Fermentation
2 of the 7 encyclopedias on this shelf carry an entry for Fermentation. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a change which occurs 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 C12H22O11+H2O=2C6H12O6. About 95 per cent. of the glucose is converted into alcohol, C6H12O6=2CO2+2C2H5-OH. 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. Fermentation takes place most readily at about 24° to 30°. The saccharine liquid becomes turbid, gives off CO2, and becomes warmer than the air; when the evolution of CO2 ceases, the yeast or ferment, torula cerevisiæ, separates from the liquid which 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 alcohols, homologous with ethylic alcohol, forming fusel oil, which contains propyl, butyl and amyl alcohols, also a small quantity of caprioic enanthyl, and caprylic alcohols. Pope. In 1796, the French entered Ferrara, and made it the capital of the department of Basso Po. In 1814, the Church again recovered it, but in 1859 it became a part of the new Kingdom of Italy. Pop. of commune about 90,000. Butyric fermentation is the conversion of lactic acid, etc., into butyric acid, due to the presence of Vibrio, according to Pasteur. Lactic fermentation is the conversion 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 pounds of zinc white; the mixture is kept at a temperature of 30° for some weeks. If the fermentation is allowed to go further, the lactic acid, CH CH OH COOH, is converted into butyric acid, CH₂CH₂CH₂ COOH. Mucus fermentation is the conversion of sugar into mannite, CoH12O6, gum, C12H20O10, and carbonic acid, CO2 under the influence of a peculiar ferment. Tannous fermentation is the conversion of tannin, in a solution of galls, into gallic acid, C27H22O17+012=3C7H6Os +CO2+2H2O.
Aiton's Encyclopedia (1910)
a composition or change brought about in vegetable or animal matter by the action of minute plants, or by certain active substances. The change of apple juice to hard cider, of grape juice to wine, sweet water to vinegar, malt to beer, starch to sugar, or sugar to alcohol is a process of fermentation. The souring of milk, the rancidity of butter, the formation of curds, the rising of dough, as well as the putrefaction of meat and the decay of vegetables are due to fermentation. Some of the fermenting agencies or ferments, as the yeasts, are microscopic fungi; others are bacteria; and others again, forming a class by themselves, as the diastase of the brewer and the pepsin of the gastric juice , are lifeless, though active chemical agencies. Within bounds, fermentation is not only useful but absolutely necessary in the world's economy. Without fermentation, animal and vegetable substances would not return to earth again. Fermentation may be prevented in several ways. In the first place, the germs of ferment may be excluded by canning, bottling, pickling, and other processes. It may be prevented by heat. A liquid maintained at the boiling point would not ferment in a thousand years. It may be prevented by cold. Frozen meats do not putrefy. The frozen carcass of a mammoth was found in Siberia, where it had lain for no one knows how long, probably thousands of years. Absence of moisture prevents fermentation. Dried beef keeps for a long time. The carcasses of animals that die in the Sahara dry up, and, unless torn to pieces by birds of prey, are preserved for an indefinite length of time. Alcohol, salt, an excessive quantity of sugar, and other agencies poison the germs of ferment and prevent decay. See Bacterium ; Beer ; Wine ; Vinegar ; Yeast , etc.