PROCEEDINGS

Nov l 21987

1.'98.7

February 1987

OHIO AGRICULTURAii· I RESEARGH WOOSTER, OHIO

EVELOPMENJ CENTER

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PREFACE

Approximately 150 persons attended the 1987 Ohio Grape-Wine Short Course, which was held at the Fawcett Center for Tomorrow, The Ohio State University, Columbus, Ohio, on February 16-18. Those attending were from 10 states, not including Ohio, and represented many areas of the grape and wine industry. This course was sponsored by the Department of Horticulture, The Ohio State University, Ohio Agricultural Research Ohio Agricultural Research and Development Center, Ohio Cooperative Extension Service, Ohio Wine Producers Association, and Ohio Grape Industries Committee.

Publications of the Ohio Agricultural Research and Development Center are available to all on a nondiscrimi natory basis without regard to race, color, national origin, sex, handicap, or religious affiliation.

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FRESH CONCORD JUICE MARKETING by Larry Lockshin

CONTENTS

REDUCING THE USE OF SULFUR DIOXIDE IN WINEMAKING by William D. Edinger

CROilN GALL IN GRAPES by R.N. Goodman

UNDERSTANDING SEEDLESSNESS IN GRAPES by Craig K. Chandler

GRAPE ROOT BORER - A POTENTIAL NEW INSECT PEST IN OHIO by R.N. Williams, S.R. Alm, D.M. Pavuk and F.F. Purrington

THE USE OF POTASSIUM SORBATE AND ASCORBIC ACID IN WINE by Thoma.s R. Schmidt

STATUS OF SULPHUR DIOXIDE by Domenic Carisetti

FACTORS AFFECTING GRAPEVINE BUD COLD HARDINESS by Tony K. Wolf

PRESERVATION OF FRESH CONCORD JUICE by C.L. Stamp, J.F. Gallander and J.F. Stetson

EPIDEMIOLOGY OF OOWNY MILDEW OF GRAPE by N. Lalancett, M.A. Ellis and L.V. Madden

INFLUENCE OF BACTERIAL STRAINS ON THE INDUCTION OF MALOLACTIC FERMENTATION by J.F. Gallander, R.R. Breen and J.A. Jindra

APPLICATIONS AND EFFECTS OF CARBONIC MACERATION by William D. Edinger

SUMMER PRUNING OF GRAPEVINES by Tony K. Wolf

ACTIVATED CARBON AS A WINEMAKING TOOL by Domenic Carisetti

THE PRINCIPLES AND PRACTICES OF COLD STERILE BOTTLING by Chris Stamp

MONITORING INSECT AND MITE PESTS IN OHIO VINEYARDS 1984-86 by Steven R. Alm, Daniel M. Pavuk, and Roger N. Williams

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FRESH CONCORD JUICE MARKETING

Larry Lockshin Ohio Grape Industries Program

Worthington, OH

The juice market is one of the fastest growing segments of the grocery in­dustry. Witness the recent arrival of juices from such companies as Sunkist Groto~ers, Proctor and Gamble, Nestle Company, Coca Cola as well as the 10% juice added to soft drinks. The American marketplace is filling up with hundreds of brands and styles of various juice mixtures. Where once apple juice, orange juice, and grape juice stood, we now see Cranapple, Cranblueberry, blends of five or more juices, natural juices, etc.

Why would the Ohio Grape Industries Program want to get involved in competi­tion with these major consumer products companies? And how could we go about doing it?

First, "the why". As you know, the 1970's and the 1980's have been hard for Concord grape growers. Seven consecutive large crops capped by record years in 1984 and 1985 filled the tanks of various processors to overflowing. This resul­ted in lower payments to growers as supply outstripped demand. Where once prices were over $200 per ton of Concord grapes, payments have recently been as low as $100 per ton, while operation expenses have increased tremendously.

The major buyer of Concord grape~, National Grape Growers Cooperative, the owner of Welch Foods, has made a strong marketing effort to increase the demand for grape products. This effort coupled with last year's short crop reduced in­ventories to about three months over the six months the year before. Grape prices rose to about $160 per ton this last fall. One of Ohio Grape Industries' missions, as defined by law, is to develop new products and new markets for Ohio grapes. We felt there was a need to increase the price paid for Concord grapes. The only way to do that is to enhance the value of the product. Ohio grown Concord grapes must be seen as worth more packaged in a way that adds value to the initial raw product.

One of our earlier ventures has been in the fresh Concord table grape area. We have successfully marketed a small percentage of Ohio Concords as table grapes and brought returns to the grower on the order of $400 per ton. However, this outlet will never be large enough to significantly influence the overall Ohio Concord market.

We felt that the development of the overall juice market opened some oppor­tunities for us. The public awareness of juice as a healthy alternative could be used in our favor. Also, the State of Ohio has been pushing the "Buy Ohio" cam­paign. We thought that there might be value in tying in with the Ohio theme.

Now, "the how" we went about it. Entering the marketplace with a new product is a complex process. First, the target market you wish to sell to must be chosen, then the product designed to meet the needs of that market. Once you have a product you must price it and then get retailers to carry it. Even when your product makes the retail store shelves, it will be competing with over 30,000 other items, so you must promote it.

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We decided to aim for the fresh juice buyer, the person who buys apple cider or orange juice in the plastic jugs. We felt we could make a fresh fruity, lighter Concord juice that TNOuld appeal to that market. By selling the juice in plastic jugs, we could differentiate our juice from other grape juices and give the im~ession of freshness, which glass does not give.

A series of meetings were set up with a couple of wineries interested in producing the juice and Dr. Jim Gallander and Chris Stamp from OARDC. We decided on all major production parameters from grape quality to the types of preserva­tives. Special attention was given to the ~ocess of pectic enzyme extraction of the color. Concord juice has to be purple, but we wanted to cold press in order to get a flavor different from the traditional hot ~essed Concord juice. Experience had shown that a cold pressed juice would be lighter and fruitier than hot ~essed juice. We also had to design a label. This piece of art TNOuld have to meet all federal and state requirements as well as sell the product to the consumer. In cooperation with our agency the label was designed and printed.

Once we had the product designed, we had to find a place to test market it. We wanted to market in an area where grapes -were not grown in order to get a true test of the product. Columbus has traditionally been a test market, so we decided to start there.

A fortunate association between our advertising agency and Big Bear Foods led us to contact their head produce buyer. We met and discussed the project and we were very well received. Normally, to get a new item into a chain store requires several free cases per store plus some discounting--a very expensive step for a new product. Big Bear's commitment to local products helped us avoid those extra costs.

We decided to put the juice in two different containers, one and two quarts and to place it in all 55 Ohio Big Bear stores. We then selected 12 Columbus area stores, matched for produce sales for our test. We had no idea what price people would pay for the juice. We would sell the juice to Big Bear at one price, but they would have three different retail prices in each group of four stores. We could' then monitor sales to see how price affected sales.

The following charts show that there seemed to be no effect of prices on number of cases sold. It looks as if actually more juice might have been sold at the highest price. This is merely an aberration. Statistically, there is no difference in sales among prices.

AVERAGE JUICE SALES BY PRICE

Retail Week Number Cases Price 1 2 5 6 Total

Half Gallons $2.19 3.25 9.75 4.75 1. 75 78 $2.39 4.0 6.75 2.0 1.5 55 $2.59 4.76 9.25 6.5 2.5 84

Quarts $1.29 1.5 8.1 2.0 1. 75 52 $1.49 1.3 9.25 1.25 2.0 56 $1.69 2.5 8.5 3. 2 2.1 76

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This campaign proceeded with very little promotion. We wanted to see what the true market response to our product was without a lot of short-term promo­tion. We did pour free samples of the juice on the second Friday of sales. This accounts for the large number of sales of the juice in week number two on the ac­companying chart.

Our overall feeling is that this was a very successful project. We have developed a good product and ascertained that consumers will buy it at a price we can live with. Next year we are planning to increase our efforts to a wider range of markets. We will probably expand our promotional efforts in order to sell more juice. We are working on some new products for the future as well. We are pleased that both the grape growers and the processors felt the program was beneficial and provided a good return. We plan to maintain that return as our top priority.

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REDUCING THE USE OF SULFUR DIOXIDE IN WINEMAKING An Overview of Methodologies

William D. Edinger Hort. Prod. lab, H.R.I.O.

Vineland Station, Ontario, Canada

Sulfur dioxide (S02) and sulfites are important tools in winernaking due to their multiple benefits, minimal cost, and ease of use. However, reducing the use of sulfites is a subject for wine industry to consider more closely than ever before, not only because of reported health implications, but also because it is part of an efficient and well-managed operation and contributes to making a bet­ter ~educt. While a complete substitute for 502 is not available, there are now processing techniques which minimize the amount of sulfite used, while maximizing its effectiveness. It should be kept in mind that when properly used, 502 can be much more effective in small doses than at much larger doses which have not been strategically applied. This review discusses the uses of 502, the reasons for using less, a brief explanation of the chemistry involved, and several sugges­tions for limiting the amounts used and maximizing the usefulness of those lower amounts.

Reasons for Using Sulfur Dioxide

Sulfur dioxide acts as an antioxidant in wines my inactivating oxidizing en­zymes and acting as an oxygen acceptor, or reducing agent.· It also exhibits the growth of wild yeasts and all bacteria, and solubilizes anthocyanins and other phenolics, thus intensifying color. The protection afforded by sulfite ranges from stopping Botrytis rot in over-ripe grapes to bottling ~ocedures to prevent oxidation. It is important to note, however, that during fermentation sulfites are completely ineffective in their ~otective properties and in fact can seriously hurt the quality of the ~educt if added during this phase.

Reasons for Using Less Sulfur Dioxide

The economy and ease of use of sulfites has led to occasional over-use, less a problem today than in the past. Nevertheless, there is still room for improve­ment in the efficiency of sulfite use, without eliminating it completely.

A few compounds can be used to partially replace sulfite, including ascorbic acid as an antioxidant, and sorbic acid to prevent yeast growth (sorbate must never be used without sulfite, or geranium-odor may occur). Clarification, refrigeration, and sterile filtration today permit good biological stability, and reduce the requirements for the reliance on so2• Thermal treatments can also be used to great advantage.

It is good ~actice to try to obtain wines with the lowest possible content of total so2 while maintaining a content adequate for ~otection. Addition of so2 to grapes before crushing leads to increased extraction of phenolics, which can produce a stemmy, bitter, harsh taste in the wine ~oduct, and too much free so2 will always affect the organoleptic character of a wine. Excess total 502 can result in hydrogen sulfide and "rubber boot", or bockser odors, which are largely intractable unless treated very soon after they appear.

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Chemical Nature of SO~. in Wine

There are three forms of so2 which should be kept in mind when determining needs: bisulfite, molecular so2, and bound so2• When sulfur dioxide is added to juices or wines directly as a gas or by use of compounds which release so2 into aqueous solutions, the so2 ionizes to several "free" forms ("bisulfite" and "molecular"), and may also recombine with other compounds to become "bound" so2, which is mostly ineffectual.

The most important aspect of understanding the chemistry of so2 is its relationship to pH. At the pH of most wines, free sulfur dioxide is found only as bisulfite ion (Hso3 -) and molecular so2•

Low pH

HSO + 3

Bisulfite

so++ 3

Sulfite

High pH (not significant in wines)

It is molecular so2 which is effective against microorganisms: only about 1-2 ppm of molecular so2 is necessary for complete microbial protection. Within the expected pH ranges of wine, at pH 2.8 about 10% of the free sulfur dioxide is· present as molecular so2, and at pH 3.8 only about 1%. Thus, pH conditions which maximize the amount of molecular so2 require less total so 2• Figure 1 indicates the amount of free so 2 required at a given pH to achieve effective microbial in­hibition. (Molecular so2 can be calculated according to the formula: pH = pK + log[HS03-J/[So2]; log [HS03-J/[S02] =pH- 1.81.)

100

90 80

Free 70 60

502 50 (ppm) 40

30 20 10

u!=====!==·a 0

i:iii:i:;;;:;

2.8 3.2 3..4 3.6 3.6 pH

F !g. 1. Free~.< mg/1) y1eldlrl(J 1 mg/1 molecuhr ~ f(X" pH 2.8-3.8 ( tmta fnxn K IOQ et at., 1981 ).

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Binding of Sulfites: Once potassium metabisulfite (KMS) has dissociated, the bisulfite may recombine with other compounds (carbonyls) and thus, as bound so2, become ineffectual.

KMS first binds to all available carbonyls when added to must or wine. The remainder attacks oxidative enzymes, and may be destroyed in the process. Whatever is left becomes useful as free so2• Acetaldehyde is the most important binder of sulfur dioxide, since it is present in significant amounts during fer­mentation and binds with so2 essentially irreversibly (95-99% of it is bound at any given time). When it is removed from their normal metabolism, yeast cells simply produce more until all the free so2 is bound and normal levels of acetal­dehyde are re-established. Wines normally contain less than 50 ppm of acetal~ dehyde, but in amounts greater than that, this component may pose a danger to the color, clarity, taste, and aroma of the wine. Free acetaldehyde gives the wine an "oxidized" or aged taste, so added large amounts of so2 to the crushed grapes threatens the fruitfulness of the final product. Other carbonyl compounds (ketoacids like pyruvate and -ketoglutarate) can bind so2 reversibly, and as more of these compounds are t,Jroduced, more so2 is bound to them, and in turn more binding compounds are produced by the ferment~ng yeasts. The result is unneces­sarily high amounts of total so2 and carbonyl compounds, either of which may be detrimental to wine quality.

Timing of SO addition is important, as well, for several reasons. One is the rate of acetafdehyde production: the worst time to add so2 is when aGetal­dehyde levels are high (Fig. 2).

.: 120 :rl

i100 "' .. "' -: 80

¥ ,.. .... • 50

' ~0 JO 20 10

l/ j./

v v f7

7 1/

ll 20 JO '40 50

I I I Bindin9 of ~c•hld@h,d• f from

'With ~dd•d 502 I rftrmtnb-1 ion

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~r II '\+50 m911 $02 / so2

tnd of ! ... I fermtntat1on-+"'-· ...

without add~d S02

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9/l sugar (@rm@nt@d

(atler 11liller-Spath, 1975)

fig. 2. Consequences of ~dding so2 at various times during fermentation. (after Muller-Spath, 1975)

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STEPS TO REDUCE THE USE OF SULFUR DIOXIDE IN WINEM.A.KING

The key to using less so2 is in needing less, as indicated by the chemical processes described above: maK.e more available in its active form (i.e., keep an eye on pH) and take steps to reduce the formation of compounds which bind it. All of the processes and treatments described below are aimed at increasing the efficiency of smaller amounts of so2 and eliminating its use when not absolutely necessary.

1. Grapes: The sanitary condition of the grapes determines the kinds of precautions to take as far as so2 additions. Recent research has shown that, in general, sound, rot-free grapes ao not need any sulfite at all before crushing, and in fact it is likely to be detrimental for the reasons described above.

In the case of grapes with significant mold, a nurrber of steps can be taken. First, if possible, sorting of bunches should be considered. Separate treatment of the moldy grapes can then be carried out, such as heat treatment, use of ben­tonite, and clarification or centrifugation.

2. Transport: The deterioration of the fruit during the harvest and transport to the cellar should be minimized. Prolonged contact of the grapes with leaked juice during transport should be avoided, particularly for white grapes, in order to avoid the binding of so2 with flavones and other polyphenolic extracts from the skins. Mechanical harvesEing should be followed by immediate processing. Contamination by metals, such as iron rust, encourages oxidation and deposits, and should be eliminated.

3. Crushing: The ratio of bound S02/free so2 in musts from grapes pressed immediately after picking has been measured at abOut 1:2, while that of grapes crushed 36 hours after picking was almost 1:1. Cleanliness of equipment is of great importance in keeping contamination from molds and wild yeasts to a mini­mum. Dumping white grapes directly into the presses without crushing permits the minimal use of so2• Desternming increases the amount of bound so2, probably from the damage it does to the skins and sterns. Equipment should be used which intro­duces as little oxygen as possible to the must.

