FERMENTATION

(Lat ) When certain vegetable substances are di olved in water, and subjected to a due temperature (between 65° and 85°), they undergo a series of changes which terminate in the production of alcohol or spirit; these changes constitute the phenomena of vinous fermentation. Sugar and some ferment are e ential to the proce ; and during the formation of the alcohol the sugar disappears, and carbonic acid is more or le abundantly evolved. The simplest case of fermentation is that of must, or of the expre ed juice of the grape, which when exposed, either in close or open ve els, to a temperature of about 70°, soon begins to give off carbonic acid, and to become turbid and frothy; after a time a scum collecls upon the surface, and a sediment is deposited; the liquor which had grown warm gradually cools and clears, loses its sweet taste, and is converted into wine. The chief component parts of must are water, sugar, mucilage, gluten, anil tartar. During the fermentation carbonic acid escapes, the sugar disappears, and with it the greater part of the mucilage; the gluten chiefly forms the scum and a portion of the sediment; and the tartar, originally in solution is thrown down in the form of a coloured deposit. It appears, therefore, that the new products, which are alcohol and carbonic acid, are principally formed at the expense of the sugar; and Gay Lu ac's experiments have shown that 45 449 [s. 463]