This page intentionally blank. PREFACE Approximately 150 persons attended the 1990 Ohio Grape-Wine Short Course, which was held at the Worthington Holiday Inn in Columbus on February 18-20. Those attending were from 9 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 and Development Center, Ohio Cooperative Extension Service, Ohio Wine Producers Association and Ohio Grape Industries Committee.

All publications of the Ohio Agricultural Research and Development Center are available to all potential clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, sex, age, handicap, or Vietnam-era veteran status. 8/90-600 This page intentionally blank. TABLE OF CONTENTS Page

Surveying Winery Visitors to Increase Sales 1 by Larry Lockshin Base Wine Making and Champagne Production ...... 9 by David Munksgard Fungicides for Control of Grape Diseases in Northeastern United ... 16 States (1990), by Michael A. Ellis Monoterpenes and Their Relationship to Wine Quality ...... 23 by Jeff David Ackerson A New Sterilant for Treating Wines: Dimethyl Dicarbonate ...... 29 by Mary Calisto Hedging Effects on White Riesling ...... 37 by Tony Wolf Effective Use of Fining Agents ...... 41 by Michele Dittamo Effects of Selective Leaf Pulling With Chardonnay and ...... 44 White Riesling, by Tony Wolf Flawed Seyval Wines: Ways to Prevent Problems ...... 48 by James F. Gallander Biology and Behavior of the Rose Chafer Macrodacty7us ...... 51 subspinosus (F.), by Murdick J. Mcleod and Roger N. Williams Measurement and Removal of Tartaric Acid in Concord Grape Juice .. 55 by Kurt Wiese and Andrew Proctor This page intentionally blank. SURVEYING WINERY VISITORS TO INCREASE SALES Larry Lockshin Executive Director Ohio Grape Industries Program Worthington, OH 43210 Most medium- and small-sized wineries rely mainly on visitors for the bulk of their wine sales. Attracting and maintaining a loyal group of wine buyers should be the main goal of the marketing program for this type of winery. Wineries in Ohio are no exception. The Ohio Grape Industries Program is charged with the responsibility of developing marketing opportunities for all phases of grape products. We decided that the problem of attracting visitors to Ohio wineries could only be solved if we knew something about who we wanted to attract. Standard marketing theory advises that it is very difficult to sell the same product to everyone. The successful marketer "segments the market", divides the buyers into identifiable groups who not only are likely to be interested in the product, but also have the income to buy it and can be informed of the product. The last facet is most important. Identifying the segment is useless unless those potential customers can be reached by advertising or publicity. We decided to survey the customers at five wineries around the state. The wineries were located in NE Ohio along Lake Erie, in Sandusky, in central Ohio, and in SW Ohio outside of Cincinnati. Fifty surveys were randomly filled out at each winery during the month of June, when our "Ohio Wine Month" magazine advertising campaign was running. The surveys asked questions pertaining to demographics, wine consumption habits and psychographies. This last term refers to questions that help find out about a person's lifestyle. For instance, there may be two people who earn $40,000 per year and live in a certain city. One may be inclined to outdoor sports and luxurious restaurants, while the other spends his time home with the family and prefers to cook on the grill. These two may have totally different wine consumption habits. The demographic information does yield some useful data. The first question (see Figure 1) shows how people found out about the winery they visited. The most important source of information was word-of-mouth or friends. Signs and brochures accounted for the next most visits, with magazine ads, articles and radio ads accounting for a very small percentage. It's interesting to know this, but what can a winery owner do with this information? Increasing positive word-of-mouth is one of the best ways to increase visitors. The main way to do this is to provide impeccable customer service. Every employee of the winery should be informed and even given an incentive to treat customers kindly. A disgruntled customer will tell 15-20 people about a bad experience, while a satisfied one will tell about seven. Bad customer relations build ill will quickly. The little things, like carrying wine out to the car, make a big difference.

1 Another idea is to use your current customers to tell more people 1 ike themselves. Have special events for loyal customers and reward them for bringing friends. Have some incentives for anyone who brings a new customer. Build a mailing list of regular customers and use newsletters to increase the number of customers. Offer special memberships based on amount of wine bought or number of new customers. Signage is important. Your sign is a window to your whole operation, the same way that a label tells the customer who you are. You only have those few seconds with a sign or label to make an impression, yet that impression will either draw the customer in or not. Brochures are very ·important for a sma 11 winery. Every potentia1 p1 ace for a customer to stop within 50 miles ought to have your brochure with a map to the winery. There are many services that stock racks at motels and restaurants. These services are often an inexpensive way to cover a large area with brochures. The age of wine buyers at Ohio wineries is fairly mixed (Fig. 2). The buyers are almost equally distributed within the three age groups. However, as we will see later, different age groups buy different types of wines. Wine buyers are highly educated (Fig. 3). Over 80% of the buyers at Ohio wineries have completed college or graduate school. From a marketing prospective, this offers some unique opportunities .. A marketing program could emphasize contacting local professional groups such as doctors and lawyers to have tastings at their meetings. You could advertise in their local newsletters. A winery might also consider conducting wine appreciation c 1asses at 1oca 1 colleges in order to work with future wine buyers. The income of winery visitors (Fig. 4) is concomitant with their education. Wine buyers and visitors have higher than average household incomes. These incomes probably represent both single and dual career families. Dual income families can pay good prices for wine or other products, but they do not have a lot of extra time. Events to attract them are good, but you can't expect them to come every weekend. UPS delivery or other methods of delivering wine might work here. When one speaks of increasing revenues, we usually first think of lowering costs. Although this works, it is often hard to lower costs beyond a certain point. It is easier to increase prices. Wine that attract higher income customers ought to have higher prices than those that are mainly sold ot middle income customers. Selective pricing can be an easy source of increased revenue. It is useful to note that wine drinkers are not exactly the same as wine buyers. In other words, people come to wineries and most of them will taste wine, but not all of them buy. In this survey about 75% of those tasting purchased wine. The difference in these people can be seen in Fig. 6. Wine buyers tend to vacation more in Ohio and to read Ohio magazines, two indications that they are loyal Ohioans. Also, this indicates that these consumers can be reached by in-state tourist based publications, magazines, and catalogues.

2 People who taste, but do not buy are more likely to buy wine at grocery stores, whereas the buyer tends not to buy there. Regional magazines rather than national news magazines are read by wine buyers. Also, wine buyers tend to be a little older than the tasters. These older customers can be encouraged to visit and buy wine by having special events geared to their tastes. Big band music or other entertainment from the 40's could be used to attract an older audience. Most wine tasters liked the wines they tried (Fig. 5). The least liked wine was Concord, with only 38% liking it. Chardonnay and Vidal were the best liked, with Catawba and Cabernet slightly behind. It is interesting to look at the percentage of people who didn't like a wine. Cabernet and Vidal had a sizeable number of .tasters who didn't like the wines, while almost everyone liked Chardonnay. There is no doubt that white wines were the favorites of the winery visitors, although this is not necessarily true for the wines sold in restaurants. The data can be further broken down by the demographics and lifestyles of the persons who liked each variety (Figs. 7 & 8). This allows the marketer to target specific wines to specific groups, or even to decide to make a new variety or discontinue an old one. Catawba drinkers tended to be older and married. They are willing to buy their wines through UPS, but also shop for wine at grocery stores. These people are not that active and prefer to watch soap operas and read magazines such as Cosmopolitan and Vogue. Concord drinkers tended to be a little younger and middle aged. They prefer to vacation in Ohio. They don't buy their wines at grocery stores or by UPS. They enjoy TV sports. Seyval and Vidal drinkers were fairly similar. They tended to be single and younger to middle aged. They like to vacation in Ohio. They don't watch sports as much as the Concord drinkers, but do read fashion magazines and watch soap operas. Chardonnay and Cabernet drinkers were the youngest in age, but a sizeable portion were middle aged, as well. They do not vacation in Ohio, but do buy wine in grocery stores. They don't read fashion magazines like Cosmopolitan and Vogue or watch soap operats or sports on TV. How do you market to these different groups? First, it depends on who you want to attract. What types of people live within 50-60 miles of the winery? What are their demographics? (You can find this information in your nearest library in the U.S. Census.) What types of grapes are available? What styles of wine are you comfortable making? All these factors must be considered when you devise your marketing plan. It's good to remember that it is impossible to be everything to every customer. You will do a better job if you focus your efforts on a few of the segments, rather than trying to make a wine for every person who walks through the door. You will be able to treat those particular people better and provide wines to

3 their liking. You still can and should make different varieties of wine. Your advertising, pricing, and distribution can vary by variety. Your vinifera wines should be available in a few (or more} fine restaurants and wine shops for publicity reasons. Work with a few who will actually promote your wine. Catawba and Concord are best sold only at the winery or UPS. Why not target specific groups with special events? Advertise and promote these events through different media. A good mailing list is a treasure of information. Computer databases can easily be coded for what wines are purchased as well as addresses. Then you can see who your customers are and mail only to those you feel are likely to respond to a specific promotion. Focusing your marketing on specific groups yields better results with lower costs. Your long-term marketing plan should include data derived from your own custormers. It should utilize the strengths of your production abilities and be aimed at likely consumers living within your marketing area.

Fig., 2. Age of Wine Buyers Visitors To Ohio Wineries Age 51-65 Age 65+ 2%

Age 21-34 31% 35-50 38%

4 Fig. 3. Education Level of Wine Buyers Ohio Winery Visitors

College

Graduate High School 21% 16%

Fig. 4. Household Income of Ohio Winery Visitors

$25-35.000 24% $35-45,000 17% $10-25.000 17%

$45,000+ 43%

5 Fig. ~ Vwietal Preferences Oio Wrnery Visitors

90~------, 80 70 60 50 40 30 20 10 0 Cataw. Ccnc:d.O!ardny.Seyvl. Vidal Cabmt. -o/o Liking % Not Liking

Fig. 6. Wine Crir-Kers vs. Wine Buyers Visitors to Ohio Wineries 70r------, 60 57 50 40 30 20 10 0 Vac. Qoc. ~ Mag. Single 51-65

- w,.. Drll"lker (~

6 Fig. 7. Defl'lo0raphi¢e of Winery Visitore 6y Varietal Prererenc:e BOr------, 70 60 50 40 30 20 10 0 %Single 21-34 3~-~0

• eatim! contiiZJ SeyR-8-1 Vid 1--:.·>A 01aCJ Cab

Fig. 9. L.ifestyle Oifferencee by Variety Visitors to Olio W.neries

9Qr------~ eo 70 60 50 40 30 20 10

o~~~~~~~~~~~~~LU~~~ vac Groc. UPS Sports Soaps Mag.

• eat EEl eonl?%1 SeyK{-:1 Viet L->A 01aO Cab

7 Fig. 6. Lifestyle Differences by Variety Visitors to Ohio W.neries 90 eo 70 60 .. 50 40 30 20 10 0 vac Groc. UPS Sports Soaps Mag. • cat mil eonliZJ Seyk{-1 vid f:>>J 01aD cab

8 BASE WINE MAKING AND CHAMPAGNE PRODUCTION David Munksgard Glenora Wine Cellars Dundee, New York Quality sparkling wines are produced from quality grapes. As simple as that may sound, I'm convinced that many wineries still do not consider that when producing their sparkling products more often than not, sparkling wines are produced from leftovers, or wines that are too weak in character to go into one of the wineries more traditional bottlings. When one considers the competition that exists for shelf space at the retail level, how could anyone approach such a costly venture with such a cavalier attitude. The quality sparkling wines of the world are produced in climates that are cold and harsh, and in most cases incapable of bringing to full maturity the crop as measured by table wine standards. The champagne region in France (for example) is at the uppermost boundaries for grape growing in that country.

While I was with Chateau St. Jean, all our sparkling wines were produced from grapes from the very cool Russian River Valley, which translated into wines of delicate fruit character. Warmer climates will produce from the same variety, sparkling wines with: 1. Heavier fruit by nose and mount 2. More color 3. More phenolics 4. Less ability to age

I recently joined Glenora Wine Cellars of the Finger Lakes as winemaker. I am convinced that the cool climate of this region that is moderated in summer and winter by the long deep lakes is capable of producing world class sparkling wines. The Pinot noir and Chardonnay that grows in this region is all that I look for in cuvee material. In California, as in the Finger Lakes, the cooler regions that offer you delicacy in fruit also pose the most risk in terms of mildew and botrytis. Our harvest parameters are: A chemistry of: 17.5-19.5 Brix 0.90-1.2 T.A. 3.2-3.0 pH Free of mold or rot Free of sunburn Sound, unbruised condition Grapes harvested as cool as possible We are obviously not always able to reach all of these parameters. But, this does allow us a target to shoot for, and sends our growers a message as to the quality of grapes we expect. Currently, all our sparkling wine grapes are hand picked into 1/2 full 30# lug boxes. The are dumped by hand into our Willmes