4. Pressing: Moderate pressing of the grapes, a low level of phenolics (in the case of white wines), and the use of free-run and first-pressing juice facilitates the production of high-quality wines and the reduction of the amounts of sulfur dioxide required. This is directly related to the interaction of SO with binding substances in the skins, seeds, and pulp (see Clarification belowt. Lees production is relatively low from gently pressed grapes, and in many cases the content of polyphenols and polyphenoloxidases is reduced as well. High lees production often leads to difficulties in clarification and stabilization. Roller ~esses seem to give the best results, with screw presses least favorable because of the high solids content they produce.

Slight oxidation of the must before fermentation does not necessarily have a negative effect on the quality of wines and it favors a decrease in acetaldehyde. Intentional oxidation to remove browning compounds has not given consistently positive results and must still be considered experimental.

The compositional differences between free-run juice and press JU1ces is significant. With increased pressing there is an increase in the content of

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colloids and phenolics: this makes the treatment and filterability of the wines increasingly difficult, and increase turbidity and the tendency to form brown deposits, thus requiring more sulfur dioxide, by up to 50-100%, so avoiding heavy pressing will be conducive to lower so2 requirements.

5. Clarification, defecation: Any treatment which reduces the content of compounds capable of binding with so2 will improve the efficiency of that so2 being added. Thus, the use of bentonite in defecation of the must along witn other clarification procedures such as filtration, centrifugation, enzyme preparations, etc., will be of benefit in reducing the requirement for sulfite. Silica gel, or kieselsol, has been found to be especially helpful when used in combination with gelatin. Typical dosage is 0.25 ml of 30% silica gel per liter of wine and 25 mg/1 of 100 bloom gelatin.

6. Fermentation: The metabolites produced during fermentation largely determine the capacity of the wine to bind so2• In general, rapid fermentation has been found to produce the lowest amounts of binding substances. High fermen­tation temperatures are likely to produce more so2-binding substances, but exces­sively low fermentation tem~ratures are also unfavorable. Studies have shown that cold fermentation at 13°C produces more acetaldehyde than a fermentation at 20°C.

Pumping over of the must assists in the multiplication of yeasts moderating the temperature.

The fermentation should be completed to dryness to achieve minimum S02-binding capacity. M.y further fermentation after so2 addition can result in much higher amounts of acetaldehyde production (See Fig. 2).

Commercial yeasts generally produce fewer ketoacids and can overcome any wild strains present when used in large amounts, especially if a killer strain is used. Strains which produce only small amounts of so2, ketoacids, and acetal­dehyde should, of course, be favored when selecting cultures.

Some authorities recommend an aerated first racking at the end of the al­coholic fermentation, in order to eliminate the lees from the living yeast and to covert any residual unfermented sugar. Before doing an aerated first racking, make sure the wine has enough residual sugar to allow the remaining yeasts to "finish off" the fermentation and leave a reduced environment at the end: other­wise, oxidation may occur.

7. Bottling: Sulfur dioxide should be used only to prevent oxidation in the bottle--it should not be used to try to inhibit refermentation of residual sugars in the bottle. Besides the excessive amounts required for that use, it may not work anyway. Clean processing, sterile bottling, and possibly sorbate are the best alternatives.

The air space above the surface of the wine should be as small as possible: for each cc of air above the wine, about 1 ppm of free sulfur dioxide is lost in the course of 2-4 weeks. Having about 35 mg/1 should be adequate.

The use of reliably gas-tight closures is very important in maintaining an oxygen-free package, and requires a smaller margin of safety when making the final so2 addition.

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8. Alternative Treatments

Use of Thiamin: Thiamin has been found to significantly reduce the amounts of pyruvate and acetaldehyde produced during fermentation and allows a more vigorous growth of the yeasts. Thiamin is best used before the addition of sul­fites (and their binding) has occurred, preferrably in place of sulfite, since free so2 will destroy thiamin and carboxylase. It can be added at 0. 6 mg/1.

Replacement of Sulfur Dioxide with Hydrogen Sulfide Before Fermentation: Hydrogen sulfide creates a reducing atmosphere at least as strong as that of so2, is capable of inactivating oxidases, and is an effective antimicrobial agent. It is also a substance normally found in any wine fermentation, as is sulfur dioxide, and has been tried experimentally in winemaking.

When added as ammonium, sodium, or calcium sulfide at 5-20 mg/1 as H2s (doses above 30 mg/1 resulted in garlicky tastes and odors), H2s was reported to have almost no effect on pectolytic processes and a minimal influence on fermen­tation speed and microbial succession during fermentation, much less than that of so2• Production of acetaldehyde was notable less than in musts treated with so2• The wines were rated higher than those made with so2•

Use of PVPP: PVPP is a superior, polymerized form of PVP sold as Polyclar AT. It is-intended for white wines, and works to prevent browning or pinking by complexing rapidly with phenolic compounds from musts or wine that cause those problems. If those compounds are removed or in reduced amounts, less SO is required, and the long-term stability against oxidation and browning of the produce is enhanced. PVPP generally works best at about 50 g/hl, or 4 lbs. per 1000 U.S. gallons. It should always be considered for high-quality white wines.

Glucose Oxidase: Glucose oxidase works in the presence of small amounts of sugar to remove even minuscule amounts of oxygen, and could theoretically be used in wine in storage or just before bottling. The potential for replacing so 2 at bottling time is great.

9. General Points on Minimizing the Use of so2 During Processing: Only about 1-2 ppm of molecUlar 302 is necessary for complete microbial protection; pH conditions which maximize the amount of molecular so2 present require less total so2•

Fine or sterile filtration of wines is recommended for storing wines with residual sugar.

Containers, tanks, or storage vessels, as always, should be kept full. co2 or nitrogen should be used to fill headspace.

Determine, by chemical analysis, the amount of sulfur dioxide required for each wine. Amounts of so2 should be based on Tso2, Fso2, pH, and binding capacity of the must or W1ne.

Adding SO during the last part of fermentation without separating the yeasts from th~ wine carries with it the risk of renewed acetaldehyde production.

Minimizing the transport of the wine will minimize the risk of oxidation and loss of free so2; it also reduces chances of microbial contamination.

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Use of cool or cold storage slows considerably the loss of free so2 as well as the growth of undesirable microorganisms.

With sound grapes and fast pressing, SO addition before the end of fermen­tation can be eliminated, especially if mic~ial counts are kept down and oxygen uptake minimized.

The principal role of SO up to bottling time should be as an antioxidant. Good processing can minimize lhe requirement for antimicrobial agents by keeping cell counts minimal.

Adding more total so2 does not necessarily give more free so2• A wine with 25 ppm so2 added may have 50% of it available as free so2 , while the same wine with 100 ppm added may have only 10% available as free so2-about the same free, but much mre bound.

LITERATURE CITED

Asvany, A.L. 1985. Les technologies de vinification permettant de diminuer les doses de so2• Bull. OIV 58:621-623.

Cottrell, T.H.E. 1983. Cotmton errors in small wineries. Proce. 1983 Ohio Grape-Wine Soort Course. pp. 20-26.

Delfini, c., M. castino and G. Ciolfi. 1980. L'agfgiunta di tiamina ai mosti per ridurre i chetoacidi ed accrescere l'efficacia della so2 nei vini. Riv. Vitic. Enol. 33:572.

Edinger, W.D. 1986. Reducing the use of so2 in winemaking. H.R.I.o. Tech. Bul. Ont. Min. Agric. & Food, Vineland Station, ontario, Canada.

Marques Gomes, J. v. and M.F. DaSilva Babo. 1985. tion permettant de diminuer les doses de so2 Bul.

Les technologies de vinifica­o.r.v. 58:624-636.

Muller-Spath, H. 1975. Weniger so2 im Wein. Die Weinwirtschaft 11(1/2):27-28,30,32,34.

Ruiz Hernandez, M. 1984. Initiation of fermentation at low pressure as replace­ment procedure for use of so2 in winemaking. Semana Vitivinicola 39:2241.

Ruiz Hernandez, M. 1985. Les technologies de vinification permettant de diminuer les doses de so2• Bull. O.I.V. 58:617-620.

Usseglio-Tomasset, L. 1985. Les technologies de vinification permettant de diminuer les doses de so2 Bul. O.I.V. 58:606-616.

Valouyko, G.G., N.M. Pav1enko, and S.T. Ogorodnik. 1985. Les technologies de vinification permettant de diminuer les doses de so2• Bul. O.I.V. 58:637-644.

Wucherpfennig, K. and G. Semmler. 1972. Acetaldehydbildung im Ver1auf der Garung in Abhangigkeit vom Wuchsstoffgehalt des Garsubstrates. z. Lebensm. Unters. Forsch. 148:77-82 and 138-145.

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PART I

CROWN GALL IN GRAPES

R.N. Goodman Department of Plant Pathology

University of Missouri Columbia, MO 65211

Crown gall is caused by Agrobacterium tumefaciens. This bacterial pathogen has the widest host range of any plant pathogen, attacking more than 600 species. There are three types of crown gall called biovar 1, 2 and 3. Biovar 3, the grape pathogen is somewhat of a specialist as it only attacks grapes and a few other species. Crown gall is also unique, as it is the only pathogen of man, animal or plant that causes disease by inserting a bit of its own genetic infor­mation (DNA) into the nucleus of a wounded host cell. Tha~s-rhe extent of the infection process and it only takes one bacterial cell to do the job. In doing so the bacterium's role in the disease process is over. Hence, directing control measures at the bacterium once it has inserted its genetic information into the grape cell is fruitlesse Insertion of new information permits the recipient grape cell to make excess amounts of growth hormones. As a consequence, the grape cell is "transformed" from a normal cell into a tumor cell that starts to divide rapidly without organizing into functional organs, like stems, leaves, and roots. The net result of all this cell division is an ever-enlarging mass of cells we call a gall or tumor that may eventually girdle the trunk. Crown gall is in fact plant cancer.

The development of tumorous masses on the trunks of grapes follow a pattern that has until recently, not been fully understood. The sequence of events most commonly noted starts with a hard freeze in spring, perhaps even before bud swell. The affected vineyard almost certainly has at the moment abundant soil moisture so that root pressure has forced water up into the conducting vessels of the trunk. In fact, pruning at that time causes the canes to "bleed" profusely.

Soon after starting our crown gall research at Columbia I visited Hungary where the disease had caused great damage and where scientists had recently made an important discovery. Specifically, Dr. Janos Lehoczky had isolated the crown gall bacterium from the fluids dripping from a pruning wound. Furthermore, he found that the nearest source of infection was a root tumor more than 32 inches below the pruning wound. Dr. Lehoczky told me that both low temperatures and abundant soil moisture must be at hand simultaneously to cause widespread serial tumor formation in a vineyard. One without the other never leads to significant numbers of vines showing the disease in a single season. Furthermore, the in­cidence of widespread tumor development is greatest in young plantings, 1-5 years of age, and where soil drainage is the poorest. Hence, low spots in the vineyard, where both water and air drainage are frequently the poorest, are the most likely to be affected.

But what is the relationship of freezing temperatures and root pressure to gall formation? The discovery of crown gall bacteria in the vessel fluids sug­gests that the bacteria are already in the trunk before bud break. Then, low temperatures, say 21-22°F April 15 and 16, (as occurred in 1982) cause ice crys­tals to form in the water conducting vessels of the trunk. The ice crystals injure thousands of parenchyma cells adjacent to the ice-packed vessel cells, and

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the bacteria in the vessels infect the ice-wounded cells as soon as temperatures rise. Hence, literally thousands of plant cells in the trunk become infected almost simultaneously, causing the development of masses of tumors along the ver­tical axis of the trunk.

PART II

In part one of this series, general information on the nature of crown gall was presented in some detail. The question posed at the end of the article was how does the crown gall bacterium get into grape plants.

It has long been known that the crown gall bacterium enters the plant through a wound, it is also clear that the pathogen is a soil inhabitant. Hence, wounds in the root zone due to growth and abrasion of root surfaces, insect damage and implement injury at or near the soil line provide sites for entry. These are all logical, yet hypothetical infection routes, as it is not known how frequently such wounds are follo~d by A. tumefaciens entry. For example, we don't know how long a wound actually remains infectible. Wounding itself brings about a wound-healing process that could prevent bacterial penetration.

What ~ have found recently in our own studies, based on the discovery of a Hungarian scientist in 1978, was that propagating wood taken from grape plants free of crown gall symptoms may nevertheless carry the bacterium in its vascular system. Hence, we and other scientists now suspect that we have been disseminat­ing the disease through vegetative propagation in our commercial nurseries. Keep in mind no nursery had a suspicion of this possibility until very recently.

Well, what can be done to solve this problem? How can we provide the nur­series with crown gall-free propagating material? This became the objective of our initial research in the Department of Plant Pathology, University of Missouri, Columbia, and is supported by Missouri Department of Agriculture wine tax funds. We have, as a consequence, developed a rapid indexing procedure (a process for determining whether grape wood is carrying the crown gall pathogen). Our first publication Plant Disease 70:566-568, describes the procedure and equipment of our design that forces sterile water under pressure through soft- or hard-wood cuttings. The water flushes the xylem vessels (the plant's water­conducting tubes) which is collected aseptically and spread on an agar medium and following a 5-day incubation period is examined for the presence of the crown gall bacterium. CUttings that are bacteria-free are rooted in a mist-bed and subsequently forced into rapid growth in the greenhouse. As new growth matures stempieces are cut from the plant and flushed once again for the presence of bac­teria. If the plant is again found bacteria-free it is put in the nursery row where it will serve as a source of crown gall-free propagating material. These plants will be examined at the beginning and end of each growing season for the presence of A. tumefaciens. If a plant has become reinfected it will be removed from the nursery.

At the present time we have 100-200 plants indexed as crown gall-free of the varieties, Chancellor, Seyval blanc, Vidal blanc, Catawba and Reliance. We have sent 25 indexed plants of each of these varieties to Drs. Mike Ellis (plant pathologist) and Garth Cahoon (horticulturist) at The Ohio State University Research Center, Wooster, Ohio. OUr major planting of these indexed plants is a McMurtrey Vineyards, Mt. Grove, Missouri and some of each variety is in our greenhouses at Columbia.

12

Most pressing currently is the answer to the question: how long will crown gall-free grape plants remain free of the pathogen? In addition, can we protect these indexed plants against reinfection?

PART III

It is clear from my observations and from comments of gro~rs in Missouri that crown gall is the pr:imary disease problem. This disease not only limits crop production, but with some varieties precludes their continued profitable culture. This is doubtless true for Chancellor and in my view the disease also threatens Seyval blanc. In the latter instance, we must wait to see whether this variety can, given reasonable winters and springs, outgrow the tumors and return to normal development.

It is apparent that we now have a way of producing grape plants that are crown gall-free. However, we must also learn how long the indexed gall-free plants remain free of the disease once set in vineyard soils. This question must be answered, however, it does not mean that we should delay activating an index­ing program to provide crown gall-free nursery stock until we get that answer. It seems that our initial and perhaps only efforts in Eastern United States should be with those cultivars that are highly sensitive to crown gall and are im{X)rtant to the wine and grape industry. At this moment the three cul ti vars im­portant to Missouri that are vulnerable are Chancellor, Seyval blanc and Vidal blanc. We are in the process of developing a supply of indexed "mother plants", that can be placed in the hands of nurserymen for commercial propagation. A con­tinuing monitoring service must be maintained to insure that "clean" foundation plantings remain free of crown gall.

One may raise the question whether other varieties are sensitive to crown gall. We have to the present examined 14 varieties and, with an efficient laboratory procedure, assessed their sensitivity to crown gall. These varieties are listed below and our current view is that cultivars with callus weights of • 2o-. 25 g (grams) or less have a "tumor-{X)ten tial" which seems not crop limiting.

CALLUS PRODUCTION BY CULTIVARS AND SPECIES IN 16 DAYS ON WPM MEDIUM

1. v. cinerea 2. v. amurensis 3. Concord 4. Reliance 5. catawba 6. Villard Noir 7. Colobel 8. 1844 9. Kek Frankos

10. Chancellor 11. Seyval blanc 12. Vidal blanc 13. cabernet Sauvignon 14. J. Riesling 15. Chardonnay

13

0.05 g (grams) 0.05 g 0.15 g 0.18 g 0.23 g 0.26 g 0.37 g 0.38 g 0.51 g 0.54 g 0.59 g 0.65 g 0.69 g 0.89 g 0.96 g

We are in the I;rocess of expanding the list to include cultivars that may have applicability to Missouri: ie., Vignoles (Ravat 51), Chambourcin, Norton, Virginia Seedling, Leon Millot, Baco noir, Marechal Foch and others.

