e i c a c i d s by v a r i a t i o n of t h e m e t a l ion con t en t t o the r a d i o r e s i s t a n c e of t h e whole o r g a n i s m i s to be s t u d i e d .

Mic rob io log ica l e x p e r i m e n t s sugges t tha t i r r a d i a t i o n a f f e c t s the t r a n s -m i s s i o n of gene t i c i n f o r m a t i o n by an inhibi t ion of the f o r m a t i o n of a c e r t a i n " e l e m e n t " e s s e n t i a l f o r the dupl ica t ion of the ce l l . The d i lu t ion of th i s " e l e m e n t " by m u l t i p l i c a t i o n e r a s e s the m e c h a n i s m of r e d u p l i c a t i o n [6, 8]. It i s p o s s i b l e to c o n s i d e r the DNA a s s u c h an " e l e m e n t " s i n c e i r r a d i a t i o n i n d u c e s a de l ayed and l o w e r e d D N A - s y n t h e s i s . P r e l i m i n a r y e x p e r i m e n t s show a d e c r e a s e in DNA s y n t h e s e s in y e a s t c e l l s i r r a d i a t e d by 300 k r a d , w h i c h m y be the resu l t of an espec ia l ly high d e c r e a s e of the ATP-concen t ra t ion [19]. S i m u l t a n e o u s l y the content of n u c l e o s i d e m o n o p h o s p h a t e s i n c r e a s e s r e m a r k a b l y , s u g g e s t i n g t h a t i r r a d i a t i o n i n h i b i t s the f o r m a t i o n of d i - and t r i p h o s p h a t e s . T h e u n d e r l y i n g c a u s e f o r the i n c r e a s e d pool of A T P n e e d s f u r t h e r i n v e s t i g a t i o n .

RADIATION CHEMISTRY O F F R U I T JUICE C O M P O N E N T S

I n v e s t i g a t i o n s on the d e g r a d a t i o n of d i lu ted aqueous g lucose so lu t ions by i r r a d i a t i o n with g a m m a r a y s have been done u s i n g a m o d i f i e d t h i n - l a y e r c h r o m a t o g r a p h y t echn ique [20, 21]. M o r e d e g r a d a t i o n p r o d u c t s w e r e found by t h i s m e t h o d t h a n by p a p e r c h r o m a t o g r a p h y and s o m e of t h e s e p r o d u c t s have been i den t i f i ed . T h e da ta s u g g e s t e d tha t no s e c o n d a r y r e a c t i o n of the f o r m e d H2O2 with g lucose t a k e s p l a c e in aqueous so lu t ion .

F INAL CONSIDERATION

R e s e a r c h a t t he m i c r o b i o l o g i c a l and b i o c h e m i c a l l e v e l s h a s now p r o -g r e s s e d to the point w h e r e t h e p r o b l e m of r a d i o s e n s i t i z a t i o n can be i n v e s t i g a t e d .

R E F E R E N C E S

[ 1 ] CLARKE, I . D . , Proc. I X t h In t . Congr. Bot Montreal (1959) .

[ 2 ] VAS, К . , FARKAS, J . , A m e r . Inst. Pasteur de L i l le I I (1960) 209.

[ 3 ] JENSEN, M . , Ris«i Rpt 16. (1960) .

180 КАШ DL et a l .

[4] GAISCH, H . , KAINDL, К . , Food Irradiation 2 A (1962) 8. [5 ] GAISCH, H . , K A I N D L , K . , Z . Naturf. 186 (1963) 1070-72 .

[6] GAISCH. H . , PROSENZ, К . , STEINLECHNER, D . , Z . Naturf. 196 (1964) 430-33.

[7] K A I N D L , K . , A L T M A N N , H . , STEHLIK, G . , GAISCH, H . , Studiengesellschaft f . Atomenergie SGAE-Rpt 9 (1964).

[ 8 ] K A I N D L , К . , Biophysik 1 (1964) 325 -28 .

[9 ] PROSENZ, К . , GAISCH, H . , K A I N D L , К . , Konferenzbericht der Tagung der Biophysik (Gesellschaft von Deutschland, Österreich, Schweiz) Vienna, Sep. 1964, in print.

