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Fermentation

Before proceeding to the consideration of the manufacture of wines, beer, and spirits, a general survey of the subject of fermentation will not be out of place.

Alcholic Beverages May be divided into fermented drinks including beer and wines, and distilled drinks or spirits, which are obtained from the former by distillation.

Spirits usually contain about fifty per cent. of alcohol, beer and wines from one to twenty per cent. The alcohol in all cases results from the breaking up of the sugar in the fermenting liquid.

Sugars.

Ordinary sugar, or cane sugar; uncrystallizable, or fruit sugar; and grape sugar, or glucose, are the three most important varieties. Fruit sugar exists in all the sub-acid fruits as grapes, currants, apples, peaches, etc. When these are dried, it changes to grape sugar forming the whitish grains which are seen on the outside of prunes, raisins, etc. Grape sugar is found to a limited extent in fruits associated with fruit sugar. Cane sugar is readily changed by the action of acids or ferments into fruit sugar, and the latter into grape sugar, but the process cannot be reversed. Grape sugar is the only fermentable variety, the others becoming changed into it before fermentation. Transformation of Starch, etc.

Under the influence of acids, or diastase, a principle existing in germinating grains, starch is changed first into gum (dextrine) and afterwards into grape sugar. Hence one of our most important sources of alcohol is to be found in the starch of barley, corn, wheat, potatoes, etc. Wood may be converted into grape sugar by the action of strong sulphuric acid, which is afterwards neutralized. An attempt to produce alcohol in this way on a commercial scale was made in France, but was not successful.

Ferment.

A solution of pure sugar will remain unchanged