9 or our Bucher presses. Every attempt is made to m1n1m1ze skin maceration. Pinot nair has a very delicate skin and excess handling will result in skin maceration. This maceration, as well as warm fruit conditions, will result in wines with: increased phenolics, increased color, heavier character in nose and mouth, less aging ability, and poorer bubble quality. Only the first 130 gallons per ton extracted will be used in our sparkling program. The juice is pumped from the presses to chilled tanks. Pectic enzymes are added. SO may or may not be used. I prefer to cold settle the juice at 35-40°F to c1 ari fY, but will not hesitate to centrifuge or even 1ees filter an entire tank if harvest conditions warrant such measures. Whatever the method of clarification, my goal is a solids content of nearly 0%. After clarification, I prefer to warm the juice to 55°F and give the juice a bit of aeration. While this is being done, we are hydrating 200 mg Prise de Mousse yeast/liter of clarified juice. Once the juice is warmed, the yeast is pumped over the surface of the juice and the chillers are set to come on at 60°F. Fermentation generally reaches dryness in 14-21 days. A small portion of our cuvee material may be put through malolactic fermentation. When dry, the tank chillers are set to 40-45°F. When the wine is chilled to 45°F the SO is adjusted to 15-20 ppm free. I feel that a lot of richness in nose and moufh can be gained in cuvees by leaving them in contact with their primary fermentation lees for extended periods. Careful monitoring for off odors during this period is critical. When we do decide to separate the young wine from it's solids, we generally centrifuge followed by rough D.E. filtration. From this point, the wines are held at 32-28°F to start cold stabilization. At Glenora, we produce three sparkling wines: A Brut: 70-80% Pinot nair 15-20% Chardonnay 5-10% Pinot blanc A Blanc de Blanc: 80% Chardonnay 20% Pinot Blanc A Reserve Brut: 50% Pinot nair 50% Chardonnay Extensive tastings are held on each lot to be considered for use in the blends. Detailed notes are kept as to their taste, aroma, and intensity of variety. To begin the blending process, I load tank number, variety, gallons, acid, pH, and % alcohol into a program on my computer. In this way I can allocate gallons from various tanks to each of the three blends. The computer will readout percent composition by variety, weighted analysis of the computer blend, and let me know if I over-use gallons from any tank. This provides me with a logical starting point. Lab tastings are then completed on these trial blends. Results of these tastings reveal what changes need to be made in the blends. 10 Generally, for the Brut cuvee which is predominantly Pinot noir, I would choose Pinot noir that exhibited moderate to low varietal character. Conversely, I would choose Chardonnay for this blend that exhibited moderate to intense varietal character. The theory being that the two when blended would in essenece cancel each other out. You would end up with a blend that would not exhibit strong or dominate characteristics of the individual components. Chardonnay, with its firm, lean acidity provides the structure or framework for the blend. Pinot noir, with its abundant berry-fruit by nose and mouth provide roundness, depth, and form. Pinot blanc, with its aromas and flavors of ripe pears and spice is used to add depth to the blend, especially the middle mouth. For the Blanc de Blanc, we select Chardonnay of low to moderate varietal character which will comprise the majority of the cuvee. We then blend in a small amount of Pinot blanc of moderate intensity to balance off the blend. In this blend, much of the fruit and depth by mouth would have to come from the Pinot blanc. For the Reserve Brut, which will receive the most age in tirage, we would choose Pi not noi r and Chardonnay that are most 1ean and 1east vari eta 1 in character. A heavier Pinot nair might develop jam like aromas when aged. A heavier Chardonnay might develop vegetative and/or herbaceous aromas when aged for extended periods. Though you may not be using Pinot noir, Chardonnay, or Pinot blanc for your blends, you can probably approach the process with the same sort of reasoning. Helpful tips for trial blending might be: 1. Make absolutely sure you have good representative samples of each tank. 2. Once you have selected a blend, taste it blind three times along with your second and third choice over a three-week period to confirm your decision. 3. Keep thorough notes of all tastings. 4. I strongly suggest that a panel of at least three experienced tasters review the individual lots as well as the blends. 5. While you are bottling your selected blend, bottle down two or three cases of your second and third choice blends to see how they taste after bottle fermentation. Once the blend has been made in the cellar, stabilization for cold and heat must be completed. Cold stability for sparkling wines is extremely critial. If tartrates were to form in the bottle after disgorging, the wine would gush upon opening. THe tiny crystals would provide a point for C02 bubbles to mass to and the bubbles would evolve in one great eruption. Dirty wine slows the cold stabilization process by interfering with crystal formation--rough filtered wine is recommended. Lab trials are run in a cold box at 35°F for three weeks.

11 Once we have determined that the wine is cold stable, we then start our heat stability trials. Increments of 1/4 pound of bentonite/1000 gallons is recommended. Our trials are held at 100-104°F for two days. Trials are examined visually with a high intensity lamp in a darkened room. The sample that clears the haze formed by the heat labile protein is found. We then back up 1/2 pound. So if, for example, we found that 2 pounds cleared the haze, we would actually treat the wine with 1 1/2 pound bentonite. The reason for this is that we will be using 260 grams bentonite per 1000 gallons cuvee as a riddling aid when we bottle. Protein and its resultant amino acids are very important to bubble quality. For this reason it is very important to not strip the wine of all of its protein. Lab follow-up heat stability tests are run to ensure that we accomplished the same results in the cellar. The wine is filtered with polish pads followed by membrane filtration because portions of our cuvees undergo malolactic fermentation. Helpful tips for the stabilization/filtrate period might be: 1. Remember, even though the individual components of a blend might be stable, that does not mean that the blend itself will be. Any changes in theTA, pH, or alcohol will change the heat and cold stability. 2. Cold stabilize your wine before you run your heat stability trials. A drop in the pH will require less be~tonite. 3. After heat and co 1d stability has been achieved in the cellar no other amendments should be made without rechecking the stability. Minor S02 additions should not affect stability. It is the secondary fermentation within a sealed bottle that will transform your low alcohol, high acid, modest varietal character wine into a class of it's own. I have tried a number of yeast cultures for sparkling wines over the last ten years. I do not know of a better yeast than Scott Labs Prise de Mousse. It is easy to start and culture up, it ferments well and it riddles well. Lalvin, the company that produces Prise de Mousse for Scott has a booklet that contains an excellent build up procedure for sparkling wine cuvee bottling. We use a method very similar to that one, except that we build up to a level of volume per volume 10 to 20% active yeast culture. We are not trying to get more yeast into the bottle, we are using the culture as a medium to carry oxygen into the bottle safely. We like to bottle with at least 1 million cells per ml and at least 80% budding. Helpful tips for yeast propagation are: 1. Absolute sanitation is essential. Use only polish filtered or membrane filtered wine. 2. If possible, check the culture microscopically every day during the build up. Budding should be over 80%. The yeast cells should look healthy. Scan for other organisms. 12 3. Trust your nose. Healthy cultures smell yeasty and fruity. Sick or weak cultures smell sour (not like vinegar--more like bad lees), or even become aldehydic because the yeast are not able to utilize the oxygen from the aerations. 4. Check the R.S. on your cultures every day. Cultures should be maintained between 2.0 to 2.8 R.S. Our cuvee bottling routine goes as follows: We are shooting for a bottle R.S. of 2.6 which when fermented to 0.2 or less will give us 120 PSI at 68°F. We already know the R.S. on the "dry" portion of our soon to be bottled cuvee. We now need the sugar requirements for the yeast portion. The day prior to bottling we would draw from our yeast tank the volume we need for tomorrow's bottling. We check the R.S. on the yeast first thing in the morning then again in the afternoon. This would provide us with two points on a very rough curve to estimate what the R.S. will be on that yeast at 8:00 a.m. tomorrow morning. Since our yeast represents 10 to 20% of the volume to bottle this estimation becomes important. We calculate the sugar we need for the yeast based on our rough graph and add to that the amount needed for the dry portion of the cuvee. This volume is dissolved into a small amount of the wine to be bottled tomorrow. We use dry dextrose because it dissolves so rapidly and we also do not need to invert the sample prior to running an R.S. The day prior to bottling we also hydrate 260 grams bentonite per 1000 gallons of cuvee to be bottled. This will be added tomorrow as our riddling aid. The morning of the bottling we simply pump the wine we dissolved the dextrose in into the main lot of "dry" wine. The yeast is also pumped into the same tank. The bentonite is added to the wine, yeast, dextrose mixture and a blade type mixer keeps the whole mass homogeneous. We run a quick R.S. to ensure that we hit our 2.6 R.S. target and make corrections as needed. We are now ready to start bottling. Bottles are filled to 750 ml, a bidule is hand-inserted into the bottle and a crown cap is applied. Bidules are as important to hand disgording operations as they are to machine disgorging. For those of you not familiar with bidules, it is a plastic cylinderical cup-shaped device that fits tightly in the neck of the bottle. The open end faces the wine; the closed end is tight against the inside surface of the crown cap. The purpose of the bidule is not to provide a nesting spot for the riddled yeast as some might think. If you were to observe the mechanics of disgorging in slow motion, you would see that when you remove the crown cap to a11 ow the frozen p1 ub to eject itse 1f, you are in essence peeling that cap off at bit at a time. It is in reality, impossible to pull all of the cap off at once. So what can happen is this; if the plug containing the eyeast is not rock hard (and it should not be), as the first portion of the cap is pried away, the yeast will try to squirt through that opening. If this happens, there may not be enough pressure remaining in the bottle to force the remainder of the plug out of the bottle. With a bidule in place inside the 13 bottle, all of the cap has to come off before the bidule can start to be pushed out by the frozen plug. Then all of the bidule and all of the plug will be ejected all at once. When you consider the amount of pressure that the crown cap is expected to hold, it quickly becomes clear that the correct fitting of the cap to the bottle is essential. I find it very strange to see all the effort that some wineries go to, to ensure that they grow or buy the finest grapes to make the finest cuvess only to go haphazardly into cuvee bottling and end up with 1/3 of their bottles leaking. Placing a crow cap on a bottle is a two-step operation; first the cap is held tightly against the top of the bottle and then the edges of the cap are bent over the lip of the bottle. Using a crimp gauge tells you only about the crimp, not about how much pressure the cap will hold. For less than $150 you can make a device that will allow you to check how much pressure the cap will hold. After filling, our bottles are placed into wooden bins where they lay on their sides until time for riddling. Typically, our bottle fermentations take 4-6 weeks to reach dryness. Warehouse temperatures of 50-60°F are best to keep the fermentations from going too rapidly and for better overall wine quality. Helpful tips for bottling are: Have one other person check your sugar calculation before you add it. 0.097# dextrose per gallon of wine will raise the R.S. 1.0 grams per 100 ml. The amount of water that the dextrose contains will vary this factor somewhat. Use some sort of riddling aid; better yet, do some experimenting to see which one you like best. Keep the cuvee well mixed while you are bottling. Do not try to mix the tank by sparging it with nitrogen. This will be a mess when you get around to disgorging the wine. Use bidules. Make sure that the cap you choose to use is compatible with your bottle. Riddling is the subject that most people call me about. They usually start off by saying that they have never had a bit of problem riddling their wines in the past, but now they are. I usually ask if they have used a riddling aid and they usually say no. Riddling aids are insurance policies on your wines. Using a riddling aid does not guarantee that you will not have riddling problems, it just stacks the deck heavily in your favor. I have used them on wines for ten years and have never had a problem with riddling. The choice of dosage is the last subject that I would like to discuss. My suggestion to you in this regard would be this.

14 Make up a standard dosage equivalent to: 54.5 gallons H20 600# sucrose (not dextrose) 2194 grams citric acid 1210 grams K2S205 This will be a 60° Brix dosage. Each ml of this per 750 ml bottle will raise the R.S. by 0.1 grams per 100 ml., and raise the so2 by 2.3 ppm.

You can leave out the S02 if you wish to accelerate the age of your wine or you can increase the level if you wish to allow the aging of your sparkling wine. Ascorbic acid can have a very good effect on wines that seem a bit tired. 60 ppm ascorbic acid in conjunction with 30 ppm S02 seems to work quite well. Brandy or cognac use in sparkling wines is greatly exaggerated. It works with some very youthful and austere wines, but only in levels that are incredibly minute. I have never used more than 1/4 ml per 750 ml bottle. TO SUMMARIZE Plan your cuvees as carefully as you plan your table wines--do not treat them as an afterthought. Whole cluster press and hand-pick fruit if possible to minimize skin maceration. Stabilize your cuvees after blending. Heat stabilize after cold stability to minimize protein stripped cuvees. Acclimatize your yeast. Use riddling aids. Use bidules. Make sure your crown caps are sealing adequately.

15 FUNGICIDES FOR CONTROL OF GRAPE DISEASES IN NORTHEASTERN UNITED STATES (1990) Michael A. Ellis Department of Plant Pathology OARDC/OSU, Wooster, OH 44691 The most important grape diseases caused by fungi in the eastern United States include: black rot, downy mildew, powdery mildew, Phomopsis cane and leaf spot and Botrytis fruit rot. Each of these diseases has the potential of causing serious losses in yield and/or quality if environmental conditions are favorable for disease development. It is also important to note that one, two or all of these diseases may be present at the same time in the same vineyard. Most of these diseases are controlled through the proper use of fungicides and implementation of various cultural practices. Because of the fungi that cause these diseases are physiologically different, it may be necessary to use different fungicides to control specific diseases. None of the currently available fungicides for use on grapes will provide excellent control of all the grape diseases; therefore, it is extremely important to know what grape disease or diseases are present or have the potential for developing in the vineyard in order to select the proper fungicide or fungicide combination for successful disease control. . Although we are in danger of loosing many of our most effective fungicides, we still have fungicides available for control of most grape diseases. Whereas, some fungicides may be more effective than others for controlling a specific disease, it must be remembered that the effectiveness of any fungicide is largely dependent upon how and when it is used. To use any fungicide effectively, the following points must be considered: 1) correct disease identification in order to select the proper fungicide or fungicide combination, 2) proper timing of application, and 3) thorough coverage of all susceptible plant parts. The purpose of this paper is to review the efficacy of various fungicides that should be available for use on grapes in 1990. Due to constantly changing label information and the withdrawal of many fungicide registrations on various food crops, it is extremely important that growers obtain, read and understand the most current label for any fungicide prior to its use. In the following text, I will discuss the fungicides available or recommended for individual diseases, as well as various combinations of diseases that often need to be controlled simultaneously in the vineyards. BLACK ROT Ferbam, mancozeb, and maneb +zinc are very effective for controlling black rot when used in a protectant spray program. These fungicides are strictly protectants and provide no curative activity. They will not "burn out" infections after they have occurred. I feel that mancozeb provides an excellent foundation for a protectant spray program for grapes in the northeastern U.S. Mancozeb is an EBDC (Ethylene-Bis-Dithocarbamate) and is under pressure from consumer groups to be removed from use; however, it is still labeled for use on