Our callus production procedure has remained 100% correlative, that is to say, high callus production indicates high sensitivity to crown gall. Hot.Never, tNe know that there are other factors that influence "sensitivity" (here we mean actual gall size that develops in the field). One of these is earliness of bud break (or time of tissue reactivation in spring). For example, Marechal Foch and Leon Millot are obviously field sensitive and they are very early varieties. The same is true for Vignoles, and, although we have not tested these varieties yet for callus production. We are in the process of checking these and other cul­tivars now. I believe that early activation of plant cell activity in a variety places it at greater risk of damage by spring frosts.

Another mitigating factor in cultivar sensitivity is, we believe, sen­sitivity to the native hormones indole-3-acetic acid and cytokinins. Research in our laboratory is in full swing concerning this question. It should be possible with relatively simple experiments to determine, with high accuracy, which cul­ti vars are crown gall risks.

Other research in progress is concerned with selection from Chancellor cal­lus, cells frcm which whole plants can be derived that are "insensitive" to crown gall. We are also testing the activity of an Agrobacterium radiobacter isolate that is antagonistic to the biovar 3 form of Agrobacterium tumefaciens. success in the latter aspect would permit us to protect iridexed Plants agamst reinfection.

14

UNDERSTANDING SEEDLESSNESS IN GRAPES

Craig K. Chandler Department of Horticulture Ohio State University/OARDC

Wooster, OH 44691

To classify certain grape varieties as seedless is somewhat of an over simplification. Very few varieties of grapes are truly seedless. In most seed­less varieties, seeds start to develop, but at some point before the seed coat hardens, the embryo of the seed aborts and the seed begins to degenerate. Depending on when seed development stops, the degree of seedlessness can range from vestiges of seeds barely visible to relatively large, soft seeds.

The length of seed development can vary from variety to variety, and even from location to location. For example, the variety Venus when grown in Arkansas is considered seedless. When grown in Ohio, Venus produces hard seeds.

Chemical treatment can also affect seedlessness. In some normally seeded varieties, gibberellic acid applied to immature flower clusters will cause ber­ries to be seedless. Japanese growers dip flower clusters in a solution contain­ing gibberellic acid to produce seedless grapes on the variety Delaware.

Pollination is usually required in seedless varieties for adequate fruit set, and the size of the mature berry is related to the number of partially developed seeds.

~though seedless grape varieties have been arot.md for centuries, the cause of seedlessness (i.e., embryo abortion) is not fully understood.

Seedlessness in some crops is due to male and female sterility resulting from an unbalanced number of chromosomes in the parents. The cultivated banana plant is a good example of a seedless crop that is both male and female sterile: it produces neither viable pollen or ovules. Unlike most grape varieties which have 2 sets of chromosomes, the cultivated banana plant has 3 sets of chromosomes. It is the extra set of chromosomes that causes sterility. Seedlessness in bananas is mu:::h more complete than it is in grapes: whereas seeds in banana are nonexistent, mature, hard seeds have been reported in practically all seedless varieties of grapes.

~though we don't know exactly what causes seedlessness in grapes, we do know that there is some genetic control of seedlessness. In other words, the seedless trait can be transmitted from parent to offspring.

Because seedless grapes are so popular and there are relatively few commer­cially acceptable seedless varieties, the development of new seedless varieties is one of the principle objectives of grape breeders.

Unfortt.mately, the development of seedless varieties has been hampered by 3 major problems: 1) until very recently, seedless varieties could only be used as male parents. Their pollen is generally viable so they work fine as males, but because their seeds fail to mature, they haven't been suitable as females. 2) The frequency of seedlessness in the offspring of crosses between seeded and seedless parents is very low, averaging about 15%. 3) There is no way to tell at

15

an early age whether a seedling is going to be seedless or seeded. Seedlings must be planted in the field and fruited before a determination can be made. Because, on average, only 15 out of 100 seedlings turn out to be seedless, breed­ing for seedlessness is very expensive in terms of land and labor.

Despite the inefficiencies of breeding seedless grapes, breeders have had some success. Jim Moore of the University of Arkansas selected the variety Reliance from the offspring of 'Ontario' by 'Suffolk Red'. 'Ontario', the female parent, is a seeded variety, and 'Suffolk Red', the male parent, is a seedless variety.

Breeders, of course, are interested in increasing the percentage of seed­lessness in their breeding populations, and there is reason to believe they can. It is now thought that seeds of seedless varieties abort, or fail to mature, not because of any problem with the seed per se, but because there arises a type of incompatibility between the seed and the surrotmding maternal tissue. If the seeds were carefully removed from the fruit before their development ceases--or the embryo aborts--and are placed in a more favorable environment, development may proceed to completion. If normally abortive seeds can be 'rescued' in this way, it should be possible to make crosses between seedless varieties. In other words, seedless varieties could be used as both male and female parents. By having both parents seedless, the percentage of seedless offspring should be increased.

Researchers in california and Israel have recently been successful at "res­cuing" seeds before they abort. Under aseptic conditions, they remove developing seeds from fruit and place the seeds in petri dishes on an artificial medium con­taining agar, sugar, certain salts, vitamins and hormones. These researchers are working to improve their seed rescue techniques so that the techniques can be used as a regular part of grape breeding programs. With these new techniques available to them, grape breeders should be able to introduce an increasing num­ber of good seedless varieties in the future.

GRAPE ROOT BORER - A roTENTIAL NEW INSECT PEST IN OHIO

R.N. Williams, S.R. Alm, D.M. Pavuk, and F.F. Purrington Department of Entomology

Ohio Agricultural Research and Development Center The Ohio State University

Wooster, OH 44691

The grape root borer, Vitacea polistiformis (Harris), is a native insect belonging to the family of clearwing moths (Lepidoptera: Sesiidae). In this family, the damage is caused by the larvae or borers which are capable of con­siderable root and trunk destruction. Other clearwing moths which attack fruit crops are: peachtree borer, lesser peachtree borer, and raspberry crown borer.

The grape root borer has been recognized as a pest of grapes for over 100 years, primarily in the southeastern United States. Even though it has been known to exist in Ohio for many years, it has never been implicated as a pest in commercial vineyards.·

Pheromone Trapping the Grape Root Borer

A common method of monitoring populations of pest Lepidoptera involves plac­ing either caged virgin females or a synthetic sex pheromone adjacent to a sticky trap. The virgin female moth or the synthetic pheromone lures male moths to the trap. Entrapped male moths can then be comted at regular intervals. Presence and relative abundance of the pest moth species can be determined by this method.

In 1986, a new synthetic pheromone (sex attractant) was available to resear­chers for the first time. Rubber septa charged with this lure were placed in Pherocon lC sticky traps, which were set out in four commercial vineyards: three in southern Ohio and one in the north near Lake Erie. The traps were placed in the vineyards on June 1, and the septa were replaced after two months. Three traps were placed in each vineyard, and the number of captured male grape root borers were counted each week. Three southern Ohio locations collected large trap catches, indicating large populations of the grape root borer. This led to further studies in the fall to determine origin of the borer. Had they perhaps flown in from wild grapes growing in the vicinity of the vineyards being ex­amined? This was determined in two ways: l) examining the ground surface under vines for empty pupal cases (exuviae) and 2) digging up and examining roots of unthrifty vines for fresence of borers. Areas around the bases of vines were ex­amined for the presence of pupal cases, and substantial numbers of pupal cases were found in all three of the vineyards. Excavation and examination of the root systems of unhealthy vines in two of the vineyards revealed grape root borer lar­vae in the roots along with considerable boring and girdling. Death of grapevines that had been previously blamed on other causes such as winter kill and disease infestations may in fact be the direct result of heavy grape root borer infestations. This was the first evidence to indicate the ootential economic importance of the grape root borer to Ohio growers. -

Description & Life eycle (Fig. 1)

The clearwing moths are characterized by having large areas of either one or both pairs of wings devoid of scales. The adults of many sesiid sr:ecies m~m~c wasps in appearance. The grape root borer itself looks very much like a Polistes

17

wasp (Fig. 2). The forewings of the grape root borer are brown and the hind wings are clear with brown borders. The body is brown with yellow markings. The length of the male moth is about 5/8 of an inch (1.6 em), while that of the female is about 3/4 of an inch (1.9 em). The wingspan of the grape root borer ranges from 1 to 1 1/2 inches (2.5-3.8 em}. In southern Ohio, grape root borer adults emerge fran pupae at the soil surface from late June through septerrber. The moths are day fliers, much like the Polistes wasp which they mimic. After mating, the female deposits eggs on weeds, grape leaves, and grape trunks, at­taching the eggs to these substrates with a weak adhesive material. A single female lays an average of about 350 eggs over an 8-day period. Upon hatching, the larvae burrow into the soil, and find their way to the roots and crown of grapevines to feed. Larvae remain in the soil approximately 22 months. When fully developed, the larvae is about 1 1/2 inches long and is white with a brown head (Fig. 3). Mature larvae move to places just under the soil surface, make silk cocoons within earthen cells and pupate (Fig. 4). Following pupation, which lasts 30 to 45 days, the pupa pushes through the tip of its cocoon and to the soil surface by way of spiraling movements of its body. The adult moth then emerges from the exuvium and climbs onto whatever substrate is available to ex­pand and dry its wings.

Conclusion

Since the grape root borer is difficult to control once the larvae have en­tered the soil and have begun feeding on the roots, it is critical that this in­sect's presence be determined at the time the adults become active. The develop­ment of a synthetic sex pheromone for the grape root borer has provided a simple method for monitoring this serious pest of grapes. Consequently, knowledge of flight activity of Vitacea polistiformis permits more accurate timing of insec­ticidal sprays for ~ts control. In addition, we now have a highly sensitive method to determine the range of the grape root borer in Ohio. Thus, the dis­covery of a synthetic sex pheromone for the grape root borer, Vitacea polistifor­mis, gives us a useful tool for monitoring and managing this insect ln Ohio vineyards.

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Spring

Soil line

LIFE CYCLE

GRAPE ROOT BORER

'lfitace~ polistiformis !Harris)

pupal case

Fig. 1. Diagram of the two-year life cycle of the grape root borer.

20

Jric;l. 2. Adult femal,e grape root borer with bright yellow bands around body.

Fig. 3. Larva of grape root borer showing damage to roots.

Fig. 4. Pupa and mature larva of the grape root borer.

THE USE OF POTASSIUM SORBATE AND ASCORBIC ACID IN WINE

INTRODUCTION

Thomas R. Schmidt Miles Laboratories, Inc.

Elkhart, IN

PART I: POTASSIUM SORBATE

The use of potassium sorbate as an antimicrobial agent throughout the food and beverage industry is well-known.

Potassium sorbate is commonly used in dairy products, baked goods, syrups, toppings, pickled vegetables, sausages, pet foods, packaging materials, prepared salads, standard wines and wine coolers.

FEDERAL REGULATIONS

Potassium sorbate, FCC, NF is "generally recognized as safe" (GRAS) as a chemical preservative under 21 CFR 182.3640 when used in accordance with good manufactur­ing practices. It is allowed in standard wines as a sterilizing and preservative agent and to inhibit mold growth and secondary fermentations at levels not to ex­ceed 0.1% (27 CFR 240.1051).

MODE OF ACTION

Fungi (yeast and molds) are the primary targets for potassium sorbate, however, certain bacteria associated with food spoilage are also inhibited. The effectiveness of potassium sorbate has been shown to be due to the inhibition of the dehydrogenase systems (Desrosier and Desrosier, 1977). In order to interfere with microbial metabolism, it is necessary for the sorbate to pass through the cell merrbrane. This leads to a very important concept in the use of these preservatives.

The cell membranes of yeast and molds are ionically charged and will not al­low the transfer of negatively charged molecules. At neutral or near neutral pH's, the sorbic acid molecules are near complete ionization resulting in nega­tively charged molecules. In this form, they cannot be transported across the cellular membrane are are ineffective. As the pH is lowered, the added hydrogen ions force the sorbic acid molecules to associate, reducing their charge and al­lowing them to be transported across the cell membrane. The ratio of the ionized form to the free acid form changes proportionately to the pH. The pH at which the ratio is 1 is defined as the pk of the acid. The pk of sorbic acid is 4.7. At pH 4.7, one-half of the sorbic a~id present will be inaits effective free acid form. As the pH is lowered below the pk of the sorbic acid, the effectiveness increases. Conversely as the pH raises,athe effectiveness decreases.

SOLUBILITY

Since the effective form of potassium sorbate is the un-ionized sorbic acid, the qu:stion that quickly surfaces is "why not use sorbic acid instead of the potassium salt?" In certain applications this is the preferred choice. However,

21

due to the limited solubility of sorbic acid, the more soluble potassium salt is more co1m10nly used. A comparison of solubilities best illustrates the point.

The solubility of sorbic acid is within the normal use ranges but its low solubility and slow solubility rate may cause problems that are more easily avoided using the potassium salt. The use of a concentrated stock solution is also not possible with the acid form.

USE OF POTASSIUM SORBATE IN STANDARD WINE

In bottled table wines, the potential for two types of microbial spoilage exist. Bacterial spoilage in bottled wines is in most cases caused by lactic acid producing bacteria. Adequate levels of sulfur dioxide will inhibit this bacterial growth and spoilage in wines. Secondary fermentations in bottle table wines are also possible and caused by yeast growth. Secondary fermentations can be inhibited by the addition of potassium sorbate. Care must be taken to ensure that adequate levels of sulfur dioxide are present to prevent lactic acid spoilage, or an unpleasant geranium off-odor may be produced by the lactic acid producing bacteria in the presence of potassium sorbate. This very intense, un­pleasant odor is formed by the action of lactic acid producing bacteria on sorbic acid in the presence of ethanol (Cromwell and Gaymon, 1975). Both the sulfur dioxide and potassium sorbate must be present in adequate quantities to prevent spoilage of bottled table wines.

The actual amount of potassium sorbate added to a wine will depend on sugar concentration, acid concentration, alcohol concentration and the level of sulfur dioxide used. Evidence suggests that white table wines need less potassium sor­bate than to red table wines. In white wine 75 ppm potassium sorbate with 200 ppm total sulfur dioxide was found to be adequate, whereas, 100 ppm potassium sorbate with 300 ppm total sulfur dioxide was required in red wine to achieve equal results (Auerback, 1959). Wines with high alcohol content require little or no potassium sorbate or sulfur dioxide since the alcohol has a preservative effect of its own. The lower alcohol sweet table wines require high sulfur dioxide levels with potassium sorbate added.

The use level of potassium sorbate can also be self-:limiting due to its taste threshold in wine. Taste threshold values of potassium sorbate in wine have been reported in a range of 135 ppm for trained panels OUgh and Ingraham, 1960) to 300 ppm for untrained panels (Rzedowski and Wajcieszak, 1960).

The normal use level of potassium sorbate in wine is 150 to 200 ppm.

METHODS OF ADDITION

To ensure ease of incorporation of potassium sorbate into an acid containing system such as wine, a few basic steps should be followed.

If potassium sorbate is added directly to an acid containing system, the likely result will be localized pcecipitation of sorbic acid. It will eventually dissolve in the system if used within legal limits but time and agitation will be required and in some cases heat. To avoid unnecessary delays, it is best when­ever possible to dissolve the potassium sorbate in a small amount of water before addition to the wine.

22

Most beverage processors prepare a concentrated stock solution of the preservative for later addition to the formulation. In situations where it is necessary to add the preservative system into the acid containing portion of the formulation, it is almost imperative that a predissolved stock solution be slowly added with constant agitation to prevent localized precipitation.

Potassium sorbate and sulfur dioxide when used in conjunction with good manufacturing practices will effectively prolong the storage life of wine products and inhibit spoilage.

LITERATURE CITED

Auerbach, R.D. 1959. Sorbic acid as a preservative agent in wine. Wines & Vines 40:26-28.

BATF, 1986. Code of Federal Regulations, 27 CFR 240.1051.

Cromwell, E.A. and Guyman, J.F. 1975. Wine constituents arising from sorbic acid addition and identification of 2-ethoxyhexa-3,5-diene as a source of gerani~like off-odor. Am. J. Enol. Viticulture 26(2):87-102.

Desrosier, N.W. and Desrosier, J.N. 1977. The technology of food preservation. AVI Publishing Co., Inc. Westport, CT.

