1. Wine and Alcoholic Fermentation (I)

2. Wine Fermentation  Grape cultivation and wine making from Zagros Mountains and Caucasus region of Asia from 6000 B.C.E.  Wine-like product with honey and fruit from China ~7000 B.C.E.  One of the oldest of all fermented products been commercialized, mass produced and studied

3. Wine Fermentation  75% made in the Mediterranean areas of Europe France, Italy, Spain produce more than half of the 27 billion liters produced from around the world  Knowledge of biochemistry and microbiology started from understanding wine fermentation Pasteur

4. Wine Fermentation  Australia, South Africa, Chile >10% world production, significant export  US more than 2 billion liters/year, 90% from California  Impact of California wine industry ~$33 billion  France, Italy, US, Germany, Spain top wine consuming countries  Luxembourg France and Italy drink >50 L /person.year; US~9 L/person annually

5. Wine fermentation  “Value added” process  A bottle of wine from 1847 France sold for $71,675 in LA in 2004  Wine vs. beer fermentation Alcoholic fermentation Different yeasts and substrates  99% wine from grapes, rest from juices of other fruits with enough sugar (make >12% ethanol by vol) Distinct products Consume fresh vs. aged Quality dependent on the quality of raw materials

6. Viticulture and Grape Science  Varies in grape species and cultivars Vitis vinifera, V. labrusca Cabernet Sauvignon, Chardonnay, Gamay, Mission, etc. refer to different varieties or cultivars of the Vitis vinifera Cabernet Sauvignon Chardonnay Gamay Mission Different in compositions (sugar contents, pigmentation, etc.) Different climates and soil preference Wine quality varies greatly  Climate factors have important effect on grape quality and maturity

7. Grape Composition  Water 70-85% of the juice vol  About 20% sugar Simple sugars largest constituent of grapes or must Important for S. cerevisiae to produce ethanol Glucose (~50%), Fructose (~50%, increase in over- ripened grapes), sucrose (<1%, in V. labrusca up to 10%) Other sugars very low conc.  Sugar content in final product “dry”: 0.1%-0.2% “sweet” >10g/L “very sweet” as much as 100g/L-200g/L

8. Other Components  Organic acids Second plentiful non-water constituent in must Extremely important in wine quality  Provide low and well buffered pH (3.0-3.5)  Antimicrobial activities  Stabilizes anthocyanins (color, antioxidant, desirable flavor)  Volatile acids (acetic acid and others) very low  Fixed acids (malic acid and tartaric acid ~5:1) important to maintain the right acidity of wine and anti-spoilage, affected by environmental factors

9. Nitrogenous Compounds  Total N range from 0.2g/L to 0.4g/L  Generally adequate for rapid growth of yeast  Presence of biogenic amines (histamine and tyramine) in wine (by wine bacteria) can cause adverse reactions  Ethyl carbamate potential carcinogen, conc. increased by heat treatment and high urea conc.

10. Sulfur Compounds  Hydrogen sulfide (H 2 S) and other organic derivatives (mercaptans) by grape yeasts impart offensive flavor  Sulfur dioxide (SO 2 ) and derivatives naturally produced by yeast Also added due to antimicrobial, antioxidant, antibrowning properties

11. Phenols Tannins and Pigments  Phenolic and polyphenolic compounds naturally occurring in grapes, some be introduced later  Contribute to color, flavor, aroma, mouth feel to the wine

12. Wine Making  Harvesting and preparing grapes for wine making Harvest at right level of maturity  Manually picked grapes for premium wine  Manual picking also for sweet wines from noble rot grapes, or certain wines with regulated grape harvesting methods Crushing and Maceration  Remove extraneous material  Crush  Maceration: crushed grape material allowed to sit to extract more compounds  Long and high temp for darker-colored red wine  Very short and low temp for white wine (some remove seed sand skin right away)