16 grapes. It is a good protectant fungicide that will provide good to excellent control of not only black rot, but also downy mildew and Phomopsis cane and leaf spot. In addition, it is relatively inexpensive. The major problem with mancozeb is a 66-day preharvest interval (PHI) on grapes. It cannot be applied within 66 days of harvest. With this in mind, I feel it is important to use a good protectant program with mancozeb at the 3 to 4 lb per acre rate early in the season (pre-bloom). The idea here is to keep diseases from developing in the planting early in the season, so they are not a problem later in the season when mancozeb cannot be used. Regardless of what fungicide is used, we need to put more emphasis on early season (pre-bloom) disease control. If we let disease get established early, we must fight them throughout the remainder of the season. In wet growing seasons, the results of early season disease development in the vineyard are usually disastrous. Mancozeb is available under many trade names. Some common ones are Dithane M-45, Manzate 200 and Penncozeb. Once the 66-day PHI for mancozeb has been reached, a good alternative to switch to has been maneb + zinc. Maneb + zinc is almost the same fungicide as mancozeb, but it has a 7-day PHI (can be applied up to 7 days before harvest). Prior to 1987, maneb +zinc was available in many trade names and formulations. Since then, most companies have voluntarily withdrawn their registration of the material. At present, maneb + zinc is available, but labels differ significantly. Pennwalt's maneb +zinc 4F (flowable fungicide) is the only one I can find that still has a 7-day PHI. Some maneb +zinc labels state that they cannot be applied to grapes past fruit set. Remember to always read the label. There may be different labels for the same fungicide, depending upon the manufacturer. A major problem with maneb + zinc 4F is that after fruit set, a maximum of 1.5 qt per acre can be applied. The 1.5 qt per acre rate is equivalent to 1.5 lb of maneb per acre and will probably provide adequate control under low disease pressure where early season disease control has been achieved. Under heavy disease pressure in wet growing season, this rate will not provide adequate control. I have spent considerable time here describing mancozeb and maneb + zinc because, until something changes, I feel they should play an important role in the grape disease control program for the midwest and northeast U.S. It is important to note that some food processors may not accept mancozeb­ or maneb-treated fruit. This also applies to captan. Growers need to know where they are selling their fruit and if the buyer has any restrictions on pesticides prior to initiating a control program in the spring. Ferbam will provide excellent control of black rot, but will not provide effective control of downy mildew. In addition, the last label I read stated that no more than three applications. could be applied per season on grapes. This three application per season limitation may change. If it does not change, the use of ferbam for black rot control is very limited. Again, make sure you read and understand the label. The systemic fungicides, Bayleton and Nova, are also highly effective against black rot and will provide some post-infection (curative) activity of the 17 disease if applied at the higher labeled rates and within 72 to 96 hours (3 to 4 days) after the initiation of an infection period. Post-infection or curative control must be achieved prior to symptom development on leaves or fruit. Once the symptoms are present, these fungicides will not eradicate or burn out the fungus. Both Bayleton and Nova also appear to provide good protectant activity against black rot if applied at the lower labeled rates in a good protectant program. Captan, Benlate and copper fungicides (fixed copper or Bordeaux mixture) are only slightly to moderately effective against black rot and will not provide adequate control if applied alone under heavy disease pressure. Rubigan was recently registered for use on grapes and will provide moderate control of black rot if applied in a protectant program. Rubigan is in the same general class of fungicides as Bayleton and Nova; however, it does not provide adequate curative or post-infection control of black rot. DOWNY MILDEW Captan, mancozeb, maneb + zinc and copper fungicides (fixed coppers and Bordeaux mixture) are all considered to be highly effective for control of downy mildew. All of these fungicides are only effective when used in a protectant spray program. They will not provide post-infection or curative activity and will not eradicate or "burn out" the fungus after symptoms appear. A good protectant program of mancozeb and maneb + zinc should provide good to excellent downy mildew control; however, the problems described with their use for black rot control also apply to downy mildew. Captan will also provide good to excellent control if applied in a good protectant program; however, it will provide little control of black rot. The fact that certain food processors, such as National Grape Cooperative, would not accept grapes treated with captan in 1989, raises some serious concerns about our ability to effectively control grape diseases in the eastern U.S. If a grower cannot use captan, mancozeb or maneb + zinc to control downy mildew, the only alternative material is copper. Copper should provide good downy mildew control on most cultivars, but is only slightly effective for black rot. There are many formulations of fixed copper available and the old standard (Bordeaux mixture) can still be used. I personally would not be comfortable recommending a full season protectant program (four to eight applications) of copper for grape disease control. A major reason the grape industry generally changed from using copper to the new organic fungicides such as captan and mancozeb in the 1950's was phytotoxicity. The use of copper on Concord grapes has been shown to result,in slight vine stunting as well as reduced vigor and yield. In addition, foliar and fruit injury can be quite severe if sufficient copper is applied under the proper environmental conditions, such as low temperature and slow drying conditions. Many questions are currently being asked about the use of copper on grapes, and in my opinion, we simply do not have all the answers. Current research is 18 needed to evaluate the various formulations of copper on a wide range of currently grown cultivars for their phytotoxicity as well as their efficacy in controlling the major diseases. I feel that the use of copper as a fungicide will increase on grapes, at least temporarily, in the near future. My recommendations to growers using copper are: 1) realize that copper may not provide adequate control of black rot; 2) remember that problems with phytotoxicity may be greater under cool temperatures or slow drying conditions; and 3 ) follow all label instructions. BLACK ROT PLUS DOWNY MILDEW Black rot and. downy mil dew are among the most common and destructive diseases that require some level of control in most years, especially in wet growing seasons. Often, both diseases are present at the same time in the vineyard. Therefore, it is important to have fungicides in the spray program that will control both diseases. The following is an example of what can happen if the proper fungicides are not used. A grower in southern Ohio had approximately 10 acres of Chancellor (which are highly susceptible to downy mildew). He had a black rot problem in 1978, so in 1979 he used ferbam rather intensively. He obtained perfect black rot control in 1979, but lost the entire crop due to late season infection by downy mildew. It is imperative that the spray program controls all major diseases in the vineyard. Mancozeb and maneb +zinc are the only fungicides currently available that have been rated as being highly effective against both diseases. Some problems involved in using these fungicides are discussed under black rot. Copper fungicides used alone may be sufficient to control both diseases under slight moderate conditions for disease development, but will probably not control black rot under heavy disease pressure. Problems related to phytotoxicity are also a concern. A fungicide combination that has provided good control of both diseases, and is currently legal for use, is captan (for downy mildew) plus ferbam (for black rot). When using this combination, I recommend using both fungicides at their full labeled rates. Other fungicide combinations that would be legal, but to the best of my knowledge have not been evaluated, are either Bayleton or Nova (for black rot) plus a fixed copper or captan (for downy mildew). POWDERY MILDEW Sulfur, finely ground wettable powder or flowable, is highly effective against powdery mildew if used in a protectant program with a minimum of 7 to 10 days between applications, but has little or no effect on the other grape diseases. It is important to remember that sulfur can cause severe injury on some varieties. Sulfur should only be used on varieties known to be sulfur tolerant. Sulfur injury may occur even on sulfur tolerant varieties when temperatures 85°F or higher are experienced during or immediately after application. 19 Copper fungicides have been rated as moderately effective against powdery mil dew; however, care must be taken when using copper due to the danger of foliage injury (phytotoxicity). Dinocap (karathane) is rated as highly effective for powdery mildew; however, several varieties are sensitive to foliage damage from karathane. As with sulfur, damage may also occur on karathane tolerant varieties if high temperatures occur during or shortly after application. Benomyl is very effective against powdery mildew in areas where benomyl­ resistant strains of the powdery mildew fungus are not present. Where resistance is not present, benomyl should do an excellent job of controlling powdery mildew and is very safe to foliage and fruit. Bayleton, Nova, and Rubigan are all highly effective for cotrol of powdery mildew. They will also provide control of black rot, but it is important to remember that they will not control downy mildew. The development of strains of powdery mildew fungus with resistance to the ergosterol biosynthesis inhibiting fungicides (Bayleton, Nova, and Rubigan) is a serious threat to their continued use for powdery mildew control on grapes. There is good evidence that resistant strain have developed against Bayleton in New York, Pennsylvania and California. In order to prevent or delay the continued development of resistance, Bayleton, Nova and Rubigan should not be used alone for season-long control of powdery mildew. This means another fungicide with good activity against powdery mildew should be incorporated into the spray program at some point during the growing season. If benomyl cannot be used due to the presence of benomyl-resistant strains, the only alternatives at present are sulfur and karathane. BLACK ROT, DOWNY MILDEW AND POWDERY MILDEW At times, it is necessary to control all of these diseases simultaneously. In my opinion, the best fungicide combination for control of all these diseases is mancozeb or maneb +zinc plus either Bayleton or Nova. The mancozeb or maneb +zinc in a good protectant program should provide control of black rot and downy mildew. The Bayleton or Nova will provide additional control of black rot in addition to powdery mildew. Copper fungicides will provide some level of control for all three diseases; however, they are weak for black rot control and the potential for phytotoxicity is present. The combinations of either Bayleton or Nova plus copper fungicide or captan is also an alternative. Some growers of French hybrid and vinifera cultivars have also reported using sulfur plus mancozeb or maneb + zinc.

20 PHOMOPSIS CANE AND LEAF SPOT Captan, mancozeb and maneb + zinc are moderately to highly effective against this disease. BOTYRTIS FRUIT ROT (GRAY MOLD) Rovral is highly effective against Botrytis and it would be my fungicide of choice for control of Botrytis on grapes. A major problem with Rovral is cost. Benlate will provide moderate to good control of Botrytis, if Benlate-resistant strains of the fungus are not present. Effectiveness of Fungicides for the Control of Grape Diseases Phomopsis cane and Black Downy Powdery Botrytis Fungicide leaf spot rot mildew mildew rot

Bayleton 0 +++ 0 +++ 0 Ben late + + 0 +++ ++ Captan +++ ++ +++ 0 + Dinocap (karathane) 0 0 0 +++ 0 Ferbam + +++ + 0 0 Fixed copper and lime + + +++ ++ + Mancozeb or Maneb + zinc +++ +++ +++ 0 0 Nova 0 +++ 0 +++ 0 Rovral 0 0 0 0 +++ Sulfur + 0 0 +++ 0 Rubigan 0 ++ 0 +++ 0 +++=highly effective; ++=moderately effective; + = slightly effective; 0 = not effective. Where Benlate-resistant strains of the powdery mildew and Botrytis fungi have been detected, Benlate will be ineffective and should not be used. NOTE: The above ratings are intended to pro vi de the reader with an ide a of relative effectiveness. They are based on published data and/or field observations from various locations. Ratings could change based on varietal susceptibility and environmental conditions for disease development.

21 Leaf Wettness Duration-Temperature Combinations Necessary for Grape Foliar Infection by Black Rot Minimum leaf wetness Temperature duration for light (C) (F) infection (hr}

10.0 50 24 13.0 55 12 15.5 60 9 18.5 65 8 21.0 70 7 24.0 75 7 26.5 80 6 29.0 85 9 32.0 90 12 *Data represent a compilation from several experiments with the cultivars Concord, Catawba, Aurora and Baco noir.

22 MONOTERPENES AND THEIR RELATIONSHIP TO WINE QUALITY Jeff David Ackerson Department of Horticulture The Ohio State University The Ohio Agricultural Research and Development Center Wooster, OH According to Amerine and Singleton the best wines tend to be those with the most distinctive, most intense, but still mild flavors (1). One varietal wine noted for it's intensely fruity aroma is Muscat. The aroma of Muscat variety has been attributed to compounds known as monoterpenes. Evidence shows that these compounds exist in two forms, free volatile terpenes, F.V.T., and nonvolatile bound forms know as potentially volatile terpenes, P.V.T. (3,4). F.V.T. such as geraniol, hotrienol, 1 inalool and a-terpinol generate aromas which have been characterized as floral, pine and coriander. The linalool, nerol and rose oxides generate camphoraceous, gerani urn, herbaceous and unripe green fruit aromas (13,15). In contrast, P.V.T. have little to no aroma, because they are bound to sugars such as arabinose, glucose, rhamnose and rutinose by a glycosidic bond (20). Glycosides can not be detected in model wine systems, and in water solutions they have been reported to have a very low fruity, floral or tea-like flavor (14). Wines may lack aroma due to low concentrations of monoterpenes. Figure 1 VARIETY illustrates that grapes associated with P.V.T. neutral varieties of wine tend to contain Muscat of Alexandria 1.00 5.60 less of the F.V.T. and P.V.T .. Wine flavor Canada Muscat 0.93 4.10 quality may be increased by extracting low Traminer 0.54 1.90 Delaware 0.46 1.60 concentrations of monoterpenes found in Riesling 0.28 0.88 these neutral varieties. Research indicates Chardorvlay 0.16 0.22 low concentrations of monoterpene alcohols are important, because they can act as aroma synergists in VHjs vjnjfera. One component Figure 1: Terpene content in mg/L of ripe grapes. (5) can increase the aroma of another, and a mixture could become more aromatic than the most aromatic single component which belongs to the mixture (18). Processes which increase the amount of F.V.T. and P.V.T. in wines are likely to increase the aroma quality of a wine (14). These processes can be classified into environmental, cultural and processing practices. Environmental conditions which favor the production of monoterpenes center around the amount of light exposure which grape clusters receive. Gewurztraminer berries which received full sunlight contained higher amounts of F.V.T. and P.V.T. than berries which were shaded (17). This suggests that hedging, crop level reduction and basal leaf removal should increase the amounts of monoterpenes in grapes (16). In addition to increasing the level of monoterpenes, this process increases 0 8rix. It also reduces titratable acidity, pH, potassium, and botrytis bunch rot which should increase wine quality (17).

