199. Inspection of Baking Powders.--Many of the states have enacted laws seeking to regulate the sale of alum baking powders. Some of these laws simply require the packages to bear a label setting forth the fact that alum is one of the ingredients; others require the baking powder packages to bear a label naming all the ingredients of the powder.
200. Fillers.--All baking powders contain a filler of starch. This is necessary to keep the materials from acting before the powder is used. The amount of filler varies from 15 to 50 per cent; the least is found in the tartrate powders and the most in the phosphate powders. The amount of gas which a powder gives off regulates its value; it should give off at least 1/8 of its weight.
201. Home-made Baking Powders.--Baking powders can be made at home for about one half what they usually cost and they will give equal satisfaction. The following will make a long-keeping powder: cream of tartar, 8 ounces; baking soda, 4 ounces; corn starch, 3 ounces. For a quick-acting powder use but one ounce of starch. The materials should be thoroughly dry. Mix the soda and starch first by shaking well in a glass or tin can. Add the cream of tartar last and shake again. Thorough mixing is essential to good results. Cream of tartar is often adulterated, but it can be obtained pure from a reliable druggist. To insure baking powders remaining perfectly dry, they should always be kept in glass or tin cans, never in paper.
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: