FERMENTATION, a change which oc curs in an organic substance, by which it is decomposed.
Alcoholic fermentation was known to the ancients, and is the change which sugar undergoes under the influence of yeast. Before fermentation takes place, cane sugar is transformed into glucose, thus C=112...0ii-1-1120=2C.H,20.. About 95 per cent. of the glucose is converted into alcohol, Of the other 5 per cent., about 1 part is used by the growth of the yeast, the other 4 parts are converted into succinic acid, glycerin, carbonic acid, and free hydrogen: a larger quantity of these secondary products is formed if the fermentation is slower, or is made with more exhausted and impure yeast. Fer mentation takes place most readily at about 24° to 30°. The saccharine liquid becomes turbid, gives off CO2, and be comes warmer than the air; when the evolution of CO. ceases, the yeast or ferment, torula cerevisi<•, separates from the liquid which now contains alcohol, glycerin, and succinic acid in the place of the sugar. A small quantity of acetic acid is always formed, probably from the decomposition of the yeast. Most of the natural saccharine juices, as beet-root, potato, and grape juice, when fermented, yield small quantities of alco hols, homologous with ethylic alcohol, forming fusel oil, which contains propyl, butyl and amyl alcohols, also a small quantity of caprioic cenanthyl, and cap rylic alcohols.
Butyric fermentation is the conveys :or. of lactic acid, etc., into butyric acid, due to the presence of V ibrio, according to Pasteur. Lactic fermentation is the con version of sugar into lactic acid, said to be due to the presence of Penicillium glaucum. It takes place when 2 gallons of milk are mixed with 6 pounds of raw sugar, 12 pints of water, 8 ounces of putrid cheese, and 4 poun,ds of zinc white; the mixture is kept at a tempera ture of 30° for some weeks. If the fer mentation is allowed to go further, the lactic acid, is con verted into butyric acid, CH..CI-I..CH.. CO-OH. Mucus fermentation is the con version of sugar into marmite, C.H•O., gum, C.11200,., and carbonic acid, CO., under the influence of a peculiar fer ment. Tannous fermentation is the con version of tannin, in a solution of galls, into gallic acid, C27H22017+ 012 .= 3C711605 2H.O.