23 Cultural practices such as irrigation, harvest temperature, post-harvest handling and maturity at harvest influence grape monoterpene levels. Irrigation was found to lower P.V.T. by 50%, but there was no observable change in the development of F.V.T.. Cluster thinning of unirrigated vines resulted in a significantly higher concentration of P.V.T. (12). These results are expected, since glycosidically linked monoterpenes are more water soluble than there unbound counterparts. As a result, these P.V.T. may be diluted. It is advisable to harvest cool fruit, preferably early in the morning. The grapes should be carefully handled and immediately delivered to the winery for processing. Delays in the vinification process tend to lower the quality of the wine (6). Rough handling ruptures grape skin cells releasing enzymes which may act on P.V.T. components. These aromas may be released in the field during storage. The released compounds represent a reduction of flavor compounds in the final product. Also, harvested grapes should not be allowed to sit in direct sunlight in crates. The heat can change the monoterpene and flavor profile by molecular rearrangement. Today, growers and wineries harvest and process their wine grapes over a range of soluble solids (0 8rix). In cool climates, winemakers and growers generally harvest at a peak maturity corresponding to the highest sugar content ( 0 8rix). However, harvests at different mat~rities represent changes in terpene aroma constituents. This is because during ripening the concentration of F.V.T. and P.V.T. increases, and there ratios change until the fruit becomes overripe (4). For example, in Muscat of Alexandria the concentration of F.V.T. peaks and then falls 14 days before overripeness occurs (5). In addition, the concept that the best wines are made from the highest 0 8rix grapes is not always true. Sensory evaluation studies of some Ohio wines indicate otherwise (8). The majority of grape monoterpene maturity research has been conducted with more aromatic varieties of Vitis vinifera. However, limited research has been done with the French-American hybrids. They have aromas which are associated with neutral cultivars. The monoterpene content of wines may be increased by various processing techniques. Before fermentation, techniques such as method of pressing, heating, acid hydrolysis and skin contact have an effect on monoterpene content. Grapes which are subject to a harder press generally yield musts which contain more monoterpenes. However, the use of pressing-aid material reduced aroma constituents by 38% in Mario-Muscat and 34% for Muller-Thurgau (10). Edinger reported that other components of the skin such as phenolics are also extracted with a harder press. Therefore, the degree of pressing would have to be balanced with other undesirable effects (6). Heating the must may also extract monoterpenes and convert them to F.V.T. by breaking the glycosidic linkage. However, heating can cause rearrangement of the terpenes to isomers which are not as aromatic. Therefore, a balance is needed to ensure that the terpenes responsible for flavor do not rearrange. Acid hydrolysis functions in a similar manner allowing the glycosidic linkage to be broken. However, this process involves a deacidification step which brings about other changes which adversely effect wine quality.

24 For the variety Gerwurztraminer, skin contact at low temperature has been shown to increase wine quality and the amount of terpenes present (11). However, prolonged high temperature extraction was detrimental to wine quality. This was due to the extraction of compounds such as phenolics and acetamides (7). Again, this method of extracting monoterpenes must be balanced and used in combination with other techniques. Increased skin contact has the potential to haze wines due to a reaction between phenolics and proteins (19). After fermentation fining, aging and enzymes have effects on the monoterpene content of wines. While fining can generally aid the color quality of wines, overfining reduces the flavor aroma quality in a wine (19). As a wine ages and deve 1ops a more intense bouquet, it is genera 11 y observed that the terpene aroma is lost. This is due to rearrangements of the more aroma intense terpene alcohols to terpene oxides. One way to prolong the presence of the terpene alcohols is to cover the wine with an inert gas such as nitrogen after fermentation. This process helps to avoid the formation of aldehydes which will mask the aroma of monoterpene alcohols (15). Enzymatic hydrolysis of the bond between the monosaccharide or disaccharide and terpene has meet with mixed success (2). However, mixed pectinases tend to yield more positive results. In general, natural grape and almond B-glucosidases do not work well, because of inhibition by low pH and high sugar concentrations. The aim of my research and this literature review is to aid the Ohio grape wine producers in making a more flavorful and aromatic high quality French-American hybrid wine. In my project, grapes and wine shall be examined from verasion to overripness for terpenoid aroma constituents. This data shall be plotted along with conventional must analysis data and correlated to sensory evaluations of wines from various maturities. Figure 2 illustrates sugar content and average berry weight data for Seyval during the 1989 season. For these studies frozen grapes, from a commercial vineyard in northern Ohio are being analyzed for their monoterpene content at various maturity levels (0 Brix). Correlation of this data to sensory evaluations of wines made at several stages of maturities may assist winemakers and growers in determining the approximate harvest time for peak wine aroma. However, no recommendations can be made at this time. The F.V.T. may peak before or after the peak in sugar (0 Brix) (Figure 2). It is my hope that this review on monoterpenes and their relationship to wine quality has illustrated the fact that monoterpenes are an important flavor and aroma constituents in some wines. If growers and wineries use environmental, cultural and processing techniques in combination, we would expect to increase monoterpenes. Wine made from these grapes should be of superior quality. In general, they should be more fruity and floral.

25 SEYVAL BLANC MATURATION STUDY POSSIBILITIES

...... 0 m ::::!. ~ 0 0 0 10 20 30 40 50 60 70 80 Days After August 1, 1989

-Average Berry weight -+- Soluble Solids

Figure 2: Seyyal Blanc maturation data for the 1989 season. A peak in F.V.T. may not necessarily correspond to a peak in •srix. (Ackerson and Gallander, Unpublished data)

26 LITERATURE CITED 1. Amerine, M. A. and V. L. Singleton 1977. Wine: An Introduction. Berkeley: University of California Press. 2. Aryan, A. P., B. Wilson, C. R. Strauss, and P. J. Williams. 1988. The Properties of Glycosides of Vitis vinifera and a Comparison of Their B-Glucosidase Activity With that of Exogenous Enzymes. An Assessment of Possible Applications in Enology. Am. J. Enol. Vitic. 38: 182-188. 3. Bayonove, C. L. and R. E. Cordonnier. 1982. Les Consituants de 1 'Arome des Muscat. Bull. Techn. Pyren. Orient. 105: 99-106. (Translated from French by Christine Kermizis and Efrian Salzar) 4. Bayonove, C. L. and R. E. Cordonnier. 1970. Recherches sur L'arome du Muscat. I. Evolution des Constituants Volatiles au Curs de la Maturation du Muscat d'Alexandrie. Ann. Technol. Agric. 19: 79-83. 5. Dimitriadis, E. and P. J. Williams. 1984. The Development and Use of a Rapid Analytical Technique for Estimation of Free and Potentially Volatile Monoterpene Flavorants of Grapes. Am. J. Enol. Vitic. 35: 66-71. 6. Edinger, W. D. 1988. Enhancement of Varietal Character Through Liberation of Bound Monoterpenes. Horticultural Research Institute of Ontario Enology Laboratory Technical Note. Vineland Station No. 8: 1-5. 7. Gallander, J. F. and C. Stamp. 1990. Skin Contact: Time and Temperature Makes a Difference in Wine Quality. In: Proceedings of The 1990 Ohio Grape Wine Short Course. Horticulture Department Series. Wooster: The Ohio State University/The Ohio Agricultural Research and Development Center. 8. Gallander, J. F. and J. F. Stetson. 1989. Maturity Assessment For Improving Wine Quality. In: Proceedings of The 1989 Ohio Grape Wine Short Course. Horticulture Department Series 598. Wooster: The Ohio State University/The Ohio Agricultural Research and Development Center. pp 33- 34. 9. Gallander, J. F. and J. F. Stetson. 1988. Relationship of Fruit Condition Maturity To Wine Quality. In: Proceedings of The 1989 Ohio Grape Wine Short Course. Horticulture Department Series 590. Wooster: The Ohio State University/The Ohio Agricultural Research and Development Center. pp 39-51. 10. Kinzner, G. and P. Schreier. 1980. Influence of Different Pressing Systems on the Composition of Volatile Constituents in Unfermented Grape Musts and Wines. Am. J. Enol Vitic. 31: 7-13. 11. Marais J. and A. Rapp. 1988. Effect of Skin-contact Time and Temperature on Juice and Wine Composition and Wine Quality. S. Afr. J. Enol. Vitic. 9: 24-30.

27 12. McCarthy, M. G. and B. G. Coombe. 1985. Water Status and Winegrape Quality. Acta Hortic. 171: 447-56. 13. Meilgaard, M. 1975. Flavour chemistry of beer: Part II: Flavour and threshold of 239 aroma volatiles. Tech Q. Master Brew. Assoc. Am. 12: 151- 68. 14. Noble, A. C., C. R. Strauss, P. J. Williams and B. Wilson. 1988. Contribution of Terpene Glycosides to Bitterness in Muscat Wines. Am. J. Enol. Vitic. 39: 129-131. 15. Simpson, R. F. 1979. Some Important Aroma Components of White Wine. Food Tech. Aust. :522-18. 16. Reynolds, A. G., and D. A. Wardel. 1988. Canopy Microclimate of Gewurztraminer and Monoterpene Levels. In: Proceedings of the Second International Cool Climate Viticulture and Oenology Symposium. pp 116-22. Summerland Research Station, Summerland, British Columbia, Canada. 17. Reynolds, A. G., and D. A. Wardel. 1989. Impact of Several Canopy Manipulation Practices on Growth, Yield, Fruit Composition and Wine Quality of Gewurztraminer. Am. J. Enol. Vitic. 40: 121-9. 18. Ribereau-Gayon, P., J. N. Boidron and A. Terrier. 1975. Aroma of Muscat Grape Varieties. J. Agric. Food Chern., 23: 1042-47. 19. Watson, B., D. Heatherbell and P. Lombard. 1983. An Overview of Several Wine Grape Varieties in Western Oregon. Oregon Horticultural Society Annual Report. Portland: The Society. 74: 298-305. 20. Williams, P. J., C. R. Strauss, B. Wilson and R. A. Massy-Westropp. 1982. Novel Monoterpene Disaccharide Glycosides of Vitis vinifera Grapes and Wines. Phytochemistry. 21: 2013-20. 21. Wilson, B., C. R. Strauss, and P. J. Williams. 1984. Changes in Free and Glycosidically Bound Monterpenes in Developing Muscat Grapes. J. Agric. Food Chern. 32: 914-924.

28 A NEW STERILANT FOR TREATING WINES: DIMETHYL DICARBONATE Mary Calista Senior Technical Sales Representative Mobay Corp., Pittsburgh, PA Velcorin beverage sterilant or dimethyl dicarbonate (DMDC) has a unique set of properties which allow it to be used as a means of obtaining microbiological stability at the time of wine bottling. Microbiological stabilization is generally achieved in the wine industry through the use of cold filling techniques. Among those techniques one would include sterile filtration or the use of membrane filters to remove microorganisms. This cold sterile process has the advantage that microorganisms are removed without any damage to the constituents that determine the taste and quality of the beverage. Unfortunately, cold sterile bottling alone can be very risky because there is nothing to ensure that the wine will not be reinfected after being filtered ( 1). The di ffi cul ty 1 i es in the guaranteeing that the filling line is entirely sterile, the weakest points being the sterility of the bottles and the closure operation. When sterile filtering cannot be insured, this technique is generally combined with the use of chemical preservatives such as potassium sorbate or sodium benzoate in conjunction with sulfur dioxide. The use of such chemical preservatives results in impairing the taste of the wine (2). In fact, sorbic acid may be reduced by certain lactic acid bacteria leading to the formation of 2-ethoxycarbonyl-3,5-hexadiene which causes the notorious "geranium" taste (3). Thus, cold sterile filtering, while certainly more desirable than pasteurization or flash pasteurization, often needs to be supplemented to ensure the reliability of the filling operation while protecting the integrity of the wine or wine product. The use of Velcorin sterilant, when combined with good manufacturing practices, can promote the stability of a finished wine product. Velcorin dimethyl dicarbonate was approved for use as yeast inhibitor in wines at the point of bottling by the United States Food and Drug Administration on October 21, 1988. The FDA approved Mobay's Food Additive Petition for the use of Velcorin in concentration levels not to exceed 200 ppm. This final rule is listed under section 172.133 in the Code of Federal Regulations (4). Velcorin has also been used successfully in the Federal Republic of Germany to treat sweet non-alcoholic beverages since 1978. In New Zealand, Velcorin has been approved for the cold sterilization of wine as well. The use of Velcorin as a cold stabilization agent features a number of important advantages over alternative techniques including: - Activity against a wide range of problematic microorganisms. - Status as a "processing aid" not a chemical preservative by the FDA, so that listing on the ingredient statement is not required. - Undergoes rapid hydrolysis to naturally present levels of methanol and carbon dioxide. 29 - No affect on final beverage quality (taste, bouquet, or color). Chemically, Velcorin is dimethyl dicarbonate or dimethyl pyrocarbonate.

Dimethyl dicarbonate: CH30-CO-O-CO-OCH3 C4H605 At room temperature, Velcorin is a colorless liquid with a slightly pungent odor; it boils at 82°C/26.6 mbar and solidifies at temperatures below l7°C. Further physical data concerning DMDC are listed in Table 1.

Table 1. Velcorin Sterilant - Physical Data (5) Density (+20°C) 1.25 Flash point 85°C Viscosity ( +20°C) 2.1 cps - mPa.s Vapor pressure ( +20°C) 0.07 Kpa (0.7 mbar)

As sold, Velcorin sterilant has a purity of a minimum of 99.8%. If moisture is excluded, it can be kept at the recommended storage temperatures of 20-25°C for at least one year. The solubility of Velcorin in water is 3.65%; the dissolution of Velcorin in water is accompanied by hydrolysis. The reaction between Velcorin and water is rapid and complete; it leads to the formation of carbon dioxide and methanol. at pH 2-6, the hydroll,sis rate is practically independent of the hydrogen ion concentration. At 21 C, Velcorin has a half-life of 13 minutes (6). Velcorin hydrolyzes not only in water, but in all aqueous substrates, e.g., bevera~es. At +10°C, its hydrolysis is complete after 4 hours and 20 minutes, at +20 C, after 80 minutes, and at +30°C, after about 50 minutes (7). Carbon dioxide, which may be present in carbonated beverages at positive pressures of up to 6 bar, has no significant influence on the rate at which Velcorin is hydrolyzed (8). After the addition of Velcorin sterilant to beverages, several reations take place simultaneously .. A survey of DMDC reactions is presented in Figure 1.