FDA, a. 1986. Code of Federal Regulations, 21 CFR 182.3640.

FDA, b. 1986. Code of Federal Regulations, 21 CFR 184.1733.

Ough, C.S. and Ingraham, J.L. 1960. Use of sorbic acid and sulfur dioxide in sweet table wines. Am. J. Enol. Vitic. 11:117-122.

Rzedowski, w. and Wajcieszak, P. 1960. use of sorbic acid in wine preservation. Przemysl. Spozywczy. 14:454-459.

23

PART II: ASCORBIC ACID

INTRODUcriON

Ascorbic acid has been used extensively by the food industry since 1795, when the British physician James Lind successfully treated scorbutic sailors with citrus juices. One of the first modern food applications of ascorbic acid occur­red over 35 years ago when it was used to stabilize beer. Today ascorbic acid is used in foods and beverages as a vitamin, an acid, a curing agent, an anti­oxidant, and anti-browning agent, a color stabilizer, a bread impc-over, and a clarity improver in beer.

FEDERAL REGULATIONS

Ascorbic acid, FCC, USP in "generally recognized as safe" (GRAS) as a chemi­cal preservative (21 CFR 182.3013), a dietary supplement (21 CFR 183.5013) and a nutrient (21 CFR 182.8013).

PHYSICAL PROPERTIES OF ASCORBIC ACID

Ascorbic acid is available as white, odorless crystals or powder. It is a water soluble acid that forms salts and is an effective reducing agent.

In the dry form, ascorbic acid has excellent stability. If wetted or in solution, ascorbic acid is very sensitive to oxygen, heat and trace metals.

FUNCTIONS OF ASCORBIC ACID

The three major functions of ascorbic acid in foods and beverages are nutrient, oxygen inhibitor (anti-oxidant) and browning inhibitor.

Nutrient ApPlications: Numerous foods today are fortified or enriched with ascorbic acid. The recommended daily allowance (RDA) of Vitamin C for most people is 60 mg per day.

Antioxidant ApPlications: Being a strong reducing agent, ascorbic acid performs as an antioxidant by donating hydrogen ions to molecular oxygen. In doing so, ascorbic acid is pceferentially oxidized, thereby protecting the flavor and color of a number of products.

Used at a rate of 3. 3 mg per ml of air in the headspace of a packaged deoxygenated juice, ascorbic acid can provide an extended shelf-life for juices.

The effectiveness of ascorbic acid as an antioxidant is dependent upon numerous factors that affect the degradation or oxidation of ascorbic acid. These factors include temperature, solute concentration, pH, oxygen concentra­tion, enzyme activity, metal catalysts, amino acids, oxidants and reductants, initial concentration of ascorbic acid and the ratio of ascorbic acid to dehydroascorbic acid.

Ascorbic acid has been used with only moderate success as an antioxidant in wine. Although it readily reacts with dissolved oxygen, it forms hydrogen peroxide which is a very potent oxidizing agent. The hydrogen peroxide formed can rapidly oxidize other constituents of the wine or juice. If sufficient

24

sulfur dioxide is available to react with the hydrogen peroxide, most of the adverse effects are avoided. Ascorbic acid, when used in wines, is used at a usage level of approximately 100 ppm (100 mg/1).

Anti-Browning Applications: In general there are four basic types of brown­ing reactions that occur in foods and beverages: Maillard, carmelization, ascor­bic acid oxidation and enzymatic or phenolase browning.

Enzymatic browning is due to the enzyme catalyzed oxidation of phenolic com­pounds to orthoquinones. The o-quinones rapidly polymerize to form brown pig­ments or melanins. The enzymes that catalyze this reaction are commonly known as phenolases, polyphenolases, tyrosinases or catecholases.

Ascorbic acid, as a very effective reducing agent, reduces the orthoquinones formed by phenolase action to the original o-dihydroxyphenolic compounds. In the presences of sufficient ascorbic acid, the browning reaction is limited to the production of the o-quinones without further reactions to the melanins.

LITERATURE CITED

BATF, 1986. Code of Federal Regulations, 27 CFR 240.1044.

FDA, 1986. Code of Federal Regulations, 21 CFR 182.3013, 182.5013, 182.8013.

Ough, c.s. 1987 • .January 5, 1987.

Chemicals used in making wine. Chemical and Engineering News. pp. 19-28.

Tannenbaum, S. 1976. Vitamins and Minerals. "In Principles of Food Science" (0. Fennema, ed.) 1976. Marcel Dekker. pp. 360-364.

25

STATUS OF SULPHUR DIOXIDE

Domenic Carisetti Canandaigua Wine Company

Canandaigua, NY 14424

As of January 9, 1987, all new labels submitted to the BATF for approval representing alcoholic beverages affected by sulfite labelling that contain 10 ppm or more total so2 shall bear a mandatory sulfite declaration. The mandatory declaration can be generic or specific, depending on the option chosen by the producer. The BATF feels that generic statements best serve to alert individuals sensitive to sulfites. A generic statement can be "contains sulfites", "contains a sulfiting agent", or "contains sulfiting agents". A specific mandatory decla­ration identifying the sulfiting agent by its common name, such as "sulfur dioxide" or "potassium metabisulfite" is also allowed. In addition, firms will be given the option of stating, in addition to the mandatory statement, the ppm of free so2 present at bottling provided this information is preceded by a state­ment of the ppm sulfites measured as total so2 immediately prior to bottling. Statements showing free so2 without total so2 will not be allowed. Mandatory labelling may appear on neCk, strip, front or back labels.

As of July 9, 1987, all alcoholic beverages, excluding those products under 7% alcohol, shall be labeled with the mandatory sulfite declaration.

Products that wre bottled before July 9, 1987, can be removed from the premises without the declaration. As of January 9, 1988, no products can leave the winery without a mandatory labelling statement. Labels already covered by certificates of approval will not need to be resubmitted for re-approval of sul­fite labelling.

If anyone files an application for label approval for wine which is believed to contain less than 10 ppm sulfites, measured as total so2, samples must be sent to the BATF for analysis before label approval can be issued not requiring the mandatory sulfite declaration. The 10 ppm tolerance is below the threshold of sulfite-sensitive asthmatics. It is also based on analytical capability since levels under 10 ppm cannot be detected w~th the degree of reliability needed for compliance actions. The current approved method for detecting so2 at low levels is Monier-williams: however, the method is time-consuming and inefficient when running many samples. The Canandaigua Wine Company is part of a collaborative study with the BATF, AOAC and other members of the wine industry in evaluating a combination Ripper/aeration-oxidation method to measure low levels of so2 in wine in a timely and inexpensive manner.

In summary, so2 labelling has arrived and full compliance for all alcoholic beverages is mandatory by January 9, 1988. The current method for determining low levels of so2 is being evaluated and it is hoped a new method will be avail­able for use economically by all alcoholic beverage manufacturers in the near future.

26

FACTORS AFFECTING GRAPEVINE BUD COLD HARDINESS

Tony K. Wolf Winchester Agricultural Experiment Station

VPI and SU Winchester, VA 22601

Maximizing grapevine cold hardiness is a goal wherever cold-tender grapevines are grown in environments experiencing unfavorably low temperatures. we can speak of vine cold hardiness in terms of the entire plant or the hardiness of a specific tissue. My comments here apply chiefly to the cold hardiness of dormant buds. I have two reasons for emphasizing bud cold hardiness. 'First, al­though buds and the YlOOd of canes and trunks may differ in absolute hardiness, bud cold hardiness tends to parallel wood hardiness. Thus, a knowledge of bud cold hardiness provides a relative measure of vine hardiness. Second, we have a relatively convenient and rapid means of evaluating bud cold hardiness--much more direct than measuring the cold resistance of cane and trunk tissues.

Following a severe winter, we often find poor shoot development on cold­injured vines. Many nodes may fail to produce shoots. What we would like to know is why do some buds survive and produce shoots while other buds are killed by cold? Is there a random component contributing to the observed injury? How do factors such as variety, vineyard management, and environment affect bud cold hardiness and bud survival?

Although we know that grapevine species and cultivars differ in their ability to cold acclimate, we do not fully understand the physical and chemical bases of cold acclimation events. we do know that cold acclimation processes are triggered by environmental as well as internal factors that interact over time (Fig. 1). The primary environmental stimulus affecting vine cold acclimation is decreasing temperature. The environmental and internal factors cause changes in vine physiology which we can observe as a cessation of vegetative growth and the maturation of periderm (bark) tissues of shoots as they develop into canes. A number of biochemical changes occur within the tissues and cells of cold ac­climating plants. Collectively, these changes are considered to confer greater cold resistance. Note that the ultimate degree of cold hardiness attained is a function of the vine's genetic composition (Fig. 1).

Dormant grapevine buds avoid freezing by a process referred to as supercool­ing. Supercooling defers the freezing of tissues to a temperature below the freezing point of the tissue solution. In other words, if we could extract the moisture from buds that supercool to -20°F and freeze it, we might find that it froze at -3°F rather than at -20°F. Why buds supercool is not entirely clear but anatomical barriers may be involved which prevent ice, which forms in the ad­jacent node tissue and bud scales from 'seeding' or nucleating the supercooled moisture in the bud primordia. There is a limit to how cold buds will supercool. Injury to buds occurs when the supercooling is broken and the shoot primordia freeze. This freezing occurs within cells (intracellular) and is always lethal. Injury can be observed as a browning of the primordia when frozen buds are warmed and cross-sectioned with a razor. Supercooled tissues release heat when they freeze. We can detect this heat with sensitive recording equipment and thus, determine the temperature of the freezing event. Again, because freezing is as­sociated with bud death, we can determine the cold hardiness of buds by freezing

27

them mder controlled conditions. We've used this procedure to probe some of the questions posed above.

A ftmdamental factor affecting bud cold hardiness is variety. We are cur­rently examining the relative cold hardiness of some of the less commonly planted vinifera and hybrid varieties that show potential for Virginia. 'Cabernet franc' buds, for example, have exhibited greater cold hardiness than 'Cabernet Sauvignon' buds as measured in controlled freezing tests during the 1986-87 wint­er (Table 1). These data substantiate the limited field experience we've gained with 'Cabernet franc' and suggest that it may be ltl:)re apt to produce consistent crops in cold climates than 'Cabernet Sauvignon'.

There is interest in understanding, and predicting if possible, how dormant bud cold hardiness is related to ambient temperatures during the winter. It is well recognized that buds are more apt to be injured by rapid temperature changes than by gradual cooling to the same minimum temperature. Buds attain their maxi­mum hardiness during prolonged periods of sub-freezing temperatures. Transient, above freezing periods result in some loss of hardiness. Researchers at Washington State University proposed a concept suggesting that for most of the dormant period, the buds possess a "minimum hardiness level" that prevents buds from deacclimating beyond a certain level during these transient warm periods. Sub-freezing temperatures will, however, result in further increases in cold har­diness. In work we conducted in New York, the hardening effects of continual sub-freezing temperatures between early January and mid-February were apparent with five cultivars during the 1984-85 winter.

Cold acclimation and cold hardiness are dependent upon tissue maturation. Buds acquire an ability to supercool and resist freezing injury concomitant with the visual maturation of periderm at those nodes. Bud cold hardiness, as related to visual tissue maturity, was evaluated using individual 'Chardonnay' and 'White Riesling' shoots in September, 1985. Nodes and adjacent internodes of these shoots ranged in appearance from brown and well-matured basal nodes to green and non-matured at the more apical nodes. As can be seen from the data of Table 2, bud freezing resistance was associated in a positive manner with the visual maturation of the node(s) at which the bud is borne. Maximizing the degree and extent of tissue maturation is a ftmdamental means of maximizing grapevine cold hardiness. A general statement can be made that management of vines to promote sustained yields of high fruit quality is consistent with the goal of promoting maximal cold hardiness. Vine cold hardiness requires energy. This energy is derived from photosynthesis and the carbohydrate products of this light-dependent reaction. Cultural ~actices consistent with maximizing total canopy photosyn­thesis are generally conducive to maximal hardening or acclimation rates. Maximizing photosynthate production requires maintaining healthy foliage which is evenly distributed to prevent the development of heavily shaded canopy interiors. Bud cold hardiness data collected from 'Chardonnay' vines in 1985 illustrate that the location in the canopy that buds are borne affects their cold hardiness (Table 3): buds and canes borne within heavily shaded canopies are typically less hardy than buds and canes that developed in more exterior positions. This is one reason to select exterior wood for retention at pruning. Effective disease and insect control and adequate nutrient supply are also necessary for maintenance of healthy foliage. Greater than optimal rates of essential nutrients do not in­crease vine cold hardiness. carbohydrates accumulated by ripening fruit can, al­ternatively, be used by shoots to develop mature tissues in their transition to

28

canes. overcropping vines thus reduces the amount of carbohydrates available for shoot maturation and significant cane die-back is observed after fall frosts.

TABLE 1. comparison of 'Cabernet Sauvignon' and 'Cabernet franc' bud cold hardiness, 1986-87: Linden Vineyards, Virginia. Approximately 30 buds were evaluated with each cultivar at each date.

Cultivar 10/16 11/6 12/10 l/13 Median Low Temperature Exothermz

2/5

Cabernet Sauvignon 20.3 -1.4 -1.3

Cabernet franc 17.6 0.5 -2.2 -3.1

zTemperature (Op) required to kill approximately 50% of primary buds.

TABLE 2. Relationship between visual shoot maturation and the cold hardi­ness of primary buds of Chardonnay grapevines in September, 1985.

Appearance of node at which bud was obtained Sample Date Brown Transitional Green

Sept. 10 LTE Range 14 to 8.5 16 18.5 MLTE* 10.5 16 18.5

Sept. 14 LTE Range 16.5 to 15 19.5 to 16 none MLTE* 16 16.5

Sept. 22 LTE Range 14 to 8.5 19.5 to 14 17.5 MLTE* 10.5 17.5 17.5

Sept. 30 LTE Range 13 to 7.5 22 to 12 none MLTE* 8.5 16.5

*MLTE = Median low temperature exotherm; temperature (°F) required to kill ap­proximately 50% of buds.

29

TABLE 3. Effect of canopy location of node on 'Chardonnay' dormant bud cold hardiness. Buds were collected from vines having clearly defined interior and exterior regions of the canopy.

Date Canopy Location

3/30/85 Exterior

Interior

11/11/85 Exterior

Interior

Median LTE

4.1

5.0

-o.4

2.3

zTemperature required to kill approximately SO% of primary buds.

30

Endogenous Cues: Hormone Balance Shifts

Envirorunenta..l Cues: Temperature Light Moderate Physiologk S~ss

Tissue Maruration Growth Cessation Quantitative and Qualitative Changes in Nucleic Acids

Bud Rest?

0

Biochemical Changes: ·Quantitative and Qualitative Changes in the Olemical Composition of biD­membranes

• Accumulation of Compauble Solutes

Anatomical Changes

Inherent Generic Constrain

Degree of Acclimation

100

Figure 1. A hypothetical scheme of events thought to occur during the ini­tial ~hases of cold acclimation in woody ~lants such as grap:vines.

31

\ PRESERVATION OF FRESH CONCORD JUICE

C.L. Stamp, J.F. Gallander and J.F. Stetson Department of Horticulture

The Ohio State University/OARDc Wooster, C6 44691

The successful preservation of fresh Concord juice includes both color and microbial stability. With the use of refrigeration, adequate levels of sorbic acid, and good sanitation, fresh Concord juice can be stored biologically sound for at least 8 weeks. However, when packaged in plastic containers, oxidative browning becomes a ~imary problem in maintaining color stability.

Therefore, this investigation was conducted to determine the effect of cer­tain chemical additives on color stability of fresh Concord juice.

SULFUR DIOXIDE

Concord grapes were harvested by a commercial winery in Northern Ohio and trans};:Orted to OARDC for processing. After the grapes were desterrmed and crushed, the must was divided into 4 lots which were treated with O, 25, 50, and 100 ~ of sulfur dioxide~ Each lot was left on the skins for 10 minutes, and then pressed at 29 lbs/in • Table 1 details the analysis of the pressed juice before the sulfur dioxide treatments.

TABLE 1. Concord juice analysis

Harvest Date: 10-21-86 Bar.rest Location: Madison, Ohio 0 Brix: 16.4 pH: 3.38 T. A.: .69%

After cooling each juice lot to 32°F, the clear juices were racked and were treated with 500 ppn potassium sorbate. Then, the juices were filled into 1 quart plastic containers and stored at 55~ and 32°F for 8 weeks.

