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M E T H O D S USED I N S T U O Y I F I G B A C T E R I O G E i V I C P R O B l E M S I M C U R I N G A N D CANNlElS M E A T

WILLARD 0. NELSOK UNIVERSITY OF ILLINOIS

The microbiological aspects of the manufacture and processing of meats and meat products have been described as a race between man and micro- oq+nism--with the stakes going t o the winner. bacteriological information which may be c lass i f ied in to three in te r re la ted

I n t h i s race we f ind we ?%quire

categories as

1.

2.

3.

follows :

Information relative to the public health aspects of the meat industry involving the prevention of transmission of disease and food poisoning by animal products.

Information t h a t w i l l enable us t o control undesirable microorganisms i n order t o reduce product deterioration and spoilage.

Information enabling us t o cul t ivate and develop the de- s i rab le epecies i n the preparation and production of specif ic manufactured items.

Bacteriological data re la t ive t o the three categories outlined above

Once the specif ic information is gained and the f a c t s discovered and arederived from experimental inquiry i n the laboratory and under operating con- di t ions. tested, the problem then becomes one of control rather than research. The s t ructure of our control mechanism is based on cer ta in fundamental methods involving the use of asepsis, chemical substBnces, low temperatures, high t e m - peratures, fermentation, osmotic presBures, and dehydration. Bacteriological control i n t h i s sense implies retardation, reduction, and elimination of un- desirable organisms as w e l l as the encouragement and cul t ivat ion of the de- s i rab le beneficial types. Consequently, our basic packing industry practices of refr igerat ion, pickling, smoking, curing, heat t reat ing, canning, and rapid and sani tary processing of r a w materials a r e directed toward the control of the yeast, mold, and bac ter ia l population present i n the packing house products.

Before discussin& specif ic problem6 i n curing and canning and the methods employed i n solving these problems, I think it is f i rs t necessary t o es tabl ish a few concepts of meat microbiology. I believe t h a t the bacterio- log ica l qual i ty of a given product a t any given stage i s a d i rec t function of contamination, t i m e of holding, temperature of holding, and the treatment t ha t the product haa undergone. Contamination nay be a r b i t r a r i l y divided in to two types on the basis of points of origin. I have considered "primary contamina- t ion" as that present i n the t i s sues of the animal a t time of slaughter plus the contamination picked up during the dressing operations. "secondary contamination'' t o indicate the microorganisms picked up during the processing operations plus the growth of the organisms as influenced by favor - able environmental conditions, The equal importance of both types of contam- inat ion is stressed i n the solution of problems.

I use the term

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With the above points i n mind, l e t us now consider i n d e t a i l some specif ic problem that have a r i sen In curing and canning meats and l e t us examine the methods used to successfully cope with these problems. Imagine yourselves i n the position of a bacter iologis t i n the laboratory of a lmge Wcker. have returned from lunch and ese ready t o spend 8 profitable and uninterrupted afternoon c l a s s i f y i w research data and designing further research when the canning superintendent comes i n w i t h a worried look and several cans of roast beef i n various stages of swelling. causing the spoilage and how do w e control it?" the product and examining the can carefully, it is decided tha t the routine spoiled can procedure may be used t o secure the necessary information. is collected when the can, is asept ical ly opened and i s found t o be hydrogen. The roas t beef i n the can seem t o be normal i n every respect. copic examination of the can contents gives no information, and as you f ind the next day, the enrichment cultures, both aerobic and anaerobic a t 37O C . and 55' C . a r e negative. turn now? solved--but by the negative results you have established limits i n which you must work. reference t o a similar problem. With this information you formulate a working hypothesis and go in to the operating plant t o t e s t it. The flow-sheet type of analysis is i n t h i s case the method of choice. preparation and processing of raw beef into canned roast beef is carefully ex- amined with respect t o time, temperature, and contamination. Analysis of your r e su l t s indicate sat isfactory beef boning and handling cperations, 80 you have marked out the canning operations as the source of trouble. canning procedure shows that some anaerobes survive the precooking and tha t the parboiled beef i a allowed t o stand at incubation temperatures f o r considerable t i m e . i n the r e t o r t truck has been standing f o r 2 3 hours before it is f ina l ly processed. was a rapid gas forming anaerobe, which was not too r e s i s t an t t o heat. epoilage or gas formation occurred while the sealed cans were beirg accumulated i n the trucka so as t o make a f u l l r e to r t . found amow normal cans i n the r e t o r t can be accounted f o r by the di f fe ren t perioda of holding pr ior t o retorting. The s t e r i l i t y of the spoiled can is explained by the non-heat tolerance of the anaerobe. def in i te concept of your problem. gas-producing anaerobe and by studying i ts character is t ics . the incubation of the sealed can pr ior t o re tor t ing is the point of a p o i l q e a c t i v i t y by studying the rate at which gas is produced i n the cans during the holding period. Having thua determined the cause and point of spoilage, you are able t o advocate changes i n operational procedures to control and prevent spoilage. o r if it does occur, it can easily be detected by the revised and improved routine methods f o r the examination of spoiled canned meats.

