David E. Horn Goucher College Towson, Maryland 21204
Winemaking in the Chemistry Laboratory
A t Goucher ~ o l l e e durine e the nast several Januarv terms a course in winemafing and;itic;lture has met withconsiderable success as iudeed bv student evaluations and enrollment figures. The nrereauisite for this course was one semester of colleee chemistry. T h e purpose of the course wan to provide the student with something practical and interesting in an effort to introduce sound chemical principles and techniques. T h e results were positive from both the student and the professorial viewpoints. T h e course involved a~proximately40 hours of lecturedemonstration and an aveiage of 18 hours of laborawry work. Instead of requiring a specific text hook, students were asked to ourchase one book from a list 11-31. Additional references ~~were placed on reserve in t h e library. This system not only worked extremely well b u t it was responsible for many interesting classroom discussions. Students were exoeded to nroduce one d o n of wine (from a concentrate or from a fruit juice) and t o perform various analvses on the wine similar t o those renorted earlier in this ~ o u & (4). Visits were made to several area vineyards where the techniques of pruning and training were learned and to several wineries where t h e technology of wine production was observed. Student work was evaluated with one quiz and a final exam. Each student was required to write a paper and present a seminar on a specific wine region. T h e course was graded passlfail. T h e purpose of this paper is to present a topical outline for teaching a course in the chemistry of winemaking and one detailed laboratory procedure for wine production. s
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Topical Outline For a Course in the Chemistry of Winemaking - atailed Description of the Winemaking Prueess
A.
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B. Chemical 1Aerubieversus Ansembbl I. Deeradstion of Glucose via Fermentation 2. Yeasts and Yesst Gruwth 3. Enzymes 4. Use uf SO? in Winemakine
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I1 Legal Arpecir of Making Yourown Wine Ill Juicefw WinePr,,duetion A. FmnchGralles
B.
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C.
Hybrid Grapes
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IV How tu Make Your Oarn Wine (Lenure-Demonatratiml V Laboratory Analysisof W i i i i 14-71 VI W i n e and the Wine Regions of the World A. France B. Germany C. United Statos (California1 D. Eastern United stater
'Apple juice (one gallon) can be used also but he sure there is no oreservative oresent. 'Make sure the fin[ draw is sucrearful hg pmctiring heforehand on wntpr. Start siphoning near the top uningn .I-shaped &as tuhear the end of the ruhher cm Tygm tubing. Qryness refers to the absence of sugar. 'Avoid passing the wine through the air. As soon as possible immerse the end of the delivery tube in the wine. (Red wine often improves with aeration s t the fir& racking, hut be sure to rack white wine anaerobically.)
VII l3MblishingaVinoysrd A. Choice orcrape variety B. Planting, Training. Pruning, and Harvesting C. EmnomicaofGrapeP~oduetion Vlli Eatsblirhine a Wine Cellar
IX Wine Tasting X Vinc~ardand Winenivinitati"".
Experimental Directions For the Production of a Red Table Wine
File Form 1541with the Division of Alcohol, Tobarn, and Firearms of the Internal Revenue Service (obtainable uwn reouest). Make sure eauioment is clean and rinsed free of soao. Make &ai" that eauiomini which is to be used for winemaking haa never k e n uaed for other chemical experiments. If pusaible. perform the primarystage of the fermentation (aerobic) in a mom whirh is not used for any other purpose during this period. Keep the work Tea scrupulously clean! Thaw one large 12-13-oz can of Welch's@frozen grape juice' (or use a eommercisllv available winemakinp. concentrate) and add this to a plastic waste basket or to a simila;nonmetallic container with a capacity of at least 1.5 gal. Dilute to one gal. With the use of a hydrometer and table sugar (sucrose)check the initial specific gravity and add enough sugar to bring the specific gravity to 1.090. (Make small additions of sugar and wait until the sugar is completely dissolved before takings hydrometer reading.) Add 0.3 g of sodium bisulfite or potassium metabisulfite. Record the p H and determine the total titratable acidity based on tartaric acid. (Optimum range is between 0.70 and 0.75% tartaric acid.) Allow the mixture to stand overnight. Add 0.5 g ammonium phosphate, and 2.5 g ammonium sulfate and stir to dissolve. Sprinkle 0.5 g yeast on top of the mixture. Do not stir. Cover the container loosely with a piece of cardboard and allow the must to stand for 3 da or until the specific gravity drops to 1.050. Siphon2 the liquid into a container with a narrow neck. Avoid transferring as much of the particulate matter as possible. (This is the racking process.) Fit this secondary fermenter with an air lock. Ferment to dryness.3 This should ordinarily take about three or four weeks. When the fermentation is complete, no mare Conbubhles will form, no more belching through the fermentation lock will occur, and specific gravity will he about 1.000. Rack the wine anaerobically' after fermentation ceases. Check the SO2 level and bring it up to 30 ppm if necessary. This last step should take no more than 0.2 g of either s d i u m bisulfite or potassium metabisulfite. Roughly 0.5 g of the reagent added to one gallon will raise the SO?level to 50 oom. Aee the wine for 3 ma. Make even effort to be sure that the air lo& remains tight and full during this time. Do not disturb the sediment. Cool the wine in a refrigerator (35-45'F) for ?-in n~ .. .. ..d--. Check the SO2 level and adjust it to 30 ppm if necessary before anaerobically racking the cool wine into bottles. Green screw top bottles are quite satisfactory.
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Acknowledgment T h e author is extremely grateful t o Dr. G. Hamilton Mowbray of the Montbray Vineyard in Silver Run,Maryland for his assistance, encouragement, and advice in preparation of this manuscript. Literature Cited (11 Wagner. P. M.. '"American Wines and Winemaking," Alfred P. Knupf. New
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(21 Taylor. W. S., and Vine,P., "Home Winemakeis Handbaok." Award &ukr,New Ymk. 1968. (31 Mitchell, J. R., "Scientific Winemaking." Sfmdard P,ess. Andove,, Great Britain.
thor. Volume 54, Number 6.June 1977 1 375
