January 26, 2018


Fermentation is a chemical change in which certain chemical compounds are broken down into simpler forms. The change is caused by substances called enzymes, which are produced by tiny living plants or animals. Yeasts, for example, are one -celled plants which produce enzymes.

There are three main kinds of fermentation: alcoholic, acetic, and putrefactive. Each is caused by the presence of bacteria - yeasts or molds -which produce the particular enzyme responsible for the chemical change. Fruit syrups become alcoholic when yeast, containing an enzyme called zymase, is added.

Wine or cider turns to vinegar when certain bacteria, called " mother of vinegar". are present. This is acetic fermentation. Meat and animal matter decay in putrefactive fermentation after certain molds have formed on then.

Fermentation helps in the digestion of food. An enzyme called ptyalin in saliva changes the starch of foods into soluble sugar- the first step in digestion. Enzymes are also present in the stomach, the intestines, the pancreas, and in various other organs.

Yeast is put into dough to make bread light by producing bubbles of carbon dioxide which form as the enzymes attack the starches and sugars present.

Sometimes fermentation is harmful. To keep foods from spoiling, they are kept in cool places or refrigerators where the low temperature checks the growth of bacteria, yeasts, and molds. Food can be preserved by killing the fermenting agents with heat and then sealing it. This is done in canning.

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