You

The problem is quite evident - "What is After obtaining the his tory of

The gas

Direct micros-

I n other words the can is spoiled but sterile. Where do you The r e su l t s are all negative and the primary problem remains nn-

Consulting the l i t e r a tu re f i l e s i n search of a lead, you f ind a

Each s t ep and stage of the

Analysis of the

Further, you note that a f t e r being evacuated and sealed, the first can

The organism i n your reference The pattern f i ts together nicely. The

The varioua stages of spoil43e

A t th i s point you have a The solution is gained by isolat ing the

You prove tha t

By the solution of t h i s problem, spoilage of type can be prevented,

Mention has been made of the routine examination of canned meats and The canned meat samples one en- I would l i k e to b r i e f ly describe t h i s method.

counters i n the laboratory are e i ther unspoiled normal samples submitted f o r s t e r i l i t y t e s t s or f o r the so-called "hot room" test f o r keeping quality, o r spoiled samples f o r examination f o r the type and cause of spoilage. technique of examination and culturing the can contents may vary i n details i n given laboratories but the essent ia l steps are a8 follows:

The

107.

A .

B.

C.

D.

E.

F.

G.

H.

Physical examination of can.

Preparation, cleaning, and steri l ization of the can.

Aseptic opening o f can and collection of gas sample.

R m v a l .of sample (product f rac t ions such a6 fat-liquid- meat).

Inoculation and incubation of sui table cul ture medium a t spec i f ic temperatures.

Direct microscopic examination of the can contents.

Examination of t he can contents f o r odor, appearance, proteolysis, e t c .

Chemical examination.

The use of such methods enables one t o determine the primary types of spoilage and thereby ind ica te control measure8.

The solution of curing problems i s a somewhat d i f fe ren t f i e l d . I n canning it seems t h a t only a r e l a t ive ly f e w things can happen. I n curing the spoilage may take on innumerable shapes and forms and the solution of the problem may be hidden i n an obscure ear ly operational procedure and a flow chart analysis of a l l operations involved i s required. An example of a curing problem i s as follows: Some j e l l i e d whole lamb tongue was s l iced and found t o be discolored o r undercured i n the center portions. Chemical analysis indicated normal amounts of salt, n i t r a t e and n i t r i t e i n the normal areas. colored area differed only i n that n i t r i t e w a s absent. solved i n t o one of determining the cause of the absence o f n i t r i t e . normal n i t r a t e and salt content w a s encountered throughout the meat, we obvi- ously must f ind a n i t r i t e reducing contaminant. The curing va ts y i e ld a f ine harvest of such organisms, but the question arose concerning the mode by which these n i t r i t e reducers entered the curing pickle. Flow chart analysis involv- i n g the determination o f t i m e , temperature, contamination and n i t r i t e reducing contamination f o r each operation and a l l equipment l ead us all t h e way back t o the k i l l i n g f loor . Here we found t h a t t h e tongues as they were removed f rom the head were contaminated with our organism. Changes i n processing operations eliminated the spoilage.