[10] PROSENZ, К . , GAISCH, H . , K A I N D L , К . , Studiengesellschaft f. Atomenergie, SGAE-BL-12 (1964).

[11] EL-TABEY SHEHATA, А. M . , Radiat. Res. 15 (1961) 78. [12 ] GAISCH, H . , KA INDL, K . , Z . Naturf. 18b (1963) 1070-72 . [13] STEHLIK, G . , A L T M A N N , H . , Mh. Chemie 94 (1963) 1163-77 . [14] ALTMANN, H. , STEHLIK, G. , KAINDL, K., Nature 199 (1963) 823. [15] A L T M A N N , H . , STEHLIK, G . , KA INDL, K . , Atompraxis 9 (1963) 255-58.

[16 ] A L T M A N N , H . , Biophysik 1 (1964) 329-30.

[17] K A I N D L , K . , A L T M A N N , H . , Studiengesellschaft f. Atomenergie SGAE-Rpt 1 (1964)

[18] STEHLIK, G . , A L T M A N N , H . , KA INDL, K . , Studiengesellschaft f . Atomenergie, SGAE-Rpt 5 (1964). [19] K A I N D L , K . , A L T M A N N , H . , STEHLIK, G . , GAISCH, H . , Studiengesellschaft f. Atomenergie

SGAE-Rpt 9 (1964). [20] SCHERZ, H . , BACHER, E . , K A I N D L . K . , Microchim. Acta , in print.

[21] SCHERZ, H . , BACHER, E . , K A I N D L , K . , Microchim. Acta , in print.

L I S T O F P A R T I C I P A N T S

P A N E L M E M B E R S

DAGET, J .

DHARKAR, S . D .

GAUZIT, M.

GEORGOPOULOS, S. G.

GOLDBLITH, S . A .

KARDASHEV, A. V.

MASSA, D.

RHODES, D . N .

ROGACHEV, V . l .

S ANIN - SADE R, J .

Chad R e s e a r c h C e n t r e , F o r t - L a m y , Chad

B i o c h e m i s t r y and F o o d Technology Divis ion, A t o m i c E n e r g y E s t a b l i s h m e n t T r o m b a y , Bombay , Ind ia

A s s o c i a t i o n f o r the Deve lopmen t of I n d u s t r i a l App l i ca t ions of Radia t ion,

P a r i s , F r a n c e

G r e e k A t o m i c E n e r g y C o m m i s s i o n , N u c l e a r R e s e a r c h C e n t r e " D e m o c r i t u s " , A thens , G r e e c e

D e p a r t m e n t of Nut r i t ion , Food Science and Technology ,

M a s s a c h u s e t t s Ins t i tu te of Technology, C a m b r i d g e , M a s s . , Uni ted S ta t e s of A m e r i c a

Al i -Un ion Scient i f ic R e s e a r c h Ins t i tu te f o r M a r i n e F i s h e r i e s and Oceano-g r a p h y (VNIRO),

Moscow, USSR

D e p a r t m e n t of V e t e r i n a r y Service , M i n i s t r y of Heal th , R o m e , I t a ly

Mea t R e s e a r c h Ins t i tu t e , Low T e m p e r a t u r e R e s e a r c h Station, C a m b r i d g e , Eng land

Ai l -Un ion Sc ien t i f ic R e s e a r c h Ins t i tu te f o r t he C o n s e r v a t i o n Indus t ry ,

Moscow, USSR

A p a r t a d o A é r e o 5302, Bogota , Co lombia

181

182 LIST OF PARTICIPANTS

SHEA, K . G .

TALHOUK, A. S.

VAS, К .

Radiation P r o c e s s e d Foods Section, Division of Isotopes Development, United States Atomic Energy

Commiss ion , Washington, D. C . , United States of Amer ica

A m e r i c a n Univers i ty of Beirut , Bei ru t , Republic of Lebanon

Inst i tute of Food Technology and Microbiology,

College of Hor t icu l tu re and Viticulture, Budapest , Hungary

OBSERVERS

GRÜNEWALD, T .

KAINDL, К .

MOLIN, N.