30 Figure 1 Survey of DMDC Reactions CH3 Methoxycarbonylamino NH2 I acid I 0 R- c COOH I I c = 0 H I ,------> NH I R-CH-COOH

0-CH CH3 R -Methyl carbonate I 3 I 0 = c 0 I R OH I 0 > c = 0 +CH30H I I 0 = c OR +C02 \ 0-CH3

CH3 Methyl carbamate I 0 I c = 0 +CH30H NH3 I > NH2 +C02

R = alkyl or aryl

31 Velcorin sterilant performs its technical function by inactivating enzymes in the microorganisms present in the beverage. It is proposed that methoxycarbonylation of the histidine part of the enzymes alcoholdehydrogenase and glyceraldehyde-3-phosphate-dehydrogenase occurs (9a). The remaining Velcorin reacts principally with the water in the beverage. In non-alcoholic beverages, at least 96% of the added Velcorin is hydrolyzed to carbon dioxide and methanol. In this process, 65.7 parts of carbon dioxide and 47.8 parts of methanol are formed per 100 parts of Velcorin. To a minor extent, the hydroxyl , ami no and th i o1 groups of beverage constituents (e.g., polyphenols, amino acid, sugars, fruit acids) may be methoxy­ carbonylated through reaction with Velcorin. The concentration levels of the resulting derivatives are, however, so low that it is not possible to detect these substances individually. Table 2 demonstrates the reaction productions of DMDC in wine (9b). Table 2. Reaction products of DMDC in wine treatment of a white wine without C02, 10% v/v ethanol with 100 mg/DMDC. Reaction Product in mg/1

CH30H 45.4 C02 62.5 Dimethyl carbonate 0.2 Methyl ethyl carbonate 5.5 Amino acids 1.9 Polyphenols 0.05 Vitamin C 0.08 Fruit Sugar 0.15 Glycerin 0.3 Fruit Acids 0.5 Methyl carbamate 0-0.007 Other Organic substances 0.02

Ve 1 cori n cold beverage steril ant destroys yeasts, mycoderma, and fermentative bacteria even at low dosages. At higher dosages, it also destroys or inactivates other bacteria (including some pathogenic species), fungi, and certain large viruses. The minimal lethal concentrations for a selection of yeasts, bacteria, and mold fungi are given below.

32 Table 2. Minimal lethal concentration (MLC) of Velcorin Yeasts: Inoculation: 500 germs/ml Determination of MLC-effect after 3 weeks at 28°C mg/1 Saccharomyces carlsbergensis 100 (non flocculating yeast) Saccharomyces carlsbergensis 60 (flocculating yeast) Saccharomyces diastaticus 200 Saccharomyces oviformis 100 Saccharomyces bailii 120 Saccharomyces cerevisiae 40 Saccharomyces uvarum 30 Saccharomyces pastorianus 100 Saccharomyces apiculatus 60 Saccharomyces globosum 40 Zygosaccharomyces priorianus 75 Rhodotorula mucilaginosa 50 Rhodotorula glutinosa 40 Rhodotorula rubra 200 Candida krusei 200 Pichia membranefaciens 40 Pichia farinosa 100 Torulopsis candida 100 Torulopsis versatilis 100 Torulopsis stellata 65 Bacteria: Inoculation: 1 x 103 germs/ml Determination of MLC-effect after 12 hours of room temperature mg/1 Acetobacter pastorianum 80 Acetobacter xylinum 300 Escherichia coli 400 Staphylococcus aureus 100 Pseudomonas aeurginosa 100 Lactobacterium buchneri 40 Lactobacillus pastorianus 300 Lactobacillus brevis 200 Pediococcus cerevisiae 300 Proteus mirabilis 400 Klebsiella pneumoniae 400 Mold Fungi: Inoculation: 500 germs/ml Determination of MLC-effect after 3 weeks at 20°C mg/1 Penicillium glaucum 200 Byssochlamys fulva 100 Botrytis cinerea 100 Mucor racemosus 500 Fusarium oxysporum 100

33 The outstanding effectiveness of Velcorin against yeasts was confirmed by C.S. Ough (10,11) in a large number of tests on wine, grape juice and dealcoholized wine. The recommended concentration of Velcorin needed to stabilize a wine with a maximum of 500 germs/ml at the time of bottling ranges from 75-200 ppm. The concentration of Velcorin needed is determined by the particular germ strains present and level of contamination. The commercial value of Velcorin has been tested in actual bottling situations. In a trial conducted at a commercial winery in Napa, California, in conjunction with Mobay Corporation, a 1986 White Zinfandel containing 10% and 12% alcohol was treated with 150 ppm of Velcorin. The 10% alcohol and 12% alcohol wine was inoculated with Saccharomyces cerevisea var. Montrachet (Davis 522) and Saccharomyces bayanus var. Champagne (Davis 595), respectively, yeasts known for their resistance in the wine industry. The results showed commercial sterilization was achieved with the use of Velcorin in both the 10% and 12% alcohol wine. Velcorin has also been shown to be effective in treated dealcoholized wine in addition to standard wine. An experiment was conducted at a commercial winery in San Jose, where large lots of dealcoholized wine were cold sterile bottled (13). It was found that lots not treated with Velcorin resulted in contamination from Saccharomyces cerevisiae and/or Aspergillus fisherii. Those lots treated with 150 ppm of Velcorin produced a microbiologically stable product. The microbiological effectiveness of Velcorin can also aid in lowering the amount of sulfur dioxide needed in winemaking. Tests carried out by C.S. Ough et al., demonstrated that there exists a synergistic activity between DMDC and sulfur dioxide (14). At an inoculant level of 400 yeast cells/ml wine (Saccharomyces cerevisiae - Davis 522), 50 mg/1 DMDC and 25 mg/1 free S02 was sufficient to provide excellent control in a white wine, at pH 3.6 and lower. For Saccharomyces cerevisiae complete control was not obtained with the use of S02 alone; however, at 75 mg/1 DMDC complete kill was achieved. It was also found that 50 mg/1 DMDC in combination with 25 mg/1 from S02 stopped malolactic fermentation in a red wine inoculated with 120 cells/ml (Leuconostoc oenus - Davis MLW). Due to the chemica 1 reactivity of Ve 1cori n steril ant and the need for accurate and homogeneous distribution throughout the beverage system, Velcorin should be added through the use of a metering system. To ensure stability of a wine to the consumer, it is recommended Ve 1cori n be added in the bot t 1 i ng sequence just prior to the filler bowl. This helps to guarantee that the wine is sterile bottled and that any contamination arising from the filling lines, bottles or closures is controlled. A system that takes into account the desirable safety and handling considerations is the Lewa DA9 dosing meter; however, any system capable of accurate and homogeneous distribution that can provide the following features may be considered for use: - Materials resistant to DMDC corrosion. - Control system to regulate Velcorin injection rate proportional to beverage flow. 34 - Thermostatically controlled injection nozzle and storage compartment to prevent Velcorin from congealing. - Automatic alarm system and self-ventilation capability. - Calibration to monitor performance. Dosage control in the wine can be checked by two different methods; measuring increased methanol concentration from OMOC use (13) or determination of ethyl methyl carbonate (15). In handing concentrated OMOC, the manufacturer recommends certain safety precautions to protect an employee from direct contact with the chemical. This involves the use of personal protective clothings, and a well ventilated working area. Detailed handling recommendations and emergency procedures are available from Mobay Corporation (16). Thus, Velcorin cold beverage sterilant has proven to be commercially effective as a method for cold stabilizing standard wines and non-standard wine products. When used in conjunction with good manufacturing practices, bottled stability can be achieved at concentratioans of 75-200 ppm Velcorin. The major advantage of using Velcorin sterilant is that it has no effect on the taste, color or bouquet of the wine. Additionally, since it is considered a "processing aid" by the FDA, it need not appear on the ingredient label statement. Finally, the FOS has extensively reviewed all toxicology and safety data related to the use of Velcorin dimethyl dicarbonate, constituents and reaction products, concluding that OMOC may be safely used as a yeast inhibitor for wines. Any winery wishing to pursue the commercial use of Velcorin need only write the BATF expressing their intent. References 1. Wuerdig, G., Lecture given at the IVe Congres International de la vigue et du vin'. Nyon-Changins, 24.-30. July 1977. 2. Leuck, E. Antimicrobial Food Additives, p. 210 ff. Springer Verl. Berline Heidelberg, New York. 1980. 3. Wuerdig, Oer Deutsche Weinbau. 1977. 1205. 4. Federal Register, Rules and Regulations, Vol. 53, No. 24, October 21, 1988, 21 CFR Part 172. 5. Product Information 6. Medenwals, H., Bayer AG, Wuppertal-Elberfeld, 30.07.1974 Petition, Vol. II, Lit. Nr. 150, p. 1. 7. Genth, H. Brauere i -Journa 1 6, 129 (1980) . 8. Genth, H. Oas Erfrischungsgetraenk 32, 262 (1979). 9a. Temple, D.O. cit. in: L.J. Porter u. C.S. Ough. Paper presented to the American Soc. Enologists 22 Ann. Meet., San Diego, California 25.06.1981. 35 9b. Dittrick. H.H. Mikrobiologie des Weines, p. 233. Verlag E. Ulmer, Stuttgart. 1977. 10. Daudt, C.E. and Ough, C.S. Amer. J. Enol. vitic. 31, 21 (1980). 11. Ough, C.S. in Antimicrobials in Foods, Hrsg. A.L. Branen and P.M. Davidson, p. 229 ff., Marcel Dekker, Inc., New York, 1983. 12. Trial conducted November 1987 at Louis P. Martini Winery in Napa, CA. Data was submitted tothe BATF in fulfillment of approval requirements. 13. Jeff Meier, J. Lohr Winery, Private Communication. 14. Ough, C.S., R.E. Kunkee, M.R. Vilas, E. Bordeu and M.C. Huany, Amer. J. Enol. Vitic. Vol. 39, Nov. 4, 1988. 15. Mcbay Corp., Health, Environment and Safety Dept., Mobay Road, Pittsburgh, PA 15205. 16. Instructions available from Mobay Corporation.

36 ;\ J .\ \'\j ;fv\ HEDGING EFFECTS ON WHITE RIESLING (\- 0 Tony Wolf Virginia Polytechnic Inst. & State Univ. Winchester, VA INTRODUCTION One of the consequences of growing vigorous, grafted grapevines in the hot, wet environment of the mid-Atlantic region is the production of abundant vegetation. It is not uncommon to observe vines that have produced more foliage than the training/trellising system can expose to sunlight. The dense, shaded canopies that can result from that situation are often associated with poor fruit quality and reduced wood maturation. Fruit quality is especially reduced by increased fruit diseases that are promoted by poor canopy ventilation and reduced pesticide penetration into canopies. Fruit diseases can be incited by common fungi such as Botrytis cinerea, but are often preceded by fruit cracking following rains. Other opportunistic pathogens, including bacteria, yeasts, and other fungi, can also be found in rotted fruit. Dense, shaded canopies can also be associated with negatively affected fruit composition (e.t., elevated potassium and pH}, relative to more spares canopies. Efforts to manage the dense canopies of large, vigorous vines can include conversion to more sophisticated training (e.g., divided canopy) systems, removal of some of the shading foliage (e.g., summer pruning}, and reduced water and nutrient availability. Shoot topping or "hedging" is frequently the favorded approach to remedial canopy management. But, hedging can lead to delayed fruit and wood maturity if done too severely.

We 1 conducted an experiment for three seasons (1986-1988) to evaluate the responses of 'White Riesling' grapevines to shoot topping. We were interested in determining what constituted a desirable level of heading and what the consequences of altered canopy density were. In particular, we were interested in determining how altered canopy micro-climate affected fruit quality, the incidence of fruit rots, and wood quality (i.e., periderm maturation and bud cold hardiness). MATERIALS AND METHODS Vines used in the experiment were 'White Riesling' grafted to rootstock cultivar S0-4 and planted in 1983 at Prince Michel vineyards near Culpeper, VA. Vines were spaced three feet apart in rows nine feet wide. The vines were cane­ pruned and trained to the arched-cane "pendelbogen" training system. Pairs of movable catch wires were used on the trellis to promote a vertical, upright canopy. Treatments were 1) control, which consisted of no canopy modification other than shoot positioning; 2) shoot topping to retain 10 leaves per shoot; and 3) shoot topping to retain 20 leaves per shoot. A fourth treatment involving a chemical growth suppressant was included, but will not be discussed in the context of this talk. Shoots were first topped when they averaged 20 leaves in length. That was about 30 days after bloom. Hedging can be done very quickly - 1Myself, Bruce Zoecklein and our technicians.