The d i s - The problem was re-

Because

Some of the more complex curing problems of bac te r i a l or igin, such as ham and bacon souring, l ead back beyond the k i l l i n g f loors and take the invee t i - gator i n t o fields of physiology, histology, immunology and anatomy. The invest- iga tor studying discolorations of meat o r the action of microorganisms on fa ts soon f inds himself far i n t o physiological and physical chemistry, organic chem- i s t r y , physics, instrumental analysis, and enzymology i n search of a solution.

It has been shown t h a t t he flow chart analysis i s an excellent method f o r control because it does give the desired information when it i s modified f o r a spec i f ic purpose. On the other hand, t he research method i s not a rou- t ine procedure but a philosophy by which one makes an orderly approach t o the s c i e n t i f i c solution of problems i n applied biology. The research method i s composed of a log ica l sequence and relationship o f t he indeterminate s i tua t ion

108.

t o the statement of the problem, the formation of a hypothesis, the proposition f o r t ea t ing the hypothesis, the experimental design, the collection of data, t h e col l igat ion of evidence for t e s t ing the hypothesis, and,flnally, the draw- ing of warranted assertions.

Bacteriological problems i n curing and canning meat f a l l i n t o groups: The flow-chart type of analy-

The research method employed in the study of the micro-

(1) Control problems, and (2 ) Research problems. sis, modified t o the needs of the problem a t hand, i s method most commonly ueed f o r control work. biology of meat8 18 same fundamental method of approach t o the solution of problems used i n a l l phases of biology,

CHAIRMAN BUTLER: Thank you, Captain. Colonel Pearson, w i l l you con- duct t he discussion, please?

PROF, PEARSON: M r . C h a i m n , I think you have my rank wrong. I am Corporal. (Laughter)

I think that we all enjoyed D r . Nelson's t a l k this morning, and I think it serves t o i l l u s t r a t e the importance of the bacteriological approach. I think graduate students, i f they have any in t e re s t along t h i s l i ne , should be urged t o take bacteriology.

W e w i l l now have questions from the f loor t o D r . Nelson.

PROF. HECK: I would l i k e t o know i f work is being done on s t e r i l i z i n g

I8 there any way i n feeding animals -- f o r instance, animals before they are slaughtered? Professor Nelson has mentioned that there are organisms i n the meat. taking them of f feed -- t ha t i s a factor i n helping t o produce animals w i t h more nearly s ter i le t i s sue?

PROF. NELSON: I know o f no methods. Thie problem of the s t e r i l i t y of meat i s an o ld one, and you can go in to the ear ly l i t e r a t u r e on meat and f ind a couple of people verbally beating each other concerning l i v e t i s sue . One says it %a contaminated, and one say8 it i a not. enough evidence now t o ehow that it i s .

But I think we have

But a8 for s t e r i l i z i n g it, I know of no approach t o t h a t problem at a i l . s t e r i l i z i n g of meat on the hoof. throughout, because epoilage, you know, is not caused by one organism, o r ten, but vast multitudes of them. what threshold value is, of course. mind saying it, but beyond tha t point then, w e a re i n spoilage. w e are not, and I do not know of any approach t o that problem a t all.

I am not 80 Bure that the solution t o any of our problems l i e i n the I think we must t igh ten up our operations

We have a threshold value. I do not know I do not think anyone does, 80 I do not

Otherwise

PROF. PEARSON: Does anyone e l se have any questions he would l i k e t o d i r ec t t o D r . Nelson?

