Food study

While baking powders are now practically all made with soda as the carbonate, many different substances are used for acid. There are three distinct types of powders, classified according to their composition. The oldest type is made with cream of tartar. This is a substance which is found abundantly in grape juice. If grape juice stands in wooden kegs, cream of tartar crystallizes out in masses on the inside. This crude substance, argol as it is called, is then purified by being dissolved in water, filtered, often through bone black, so as to remove the coloring matter of the grapes, and then re-crystallized and ground. It makes a good baking powder, because it is not easily soluble in water and does not need much "filler" to keep it dry. When it acts with the soda, besides the carbon dioxide another substance, known as Rochelle salts, is formed. This substance is used as a purgative in medicine, but so little of it results from the amount of baking powder ordinarily used in cooking that probably it has little effect on the human system. Phosphate powders, a second type of baking powder, are usually made with acid calcium phosphate. These powders give a good deal of gas, but the gas is evolved very quickly. More filler is used because of this. The residue, like that of the tartrate powders, is also purgative, but probably no action is caused from the amount usually eaten. The third class, alum powders, contains most commonly potash alum, that is, potassium aluminum sulphate, and, since alum is very soluble, even more filler is used than in the phosphate powders. In these powders the evolution of gas is much more continuous than in the phosphate types. Much objection has been made BAKING POWDERS 229 to these powders, because it was feared there might be injurious effects from the alum used. Repeated experiments do not seem, however, to show that the residues here are any more harmful than in the other cases. Manufacturers of tartrate powders have done their best to prove alum powders injurious because, as alum is much less expensive than cream of tartar, these last powders are naturally much cheaper. Besides these three distinct types, there are mixed powders in which more than one acid is used. Alum is sometimes mixed with the phosphate powders to make the evolution of gas more continuous. Tartaric acid itself often takes the place of a part of the cream of tartar in a tartrate powder. Probably the truth of the matter is that too much of them is not good for digestion, but that, as ordinarily used, they are all harmless. Nor do we ordinarily make much account of the difference in ingredients in our actual use of baking powders. Sometimes, instead of baking powder, cream of tartar and soda are used. For one teaspoon of soda two slightly rounded teaspoons of cream of tartar are allowed. This does not give such good results as are obtained with purchased baking powders, because the measuring of the soda and acid is not nearly so accurate, nor is the mixing so thorough. Some recipes for home-made powders call for as many as a dozen siftings and are, therefore, rather laborious to make.