CHAPTER XIII
VINEGAR, SPICES, AND CONDIMENTS
202. Vinegar.—Vinegar is a dilute solution of acetic acid produced by fermentation, and contains, in addition to acetic acid, small amounts of other materials in solution, as mineral matter and malic acid, according to the material from which the vinegar was made. Unless otherwise designated, vinegar in this country is generally considered to be made from apples. Other substances, however, are used, as vinegar can be manufactured from a variety of fermentable materials, as molasses, glucose, malt, wine, and alcoholic beverages in general. The chemical changes which take place in the production of vinegars are: (1) inversion of the sugar, (2) conversion of the invert sugars into alcohol, and (3) change of alcohol into acetic acid. All these chemical changes are the result of ferment action. The various invert ferments change the sugar into dextrose and glucose sugars; then the alcoholic ferment produces alcohol and carbon dioxid from the invert sugars, and finally the acetic acid ferment completes the work by converting the alcohol into acetic acid. The chemical changes which take place in these different steps are:
| sucrose | dextrose | levulose |
| (1) C12H22O11 + H2O = C6H12O6 + C6H12O6; | ||
| dextrose | alcohol |
| (2) C6H12O6 = 2 C2H5OH + 2 CO2; | |
| alcohol | acid |
| (3) C2H5OH + 2 O = HC2H3O2 + H2O. | |
The acetic acid organism, Mycoderma aceti, can work only in the presence of oxygen. It is one of the aerobic ferments, and is present in what is known as the "mother" of vinegar and is secreted by it. When vinegar is made in quantity, the process is hastened by allowing the alcoholic solution to pass through a narrow tank rilled with shavings containing some of the ferment material, and at the same time air is admitted so as to secure a good supply of oxygen. When vinegar is made by allowing cider or wine to stand in a warm place until the fermentation process is completed, a long time is required—the length of time depending upon the supply of air and other conditions affecting fermentation.
Fig. 52.—Acetic Acid
Ferments.
(After König.)
In some countries malt vinegar is common. This is produced by allowing a wort made from malt and barley to undergo acetic acid fermentation, without first distilling the alcohol as is done in the preparation of spirit vinegar. In various European countries wine vinegar is in general use and is made by acetification of the juice of grapes. Sometimes spirit vinegar is made from corn or barley malt. Alcoholic fermentation takes place, the alcohol is distilled so that a weak solution remains, which is acetified in the ordinary way. Such a vinegar can be produced very cheaply and is much inferior in flavor to genuine wine or cider vinegar.