To monitor the color stability, juice samples were filtered through a 0.~5 :nernbrane filter and absorbance readings were taken at 420 nm and 520 nm. These readings were obtained for juices stored at O, 2, 4 and 8 weeks for both tempera­tures (32°F and 55°F).

Juices treated with 50 ppm sulfur dioxide at 0 weeks storage were highest in brightness (Table 2). At 100 ppm sulfur dioxide, the brightness of the juices •;.as lowest of the trea~~nts. This low brightness value was due to the bleaching effect of the high level of sulfur dioxide. The highest brighG,ess level occ~r­red in juices with 50 ppm sulfur dioxide, indicating that more color was extrac­ted at this level of sulfur dioxide.

32

TABLE 2. Effects of sulfur dioxide levels on the color of fresh Concord juice stored at 55°F.

so2 Level (ppm)

0 25 50

100

1 . h Ab b Br~g tness: sor ance

Brightness of Juice at zero 'Weeks

1.44 L76 2e08 1.22

at 420 nm + 520 nm

Results concerning the effect of two sulfur dioxide levels on the color stability of juices which were stored at 0, 2, 4, and 8 weeks are shown in Table 3. By visual inspection of the samples, a hue value below 1.0 indicated that these particular samples were unacceptable for color. The juice treated with 50 ppm sulfur dioxide maintained acceptable color throughout the 8 weeks storage period at 55°F. At 25 ppm sulfur dioxide, the juice was visually unacceptable after 4 weeks storage.

TABLE 3. Effects of sulfur dioxide levels on the color of fresh Concord juice at ss0p.

so2 level (ppm)

25 50

1 Hue Value of J~ce at different holding times 0 wks 2 wks 4 wks 8 wks

1.76 2.08

1.05 2.15

.91* 2.10

.63* 1.72

1Hue Value: Absorbance at 520 nm/420 nm *Juice color of these samples was unacceptable

Juices treated with 50 ppm sulfur dioxide and stored at 32°F were found to have a higher hue value than those held at 55°F (Table 4). In addition, the decrease in hue value during the 8-week storage period was less for juices stored at 32°F. However, all juices were acceptable by visual observation throughout the 8 weeks.

33

TABLE 4. Effects of temperature on the color of stored fresh Concord Juice which was treated with 50 ppm sulfur dioxide.

Temp. Hue Value1 of juice at different holding times OF 0 wks 2 wks 4 wks 8 wks

32 2.06 2.22 2.23 1.96

55 2.08 2.15 2.10 1. 72

1aue Value: Absorbance at 520 nm/420 nm

Pectic Enzyzye: For this experiment, Concord grapes were harvested from the OARDC vineyards l.n Wooster and were transported to the Department of Horticulture for processing. After the grapes were desterruned and crushed, the must was divided into 4 lots and each lot received one of the following treatments:

Pectic Enzyme so2 Lot # (oz/1000 gal) (ppm)

1 0 0 2 4 0 3 0 50 4 4 50

Then, each lot was divided into 3 sublots which were exposed to O, 4, and 12 hours of skin contact time at 55°F. After each contact time, the musts were pressed, and the juices were settled for 12 hours. Absorbance readings at 520 run were obtained for each juice treatment to determine the level of red color.

Results of this investigation indicated that the level of sulfur dioxide and pectic enzyme had a strong influence on color extraction for making fresh Concord juice (Table 5). Although the effect of skin contact on juice color was found, the influence was not as great as the other two treatments. For all treatments, the addition of sulfur dioxide and pectic enzyme, and 12 hours of skin contact time tended to produce a juice with the highest color reading. This color level was slightly above the reading for juice made from 4 hours of skin contact. Since an extended skin contact time (12 hours) may provide a juice with high mic­robial populations, a shorter shelf-life, 4 hours skin contact, plus sulfur dioxide (50 ppm) and pectic enzyme (4 oz. per 1000 gal.) seem to be the best processing practice.

34

TABLE 5. Effects of sulfur dioxide and pectic enzymes on the color of fresh Concord juice

P.E. level

so2 level Color color1 at different skin contact times

(oz/m gal) (EEm) 0 hrs 4 hrs 12 hrs

0 0 0.60 0 .. 77 0.70 4 0 0.63 1 .. 00 1.37 0 50 1.02 1.45 1.63 4 50 0.99 1.44 1.98

1eolor: Absorbance at 520 nm

Glucose Oxidase: Glucose oxidase is an enzyme derived from Aspergillus niger. This enzyme plus catalase is contained in an enzyme preparation that is often used in the beverage industry as an antioxidant. The activity of this glucose oxidase/catalase enzyme system is illustrated by the following reactions:

Glucose + o2 + HtJ Glucose oxidase D-glucono -lactone

+ H202 Catalase HtJ + 1/2 02

NET REACTION

Glucose + 1/2 o2 D-glucono- lactone

To study the effectiveness of glucose oxidase as an antioxidant in fresh juice, Concord grapes were harvested from a vineyard in Northern Ohio and transported to OARDC for processing. After the grapes were destemmed and crushed, the must was treated with 500 ppm sorbic acid. After settling at 32°F, the juice was racked and divided into 3 lots. These lots were treated with 5, 10 and 15 ml/1000 liters glucose oxidase (Biocon, Inc., Glucose Oxidase B, 1500 U/ml). Then, the juices were filled into 1 quart plastic containers and stored at 55°F. Color values for each treatment were determined at 0, 2, 4, and 8 weeks storage.

Results indicated that the glucose oxidase levels used in this study were not effective in preserving juice color (Table 6). Even the juice samples at 2 weeks for all enzyme treatments were considered as unacceptable in color. Previous results indicated that browning index values less than 1.0 usually denoted juices with undesirable color.

35

TABLE 6. Effect of glucose oxidase Q_n the browning index value of fresh Concord juice.

Glucose Oxidase level

Browning Index1 value of juice at different storage times

(ml/1000 L) 0 wks 2 wks 4 wks 8 wks

5 10 15

1 .. 16 1.26 1.29

0.60 0.64 0.63

0.47 0.51 0.53

1Browning Index: Absorbance 520 nm/ 420 nm.

0.43 0.44 0.45

Ascorbic Acid: To test the effectiveness of ascorbic acid (Vitamin C) as an antioxidant, fresh Concord juice was purchased and transferred to OARDC. This juice was filtered and treated with 500 ppm sorbic acid at the juice processor. Also, 50 ppm sulfur dioxide was added at the time of crushing. At OARDC, the juice was divided into two lots and treated with 0 and 40 mg/100 ml ascorbic acid. Then, the juice from each treatment was transferred to 1 quart plastic containers and stored at 55°F. Absorbance readings were taken at o, 2, 4 and 8 weeks storage. ·

Table 7 lists the analyses of the fresh juice prior to the addition of as­corbic acid.

TABLE 7. Concord juice analysis.

Harvest Date: 10-21-86 Harvest Location: Madison, Ohio 0 Brix: 16.5 pH: 3.40 T.A.: 0.68

Results indicated that the addition of ascorbic acid prevented the oxidation of fresh Concord juice (Table 8). Acceptable color was obtained for 8 weeks storage at 55°F. However, juice without ascorbic acid (control) was found to be visually unacceptable at 8 weeks. Also, the browning index values indicated that better juice color was obtained at each storage time by adding ascorbic acid.

36

TABLE 8. Effects of ascorbic acid on the browning index value of fresh Concord juice.

Ascorbic acid level

ml/100 m1

Browning index value 1 of juice at different storage times

0 wks 2 wks 4 wks 8 wks

40 0

1.81 1.57

1.65 1.22

1.47 1.02

1Browning index: Absorbance at 520 run/ 420 run *Juice color was visually unacceptable.

RECa-1MENDATIONS

1.02 0.94*

Fruit Condition: The grapes should be clean, sound, free of rrold, and freshly harvested. Also, the fruit should be cool and delivered to the processor as soon as possible after harvesting.

Maturity: The grapes should be harvested at peak maturity, usually between 16° and 17°Brix.

crushing and Destemming: The equipment should be clean and kept in a sanitary condition to avoid microbial contamination.

Sulfur Dioxide: The crushed grapes should be treated with 50 ppm sulfur dioxide (approximately 4 gm/100 lbs. grapes) to preserve color and to control the microbial population.

Pectic Enzyme: Also, the crushed grapes should be treated with a pectic en­zyme to aid color extraction, increase juice yields, and help juice settling. After adding the pectic enzyme, the crushed grapes should be held for 4 hours prior to pressing.

Pressing: After pressing, the juice should be transferred to a clean tank, with as little aeration as possible to minimize browning. This juice should be refrigerated and kept at approximately 32°F to prevent microbial growth and aid juice settling.

Settling and Filtration: The clear juice should be racked from the settled material. These solids contain many micro-organisms and should be removed from the clear JU~ce as soon as possible. If a filter is available, the clear juice should be filtered to further reduce the number of spoilage micro-organisms.

Ascorbic Acid: After obtaining the clear juice, 40 mg/100 ml ascorbic acid should be added during the transfer of the juice to protect against browning and oxidation.

Sorbate: Also, the juice should be treated with 500 ppm sorbic acid during racking to protect against microbial spoilage.

37

Storage: The juice should be stored at approximately 32°F which reduces microbial growth and increases shelf-life of the product. During storage, the juice should always be protected against oxygen.

Bottling: The juice should be filled into new and clean containers. Old containers, especially plastic, should not be used, for they may be contaminated with yeast and bacteria. The bottles should be filled leaving only a small amount of headspace, and always avoiding aeration. The filled bottles should be kept in cold storage.

REFERENCES

1. Amerine, M.A. and c.s. Ough. 1980. Methods for analysis of musts and wines. John Wiley and Sons, NY.

2. Koburger, J.A. 1976. Yeasts and molds. IN: Compendium of methods for the microbiological examination o'f foods. M. L. Speck ( ed.), Am. Public Health Assoc., Washington, D.C.

3. Morris, J.R., W.A. Sistrunk, J. Junek and C.A •• Sims. 1986. Effects of fruit maturity, juice storage and juice extraction temperature on quality of Concord grape juice. J. Amer. Soc. Hort. Sci. 111(5): 742-746.

38

EPIDEMIOLOGY OF COWNY MILDEW OF GRAPE

N. Lalancette, M.A. Ellis and L.V. Madden Department of Plant Pathology

The Ohio State University/OARDC Wooster, OH 44691

INTRODUCTION

Downy mildew of grape is caused by the fmgal pathogen Plasmopara viticola. The disease occurs in most parts of the W'Orld where grapes are grown under humid conditions. Thus, in the United States, the disease is most destructive in the eastern half of the country and least important on the west coast. In Ohio, downy mildew and black rot are considered the tW'O most important diseases in com­mercial grape production.

Downy mildew can affect all aerial portions of the plant: leaves, fruit, and vines. The disease causes losses by killing leaf tissues, completely destroying or decreasing the quality of fruit, and by weakening young shoots. If the weather conditions are favorable and control is inadequate, downy mildew can cause severe defoliation and easily destroy 50-75% of the crop.

Symptoms

The disease is usually first observed as small, pale yellow spots on the up­per surface of leaves. These chlorotic areas enlarge as the fungus grows through the tissues to form large yellow lesions. As the lesions age, the center area becomes necrotic (dead) and turns brown. If high humidity conditions exist during the night, as during a heavy dew or rain, then the fungus will sporulate on the lower leaf surface directly below the lesion. These sporulating areas will have a white, downy appearance.

If the fungus attacks the fruit during the early stages of growth, then en­tire clusters or sections of them can become infected. These clusters can be quickly covered with the downy growth under favorable conditions. If infection occurs when the berries are half-grown, then most of the fungal growth is inter­nal. In this case, the fruit becomes leathery and wrinkled and develops a red­dish to brown marbled coloration.

Infection of young green shoots, tendrils, fruit stalks, and leaf petioles can cause stunting and thickening. Any of these tissues can become entirely covered with the downy growth of the fungus. Eventually, the diseased tissues turn brown and die.

Life eycle

The pathogen survives the winter as oospores in leaf or fruit debris. During rainy periods in spring, the oospores germinate and produce sporangia which are then carried by wind or splashing rain drops to newly emerging leaves. While on the wet leaf surface, the sporangia germinate to produce 4 to 10 zoospores. These motile zoospores swim about on the wet leaf surface until they find a stomate, the pores through which the leaves respire. The zoospores then produce a germ tube which penetrates the leaf through the stomate, thus infecting

39

it. Within 5 to 7 days, yellow lesions appear where the infection had taken place.

After the initial or ~imary infection, subsequent infections or secondary cycles can occur. During humid conditions at night, the fungus in the infected leaves ~educes sporangia on the lower surface of the leaf directly below the le­sion. These spores are then either wind blown or rain splashed to nearby leaves where they can then cause a new infection. If they are wind blown, they remain on the leaf surface until a wetting period occurs {rain or possibly dew). The water is necessary for infection since these sporangia, like the sporangia produced by the oospores, produce mtile, swimning zoospores. If a wetting period does not occur within a sufficient time after sporulation, the the sporan­gia die~ no infection can take place until mre viable sporangia are produced.

Secondary cycles can continue to occur during spring and summer as long as young, susceptible tissue is available and weather conditions permit sporulation and infection. Eventually, leaves fall to the ground in the autunm. The fungus in any leaves that were infected during the season will then begin to produce the sexual oospores which will allow the fungus to survive the winter.

Disease Management

Management of fungal diseases on grape is heavily dependent on the use of fungicides. The usual method of control is to apply fungicides at regular inter­vals during the growing season. While this procedure has proven to be effective, in many cases it results in the unnecessary application of pesticide. During some seasons, environmental conditions are only occasionally conducive to the deve~opment of disease and fungicide need not be applied routinely. If the oc­currence of the infection periods could be l?t'edicted, then Sl?t'aying would only be performed when necessary. This procedure would save the grower both time and money and simultaneously introduce less pesticide into the environment.

Past research here in Ohio has led to the development of a disease forecast­ing system for grape black rot. Tests in the field have shown that this system can effectively reduce the number of s~ays needed, yet maintain adequate con­trol. The forecasting system is deployed in a micro-processor based predictor unit manufactured by Reuter-Stokes of Cleveland, OH. Our objective was to incor­porate into this same unit a similar forecasting system for predicting downy mil­dew. The greater the number of disease-predictive systems in this unit, the greater is its cost-effectiveness.

Forecasting Downy Mildew of Grape

Research was conducted in growth chambers and the greenhouse to determine the environmental conditions necessary for sporulation and infection of Catawba grape by P. viticola. Mathematical models were constructed from this data to al­low for prediction. The sporulation model predicts the amount of sporangia produced from two environmental variables: the duration of humidity >95% and the average temperature during that high humidity period. The infection model predicts the severity of infection given information on the duration of leaf wet­ness and the average temperature during the leaf wetness period. A third model was obtained from research performed in West Germany. It predicts the survival of the sporangia from temperature and relative humidity observation.

40

To develop the forecasting system, the above three mathematical models were combined into one single computer program. This program makes a disease predic­tion based on the weather information it receives. If humid nights occur, then the sporulation model within the program will indicate that viable sporangia have been produced and are "ready" for infecting the vines. If a rainy period im­mediately follows, then these sporangia will be splashed to healthy leaves that they can infect. The infection model will determine the severity of this infec­tion. If the wetness period was too short or the temperature too warm or cold, then either no infection or only a light infection will occur. If a rain does not immediately follow the sporulation period, then the spore survival model will be invoked. It will determine at regular intervals the proportion of spores that are still viable. A long, dry period could result in the death of all the spores produced from the last sporulation period. In this case, the infection model will not p:-edict an infection period if it rains because it "knows" that no vi­able spores are present.

The forecasting system will be tested in the field this spring. A misting system has been constructed in a catawba vineyard. This system will allow us to vary the duration of wetting for testing the infection component of the forecast­ing system. It will also allow us to induce sporulation by increasing the humidity at night. The results from these artificially-induced tests and those from natural conditions will be used to fine-tune and perfect the computer model. An initial version of the model will be programmed into the microprocessor prediction unit for on-site examination.