37 with manual or powered hedge trimmers. Shoots were then retopped once or twice per season to maintain the desired leaf number. This generally consisted of removing several lateral shoots from the last several nodes of the primary shoot. We measured the dry weight of vegetation removed from vines during the 1987 and 1988 years. Treatments were appropriately replicated to permit statistical comparisons of treatment effects. Data were collected annually on canopy light penetration, cane pruning weights, fruit yields, incidence and nature of fruit rot, fruit chemistry, wood maturation, and dormant bud winter survival. RESULTS AND DISCUSSION Cane pruning weights were comparable (0.8 lbs/vine) following the 1985 season, the year before treatments were applied. Pruning weights increased with control vines during the 1985 season and decreased with the topping treatments. Pruning weights increased with all treatments in 1987 and were similar in 1988. Average pruning weights of the three years were: control (1.3 lbs), 10-leaf hedging (0.5 lbs), and 20-leaf hedging (1.0 lbs). Differences in vine size (pruning weights) were closely related to the dry weight of foliage removed during the growing season. For example, approximately 0.7 pounds (dry weight) of vegetation was removed per vine from vines whose shoots were topped to 10 nodes. The ability of sunlight to penetrate the fruiting region of vine canopies was affected by the extent of shoot topping. Light measurements and periodic transectional probes of canopies both indicated that the control vines had denser canopies than the other treatments and that there were minor differences in canopy density between the two levels of hedging. Transectional probes also illustrated that control vines had smaller proportion of fruit clusters near the canopy exterior, compared with other treatments. The major effect of the shoot topping was the removal of shoot tops that had extended beyond the top of the trellis and were blocking the original canopy. Shoot topping was effective in maintaining a relatively small vine size that was associated with a sparse, well ventilated canopy. The size-limiting effect of summer pruning was similar to that achieved by dormant pruning, except that the summer pruning did not have the pronounced impact on fruit yields. Lateral shoot growth, following topping, was generally limited to the last two or three nodes of the topped shoot. As such, that growth did not contribute to increased canopy density in the fruit zone. Reductions in wood maturation and bud cold hardiness by canopy shade have been documented in certain cold hardiness studies. Therefore, depending upon severity, shoot topping might be expected to exert either beneficia 1 (shade reduction) or deleterious (presumably carbohydrate depletion) effects on wood maturation and bud cold hardiness. Our results indicated that topping shoots to retain 10 or 20 leaves per shoot did not affect bud survival nor did the hedging reduce wood maturity. On the other hand, control vines, perhaps because of greater intra-canopy shade, were associated with reduced wood maturation in one year (1987). It is entirely possible, however, that if our fruit yields had been greater, the proportion of mature wood could have been less, especially with vines hedged to 10 leaves per shoot.

38 Fruit yields were lower for control vines than for shoot-topped vines in 1986 and 1987. The reason for those lower yields was probably related to some whole-cluster fruit loss (observed) with the control vines due to rot. Vines that had been topped to retain only 10 leaves per shoot had lower yields than those vines that had been topped to retain 20 leaves per shoot. The reason for those lower yields appeared to originate with lower berry weights. Other studies have also shown that severe defoliation can reduce berry size. Shoot topping to 20 leaves per shoot resulted in the greatest soluble solids concentration at harvest in 1986 and 1987. The lowest soluble solids observed at harvest were generaly found with the control vines or with vines hedged to retain 10 leaves per shoot. From the standpoint of fruit maturity, the delay in sugar accumulation with the 10-leaf hedging could be considered a reflection of overly severe hedging. Neither fruit pH nor potassium differed significantly among treatments at harvest. Fruit rots at harvest were associated with various combinations of environmental (e.g., rain), physical (e.g., berry splitting), and biological (Botrytis cinerea, Phomopsis viticola, acetic acid-forming bacteria, yeast, fruitflies, etc.) factors. Symptoms and signs of rot-affected fruit varied, but most rotted fruit could be classified into one of two types: a Botrytis rot that sometimes bore sporulating conidiophores, and a second form that lacked fungal signs, but had symptoms that included softening, browning, and an acetic acid odor (i.e., sour rot). The latter rot was typically associated with potentially causal factors such as diseased berry pedicels, berry splitting, and the presence of fruitflies. Fruit rots were particularly severe in 1986 and 1987. Those years had frequent rains during August and September and berry cracking was common. Fruit rots observed at harvest were typically lowest in the shoot-topped vines and greatest in the control vines. Rot incidence was comparable between vines topped to either 10 or 20 leaves per shoot, except in 1986, in which a greater rot incidence was measured with the vines hedged to retain 20 leaves per shoot. In addition to the visual assessment of fruit rots at harvest, my colleague, Mr. Bruce Zoecklein, has analyzed juice from each of the various treatments for concentrations of compounds that are associ a ted with rot organisms. Those compounds include glycerol, acetic acid, and ethanol. Not surprisingly, the greatetst concentrations of those metabolites were typically found in fruit from control vines, which had the greatest incidence of visually rotted fruit. Reductions in fruit rots by shoot topping in this study were probably due to interactions of several fators: improved canopy ventilation, improved pesticide coverage, slightly reduced fruit maturity (susceptibility to splitting and infection), and slightly reduced berry size which could have reduced berry splitting. CONCLUSIONS AND RECOMMENDATIONS Shoot topping or "hedging" was evaluated as a means of improving grape quality with 'White Riesling' grapevines that produced excessive vegetation. Hedging reduced annual cane pruning weights and prevented shoot tops from obstructing fruit zones of upright, vertically-trained canopies. Reductions in

39 the incidence of fruit rots and levels of decay organism metabolites in grapes were the principle benefits of hedging and were noted in two of three seasons. Reasons for reduced fruit rot were presumably due to a combination of improved canopy ventilation, improved pesticide coverage, reduced berry size, and in the case of vines hedged to 10 1eaves per shoot, delayed fruit maturity/rot susceptibility. Hedging to retain 20 leaves per shoot resulted in higher fruit soluble solids at harvest than did hedging shoots to 10 leaves. Potential negative effects of defoliation, such as reduced wood maturation and decreased dormant bud survival, were not observed. Summer pruning or hedging should be considered a "last resort", remedial measure of canopy management. Other practices, such as shoot positioning, should be used prior to removing shoot tops. For very large vines, canopy division offers a more efficient means of dealing with excessive vigor. Where hedging is used, I would suggest that you not top shoots to less than 15 leaves per shoot. Topping close to harvest has the potentially negative effect of stimulating lateral shoot growth that can temporarily compete with fruit maturation.

40 i

EFFECTIVE USE OF FINING AGENTS

Michele Dittamo Ce 11 u1 o Company Cranford, NJ Fining has been around a long time. While we've learned more about the chemistry of the fining process, the noticeable difference is that there are many more fining agents on the market today from which to choose. One cannot stress enough that fining is an individual choice and that fining trials are the only way to accurately predict a product's performance on a particular batch of wine. There are fining agents available to correct specific problems in a wine, and the measurement of this type of product's performance is fairly objective. Fining agents used to enhance organoleptic characteristics of a wine obviously involve more subjective judgement of performance. Hydrogen sulfide can be removed by an easy one-step fining process. If this is done early enough, one can prevent the formation of double and triple bonded mercaptans, which are harder to remove. No doubt high copper and iron levels can cause problems in a wine, but these two can be corrected by fining agents. Wine has a greater tolerance for iron than it does for copper; many believe that the copper levels should be lower than 0.2 ppm (some say less than or equal to 0.1 ppm), while the iron level should be lower than or equal to 5.0 ppm. Today, you can choose a fining agent to remove copper and iron selectively in a ratio that allows for good predictability of fining performance. Almost everybody is familiar with determining heat stability in their wine, and the most popular fining agent to use is bentonite. The sodium form of bentonite is the preferred form for wine. It has a net negative charge and a very high surface area. Just a few pounds per thousand gallons can drop out as much as 80-90% of the protein in wine, especially the proteins that curdle in the presence of heat. Bentonite-protein floc may also remove some tannins, but this is considered minimal. The negative features of bentonite, that I am familiar with, are that it can absorb red pigment, remove some vitamins and amino acids, and give you excessive lees. The latter is the problem most people experience, and there are fining agents you can use to settle bentonite faster and give more compact lees. This kind of a fining agent, sometimes referred to as a topping agent, will also give you greater filterability which is one of the other negative aspects of using bentonite alone. Cold stabilization is normally done by just chilling the wine to 25°F for two to three weeks until excess potassium bitartrates precipitate out. One of the newer ways to cold stabilize your wine is to disperse finely divided cream of tarter crystals in the wine as it is being chilled to act as nuclei to precipitate out potassium bitartrates. This method takes only a couple of days, but a very good filtration must be done to insure success. Many winemakers using fining agents to manipulate the phenol composition in their wine to control its desirable vs. undesirable components. Sometimes carbon

41 is used on a {white) wine, but this is a relatively non-selective fining and should only be used when your purpose is to strip the wine. Normally, white wines and blush wines can contain anywhere from 75-500 ppm polyphenols. Of course, the average white wine falls between those numbers, and a saleable white wine might have somewhere around 290-300 ppm. Removing certain polyphenols can help you remove off-colors and off-flavors and the catechins that are the main substrate to browning reactions. PVPP and potassium caseinate can be used in this type of application. These fining agents can also be used simply to stabilize the color you have achieved. This is especially important in making a blush wine. To clean up an old stale or oxidized wine, potassium caseinate is best. In many instances, you may have to use a combination of PVPP and potassium caseinate to attack the molecular weight range of the phenols that you are trying to remove. Again, this can only be predicted accurately by a fining trial. PVPP removes polyphenols when they are still monomers, which presents itself in wine as a bitter taste. According to the BATF, the maximum dosage of PVPP that can be used in fining wine is 6 lbs/1,000 gallons. If you are at a dosage of 6 lbs/1,000 gallons and cannot get the desired results, you may want to try the combination of PVPP and potassium caseinate. Gelatin is often used to fine out the longer chain polyphenols that give wine its astringency. Gelatin is usually used to soften a red wine. What you must keep in mind is that the most effective gelatin will be the one with the highest molecular weight of the molecules you are trying to remove. From experience we have had with cranberry juice, we know that the polymeric tannins that are in cranberry juice tend to be difficult to remove by ordiary 100 bloom gelatin. Because of the length and size of the tannins that are present in cranberry juice, it is necessary to use a 200 or 300 Bloom gelatin, which contains longer {greater molecular weight) chains. An acceptable red wine is said to have somewhere around 1,200 ppm polyphenols, though some can go as high as 5,000 ppm. In order to adjust the level of polyphenols in your red wine, you may have to use a dosage of 6-8 ounces dry weight of gelatin per thousand gallons. Still, it is best to try a fining trial with a somewhat lower dosage, perhaps around 4 ozs./1,000 gallons. You don't want to use more gelatin than you need. Gelatin can have its negative aspects, as many people do overfine with gelatin which can cause post-bottling haze. In using a dry gelatin, you may not get all of the active sites exposed if not dissolved properly. Colloidal silica has been a good fining agent to use after gelatin to help settle out excess/unreacted gelatin, as well as increase gelatin's efficiency. There are many forms of gelatin available today. There is a traditional dry granual form, cold water soluble, and liquid gelatin. The latter two products, of course, give you greater ease of use. The questions a winemaker should ask in choosing a gelatin are: is hot water or steam readily available in my winery? Is it too laborious to use? Are my utility costs too high? Then, is the predictability of my gelatin activity crucial? What kind of storage do I have available? How do the general costs compare? In many cases, cold water soluble granular gelatin or a liquid gelatin can offer you enough advantages that 42 the difference in cost is minimal. Colloidal silica is a product that differs from silica gel or precipitated silica, in that it is a true colloid and as such has much greater surface area for fining reaction. In a colloid, the silica is present in its discrete particle size in a suspension that helps it react much faster. Colloidal silica will speed up your settling rate and give you much greater clarity, while making for a more compact lees. Also, colloidal silica increases filterability of wine, as the floc that it forms is a denser, more discretely shaped coagulant that your filter is able to remove without getting prematurely plugged. In many cases, the floc of a gelatin colloidal silica fining reaction can actually act as a filter aid once it hits the filter and extend your filteration cycle. Another fining agent worth mentioning is isinglass. Many people are familiar with flocced isinglass. Isinglass is a good product to use when you want a very gentle fining agent. It is normally used to help settle yeast and is used in low dosages, which makes up for its slightly high cost. There is now a freeze-dried isinglass available that is much easier to use, as it can be prepared and ready to fine within 20-30 minutes. This is worth looking into if you would like to use isinglass but do not have the facility or time to work with the flocced form. As a final comment, there are probably other fining agents being used that I have not mentioned that are rooted in the homemade methods of making wine which have developed over the years. None of them should be excluded from consideration, as you will never know for sure which fining agent is best for your application until you try it.

43 EFFECTS OF SELECTIVE LEAF PULLING WITH CHARDONNAY AND WHITE RIESLING Tony K. Wolf Virginia Polytechnic Inst. & State Univ. Winchester, VA INTRODUCTION The selective removal of leaves from grapevine canopies has received a great deal of attention within the last five to 10 years from the U.S. That is not to say it's a new practice; leaf pulling has been used extensively in Europe for years as a means of combating fruit rots and reducing fruit acidity at harvest. The current interest in leaf pulling relates to increased awareness of the effects of canopy microclimate on fruit and wine quality, and the recognition by many growers that their grapevines produce excessive amounts of vegetation. Benefits of selective defoliation have included improved fruit chemistry parameters as well as reductions in the incidence and severity of fruit rots. In the latter case, canopy manipulation techniques which promote air circulation, pesticide penetration, and decreased humidity could be expected to reduce the rot problem. This especially true in a region like the mid-Atlantic where precipitation during the growing season and harvest can average four inches per month, and where high humidity and high nighttime temperatures are the norm. Fruit rot development, unfortunately, often dictates harvest date with rot-prone varieties under those conditions.