DR. J. I. MILI;ER: I would l i k e t o know what the bacter iologis t ' s answer would be t o the problem t h a t most of us get occasionally when some fellow writes i n and says tha t he has cured some meat according t o the instruc- t i o n s of such and euch bul le t in . The meat spoiled, and he i a sending U B a

109.

sample. We receive a sample, and sure enough, it is spoiled. He wants t o h o w what i s wrong, how t o correct it, and w h a t t e s t we can do i n answer t o h i s problem. I would l i k e t o know how a bacteriologist would answer that question.

PROF. NELSON: I get a few l e t t e r s - l i k e tha t , too. Occasionally, though, they w i l l send me a bo t t l e of milk. may get a eample of milk i n a small medicine bot t le . ”Dear Sir: Is t h i s milk f i t t o drink?” Well, quite obviously, it i s not by the time it gets t o us, but i n re la t ion t o that problem, I think you would f i r s t associate the product that you have w i t h the types of epoilage tha t have been known t o occur w i t h that type of product, and then from then on, use your own ingenuity. “Does it have a bad color?” Is it maybe j u s t lack of proper curing so tha t the meat i s not palatable? Maybe it i s moldy.

Milk poses the same problem. We

“Is there discoloration?”

You would have t o get a l l t h e possible information tha t you can con- cerning the sample i t s e l f . How long was it held? A t what temperatures? How was it submitted t o you? Maybe the dressing operations and procedures may have a d i rec t influence on the product i t s e l f . mation, I think you could come t o a logical conclusion and ar r ive a t whether it i s spoiled o r not, and i f it i s spoiled, what type of spoilage it i s .

Then from t h i s background o f infor-

That m y involve merely examining it physically, looking at it and smelling it, or it may involve some laboratory procedures and the i so la t ion of cer ta in types of organisms.

Does t h a t agswer your question?

PROF. ZIEGLER: a l e t t e r , asking for information?

I n other words, you would have t o s i t down and write

PROF. NELSON:

I think anyone doing tha t i s going out beyond the l i m i t where he has

T h a t i s right. I would not under any circumstances give an opinion o r analyze any food products, without completely knowing the history. a r igh t t o go i n giving information, because I do not believe that you can conscientiously advise people unlese you know the en t i r e story. yourself i n a l o t of t raps otherwise.

You can get

PROF. BUGL: M r . Chairman, I might add that about 99 per cent of those d i f f i c u l t problems are solved when you ask these questions of your cor- respondent, because you w i l l never hear from h i m again. (Laughter) It works wonderfilly .

PROF. PFARSON: Do w e have any more questions, now t ha t Professor B u l l has offered h i s suggestion i n solving most of these problems?

PROF. WILMIRD: I s there any more data on this? What i e the s ta tus now of fas t ing an animal or not fas t ing an animal before slaughter?

PROF. NELSON: A s re lated t o the microbiological picture?

PROF. WILFORD: As re la ted t o your f i e l d ? Anyone can answer tha t que 8 t ion.

PBOF, NZLSODI,: Profeeeor Bull, w i l l you help m e out? I w i l l take the reeponeibil i ty up t o microbiology, and a f t e r tha t , I will c a l l on some wiser heads than mine.

110.

PROF. BULL: I have an idea that i f an animal i s f i l l ed wi th feed and bloated considerably when he is slaughtered, that the meat may be off flavor.

PROF. NELSON: I Q not think it influences the microbiological picture a t a l l , because you have very l i t t l e migration from the alimentary canal u n t i l eome time aFter the animal is slaughtered.

We had a f l o o r - f i l l of hogs hung up one time with operational d i f f i - cu l t ies , an2 they had t o hang there something l i k e eight o r nine hours at , *

room temperature. of time. UP

They were not dressed, and we had no migration i n tha t period We had a lot of autolysis and we hsd aged pork that would not f i r m

PROF. PEARSON: Are there other questions you would l i k e t o d i rec t t o Profeseor Nelson?

CHAIRMAN BUTLER: Thank you, Corporal.

We will. now have a paper on "Organoleptic Tests Developed for Meaeur- ing the Pa la tab i l i ty of Meat'l by one of our most respected veterans of meat research, Miss Bslle Lowe.

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