Conclusions

The future holds much promise for disease forecasting. Microprocessor tech­nology is rapidly advancing, allowing prediction units of greater capabilities to be utilized. Also, microcomputers for the home or business have become increas­ingly available at low costs. These computers could be used for a wide variety of business transactions as well as for disease forecasting. Furthermore, the chemical industry is producing fungicides with after-infection capabilities. Such compounds allow the most efficient disease management tactics, since they can be applied after a p:-ediction has been made. At present, metalaxyl (Ridomil) is the only fungicide that has this capability against the downy mildew pathogen. However as future after-infection fungicides are developed, they will be easily adapted for use with the disease forecasting system.

41

INFLUENCE OF BACTERIAL STRAINS ON THE INDUCTION OF MALOLACTIC FERMENTATION

J.F. Gallander, R.R. Breen1 and J.A. Jindra2 Department of Horticulture

The Ohio State University/OARDC Wooster, CH 44691

Malolactic fermentation refers to the conversion of malic acid to lactic acid and carbon dioxide by certain lactic acid bacteria. This bacterial fermen­tation usually occurs after the alcohol fermentation and results in reducing wine acidity. Since Ohio wines are generally made from grapes high in malic acid, malolactic fermentation may be a desirable means to reduce wine acidity, par­ticularly red wines. Winemakers generally agree that red table wines are better suited for malolactic fermentation than white table wines.

Although malolactic fermentation would be advantageous, the initiation of bacterial deacidification is often difficult. Many factors influence this fer­mentation in wines, such as aeration, alcohol content, time of racking, and sul­fur dioxide. In addition, bacteria capable of malolactic fermentation often are not tolerant to low pH values and temperatures. These two factors are usually characteristic of wines and cellar conditions in Ohio. Therefore, efforts to stimulate malolactic fermentation have proven difficult in many Ohio wines.

For this report, a study was initiated to determine the effect of t~mpera­ture and pH on the induction of malolactic fermentation by several bacterial strains.

PROCEDURE

Grapes from the variety DeChaunac and Foch were harvested in 1984 and 1985, respectively. These grapes were from a vineyard in southern Ohio and were transported to OARDC in Wooster, Ohio, for processing. For each season, the grapes were destemmed, crushed, and treated with 50 ppm sulfur dioxide. After 12 hours, the must was inoculated with Montrachet #522 yeast and fermented-on-the­skins for 4 days. Then, the must was pressed, and the fermenting wine was trans­ferred to a stainless steel tank. At dryness, the wine was racked and divided into 2 lots. One lot was adjusted to pH 3.10 and the other to 3.30. Then, each lot was further divided into 2 sublots, 10 one-gallon glass jugs per sublot and duplicated. Two jugs from each sublot were inoculated with one of the following bacterial strains:

Vinguiry (MCW): Winemakers Service & Res. Lab. 1600 Healdsburg Ave. PO Box 1511 Healdsburg, CA 95448

Mixed Culture: The Wine Lab 1200 Oak Ave. St. Helena, CA 94574

1Present address: Ross Laboratories, Columbus, OH

~resent address: Mile Labs, Inc., Elkhart, IN

42

PSU-1: Tri-Bio Lab., Inc. 1400 Fox Hill Rd. State College, PA 16801

ML-34: The Wine Lab 1200 Oak Ave. St. Helena, CA 94574

Oeno: Microlife Technics Box 3917-1833 57th St. Sarasota, FL 33578

The inoculum for each strain was prepared according to the directions sup­plied by each company. No attempt was made to add the same number of micro­organisms or amount of inoculum. Immediately following inoculation, the 2 sub­lots from each lot (pH 3.10 and 3.30) were placed in 50° and 65°F storage, respectively. The progress of malolactic fermentation was monitored by using paper chromatography.

RESULTS AND DISCUSSION

Results of this investigation indicated that temperature had a strong in­fluence on the initiation of malolactic fermentation (Table 1). One strain, Vinquiry, was found to produce malolactic fermentation at 50°F. These wines were pH 3.30 and the fermentation occurred in 50 and 99 days for seasons 1984 and 1985, respectively. For the most severe conditions, malolactic fermentation was not observed in wines at pH 3.10 and 50°F. In contrast, all wines underwent a malolactic fermentation under favorable conditions, pH 3.30 and 65°F. For these conditions, Vinquiry was found to complete the malic acid conversion in less time than the other bacterial strains. In 1984, this strain completed malolactic fer­mentation in 13 days. This length of time was 37 days less than the next two strains, Mixed and PSU-1. Also, the rate of malolactic fermentation for all strains decreased with a lowering of wine pH, 3.30 to 3.10. The difference of malolactic fermentation rates for the two varietal wines (1984 and 1985) cannot be explained from the results of this study.

Results from this study seem to indicate that winemakers producing wines with low pH values and storing wines at cool temperatures should consider the Vinquiry strain. However, as mentioned earlier in this report, this study did not attempt to control the inoculum, amount and number of micro-organisms. Therefore, it would be reasonable to expect that different rates of malolactic fermentation could have been obtained in this study, if the same inoculum was used for each strain.

43

TABLE 1. Rate of malolactic fermentation as influenced by bacterial strain, temperature and pH.

Temp. Strain OF EH

Vinquiry 65 3.3 Mixed 65 3.3 PSU-1 65 3.3 ML-34 65 3.3 Oeno 65 3.3

Vinquiry 65 3.1 Mixed 65 3.1 PSU-1 65 3.1 ML-34 65 3.1 Oeno 65 3.1

Vinquiry 50 3 .. 3 Mixed 50 3.3 PSU-1 50 3.3 ML-34 50 3.3 Oeno 50 3.3

Vinquiry 50 3.1 Mixed 50 3.1 PSU-1 50 3.1 ML-34 50 3.1 Oeno 50 3.1

~alolactic fermentation did not occur in 30 weeks.

bMalolactic fermentation did not occur in 20 weeks.

44

Dals To MLF 1984 1985

13 23 50 62 50 62 74 55

132 69

22 81 196 83 196 87 196 87 - a 87

50 99b

APPLICATIONS AND EFFECTS OF CARBONIC MACERATION

William D. Edinger Hort. Prod. Lab., H.R.I.O.

Vineland Station, Ontario, Canada

Carbonic maceration can be defined as the anaerobic storage of whole clust­ers of intact grapes to allow anaerobic respiration by the living grape tissues. The process was first carefully studied by Machel Flanzy in the 1930's. His ob­servations led to an improved methodology for a consistent product, and today the wines made this way in Beujolais have become famous for their young, fruity, dis­tinctive red wines. Use of this method is no longer limited to France, and there have been Italian, South African, American, and even Japanese studies of this method with an eye to the marketability of new products having a popular image and an affordable price.

Carbonic maceration is of particular interest to winemakers using red varieties of the Northeast, prime candidates being Marechal Foch, DeChaunac, and other French hybrids, as well as a few viniferas. Some of these grapes are in surplus and available at lower prices, and with reports of a renewed market in­terest in red wines, they represent a potential for profitable wine products. There are some special advantages as well as special dangers to working with car­bonic maceration, which will be discussed based on what has been used by other winemakers as well as in our H.R.I.O. experiments.

1. How is Carbonic Maceration (CM) Carried Out?

Simply holding whole grapes in a closed tank for a couple of weeks does not yield very consistent results, and most times will result in considerable micro­bial spoilage. The modern technique stipulates the use of sound, intact bunches, dumping them into a tank already filled with oo2, and carefully maintaining that carbon dioxide atmosphere. The weight of the upper grapes crushes those on the bottom, and most winemakers crush some of the grapes anyway to make sure that there is a significant amount of juice at the bottom of the tank. Either wild or added yeasts ferment that bottom juice, supplying 002 and maintaining an oxygen­free atmosphere in the tank. Until the bottom juice is actively fermenting, the tank should be flushed with oo2 to inhibit spoilage organisms. Whether or not to use sulfur dioxide is controversial, but the trend is to not use it. A malolac­tic fermentation, considered by many to be highly desirable for CM wines, will be better encouraged if no so2 is present.

The grapes are left in the closed tank for a period of from 8-10 days up to three weeks, depending on the vintner's style or facilities. The temperature is a critical factor in determining the length of duration of the treatment: higher temperatures, 85-95°F, are often recommended and will give the most color in the shortest time, perhaps 7-8 days. However, there are some limitations to heating the tank that much:

1. 30°C is the optimum temperature range for growth of acetic acid bacteria

2. It may not be practicable due to lack of facilities.

3. The cost of supplying the heat may be prohibitive.

45

Using a more moderate temperature--between 70-80°F--will take longer but can give perhaps the best results. Cooler temperatures take too long to get good color, but may be useful for roses.

Tradition has it that the tank should not be opened until CM has finished, but opening it is the only way to sample the grapes. If the tank's co2 atmos­phere is replenished after sampling and the temperature is not drastically chang­ed, then opening the tank and taking samples of the juice and berries should not disturb the process. This should be done very carefully, however: the tank will be filled with co2, posing a serious and potentially fatal hazard.

When the grapes are considered ready for removal, the free run is drained off and later added to the press juice. Although the press juice comes out very easily, fairly heavy pcessing is used to get as much color and juice yield as possible. Pectins are greatly reduced during CM, and solids content should not be a problem. If more color is desired, fermentation on the skins can be done, although this would be a break from the norm. A great range in color intensity can be obtained, depending on the temperature and duration of the CM and the final blend with other wines.

The C02 present in the CM tank encourages the growth of lactic acid bac­teria, and ehis is probably why a MLF almost always follows carbonic maceration spontaneously. There are other interrelated factors which figure in the occur­rence of a MLF and make it both likely to occur and beneficial to the product.

2. When is carbonic Maceration OVer?

Classically, this is determined by four criteria:

1. No more release of gas ( co2).

2. Decrease in sugar content of juice (to about 1° Brix) •

3. Death of the grapes in the upper portion of the tank.

The sugar in the bottom juice can be easily measured, but that may be used up well before 10-12 days, so determination of the progress of CM that way may be inexact. Color is probably the best criterion to use; when the color of the proportionately blended samples of press and free-run is at the desired level, you should be ready to press the tank. Volatile acidity is also a crucial criterion, and if there are indications that it is rising too high, the grapes should be pressed immediately and the juice sulfited.

46

3. What Are The Special Benefits of a Wine Made by CM?

The effects of carbonic maceration on red wine include:

1. Earlier maturation of the wine, with a softer taste.

2. A drop in pectin of up to 75%.

3. Development of fruity, desirable flavors and odors.

4. Significant reduction in acidity, with a rise in pH.

5. Very low acetaldehyde production.

6. Elimination of so2 additions before the end of fermentation.

7. For Labruscanas, a significant reduction in "foxiness".

The reduced pectin allows the relatively heavy pressing, which in turn gives the most color and character. The odors, taste, and rate of maturation are in­fluenced by the many factors which vary between grapes, winemakers, and styles of vinification.

The changes in acidity and pH can be quite significant, and this makes ~ a particularly appealing procedure to use with high-acid grapes. If the pH of the must is high and the acid moderate or low, CM might not be appropriate, since it can raise the pH and lower the acidity excessively, leading to problems with chemical and microbial spoilage.

Tiber Fuleki, at H.R.I.O., has shown that the "foxiness" of Concord grapes can be significantly reduced by CM. Although Concord is not likely to be used for a dry table wine, other varieties might be useful for economic or other reasons. For example, one might try a blend of 10% Ives or Vincent in the ~ tank to get more color (since unblended CM juices are often too light) without having the juice dominated by the flavors or odors of Ives or Vincent.

47

4. What Are The Problems and Risks Involved?

These include:

1. Growth of acetics and increase in volatile acidity.

2. Excessive changes in pH and TA

3. Growth of wild yeasts if no inoculum used.

4. Inconsistency from year to year.

5. Ties up a tank during the busy time (may be an advantage if help is short).

6. Only hand-picked, sound, clean, intact fruit should be used.

7. Extra steps and labor are required (no machine-harvested grapes ! )

The biggest risk in this procedure is that of microbial sp::>ilage. This may be due to growth of wild yeasts if no inoculum is used, or to the development of undesirable malolactic bacteria, such as Lactobacillus or Pediococcus, rather than Leuconostoc oenos. Also, if the pH gets too high (over 3.6), it may both

. encourage those undesirable bacteria (as well as acetic acid bacteria) resulting in a mousy character, and the low-acid, high-pH wine can be brown and flat-tasting.

High volatile acidity from wild yeasts or acetic acid bacteria is a serious threat to these wines. Using a yeast inoculum and maintaining a strict co2 at­mosphere in the tank should circumvent these problems. It should be noted that some winemakers prefer the "complexity" created by wild yeasts, so that aspect is a value judgment.

Other logistical and practical aspects should be considered, such as incon­sistency from year to year and the practicability of carrying out OM without dis­turbing the rest of the crush activities. The former may be an advantage, depending on winery style and marketing strategies. The latter, similarly, depends on individual situation.

48

5. What Are The Specific Changes Found Experimentally?

There are two fundamental aspects to CM:

1. Intracellular activity in the berries ("solid phase"),

2. Microbial fermentation in the bottom juice ("liquid phase").

In the berries, sugars are used somewhat, but malic acid is the main energy source for the grape cells. The decrease in malate raises the pH and lowers the acidity, and results in 1 to 2% ethanol aside from any contribution by yeasts. Other flavors are produced by more complex metabolic interactions. It is generally assumed, though probably not true, that the berries are secure from in­vasion by yeasts and bacteria. Actually, the berries are eventually infected whether intact or not, and significant numbers of yeasts and bacteria have been found inside the berries after about seven days (personal data).

Other aspects of the intracellular process:

1. A large amount of co2 dissolves in the berries as the oxygen level is diminished.

2. Cells break down, and pigments are selectively released as alcohol is produced.

3. Special flavors are developed: the "strawberry/rasp:>erry" odor is probably due to ethyl cinnamate, regardless of grape type: benzaldehyde (cherry flavor), quinic and shikimic acid (leads to other flavor com­pounds) are higher.

At the same time, a normal fermentation by either wild or inoculated yeasts is going on in the juice: this uses principally sugars for energy, and gives the expected changes in acidity and the usual amount of ethanol in the bottom juice.

What appears in the final blended juice is a balance of these two phases of carbonic maceration, and can be affected by how many grapes are intact and how the CM juice is blended (customarily a complete blend of the bottom- and press-juices).

The changes of interest are mostly dependent on time and temperature. Experimental changes found for OeChaunac grapes from 1986 are shown below. The average amount of acetaldehyde in dry table wines are been reported as about 50 mg/L, or perhaps a little less (Amerine & Ough, Wine and ~ust Analysis, 1980); the amounts reported here for juices were not found to increase significantly af­ter fermentation.

The most alcohol that can be expected solely from intracellular metabolism is about 2%: the higher amounts here suggest activity by yeasts inside the ber­ries (these samples contain only intact clusters of grapes, no free juice).

The pH rose excessively in these DeChaunac grapes; it was lowered in some cases when the VA became excessive (the apparent decline in VA on day 21 is be­cause separate samples were used for each period of rreasurement).

49

Acetaldehytle Pnuruction during Cnrhnnic llneernlion

70 .............................................. -......................... .

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Ethonol PrntJuction dur1ng r.orhon i c Hoceroti on

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30 :·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:·:· 20 :.;.: .. : .. :L· .. :.:.;.: .. :.: .. ~.:.:.: .. : .. :.:.: .. ~.:.: .. :.:.: .. ~.:.:.: .. ~.:.:.:.~ •

:====~; %1t•ol. 2 -···--··-····-···-zr,.Z·--

........... 7L.. ............ 7 ••.••••.•••••••••••••••••••••••••• ..,...r:=~ __ .II _,... g---::= _Q ..___ ___ _. 1 0 .C-w::":: ....... (j;:.:,.'C...<-.,ft~::::::::;: ............ .

o~l----~----+----/ /=---·_,.,-. •r-

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pll

12

10

4

2

0

1 1 t1 21

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f:m hnnh: fiiH:fH nliun: fJII vs. Vu In li I H 1\r. i flit !J

3 .a ··································;·:·~·~:·····················;~·························:;·} r~ 2r:~: 3.7 ........................................... ~ ... ~;:~···r·''v.'io·;;FI",.."I':: ....... L.1E .. . 7'1; ,... ··-. ____ ,... 1 o 1 t=.n

0 7 14 21

days of CM

3.6 .............................................. ;~;·~,~~r\l"'.,.....a~:! ..... -=: •. ~~·:;•lJ ():I •~(:1

3.5 ................. .. ......... .,.! ... ,...1'!': ..... /............................................. 0.1 20

3.4 ........... 7 ....... /... ................. ./ ............ ~ .... , ........................ n lOll .,~ .' ,-·· .,_.,."'··· - ...• ' ~·' ·•·• • s fi fn":ln V .I\. 3.3 •••••7 oooooooooooooOoooooooooool;:;-;.o·'·••oooo••••o•o••••••••oooo••••••••::>?~IJ (~[,~(1

·•· plf, I 5"'

·•· pll, 25"

..... plf, 35"

0 - V . A. , 1 5"

D- VA ~'5° 3.2 , ............................... ~· ............................................ ~, .. ,:: .......... .

lW~----··t'l .. ·· ..-- n n.1f+ 3.1 t ................ =~::::.:~/:·:··::::.::·······~:::::::g ,.::~:.:................... () ~+20 ··~~ --o---

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50

12

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The use of CM at 15° did not produce major changes in acidity or pH even after 21 days~ excessive VA at 35° after 7 days makes treatments longer than that unwise; 25° gave the most desirable changes, and scored best in taste panels for the 1985 wines.

