FERMENTATION. Fermentation is that decomposition or decay which apparently acts spontaneously on animal and vegetable sub stances, involving beat and a rapid evolution of gas. The primary cause of fermentation is from microscopic fungi, acting as a ferment. Thus any organic body, not living, in the presence of moisture and heat will fertaent, since the germs are floating everywhere, and may even find lodgment in the pores of wood. The act of fermentation is taken advantage of by gardeners, in preparing hot beds, iu composting, and in a variety of ways; in the first place to produce, with manure, bottom heat for the propagation of plants (see Hot-beds); also by brewers, wine makers, distillers, etc.. in the preparation of their pibducts; by the housewife in making bread, vinegar, etc., and the process is constantly going on naturally, entirely unknown by the ordinary observer. This process once begun, oxygen is set free, which, again uniting with the elements of the body, accelerates and facilitates the pro gress of the phenomenon. Salt retards fermen tation, if present in considerable quantity; consequently it is used in preserving meat. Applied in small quantities to the compost heap it retards fermentation and combustion, and prevents fire fanging. Fermentation is of three stages--the vinous, producing alcohol; the acetous, producing vinegar; and putrefactive, producing decay of all the parts. Vinous fermentation is produced by oidium. The second, as in the souring of milk, by penicillium, and the third is supposed to be from the action of infusoria. A fourth ferment is denominated panary, but it is not generally recognized by chemists. Panary fermentation is what was stated to take place in the fermentation of dough in making bread, but this is precisely the same, without doubt, and may be referred to the vinous and the acetous. Fermentation must not be confounded with effervescence. Fermentation is confined to ani mal and vegetable substances, effervescence to minerals. Fermentation is spontaneous, effer vescence the result of the intimate mixture of two bodies, as an alkali and an acid. Cider, beer, wine, etc., ferment; soda-water effervesces.
One causes active decay, the other a neutraliza tion of two bodies, acting one on the other. A single illustration will suffice: The simplest case is the fermentation of the must or expressed i juice of grapes which, when exposed either in close or open vessels to a temperature of about 70°, soon begins to give off carbonic acid, and to become turbid and frothy; after a time a scum collects upon the surface, and a sediment is deposited; the liquid which had gfown warm gradually cools and clears, loses its sweet taste, and is converted into wine. The chief compo nent parts of must are water, sugar, mucilage, gluten, and tartar (bitartrate of potassa). Dur ing the fermentation carbonic acid escapes, the sugar disappears, and with it the greater part of the mucilage; the gluten chiefly forms the south and a portion of the sediment; and the tartar originally in solution is thrown down in the form of a 'colored deposit. Sugar and. water alone will not ferment; the ingredient requisite to the commencement of the change is the gluten, which absorbs in the first instance a little oxygen from the air, becomes insoluble, and induces the subsequent changes. The reason why grapes never ferment till the juice is expressed, seems to depend upon the exclusion of air by the husk or membranes. In beer the alcohol is derived from the sugar in the malt. When wine is exposed to air and a due tempera ture, a second fermentation ensues, which is called the acetous fermentation, and which terminates in the production of vinegar. During this process oxygen is absorbed, and more or less carbonic acid is evolved; but the apparent cause of the formation of vinegar is the abstraction of hydrogen from the alcohol, so as to leave the remaining elements in such proportions as to constitute acetic acid. Thus alcohol has been theoretically and quaintly stated as constituted of charcoal, water and hydrogen, and acetic acid of water and charcoal only; the oxygen of the air, therefore, converts the hydrogen of the alcohol into water, and so effects the change into vinegar.