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Wine and Alcoholic Fermentation

(I)

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Wine Fermentation

Grape cultivation and wine making fromZagros Mountains and Caucasus region ofAsia from 6000 B.C.E.

Wine-like product with honey and fruitfrom China ~7000 B.C.E.

One of the oldest of all fermentedproducts been commercialized, massproduced and studied

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Wine Fermentation

75% made in the Mediterranean areas ofEurope

France, Italy, Spain produce more than half of

the 27 billion liters produced from around theworld

Knowledge of biochemistry andmicrobiology started from understanding

wine fermentation Pasteur

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Wine Fermentation

Australia, South Africa, Chile >10% worldproduction, 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

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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 withenough sugar (make >12% ethanol by vol)

Distinct products Consume fresh vs. aged

Quality dependent on the quality of raw materials

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Viticulture and Grape Science

Varies in grape species and cultivars Vitis vinifera, V. labrusca

Cabernet Sauvignon, Chardonnay, Gamay, Mission, etc. referto 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

http://images.google.com/imgres?imgurl=http://www.winepros.org/images-content/gwg_mission.jpg&imgrefurl=http://www.winepros.org/wine101/grape_profiles/mission.htm&h=229&w=190&sz=8&hl=en&start=9&tbnid=I39dWW2RmEmI_M:&tbnh=108&tbnw=90&prev=/images%3Fq%3DMission%2Bgrape%26gbv%3D2%26svnum%3D10%26hl%3Denhttp://images.google.com/imgres?imgurl=http://www.kobrandwine.com/grape_library/images/gamay_noir.jpg&imgrefurl=http://www.kobrandwine.com/grape_library/show_grape.php%3Fg%3DGamay%2520Noir&h=301&w=350&sz=37&hl=en&start=1&tbnid=gcG015TONbCXaM:&tbnh=103&tbnw=120&prev=/images%3Fq%3DGamay%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DGhttp://images.google.com/imgres?imgurl=http://www.kobrandwine.com/grape_library/images/chardonnay.jpg&imgrefurl=http://www.kobrandwine.com/grape_library/show_grape.php%3Fg%3DChardonnay&h=338&w=350&sz=41&hl=en&start=2&tbnid=1B4z4PAIUrxGSM:&tbnh=116&tbnw=120&prev=/images%3Fq%3DChardonnay%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DGhttp://images.google.com/imgres?imgurl=http://www.kobrandwine.com/grape_library/images/cabernet_sauvignon.jpg&imgrefurl=http://www.kobrandwine.com/grape_library/show_grape.php%3Fg%3DCabernet%2520Sauvignon&h=350&w=345&sz=56&hl=en&start=1&tbnid=X_1UhPxYoRFVMM:&tbnh=120&tbnw=118&prev=/images%3Fq%3DCabernet%2BSauvignon%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

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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 (10g/L

very sweet as much as 100g/L-200g/L

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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, desirableflavor)

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 andanti-spoilage, affected by environmental factors

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Nitrogenous Compounds

Total N range from 0.2g/L to 0.4g/L

Generally adequate for rapid growth ofyeast

Presence of biogenic amines (histamineand tyramine) in wine (by wine bacteria)can cause adverse reactions

Ethyl carbamate potential carcinogen,conc. increased by heat treatment andhigh urea conc.

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Sulfur Compounds

Hydrogen sulfide (H2S) and other organic

derivatives (mercaptans) by grape yeasts

impart offensive flavor

Sulfur dioxide (SO2) and derivatives

naturally produced by yeast

Also added due to antimicrobial, antioxidant,

antibrowning properties

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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

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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 seedsand skin right away)