TEÄR, J .

F e d e r a l R e s e a r c h Institute for Food P r e s e r v a t i o n ,

K a r l s r u h e , F e d e r a l Republic of Germany

Inst i tute fo r Biology and Agriculture, Reac to r Cent re Seibersdorf , Se ibersdor f , Aus t r i a

Swedish Inst i tute fo r Food Prese rva t ion Resea rch ,

Kallebäck, Göteborg, Sweden

R e s e a r c h Depar tment , A . B . B jä re , Hals ingborg, Sweden

REPRESENTATIVES OF INTERNATIONAL AGENCIES

KREUZER, R. F i s h P r o c e s s i n g Section, F i s h e r i e s Division, Food and Agr icu l tu re Organization, Rome, Italy

GORESLINE, H. E . Atomic Ene rgy Branch, (Scientif ic Sec re ta ry ) Food and Agr icu l tu re Organization,

Rome, I taly

183 LIST OF PARTICIPANTS

FRIED, M. (Scientific Secre ta ry)

Unit of Agr icu l tu re , Depar tmen t of Resea r ch and Isotopes, In ternat ional Atomic Energy Agency, Vienna, Aus t r i a

IAEA SALES AGENTS

O r d e r s for Agency p u b l i c a t i o n s can be p la a g e n t s l i s t e d be low :

A R G E N T I N A C o m i s i o n N a c i o n a l de E n e r g i e Atomic a A v e n i d a de l L i b e r t a d o r G e n e r a l San Martin 8 2 5 0 B u e n o s A i r e s • Sue . 29

A U S T R A L I A Hun te r P u b l i c a t i o n s « 23 McKi l lop S t r e e t Me lbourne , C . l

A U S T R I A Georg Fromme & Co, S p e n g e r g a s s e 39 A - 1 0 5 0 . V i e n n a V

B E L G I U M O f f i c e i n t e r n a t i o n a l de l ib ra i r i e 30, a v e n u e Marnix B r u s s e l s 5

B R A Z I L L i v r a r i a K o s m o s E d i t o r a Rua do R o s a r i o , 135-137 Rio de J a n e i r o

A g e n c i a E x p o e n t e O s c a r M. S i lva Rua X a v i e r de T o l e d o , 1 4 0 « I e Ander (Ca ixa P o s t a l No. 5 .614) Sâo P a u l o

BYELORUSSIAN S O V I E T S O C I A L I S T R E P U B L I C

See u n d e r USSR

CANADA T h e Q u e e n ' s P r i n t e r O t t a w a , Onta r io

C H I N A ( T a i w a n ) B o o k s a n d S c i e n t i f i c S u p p l i e s S e r v i c e , L t d . , P . O . Box 83 T a i p e i

C Z E C H O S L O V A K SOCIALIST R E P U B L I C S . N . T . L . S p o l e n a 51 Nové M e s t o P r a g u e 1

D E N M A R K E j n a r M u n k s g a a r d L t d . 6 N o r r e g a d e C o p e n h a g e n К

d wi th your b o o k s e l l e r or any of our s a l e s

F I N L A N D A k a t e e m i n e n K i r j a k a u p p a K e s k u s k a t U 2 H e l s i n k i

F R A N C E

O f f i c e i n t e r n a t i o n a l de d o c u m e n t a t i o n e t l i b r a i r i e 48, rue G a y * L u s s a c P a r i s 5 e

G E R M A N Y , F e d e r a l R e p u b l i c of R. O ldenbourg R o s e n h e i m e r S t r a s s e 145 8 Munich 8

H U N G A R Y Kul tu ra Hunga r i an T r a d i n g Co. for Books and N e w s p a p e r s P . O . B . 149 B u d a p e s t 62

I S R A E L H e i l i g e r and C o . 3 N a t h a n S t r a u s s S t r e e t J e r u s a l e m

I T A L Y A g e n z i a E d i t o r i a l e I n t e r n a z i o n a l e O r g a n i z z a z i o n i U n i v e r s a l i ( A . E . I . O . U . ) Via Merav ig l i 16 Milan

J A P A N Maruzen Company L t d . 6 , Tor i Nichome N i h o n b a s h i ( P . O . Box 605) T o k y o C e n t r a l

M E X I C O L i b r a r i a I n t e r n a c i o n a l Av. Sonora 206 Mexico 11, D . F .

