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FERMENTATION is any chemical process that breaks down complex molecules into simpler ones and also releases gas. The basis of Nature is creation and decay. Without decay, the earth would long ago have covered itself in dead plant and animal bodies.

Fermentation is part of this cycle of decay. When organic household garbage (not recyclables) is piled and mixed with earth, bacteria begin to break down the matter to its basic elements, releasing methane gas and heat. Composting is then one type of fermentation. Fermentations produce antibiotics, vitamins, bakery products, dairy foods such as cheese and yogurt, and are necessary to tan leather, cure tea and coffee, and produce industrial as well as beverage alcohols in beer, cider, mead, and wine.

PRIMARY FERMENTATION is the alcoholic fermentation of wine, where yeast converts grape sugar into roughly equal parts of ethanol and carbon dioxide and producing heat. An enzyme (zymase) in the yeast actually breaks down the sugar. No matter how high the sugar level, natural fermentation will stop when the alcohol concentration is too high, at 16.5% under the most ideal conditions, or most often before it reaches this level. The theory of alcoholic fermentation was first proposed in 1697 by German physician and chemist Georg Stahl and later refined and proven by Louis Pasteur.

SECONDARY FERMENTATION can take two separate forms in wine. Malo-lactic fermentation is produced by a bacteria that converts malic acid into lactic acid. Sparkling wines get their bubbles from a secondary alcoholic fermentation. They begin just like table wines, with an alcoholic primary fermentation; a secondary fermentation is then induced by adding sugar and yeast.

RELATED LINKS: Microbial Fermentations (Skyline College) • Alcoholic Fermentations (Dawson College)

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