6. Use of carbonic Maceration for White Varieties

Experiments have been conducted in the past using Om with white grapes, but results were not encouraging and it does not appear to be of much value.

7. Recommendations

1. Until some experience has been acquired under production conditions, large amounts of grapes (and money) should not be committed to a car­bonic maceration project.

2. Grapes should be picked based on acid and pH more than °Brix. Overly ripe grapes are not well-suited to CM.

3. Yeast autolysate has been suggested as an additive in CM bottom juice to encourage MLF, after considered essential for CM wines.

4. Blending of free-run with press juice (or other varieties) provides an opportunity for adjustment of color, body, character, etc.

5. co2 piped in from other fermenters can be used to flush the CM tank.

6. Experimentation is necessary to get the optimum effect. What results from your efforts, though a good, sound product, may not be exactly what you expected., However, this provides an opportunity for the art and creativity of wine blending, product development, and marketing.

SUGGESTED LITERATURE

Beelman, R.B. and J.F. Gallander. 1979. Wine deacidification. Advances in Fd. Res. 25:38-42.

Blackburn, D. 1984. Whole berry fermentation. Prac. Wine. Jan/Feb. 1984:30-35.

McCorkle, K. 1974. Carbonic maceration ••• A Beujolais system for producing early-maturing red wines. Wines & Vines 55(4):62,64-5 (April, 1974).

Wagner, P. 1984. Introduction to carbonic maceration. East. Grape Grow. & Wine. News 10(4):26-28 (Aug/Sept, 1984).

Welsch, D. 1985. weedy quality).

Use partial carbonic maceration to ferment Foch (weed out that East. Grape Grow & Wine. News 11(4):26-28. (Aug/Sept)

Journees of Maceration carbonique, 10 et 11 fevrier. Avignon, Institut National de la Recherche Agronomique. 240 pp. (1971).

(various authors) Ann. Technol. Agrtic.: (Vol. #and page #s) 11:233-44 14:173-178 (what happens to the grape berries) 16:27-34, 89-107 (changes in

51

organic acid content) 16:109-116, 117-123 (results of vinification by carbonic maceration)

castno, M. & M. Ubigli. 1984. Prove di macerazione carbonica con uve Barbera. Vini d'Italia 26(6):7-23.

Usseglio-Tomasset, L. 1986. Interventi e trattamenti nella produzione dei vini rosati per mezzo della macerazione carbonica. Vini d'Italia 28(3):65-70.

52

SUMMER PRUNING OF GRAPEVINES

Tony K. Wolf Winchester Agricultural Experiment Station

VPI and SU Winchester, VA 22601

A fundamental goal of commercial viticulture is the production of large crops of high quality fruit. Managing vines to produce an abundance of healthy, well exposed foliage is central to realizing this goal. Vegetative growth weakened by nutrient deficiency, over-cropping, drought, or pests reduces the photosynthetic area of the vine which leads to reduced yields and fruit quality. On the other hand, when virus-free vines, grafted to pest-resistant rootstocks, are planted in fertile soils, they often produce more foliage than can be adequately exposed to sunlight. This abundance of growth ("high vigor") frequently results in dense canopies having many layers of leaves and, con­sequently, shaded canopy interiors. Very dense canopies may have 10 or more layers of leaves from one side of the canopy to the other. Sparse canopies, con­versely, would consist of less than three layers of leaves. The interior region of canopies will have an environment (micro-climate) different from that at the canopy exterior with respect to levels of sunlight, temperature, humidity, and air speed. The relative differences between the interior environments of dense and sparse canopies can be summarized as:

Physical Characteristics

Irradiance level Relative humidity Air speed Day temperature of fruit and leaves Night temperature of fruit and leaves

Dense Canopy

Low High Low Low High

Sparse Canopy

High Low High High Low

The deleterious consequences of excessively shaded canopy interiors are manifold. Shaded leaves are not as photosynthetically active as exposed leaves and may prematurely yellow and abscise. Buds of shaded nodes are not as fruitful as buds which receive sunlight during their development. Tissue maturation on shaded shoots is inferior to that of well exposed shoots and, consequently, cold hardiness of shaded buds and wood is often reduced.

Pesticides do not penetrate dense canopies as readily as they penetrate sparse canopies. Densely shaded fruit typically exhibits:

-Decreased soluble solids accumulation -Higher titratable acidity -Less pigmentation -A greater incidence of fungal disease such as Botrytis bunch rot

In addition, potassium appears to accumulate to a greater extent in shaded shoots than in shoots '-~ell exposed to sunlight. The subsequent translocation of potassium into maturing fruit can be associated with elevated must and wine pH, especially in fruit of low total acidity.

53

There are several approaches to correcting excessively dense vine canopies, including:

-Alter the training/trellising system to expose a greater proportion of foliage to sunlight

-Practice more severe dormant pruning (i.e., leave less nodes) -Remove either the shaded or the shading vegetation {i.e., shoot

topping, shoot thinning, leaf removal) -Slow or stop vegetative growth with chemical growth regulators

Altering the training and trellising designs to utilize the abundant leaf area of large vines is probably the ideal means of minimizing canopy shade while simultaneously increasing yields. Such thinking led to the Geneva Double CUrtain in New York, the "lyre" or u-shaped trellis developed in Bordeaux, France, and the Te Kauwhat tow-tier system devised in New Zealand. A common feature of these training systems is a divided canopy which increases the number of leaves, per unit length of row, exposed to sunlight.

Unfortunately, there is a reluctance on the part of grape growers to adopt or even experiment with novel training and trellising systems. The greater ini­tial expense of the more elaborate systems is an understandable deterrent. The alternative strategy to reducing canopy density that growers are more willing to opt for is some form of summer pruning, such as shoot topping or hedging of canopies. Shoot topping refers to the removal of several- to many-inches of shoot tips in an effort to prevent this portion of the shoot from blocking sun­light's penetration into the fruiting region of the canopy. The extent of shoot topping that is required to produce this result will depend upon the training system, cultivar, and degree of shading that exists.

We conducted a summer pruning experiment with 'Chardonnay' vines in New York (1) to determine how shoot tipping, shoot thinning, selective leaf removal, and ethephon application affected fruit quality. Vines were trained to a double off­Guyot system where canes were tied horizontally and bilaterally to a wire ap­proximately two feet above the ground. Foliage catch wires were used to confine developing shoots to a relatively thin vertical canopy. Treatments included: 1) No canopy manipulation other than shoot positioning; 2) Ethephon application (600 ppm) to shoot tips when shoots were approximately 60 inches long; 3) Repeated shoot tipping to maintain shoots approximately 60 inches long; 4) A combination of treatments 2 and 3; 5) Removal of all lateral shoots in the fruiting region of canopy; 6) a combination of treatments 3 and 5; and 7) Removal of leaves from the basal three or four nodes of shoots.

One potential problem with summer pruning is that the removal of shoot tips removes the apical dominance that tends to inhibit lateral shoot growth. Consequently, lateral shoots of tipped vines may grow quite vigorously. This prolific vegetative growth can delay fruit maturation by creating competitive photosynthate sinks. This problem was not observed in our study, perhaps because the shoot tipping was done fairly late in the growing season (about five weeks post-bloom). Ethephon application was as effective as shoot tipping in controll­ing shoot growth. Ethephon inhibits vegetative growth and also inhibits lateral shoot growth.

Treatments involving lateral shoot removal were the most effective in increasing the amount of sunlight penetrating the fruiting region of canopies.

54

Lateral shoot removal and basal leaf removal both significantly increased the number of clusters receiving direct sunlight. The number of yellowing leaves counted in late-summer, which is an indication of mutual leaf shading, was least where laterals were removed.

In terms of fruit composition, lowest titratable acidity values were as­sociated with vines subjected to lateral shoot removal. Given the greater ex­posure of fruit from these vines to sunlight, it is reasonable to assume that fruit of these vines was frequently warmer than shaded fruit due to radiant heat­ing. We know that high fruit temperatures hasten acid metabolism which probably accounts for the reduction in TA with fruit of vines subjected to lateral shoot removal. Fruit pH and soluble solids were not affected by canopy manipulation. Removal of basal leaves--essentially those from around the fruit clusters-­resulted in a significant reduction in botrytis bunch rot. Removal of these leaves likely increased fruit drying following wetting and increased the extent of pesticide penetration to developing fruit. Ethephon application did have the undesirable effect of increasing botrytis bunch rot. It is thought that ethephon softens the fruit resulting in greater fungal infection and disease development. Ethephon's use, therefore, will probably be limited to those areas where bunch rot pressure is great.

Summer pruning may or may not be desirable in your vineyard. Excessive or unnecessary foliage removal can delay or ~event adequate fruit and wood matura­tion. Research has shown that eight to 10 square centimeters of leaf area are required to mature a gram of fruit. Considering cultivar variability in leaf size and cluster weight, one can extrapolate that requirement to be above 15 to 20 mature leaves per shoot. This requirement would be higher for very fruitful varieties such as 'Seyval'. Topping shoots to less than 15 nodes is apt to retard fruit maturation. Even if fruit matured with acceptable harvest para­meters, severely topped shoots would be susceptible to extensive winter die-back, even during a relatively mild winter.

I suggest you consider several guidelines in the event you choose to summer prune or hedge vines:

I. Consider the impact of your actions.

A. Will the removal of shoot tips improve spray penetration or is there a fundamental problem of excessive shoot density? The latter may be better corrected by shoot thinning, decreased node retention at dormant pruning, or by use of a divided canopy training system.

B. Would the addition of foliage catch wires or the adoption of a different training system be a better long-term solution?

II. If summer pruning by shoot topping is practiced, delay it as long as possible to minimize the risk of stimulating excessive lateral shoot growth.

III. Try to leave at least 15 main leaves on topped shoots.

55

LITERATURE CITED

1. Wolf, T.K., R.M. Pool, and L.R. Mattick. 1986. Responses of young Chardonnay grapevines to shoot tipping, ethephon, and basal leaf removal. Am. J. Enol. Vitic. 37:263-268.

56

ACTIVATED CARBON AS A WINEMAKING TOOL

Domenic Carisetti Canandaigua Wine Company

Canandaigua, NY 14424

OUTLINE

A) BATF Regulations Pertaining to Use of Activated Carbon in Juices and Wines; subpart ZZ: 240.1051

B) Properties to Consider in Selecting Activated Carbon

1) Adsorptive capacity 2) Bulk Density

C) Applications in Juices and Wines

1) Juice

a) Decolorizing oxidized white juice b) Reducing pink color in early harvested red juice to produce white or blush wines. c) Reducing overripe varietal character

2) Wine

a) Decolorizing white and pink wines b) Reducing off-odors produced by fermentation c) Decolorizing Sherry

D) Activated Carbon as a Fermentation Aid

E) Summary

57

ACTIVATED CARBON

A) BATF Regulations Pertaining to Use of Activated carbon in Juices and Wines: Subpart ZZ: 240.1051

Within the Code of Federal Regulations (CFR) Part 240, that pertain to wine production, Subpart ZZ specifically recognizes materials and processes authorized for treatment of wine and juice. There are five general areas where activated carbon is permitted.

1) To assist precipitation during fermentation. 2) To clarify and to purify wine. 3) To remove excess color in white wine. 4) To remove excessive color in pale dry sherry or cocktail sherry. 5) To reduce color in the juice from red and black grapes.

The BATF restricts the use of activated carbon in juice and in wine because it is easy to alter the vinous character by uncontrolled use.

B) Properties to Consider in Selecting Activated Carbon

Activated carbon can be used to decolorize or to deodorize JU~ces and wines. Various grades of carbon are available to do this. A decolorizing carbon will decolorize preferentially over deodorizing. It is important to decide what you want to accomplish with activated carbon, research the properties of carbons available to you, then set up laboratory trials to determine the min­imum quantity of carbon to achieve your goals.

1) Adsorptive Capacity: Carbon has a tremendous adsorptive capacity because its area is contained in a small weight. Adsorptive area may range from 70 to 140 acres per pound and is contained within the microscopic pore structure of the carbon particles. This capacity is conferred upon wood, lignite, coal or other raw material in the manufacture of ac­tivated carbon by charring the material and treating it with air, steam or other oxidizing agents at high temperature.

2) Bulk Density: Weight in pounds per cubic foot refers to bulk density. High bulk density can be advantageous in that it results in less reten­tion of liquid in the filter. Low bulk density carbon may require in­creased filter teardowns with greater loss of liquid.

C) Applications in Juices and in Wines

As a winemaking tool, activated carbon has many uses in juices and in wine:

1) Juice

a) Decolorizing oxidized White Juice: Decolorizing carbon is effective in removing browning in oxidized white juice. Carbon should be added as a slurry to a portion of the juice to be treated, with the slurry added back to the untreated portion. A small amount of bentonite, Sparkolloid or Klear-More should be added to the carbon treated juice to allow rapid settling of the carbon. The juice should be clarified for storage or for fermentation within 24 hours.

58

b) Reducing Pink Color in Early Harvested Red Juice to Produce White or Blush Wines: Early harvested red varieties can be decolorized to make white or blush wines provided that the varieties are harvested early (5-8 brix), treated with the allowable quantity of high surface area activated carbon, racked/centrifuged and fermented rapidly.

c) Reducing Overripe Character: Often, juices made from late harvested fruit may have too much varietal character. The amount of varietal character can be controlled by separating the juice into two frac­tions, treating one fraction with deodorizing carbon to strip out all varietal character, then blending back with untreated juice to obtain the level of character desired.

2) Wine

a) Decolorizing White and Pink Wines: The best time to add carbon to decolorize wine is as soon as possible after fermentation but before bentonite addition. Again, lab trials must be done to determine the degree of decolorization desired. Any amount added during fermenta­tion must be subtracted from the total allowed in wine. Carbon added by itself is difficult to remove by filtration and should be followed by additional fining. Incomplete removal of carbon can result in a haze that makes membrane filtration difficult. To retain varietal character, treat a separate portion of the wine, then blend into the untreated portion at desired levels. For pink/rose wines, keep some young red wine on hand to blend back and enhance the red tint.

b) Reducing Off-odors Produced by Fermentation: Carbon is not as ef­fective in reducing off-odors produced by fermentation compared to preventative measurements and is discouraged from use to remove off­odors. If carbon is used to strip the wine completely, then it should be considered as a blending wine and used over time in other products. If the wine requires more than nine pounds per 1,000 gal­lons carbon, application should be made to the Regional Director of the BATF.

c) Decolorizing Sherry: Sherry that develops a burnt character during baking often benefits by the addition of deodorizing carbon. Up to 25 pounds per 1,000 carbon can be added to sherry to lighten the color and/or flavor.

D) Activated Carbon as a Fermentation Aid

In a study done with fermented wort, activated carbon addition during fermen­tation was preferred over diatomaceous earth addition as an aid to improve fermentation rate. carbon addition leads to higher yeast viability by bind­ing lipids and C02 which are inhibitory to yeast. Carbon helps keep the yeast in suspension which has been shown to increase the fermentation rate.

E) Sunmary

In summary, activated carbon is an excellent tool in winemaking as a fermen­tation aid, decolorizer and deodorizer. Lab trials followed by a selection

59

of the most effective grade of carbon is important before any attempt is made to use carbon in the plant.