N E T H E R L A N D S N.V. Mar t inus Ni jhoff L a n g e Voorhou t 9 T h e H a g u e

N E W Z E A L A N D Whiteombe & T o m b s , L t d . G . P . O . Box 1894 Wel l ing ton , C . l

N O R W A Y _ J o h a n ' G r u n d t Tanum ' Kar l J o h a n s ga te 43 O s l o .

P A K I S T A N K a r a c h i E d u c a t i o n Soc ie ty Haroon C h a m b e r s South N a p i e r R o a d

' ( P . O . Box No . 4866) K a r a c h i 2

" P O L A N D O s r o d e k R o z p o w s z e c h n i a n a Wydawnic tw N a u k o w y c h P o l s k a A k a d e m i e Nauk P a i a c Kultury i N a u k i Warsaw

R O M A N I A Car t imex Rue A. Br iand 14-18 B u c a r e s t

SOUTH A F R I C A Van S c h a i k ' s Books to re ( P t y ) L t d . L i b r i Bu i ld ing Church S t r ee t ( P . O . Box 724) P r e t o r i a

S P A I N ' Librarxa B o s c h Ronda de la U n i v e r s i d a d 11 B a r c e l o n a

S W E D E N C . E . F r i t z e s Kungl . H o v b o k h a n d e l F r e d s g a t a n 2 S tockholm 16

S W I T Z E R L A N D Lib ra i r i e P a y o t Rue Grenus 6 1211 G e n e v a 11

T U R K E Y L i b r a i r i e H a c h e t t e 469 , I s t i k l â l C a d d e s i B e y o g l u , I s t a n b u l . ^ 4

UKRAINIAN S O V I E T SOCIALIST R E P U B L I C

See u n d e r USSR

UNION O F S O V I E T SOCIALIST R E P U B L I C S

Mezhduna rodnaya Kniga . S m o l e n s k a y a - S e n n a y a 32*34 Moscow G-200

U N I T E D KINGDOM O F G R E A T ' BRITAIN AND N O R T H E R N I R E L A N D

Her M a j e s t y ' s S ta t ionery O f f i c e P . O . Box 569 L o n d o n , S . E . I

U N I T E D S T A T E S O F AMERICA N a t i o n a l Agency for . I n t e r n a t i o n a l P u b l i c a t i o n s , I n c . 317 E a s t 34th S t ree t New York , N . Y . 10016

V E N E Z U E L A Sr. Brau l io Gabr i e l C h a c a r e s Gobernador a Cand i l i t o 37 San ta R o s a l i a * (Apar tado P o s t a l 8092) C a r a c a s D . F .

Y U G O S L A V I A J u g o s l o v e n s k a Knj iga T e r a z i j e 27 B e l g r a d e

IAEA p u b l i c a t i o n s can a l s o be p u r c h a s e d r e t a i l a t the Uni t ed N a t i o n s Bo'okshop a t Un i t ed N a t i o n s H e a d q u a r t e r s , New York, a t the n e w s - s t a n d a t the A g e n c y ' s H e a d -q u a r t e r s , V i e n n a , and at mos t c o n f e r e n c e s , s y m p o s i a and s e m i n a r s o r g a n i z e d by the A g e n c y . t

In order to f a c i l i t a t e the d i s t r i b u t i o n of i t s p u b l i c a t i o n s , the Agency i s p r e p a r e d to a c c e p t p a y m e n t in U N E S C O coupons or in l o c a l c u r r e n c i e s . ' 1

Orde r s and , inqui r ies from c o u n t r i e s whe re s a l e s a g e n t s have no t y e t b e e n a p p o i n t e d may be s e n t to :

D i s t r ibu t ion and S a l e s Group, I n t e r n a t i o n a l Atomic Ene rgy A g e n c y , Kä rn tne r Ring 11, A-1010, Vienna I, Aus t r i a

INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1966

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TECHNICAL REPORTS SERIES No. 54 Application of Food