We 1 conducted a three-year study to examine the effects of selected leaf removal under the growing conditions of northern Virginia. In particular, we were interested in determining if this remed i a1 canopy management too 1 was effective in reducing fruit rots. We were also interested in the effects of leaf pulling on fruit chemistry in our hot, humid environment where elevated fruit pH is sometimes problematic. My comments here will focus primarily upon effects on fruit rot incidence. METHODS AND MATERIALS The experiment was conducted in two different vineyards using two varieties: Chardonnay and White Riesling. In one vineyard (Meredyth), both varieties were trained to a high-wire {about six feet above ground), bi-lateral cordon. Shoots were combed down during the growing season to maintain a vertical canopy. In the other vineyard {Naked Mt.), the two varieties were trained to a mid-wire {about four and one-half feet above ground) bi-lateral cordon. Catch wires were used above the cordon at Naked Mt. to train the shoots upward during the growing season. Shoot hedging {to retain at least 15 nodes/shoot) was used at Naked Mt., but not at Meredyth. Treatments were {1) leaf pulling and {2) no leaf pulling {control). Leaf pulling consisted of shoot positioning and manually removing two or three leaves per shoot from immediately around fruit clusters. This treatment was applied

1 Myself, Bruce Zoecklein, Nancy Duncan (of Meredyth Vineyards) and our technicians. 44 about four weeks after bloom. The control vines received only shoot positioning. Care was taken with the high-trained vines at Meredyth to leave a thin canopy of leaves (generally from lateral shoots) above the fruit zone to prevent excessive exposure of fruit to direct sunlight. All vines were balanced-pruned in each year and the shoot numbers were adjusted after bud-break to a 20 + 20 schedule (20 shoots retained for each pound of cane prunings). We used three methods during the growing season to quantify the effects of leaf pulling on canopy porosity and/or light microclimate. Those methods included (1) measuring light within the fruit zone; (2) transect analyses of the canopy (a measure of leaf layers); and (3) use of spray paper in the fruit zone to determine spray penetration. The spray paper is commercially available and is most often used to assess sprayer performance. The bright yellow strips turn blue specifically where wetted. We mounted strips in representative canopies and sprayed them with water from an air-blast sprayer simulating a pesticide application. The area of each strip that turned blue was later quantified and used as a measure of canopy porosity (Figure 1). Data were collected at harvest on fruit weight, components of fruit yield, and fruit rot incidence. Fruit samples were collected periodically prior to harvest and on the day of fruit harvest for analyses of fruit chemistry. My colleague, Bruce Zoecklein, has conducted the various fruit chemistry analyses. RESULTS AND DISCUSSION As might be imagined, the amount of sunlight that penetrated "leaf-pulled" canopies was consistently greater than achieved with control vines; however, there was more direct (as opposed to diffused) sunlight penetration with the high-trained vines than the low-wire training system. The transect (also called point quadrat) analysis of canopies typically illustrated greater fruit exposure and more canopy gaps with the leaf pulling treatment. In addition, the quantification of spray penetration of fruit zones illustrated that leaf pulling produced a more porous canopy that permitted greater spray penetration (Fig. 1). The leaf pulling treatment was associated with some fruit sunburning with the high-trained vines. One of the recommendations in leaf pulling is that the practice be done early in the season (e.g., soon after fruit set) to minimize the likelihood of sunburning fruit. We saw no sunburning with the low-trained vines that had abundant leaf area direclty over the fruit zone. We found no evidence that leaf pulling had any impact on vine fruitfulness in any year. The principle benefit of leaf pulling that we observed in this study was a reduction in fruit rots in two (wet) of the three years. We measured up to a 20% reduction in rot incidence and a 10% reduction in severity with leaf pulling. The reductions were greater and more consistent with White Riesling than with Chardonnay. That was not too surprising given Riesling's tendency to crack and rot with rains near harvest. As with our summer pruning work, the visual reductions of fruit rot due to leaf pulling were usually accompanied by reductions in glycerol, acetic acid, and ethanol in the juice. Those compounds are associated with, and presumed due to, the growth of fruit spoilage organisms. The reductions in fruit rots with leaf pulling were likely due to the interaction of several factors such as increased pesticide penetration into fruit zones and improved air circulation and drying conditions within the canopy. 45 The effects of pulling on basic fruit chemistry varied by year. Fruit soluble solids and pH were generally unaffected. The latter was somewhat surprising in that several published reports elsewhere have indicated that leaf pulling had a reductive effect on must pH. Titratable acidity was typically reduced (by harvest) by up to 1.0 g/L in the high-trained vines at Meredyth, and less so with the low-trained vines at Naked Mt. The reductions in titratable acidity were accompanied by reductions in malic acid, which were likely due to elevated berry temperatures (measured) as a result of increased fruit exposure. One aspect of leaf pulling that we observed, but did not quantify, was the fruit of leaf-pulled vines could be harvested much more rapidly than fruit of control vines. Pickers spent less time hunting within the canopy for clusters. Increased harvest efficiency should be considered when evaluating the economics of this practice. CONCLUSIONS AND RECOMMENDATIONS Selective defolation of Chardonnay and White Riesling grapevine canopy fruit zones was evaluated for three years in hot, humid growing environment. The principle benefit realized was a reduction in the incidence and severity of fruit rots at harvest. The principle disadvantage of leaf pulling is the amount of labor involved. Recommendations are to experiment with leaf pulling with those varieties in which fruit rots at harvest have been problematic. Do not remove too many leaves; a rule of thumb might be to remove no more than two or three leaves per shoot. Concentrate on removing only those leaves that block air circulation around fruit clusters. Leaves should be pulled soon after fruit set. Experience elsewhere suggests that the potential to sunburn fruit increases as the time of leaf pulling is delayed.

46 100 b Ql 90 Ol «) \,.. Ql 80 > u0 70 ti; 60 c: -Ql 50 0 ., Q.- 40 • -0 -.. 30 ....c: •'- Ql c: 0 20 - \,.. ~ QJ n. 10 0

Chardomay Whtte RtesltnQ (25 gallons water/acre) {50 gallons water/acre)

Figure 1. Effects of leaf pulling on spray (water) penetration of Chardonnay and White Riesling fruit zones. Water-sensitive spray paper strips were mounted in fruit zones and sprayed with either 25 (Chardonnay) or 50 (Riesling) gallons of water per acre using an air-blast sprayer. The percentage obliteration of spray strips were compared with "check" strips set in unobstructed regions of the trellis. The checks were set to 100% obliteration. "Untreated" vines were vines that had no shoot positioning. "Control" and "leaves pulled" vines were shoot positioned. Thus, shoot positioning, leaf pulling, and increased gallonage all resulted in greater spray penetration.

47 FLAWED SEYVAL WINES: WAYS TO PREVENT PROBLEMS James F. Gallander Department of Horticulture OARDC/OSU, Wooster, OH Seyval is a leading French hybrid grape for making white table wines in eastern United States. Many Ohio wineries vinify Seyval with pleasing and delicate varietal characteristics. Generally, winemakers produce two different styles of Seyval, which differ significantly in aromas, bouquet and composition. Some are fruity, grapy, and semi-dry, while others are oaky, complex, and dry. Since the industry has not settled on one style, many winemakers frequently experiment with their vinification techniques in an attempt to improve their style of Seyval. Unfortunately, this lack of a recognized style and established winemaking practice has led to some defective Seyval wines. Also, the concern of sulfur dioxide usage has added to the problem of making good-quality wines without noticeable faults. The apparent problem of having common defects in Seyval was recognized and identified by the judges at the 1989 and 1990 Ohio Wine Competition. These unnecessary defects were also recognized by the enology staff at OARDC/OSU, and their presence and apparent increase over the past few years is a great concern. The majority of the faults can be classified as "common wine defects" which could have been avoided or minimized by using standard enological practices, such as proper sulfur dioxide usage. Some of the other common defects which include hydrogen sulfide, moldy, flat, stagnate, and dirty were not identified in the Seyval wines. In addition to the noticeable defects, several Seyval wines were considered only acceptable in quality, because of their lack of sufficient varietal aroma. Certainly, fine Seyval wines should have distinguishable varietal character, aroma and flavor. The primary cause for the development of oxidized and lactic odors in wines is related to the improper use or lack of sulfur dioxide. The addition of sulfur dioxide in wines serves two major functions: 1) control of spoilage microorganisms, and 2) prevents oxidation. The overall effectiveness of sulfur dioxide is related to the amount and time of application during vinification. The proper use of sulfur dioxide is extremely important in making white table wines. These wines are usually delicate in varietal aroma characteristics and are unable to tolerate slight vinification problems, notably oxidation and lactic acid spoilage. In general, sulfur dioxide is added at the beginning of the winemaking operations and usually 25 to 35 ppm of free sulfur dioxide is maintained after fermentation. Recently, some winemakers advocate the use of no sulfur dioxide prior to alcoholic fermentation. These wi nemakers found that musts without sulfur dioxide produce wines with improved qua 1 i ty and consumer acceptability. However, research at OSU/OARDC has indicated that delaying sulfur dioxide addition after fermentation was an unacceptable practice in terms of the sensory quality (4). For this study, Seyval blanc grapes were divided into 4 lots, and the lots were treated with 50 ppm sulfur dioxide after different stages of vinification: crushing, pressing, juice clarification, and alcoholic fermentation. After dryness, approximately 25 ppm free sulfur dioxide was maintained in the wines. The results of the sensory evaluation indicated that the judges preferred those wines made with a sulfur dioxide addition after crushing. These wines were 48 scored highest in aroma, taste, and overall quality. Wines receiving sulfur dioxide after alcoholic fermentation were ranked lowest by the taste panel. The comments from the judges about those wines treated with sulfur dioxide after fermentation included: lack of varietal character, slightly oxidized and noticeably acetic. Although the grapes were in good condition, free from rot and disease, adding sulfur dioxide after fermentation is not a recommended practice. Failure to add sulfur dioxide at the correct time and amount during vinification is a major cause of defective Ohio Seyval wines. The problem of treating wines with the proper amount of sulfur dioxide was recognized by our laboratory at OSU/OARDC. Approximately 60% of the Seyval wines tested for free sulfur dioxide was below the recommended level. Sensory examination of the wines indicated that most were only acceptable in quality with low varietal intensity and slight oxidized sensation. Causes for poor varietal character may also be related to fruit condition, maturity, juice solids and fermentations. In order to produce Seyval wines with a characteristic and recognizable varietal aroma, sound fruit, free from rot, must be utilized and, juice clarification is essential prior to alcoholic fermentation. Several studies (1,3,7) have been conducted to show that wines made from diseased grapes were lower in quality than those made from sound fruit. For clarification, low levels of solids in juice prior to fermentation improves the quality of white wines. Studies by Singleton et ~ (5), Williams et ~ (8), and VanWyk (6) indicated that wines prepared from clarified juice were higher in wine quality. These wines were characterized as being fresh, clean, delicate, and fruity. With regard to fermentation temperatures, it has been well established that lower temperatures yield better quality wines than those made at higher temperatures. Ough and Amerine (2) reported that white wines fermented at 55°F were rated best in sensory quality. Another important consideration in making high quality Seyval wines is harvesting the fruit at peak maturity. In cool regions, such as Ohio, the usual criterion for picking grapes is measuring the sugar content (0 Bri x) of the grapes. Although the general concept that the best wines are made from the highest 0 Brix grapes, studies in Ohio have found that this is not necessarily true. The results of sensory evaluations indicated that some varietal wines (Vidal blanc, Catawba, and Niagara) were preferred from grapes at the mid­ maturity stage. The same may be true for Seyval grapes, and the highest 0 Brix may not be the best level of maturity for making high quality wine. Recently, the judging of several commercial Seyval wines found that the wines were not distinctive and were probably made from overly ripe fruit with some rot present. It is our suggestion that the harvesting of Seyval grapes should not be delayed for the sole purpose of small increases in sugar content (0 Brix). LITERATURE CITED 1. Loinger, C., S. Cohen, N. Dor, and M.J. Berlinger. 1977. Effect of grape cluster rot on wine quality. Am. Soc. Enol. Vitic. 28:196-199. 2. Ough, C.S. and M.A. Amerine. 1961. Studies with controlled fermentation. VI: Effects of temperature and handling on rates, composition, and quality of wi ne s . Am . J . Enol . Vit i c . 12 : 11 7 - 12 8 .

49 3. Ough, C.S. and H.W. Berg. 1979. Powdery mildew sensory effect on wine. Am. Soc. Enol. Vitic. 30:321. 4. Stamp, C. and J. Gallander. 1989. Sulfur dioxide: amount and time of application for better wine quality. Proc. Ohio Grape-Wine Short Course, OSU/OARDC, Hart. Ser. 598:13-17. 5. Singleton, V.L., H.A. Sieberhagen, P. de Wet, C.J. VanWyk. 1975. Composition and sensory qualities of wines prepared from white grapes by fermentation with and without grape solids. Am. J. Enol. Vitic. 26:62-64. 6. Van Wyk, C.J. 1978. The influence of juice clarification on composition and quality of wines. Proc. Int. Enol. Symp. Auckl~nd, New Zealand. 33-45. 7. Wagener, G.W.W. 1981. The effect of botrytis rot on wine quality. Oenol. & Vitic. Stellenbosch S.Afr. 1-3. 8. Williams, J.T., C.S. Ough and H.W. Berg. 1978. White wine composition and quality as influenced by method of must clarification. Am. J. Enol. Vitic. 29:92-96.

