FERMENTATION

in its broadest sense, is the chemical change by which organic substances are decomposed and re-combined in new iorencamrennal substances or compounds. Ferments are of two cla es—‘‘organized,’’ or living, as yeasts and lactie acid bacteria; and ‘‘unorganized,’’ as diastase and pepsin. In the significance most widely used and understood among laymen, fermentation is the chemical change produced in liquids containing sugar in solution by which the sugar is converted into a liquid, alcohol, and a gas, carbon dioxide. Wine and beer fermentation is called vinous. Under favorable conditions of temperature, etc., fermentation continues until the growth of the yeast cells is stopped by the exhaustion of the particular chemical components adapted for their subsistence, or by the formation of other substances in quantities inimical to their growth. As already noted, alcohol is one of the chief results of vinous fermentation, but it is itself adverse to yeast growth, and will stop it entirely, and with it fermentation, if a sufficient quantity is added to the liquid, or is formed in it. Vinous fermentation is followed under certain conditions by acetous fermentation—a cla of acetic bacteria oxidizing the aleohol and producing vinegar. The ‘‘sonring’’ of milk is lactie fermentation—some of the milk-sugar being converted by the action of lactic acid bacteria into lactic acid. Putrefaction of meat, ete., is putrefactive fermentation.