60

THE PRINCIPLES AND PRACTICES OF COLD STERILE BOTTLING

Chris Stamp Department of Horticulture

The Ohio State University/OARDC Wooster, OH 44691

Strictly speaking, the actual practice of cold sterile bottling requires that wines be sterile filtered, aseptically filled into sterile containers, and sealed with sterile closures. Although many wineries are not adequately equipped to carry out this sterile bottling, it is to their advantage to approach "sterile bottling" as much as time, money and equipment will allow.

The foundation of producing a stable wine is sanitation. Sanitation applies to all wine operations, whether or not wineries carry out a full scale sterile bottling operation. The lack of sanitation leads to biologically unstable wine.

For this report, sterile bottling has been divided into three areas: winery sanitation, filtration, and bottling. Each will be discussed in the following paragraphs.

Winery Sanitation

A winery without good sanitation is like a giant culture plate, growing and harboring many types of undesirable organisms. The purpose of sanitation is to eliminate as many of these sources of contamination as possible.

Stagnet water and wine spills should be washed away immediately, and the areas sanitized as soon as possible. Mold on the walls and floors should be removed by washing and the area treated with an approved fungicide. Also, a dehumidifier may aid in preventing mold growth during the summer months. Pomace in and near a winery can harbor fruit flies and should be removed daily and the area cleaned

If an area is cleaned well, the source of nutrition for microorganisms is removed from the winery. Therefore, the microorganisms will not be able to mul­tiply and spread their contamination. This makes future sanitation easier and more effective.

It is important to remember that clean equipment will last longer and clean easier.

Filtration

Filtration is not only a means of clarifying a wine, but also an invaluable tool in biological control.

Filter pads, or "depth filters" are not simply barriers with holes of a given radius. On the contrary, the wine being filtered must pass through a series of treacherous, angular paths that weave in and around silicates and fibers. Due to their nature, pad filters are not rated according to pore size but classified in terms of their general retention, or degrees of tightness, such as rough, polish and sterile pads.

61

Pad tightness affects the allowable rate of flow through the pad and capacity, or the amount of debris a pad will hold before clogging. The manufac­turer will state acceptable flow rates and ~essure differentials for each pad type.

Since the capacity of a sterile pad will be much less than a rough pad, it is necessary to ~perly ~efilter a wine with the required rough and/or polish pad. This also reduces the bacterial load of the wine, thereby decreasing the chance that bacteria or yeast will find a passage through the sterile pad.

Sensitive wines like those with residual sugar, high pH or malic acid, should all receive a sterile filtration.

Just as maintaining sanitation makes routine cleaning easier and more effec­tive, so does maintaining lower contaminant levels in wine make filtration easier and more effective.

Bottling

In the case of sterile bottling, it is necessary to heat sterilize the fil­ter pads, filter ~ess, membrane, and bottler ~ior to usage. If sanitary bot­tling is desired, the filter press and other equipment should be rinsed, washed with a sanitizing solution (chlorine and water work well) and rinsed again with clean water before being assembled. A solution of one pound citric acid/30 gal­lons water and 200 ppm so2 should be circulated slowly through the filter pads and flushed with clean wafer.

For heat sterilization, all wine contact surfaces must receive a minimum heat treatment, of 180~ for at least 20 minutes. Hot water or steam may be used for this practice. Hoses that will not withstand this heat treatment should be soaked overnight in a strong iodophor or chlorine solution and flushed with sterile water from the filter ~ess.

Sterile filtration should be bottling equipment. Ideally, the should be sterilized as one unit. tion. Figure 1 illustrates ideal

scheduled near the bottling time and near the pad filter, meni:lrane, and bottling machine This will reduce the chance of recontamina­

sterile bottling system.

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BOTTLING TAN I<

BOTTLING FILTRATION SCHEMATIC

PAD FILTER

0

n MEMBRANE

FILTER

BOTTLING LINE

~ l PRESSURE

I SENSOR

I I I I I I

~ONE-WAY FLOW I _ CHEC~VALVE ________ j

~AIR ACTIVATED

BY-PASS VALVE

Figure 1. Sterile Bottling System

63

Once filtration has begun, stops and starts should be avoided for this may cause particle migration through the pad. With in-line systems, such as in Figure 1, a by-pass valve should be installed down stream of the filter pad. This valve will open when the filler bowl reaches capacity, thus recirculating the wine back to the tank, and the flow through the filter is not interrupted.

A ment>rane is like an insurance policy. In the event the pad filter does not function properly, the membrane will retain the contaminants. The membrane is not like a depth filter, but is composed of a thin layer of some resiliant material with pores not exceeding a given size. Since membranes lack depth, their ability to hold large amounts of debris before clogging is small. Therefore, it is essential that the wine be filtered through a sterile pad before passing it through a membrane. Ment>ranes are classified according to their pore size, such as 0.65 and 0.45 micron. These membranes are the most popular in the wine industry.

The filter, membrane and bottler should be cooled after sterilization by en­tering cold water ahead of the pad filter. When the system is cool, it is neces­sary to test the integrity of the membrane to certify it was not damaged during sterilization. The "bubble point" test is used to check membrane integrity by determining the pressure required to force a gas through its moistened surface.

64

TESTING MEMBRANE

INTEGRITY

GAS

__ ----.CD CliiJ:::-------" PAD

FILTER "1~------'

@ __ __;:;;q

1.4EMBRAHE FILTER HOU~ING

Figure 2. Integrity Testing of Membrane Filter.

65

To perform the bubble point test (refer to Figure 2), close valve or cap hose at location #1, attach gas (C02 or N2) hose and clamp to small valve on menhrane housing (location #2). It may be necessary to insert a small stopcock valve at "location #2". Next, the hose at location #3 is disconnected and placed in a bucket of strong chlorine, or iodophor solution. Increase gas pressure slowly and watch the immersed hose for the first burst of finely divided gas bub­bles. Record the ~essure reading on the gas regulator, this is the bubble {X)int. Compare this pressure reading with the manufacturer's recommended bubble point. A low bubble {X)int ~essure is indicative of a faulty membrane.

After testing the membrane, reconnect the hose to the filler bowl and flush the system with wine to remove all water prior to bottling.

Preferrably, the bottler and corker should be located in a small and easily cleaned room, which is equipped with forced filtered air to help exclude less pure ambient air. The bottles enter and exit this room through small portals. The inside of the bottling room should be cleaned and sprayed with an iodophor solution.

A spray bottle containing a 70% ethanol solution may be used to periodically spray down the corker jaws and filler spouts. The cork bin should be sprayed thoroughly before filling with sterile corks.

It is usually unnecessary to sterilize new bottles, especially if they are clean and handled carefully. Bottles should be removed from their cases im­mediately before filling. Also, handling bottles should be restricted to areas below the neck, even clean hands can contaminate the product. Any bottles hand­led carelessly should be kept separate from others.

All workers should wear unsoiled clothes, and white lab coats are recom­mended in the bottling room. Also, workers should wash their hands periodically.

Although many wineries are not equipped for sterile bottling, understanding and using sound sanitary practices, especially at the point of bottling, will reduce the risk of bottling biologically unstable wines, increase the quality of the product, extend equipment life and improve morale of the worker. It is a worthy goal for all wine producers.

66

REFERENCES

1. Anonymous. 1984. Winery cleaning manual. Premier Chemical Corp, Stonehurst, Ct.

2. Amerine, M.A., R.E. Kunkee, c.s. Ough, V.L. Singleton, and A.D. Webb. 1980. The Technology of Winemaking. 4th ed. AVI Publ. Co., Inc., Westport,CT. pp. 336-41.

3. Guthrie, R.K. Westport, CT.

1980. Food Sanitation. 2nd ed. The A VI Publ. pp.68, 73-94.

Co., Inc.,

4. John, T.N. 1983. Sterile filter myths and fables. Practical Winery 4( 1): 65-66.

5. Neradt, F. 1982. Sources of reinfection during cold-sterile bottling of wine. Am. J. Enol. Vitic. 33:140-4.

67

f'

MONITORING INSECT AND MITE PESTS IN OHIO VINEYARDS 1984-86

Steven R. Alm, Daniel M. Pavuk, and Roger N. Williams Department of Entomology

Ohio Agricultural Research and Development Center The Ohio State University

Wooster, OH 44691

INTRODUCTION

The objective of monitoring insect pest populations is to predict when in­sects have reached, or will soon reach economic injury levels to prevent crop losses. The tools and techniques presently available to monitor grape insects include pheromone traps and field observations. Pheromone traps monitor male in­sect flight activity and are available for the grape berry month, Endopiza viteana (Clemens), the red-banded leafroller, Aryrotaenia velutinana (Walker), and the grape root borer, Vitacea polistiformis Harris). Field observations consist of looking at buds, leaves, vines, and clusters for insects and their damage. Through this study we have also demonstrated the importance of monitor­ing the root zone for pests such as the grape root borer, grape phylloxera, and periodical cicada nymphs.

The benefits of insect monitoring include determining which pests are the most damaging, where they are located in the vineyard, and when control measures should be applied. Several pest management programs have demonstrated there is a cost savings benefit associated with monitoring insect populations. Increased savings are the result of spraying only when necessary and timing sprays to achieve maximum effect. Prevention of resistance development through judicious pesticide usage is another benefit.

MATERIALS AND METHODS

Eleven vineyards were selected throughout Ohio to represent the two major grape growing regions in the North and South. The Northern vineyards monitored were in Ashtabula, Lake, Lorain, and Erie counties (Fig. 1). The Southern vineyards monitored were in Warren, Brown, Miami, and Adams counties (Fig. 1). Various spray schedules and pesticides were used at each location. Vineyards were monitored weekly during the 1986 growing season for arthropod pests. One to six stations per vineyard were monitored for pests. Each station consisted of a 10-vine plot in which fifty buds (early), leaves, shoots, and berry clusters were checked for arthropod damage. Each station also included a yellow sticky trap (Trece, Salinas, CA) for leafhoppers, and a pheromone trap (Trece, Salinas, CA) for each species; grape berry moth, Endopiza vitiana (Clemens), and red-banded leafroller, Argrotaenia velutinana (Walker). Four vineyards were selected to monitor the grape root borer, Vitacea polistiformis (Harris) with pheromone traps.

RESULTS AND DISCUSSION

The pests which were found to be the most damaging were the grape berry moth, grape phylloxera, grape root borer, grape leafhopper, and Japanese beetle (Tables 1-3). Other pests that are capable of causing economic losses include the grape flea beetle, rose chafer, and climbing cutworms (Tables 1-3). Pests that were found, but rarely caused economic injury, include the grape cane

68

gallmaker, grape cane girdler, European red mite, erineum mite, grapevine aphid, and potato leafhopper (Tables 1-3).

The grape berry moth is a direct fruit pest and is present in all grape growing areas of Ohio. Research efforts have been in the area of predicting when to apply pesticides to prevent berry damage. Control spray timing at present is based on the experience of the grower. A more accurate method of timing sprays is possible based on pheromone trap captures. Data were combined for the vineyards in the Northeast, Northwest, and Southern regions for presentation in Fig. 2. This representation is to provide a general pattern of when moths are present in the different localities. Results of the three-year study have shown that populations vary greatly between vineyards even in the same county. Each grower then, should monitor his own vineyard for optimal spray timing. We sug­gest four grape berry moth pheromone traps around the perimeter of a block. Roberts and Simpson (1982) suggest spraying for grape berry moths 3 days after a peak in trap captures.

The percentage of grape berry moth damaged clusters is high in some loca­tions and may be an indication that this pest is becoming resistant to some chemicals (Tables 1-3). This pest may be especially troublesome in table grape where 100% clean fruit is desired. Since this pest has the potential to cause significant economic injury, more detailed research on actual damage, control, and possible resistance is needed. Similarly, damage by other leaf and/or shoot feeders (Tables 1-3) needs more detailed study of actual economic losses.

The grape phylloxera, grape ieafhopper, and Japanese beetle cause economic injury indirectly to the grape crop by damaging leaves. This damage reduces the photosynthetic capacity of the leaves which affects vine vigor and winter hardi­ness. Phylloxera also feed on roots which reduces vine vigor. Chemical control of these pests is presently adequate, although improvements are certainly possible.

The grape root borer was found to be a pest causing significant economic in­jury in some areas of Ohio. The larvae weaken or kill vines outright or provide entry points for disease organisms (Dutcher and All, 1979). Larvae have been found on DeChaunac, Chambourcin, and Niagara grapevines in Southern Ohio. Control tactics for this pest are not clearly defined and more research is neces­sary to determine the extent of the problem in Ohio and how to control it (see article by Williams et al. in these proceedings).

Insect population monitoring has been shown to be important on a statewide basis for determining new insect pest problems (e.g., grape root borer). ~onitoring is also important on an individual vineyard basis to optimize pest control tactics for the unique pest/predator/parasite complex in each vineyard.

REFERENCES

Dutcher, J.D. and J.N. All. 1979. Damage impact of larval feeding by Vitacea polistiformis in a commercial Concord grape vineyard. J. Econ. Entomol. 72:159-161.

Roberts, W.P. and C.M. Simpson. 1982. Monitoring and predicting spray dates for the grape berry moth on the Niagara peninsula. Ministry of Agriculture and Food. Agdex order No. 82-036.

69

TABLE 1. Grape ~thropod pest damage in four vineyards in Northeast Ohio 1984-86 •

% Damaged flower clusters, berry cluster, leaves2 or shoots and relative infestation of leafhoppers Vineyard U Vineyard #2 Vineyard #3 Vineyard #4

Type of Pest Damase 84 85 86 84 85 86 84 85 86 84 85 86

GEM damaged clusters 2 15 12 16 9 12 41 41 12 53 27 9 JB damaged leaves 21 48 15 31 45 30 37 70 73 57 45 22 Gallmaker damaged shoots 9 27 15 14 13 7 Girdler damaged shoots 8 7 4 10 7 10 Phylloxera damaged leaves 3 14 14 Flea beetle damaged leaves 15 41 RC damaged flower clusters 46 RC damaged leaves 17 24 ERM damaged leaves 10 Erineurn mite damaged leaves 27 Potato leafhopper L L L L L L L L L L L L Grape leafhopper L H H H

1GBM (grape berry moth) : JB (Japanese beetle) : RC (rose chafer) : ERM (European red mite). ·

~eafhopper infestations were rated as light (L), moderate (M), or heavy (H).

70

TABLE 2. GraJ;:e ~thropod J;:eSt damage in four vineyards in Northwest Ohio 1984-86 •

% Damaged berry clusters, leaves, or shoo2s an relative infestation of leafhoooers

Vineyard #5 Vineyard #6 Vineyard #7 Vineyard #8 Vineyard #9 Pest-Damase Type 84 85 86 84 85 86 84 85 86 84 85 86 84 85 86

GEM-clusters 3 38 14 6 16 8 5 31 6 14 12 2 4 JB-leaves 29 54 33 38 32 82 8 38 3 44 22 8 8 Gallmake-shoots 17 15 10 Phylloxera-leaves 5 8 25 Flea beetle-leaves 14 42 Potato leafhopper L L L L L L L L L L L L L L L

1GBM. (grape berry moth) : JB (Japanese beetle ) •

~eafhopJ;:er infestations were rated as light (L), moderate (M), or heavy (H).

71

TABLE 3. Grape !lthropod pest damage in four vineyards in Southern Ohio 1984-86 •

% Damaged berry clusters, leaves, or shoot~ and relative infestation of leafhoo~rs

Vineyard U Vineyard #2 Vineyard #3 Vineyard #4 Type of Pest Damage 84 85 86 84 85 86 84 85 86 84 85 86

GBM damaged clusters 5 19 20 15 7 18 1 12 JB damaged leaves 34 38 24 65 42 11 23 44 70 Gallmaker damaged shoots 2 15 7 18 Girdler damaged shoots 1 4 5 Phylloxera damaged leaves 18 18 5 27 51 20 15 39 31 Flea beetle damaged leaves 4 14 32 Aphid damaged shoots 21 Potato leafhopper L L L L L t L L L L L L Grape leafhopper L

1GMB (grape berry !tCth); JB (Japanese beetle).

~eafhopper infestations were rates as light (L), rooderate (~), or heavy (H).

72

Fig. 1 Locations Qf monitore~ vineyards, 1984-86.

73

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