50 BIOLOGY AND BEHAVIOR OF THE ROSE CHAFER Macrodactylus subspinosus (F.) Murdick J. Mcleod and Roger N. Williams Department of· Entomology OARDC/OSU, Wooster, OH 44691 INTRODUCTION The rose chafer, Macrodacty7us subspinosus (F.) is distributed across much of North America east of the Rocky Mountains (Fig. 1). Also known as "rose bug", the rose chafer belongs to the Scarabaeidae, a family which includes the May or June beetles. This insect is especially abundant in areas of light, sandy, soil where beetles may appear suddenly in large numbers when host plants begin to blossom. The rose chafer feeds on a variety of fruit and ornamental plants causing considerable damage to flowers, fruit, and foliage. In severe cases, defoliation of young fruit trees can result in death of the trees. DESCRIPTION The adult rose chafer is about 1/2 inch (13 mm) in length with long, spiny, reddish-brown legs which gradually become darker near the tip (Fig. 2). The ungainly beetles have a straw colored body, reddish-brown head, and black undersurface. Eggs of the rose chafer are oval, white, shiny in appearance, and about 1/20 of an inch (1 mm) long. Larvae are C-shaped white grubs about 3/4 inch (19 mm) long. When fully developed they have three distinct pairs of legs, a brown head capsule, and a dark rectal sac visible through the integument. Larvae are found in sandy soil feeding on grass roots and can be identified by a distinctive rastral pattern. The pupa is about 3/5 inch (IS mm) long and light yellowish­ brown. LIFE CYCLE Adult rose chafers become active in NE United States from late May to early June. They may appear suddenly and in great numbers when grapes begin to blossom. Beetles feed and mate soon after emerging from the soil. Females deposit eggs singly at a depth of four to six inches. Mating and egg laying occur continuously for about two weeks with each female depositing 24 to 36 eggs. Beetle activity lasts from four to six weeks, and the average lifespan is three weeks (Fig. 3). Approximately two weeks after being deposited, eggs hatch into tiny, white, C-shaped grubs. The larvae feed on the roots of grasses, weeds, grains, and other plants throughout the summer, becoming fully developed by autumn. Larvae move downward in the soil as soil temperatures decline and form an earthen cell in which they overwinter. In the spring larvae return to near the soil surface, feed for a short time, and pupate in May. After two weeks in the pupal stage the adults emerge and crawl to the soil surface to begin their cycle again. There is one generation each year. DAMAGE

51 Despite its common name, the rose chafer attacks the flowers, buds, foliage (Fig. 4), and fruit of numerous plants including grape, rose, strawberry, peach, cherry, apple, raspberry, blackberry, clover, hollyhock, corn, bean, beet, pepper, cabbage, peony, and many more plants, trees, and shrubs. Adults emerge about the time of grape bloom and often cause extensive damage to fo l i age. Blossom buds (Fig. 5) are often completely destroyed, resulting in little or no grape production. Feeding activity on various plants may continue for two to four weeks. Damage can be especially heavy in sandy areas, the preferred habitat for egg laying. A toxin present in the beetles may kill poultry if they feed on them. CHEMICAL CONTROL Beetles emerge in mass, therefore, timing of control is important to protect valued plants. Foliar applications of insecticides may need to be repeated at weekly intervals or after periods of rain to protect flowers, fruit, and foliage. The great number of beetles and their voracious appetites can result in plant destruction in spite of pesticide applications. Consult your Cooperative Extension Service for specific insecticides to use against rose chafer adults on a specific crop or plant. CULTURAL CONTROL When only a few beetles are present, they may be hand picked from valuable plants and destroyed. Occasionally, ornamental plants may be temporarily protected with cheesecloth netting. The pupal stage is extremely sensitive to disturbance, therefore plowing or cultivating may be effective in destroying them. Beetles also may fly to attractive plants from some distance, therefore controlling larvae in the immediate vicinity of valued plants may not preclude damage by adults. REFERENCES Marlatt, C. L. 1898. The principal insect enemies of the grape. U.S.D.A. Farmers' Bull. 70. Slingerland, M. V., and C. R. Crosby. 1922. Manual of fruit insects. MacMillan, New York. 503 pp. Williams, R.N., T. P. McGovern, M.G. Klein, and D. S. Fickle 1990. Rose chafer (Co7eoptera:Scarabaeidae): Improved attractants for adults. J. Econ. Entomol. 83(1):111-116.

52 Figure 1. Rose chafer distribution (Hartzell 1910).

Fig. 2. Rose chafer life cycle (Marlatt 1898) 53 Fig. 3. Rose chafer life cycle Fig. 4. Raspberry foliage damaged (Marlatt 1898) by rose chafer.

Fig. 5. Grape cluster completely destroyed. 54 MEASUREMENT AND REMOVAL OF TARTARIC ACID IN CONCORD GRAPE JUICE Kurt Wiese and Andrew Proctor Department of Food Science & Technology OSU/OARDC, Columbus, OH 43210 INTRODUCTION When tartrates precipitate from wine, initially they cause the wine to appear cloudy, then the tartrate crystals are deposited on the bottom of the bottle (Amerine and Singleton, 1977). Although neither of these conditions pose any health risk, they lower the wine quality by causing it to lose visual .appeal. To predict the tartrate stability of wines, analytical techniques were developed by Berg and Akioshi (1971), Berg and Keefer (1958), Berg and Keefer (1959), Boulton (1984), and Pilone and Berg (1965). These techniques are based on 1) solubility product of potassium bitrate (KHT) in alcohol solutions at various temperatures, 2) conductivity, and 3) concentration of calcium and potassium cations. These same techniques plus others can be applied to evaluating tartrate stability in grape juice. Tartaric acid has two dissociable hydrogens, and when one dissociates, the anions (HT-) can combine with potassium to form KHT, which is practically water insoluble. When KHT precipitates out of solution, the titratable acidity should decrease as well as the soluble solids. This would also decrease the total ion content of the grape juice as measured by conductivity. The objectives of this research were: 1) to mathematically model the changing tartrate levels of grape juice over time by measuring pH, titratable acidity, potassium content, conductivity, turbidity, and soluble solids and 2) to measure changes in tartrate after various juice treatments to enhance removal of the tartaric acid. MATERIALS AND METHODS Grape juice was obtained from a local winery. The grapes for this juice had been destemmed, crushed, pressed, and stored in a cooler. No additives or preservatives were present in the juice. The juice was divided into the following treatments: control, potassium bitartrate (100, 1000 and 10,000 ppm), and calcium chloride (100, 1000, 10,000 ppm). Two 16 oz. plastic bottles were prepared for each treatment and stored at 35°F. Samples from each bottle were examined at 0, 3, 5, 7, 10, 13 and 18 days after treatment. The samples were analyzed for: 1) tartaric acid content by the metavanadate method (Ough and Amerine, 1988); 2) soluble solids by refractive index; 3) potassium content by a potassium electrode; 4) pH and titratable acidity by a computer aided titrimeter (using 0.0839N sodium hydroxide); and 5) conductivity as measured on a conductivity meter. The data was statistically analyzed to include correlations, regression analysis, and ANOVA.

55 RESULTS AND DISCUSSION Predictor Equation: As shown in Figure 1 and Table 1, the tartaric acid level of the control grape juice decreased from 3387.5 ppm to 3160 ppm after 5 days of storage. Then the level increased to 3667 ppm after 18 days of storage. This in an 8.2% increase above the original level, implying that tartaric acid was going back into solution. The tartaric acid levels were correlated to the various measuring techniques used (Table 2). Conductivity gave the highest correlation followed by titratable acidity, potassium content, and turbidity. pH and soluble solids were expected to be highly correlated to the tartaric acid level in this experiment; however, they were not. The techniques with the highest correlation were leading variables to be included in the predictor equation for the tartaric acid level. The progression of choices for the variables in the equation is shown in Table 3. The R2 value in the table indicates the percent variability that is explained by including that factor in the equation. The adjusted R2 value weighs the statistical cost of adding one more variable to the equation. If the adjusted R2 decreases or remains constant although the R2 value increases, the addition of the variable to the equation is not advisable. For this data, the highest adjusted R2 occu~red for the group of variables conductivity A2, conductivity, titratable acidity, and potassium content. Including other variables in the equation decreased the adjusted R2 value. Diagnostic plots of true value vs predicted value (Figure 2) and normalized residuals vs the variables (as in Figure 3) were examined to ensure proper fit of the data to the equation. The equation to determine the tartaric acid level was: Tartaric acid = 161.05* conductivity A2-2996.5* conductivity +32,808.5* titratable acidity-839.1* potassium content + 11,819.99 ENHANCING TARTARIC ACID REMOVAL To aid in the tartrate removal from grape juice, calcium, magnesium, potassium, and potassium bitartrate were added. Table 4 gives the two-way ANOVA table of the main effects of time and treatments. There was a significant interaction of treatment over time indicating that generally the treatments decreased the tartaric acid level during the storage period, as shown in figures 4-6. Initially, all the treatments of calcium, magnesium, and potassium increased the tartaric acid level above the time 0 value of the control. After 3 days, all the ion treatments had decreased the tartaric acid level in the juice drastically, while the control remained essentially unchanged. For calcium and potassium, adding 10,000 ppm to the juice produced the lowest tartrate in the juice of the 3 levels of ions added to the juice samples. For magnesium, the tartrate levels of 1000 and 10,000 ppm paralleled one another 56 during the storage period with the 10,000 ppm level exhibiting the greater tartrate level. Although the magnesium decreased the tartrate level from its initial value, the tartrate level was not reduced below that of the initial value of the control juice at time 0. This is in agreement with the statement of Berg and Keefer (1958) that magnesium tends to increase tartrates in solution. Both calcium and potassium decreased the amount of tartrate in solution when compared to the initial control value at time 0, and the greater quantity of these cations increased the amount tartrates being removed from solution. The addition of potassium bitartrate crystals initially increased the amount of tartrate in solution, but this value quickly declined after 3 days. During the remainder of the experiment, the tartrate level of these treatments were essentially constant and following the tartrate levels of the control during the storage period. REFERENCES Amerine, M.A. and V.L. Singleton. 1977. Wine. 2nd edition. Univ. CA Press. Berkley and Los Angeles. Berg, H.W. and M. Akiyoshi. 1971. The utility of potassium bitartrate concentration product values in wine processing. Am. J. Enol. and Vitic. 22:127. Berg, H.W. and R.M. Keefer. 1958. Analytical determination of tartrate stability in wine. I. Potassium bitartrate. Am. J. Enol. and Vitic. 9:180. Berg, H.W. and R.M. Keefer. 1959. Analytical determination of tartrate stability in wine. II. Calcium bitartrate. Am. J. Enol. and Vitic. 10:105. Boulton, R.B. 1984. Evaluating potassium bitartrate by conductivity. Vinifera Wine Growers Journal. Fall :154. Devore, J.L. 1987. Chapter 13: Nonlinear and multiple regression in "Probability and Statistics for Engineering and the Sciences". 2nd edition. Brooks/Cole Publ. Col. Belmont, CA. Ough, C.S. and M.A. Amerine. 1988. Chapter 2: Acidity and Individual Acids. pp. 50-80. IN: "Methods for Analysis of Musts and Wines", 2nd edition. John Wiley and Sons. New York, Chichester, Brisbane, Toronto, and Singapore. Pilone, B.F. and H.W. Berg. 1965. Some factors affecting tartrate stability in wine. Am. J. Enol. and Vitic. 16:195.

57 Table 1. Tartaric acid level. Davs Tartaric acid (poml

0 3387.5 3 3353.0 5 3160.0 10 3488.0 13 3538.5 18 3667.5

Table 2. Tartaric acid level correlations to the measurement technqiues

R2 Titratable acidity 0.306 pH 0.011 Conductivity 0.915 Potassium content 0.202 Turbidity 0.201 Soluble solids 0.029

58 Table 3. Variables examined to model the tartaric acid level (R2-regular correlation coefficient. R2 adjusted-cost of adding another variable to the equation (Devore, 1987). Variables included R2 R2 adjusted

Conductivity 0.9151 0.8585 Conductivity, TA 0.9169 0.8615 Conductivity2 TA, pH 0.9171 0.8617 Conductivity 0.9186 0.8643 Conductivity2 , acidity 0.9206 0.8677 Conductivity2 , acidity, K 0.9472 0.9119

Table 4. Analysis of variance (ANOVA) of juice treatments (calcium, magnesium, potassium, and potassium bitartrate addition) and time. Source OF Sum Squares Mean Squares F Value Treatment 12 14103273 1175273 179.2 Time 5 22567394 4513479 688.0 Interaction 60 16439192 273987 41.8 Error 78 511650 6560 Total 155 53621508

Table 5. % Decrease in tartaric acid level of cation-treated samples compared to the initial level of the control grape juice after the 18 days storage (negative value indicates an increase in the tartaric acid level). Magnesium Calcium Potassium 100 ppm - 2.90 0.62 4.80 1000 ppm - 1.06 3.10 5.65 10000 ppm -10.60 21.0 29.06

59 ""0 6500 u

Time (days)

-+- --(>-- Control 100oom 1 OOOr:ll:lm --­ KHT KHT

60 3700 • 3600 • Q) • -::J 3500 ro • • > 3400 Q) ::J r-I.... 3300 3200 I Figure 2.1 3100 3100 3200 3300 3400 3500 3600 3700

Predicted Value

61 1.5 (/) • ro :J 1.0 "'0 (j) • (]) 0.5 • • (I • 0.0 I ""0 (]) N -0.5 • I ro • E I.... -1.0 • 0 I Figure 3.1 z -1.!::> • L 2.28 2.30 2.32 2.34 2.36 2.38 2.40 2.42 2.44 2.46 2.48

Conductivity

62 --"'0 4200 u .

Time (days)

- +-· 1()()ppm-·- 100Cllxlm 10C)(lQ)am- ·- Calcium Calc1um Calc1um

63 "'0 - 5000 ~------~ () 4: 4500 ,, Figure () \ ,, I 5.1 \' ro 4000 \ '' \ ' +--' \ ' -- -+, \ ro 3soo \ \ 1- \ \ ·~' ·-----::-::~·' 3000 \ ' 4-- \ ' \ 0 \ 2500 ------· E ·----·------··------·-- §t2ooo ~--~----~--~--~----~--~----~--~--~ 0 2 4 6 8 10 12 14 16 18

Time (days) - +- -·-100ppm 1000ppm 10000ppm- ·- Potassium Potassium Potass1um

64 v 4600 u- <{ 4400 ' ' ' u 4200 ' I Figure 6.1 ;,._ ' ' ro ' ' 4-J 4000 ' L '+, \ ro ' 3800 ' ' 1- \ ' \ ' '+------·-- ·- --- ~ 3600 \~ ------.----- 0 '+- -- +------~- - - - E 34oo ~~+~• §t3200 L----L----L---~----~--~----~--~----~--~ 0 2 4 6 8 10 12 14 16 18

Time (days)

- +- - -·-100ppm 100()pprn 10000ppm·- Magnesium Magnes1um Magnes1um

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