(1) By using an acid with a carbonate.

(2) By yeast fermentation.

(3) By machinery.

Yeast fermentation is studied in the chapter on bread making (Chapter XII), and the mechanical method is a commercial process exclusively. Only the first method will be treated in this chapter.

When an acid and any alkaline carbonate are dissolved together, a chemical action takes place, a gas is given off (carbon dioxide) and another substance is formed that is neutral, being neither acid nor alkaline, and known as a "salt." In selecting the two substances we must bear in mind this neutral substance that remains in the batter and insure its harmlessness.

The _lactic acid_ of sour milk is probably the earliest used, being a domestic product. The lactic acid is neutralized by bicarbonate of sodium, the latter being also called "baking soda." The resulting salt is harmless.

_Acid mola.s.ses_ with soda is another old-fashioned method. Here the acid is developed by the fermentation of the mola.s.ses.

_Cream of tartar_ (acid pota.s.sium tartrate), obtained from crystals deposited in wine vats, came into use later, neutralized by bicarbonate of soda, two parts of cream of tartar to one of soda.

_Baking powder._--The first baking powders were made of cream of tartar and bicarbonate of soda, mixed with a starch, to prevent the slight chemical action which would cause the powder to lose strength; and these two substances are now used in the best baking powders. The resulting salt is the Roch.e.l.le salt of medicine.

An _acid phosphate_ is sometimes used with soda, and this gives a harmless neutral substance.

Cheaper acids have sometimes been used, especially _alum_. It is best not to use an alum powder. Select a standard kind, avoiding those that offer prizes for a certain number of boxes purchased. Even if these latter do not contain alum, there is probably an excess of starch or flour.

The advantage of baking powder is in the accuracy of the proportions of the two substances by weight. Even though the measuring of the cream of tartar and soda separately is accurate, the proportions may not be correct. There is no great advantage in homemade baking powder. It costs almost as much as the manufactured, and is not as perfect a product.

=The proportions of the main ingredients.=--Attempts are made to define the degrees of stiffness of batters and doughs, but these distinctions are not very accurate. A "pour batter" is liquid enough to pour, and a "dough batter" soft enough to drop from a spoon; a "soft dough" is next in grade, and "dough" is the stiffest of all.

To understand proportioning the ingredients, the nature of the ingredients when heated must be taken into account. b.u.t.ter and other fats melt when heated, and behave like a liquid in the mixture. Therefore, when there is a very large amount of b.u.t.ter, no other wetting is necessary, as in pound cake. We may make a scale, with a thin popover mixture at one extreme, with no b.u.t.ter in it, and the stiff pound cake at the other, with b.u.t.ter the only liquid (except the flavoring). Between these two are the mixtures of medium stiffness, with both b.u.t.ter and liquid. This general rule may be given: As the quant.i.ty of b.u.t.ter is increased, the batter must increase in stiffness, and there must be either less liquid or more flour.

A beaten egg looks like a liquid and behaves so during the mixing, but in the oven it stiffens. For this reason we can make a sponge cake with many eggs and no liquid in the mixing, and use no other leavening agent than the air beaten into the egg.

One old-fashioned rule for sponge cake reads: Take the weight of the eggs in sugar and half their weight in flour, with the juice and rind of a lemon for ten eggs. Such a rule was adapted to the days when eggs were cheap. We should now use fewer eggs in sponge cake, and this means that water and baking powder must replace the eggs omitted.

=Methods of mixing.=--(1) _For popovers, griddlecakes, m.u.f.fins, and plain cake._

Sift together the dry ingredients.

Beat the eggs, without separating the yolk and white, and stir the eggs and milk together.

Pour the liquid gradually into the flour, first stirring, then beating.

Melt the b.u.t.ter or other shortening, and beat it into the batter.

(2) _Biscuits and shortcakes._

Sift together the dry ingredients.

Cut in or chop in the b.u.t.ter.

Add the wetting slowly.

(3) _A richer, fine-grained b.u.t.ter cake._

Sift together the dry ingredients.

Cream the b.u.t.ter, and beat in the sugar.

Beat the whites and yolks of the eggs separately.

Beat the yolks into the creamed b.u.t.ter and sugar.

Add the flour and milk alternately; that is, a quarter or third of the flour, then a portion of the milk, and so on. First stir, then beat vigorously.

Fold in the beaten whites lightly and do not beat the mixture again.

(4) _Sponge cake._

If baking powder is used, sift with the flour.

Beat the whites and yolks of the eggs separately.

Beat the sugar into the yolks, and add the liquid and flavoring.

Add the flour and beaten whites in alternate portions, dividing both into quarters or thirds.

=Baking.=--This is a science and an art that requires much practice. Do not be discouraged if you do not succeed at first.

Concerning the utensils for baking, see Chapter II. The cups or pans are prepared by warming and greasing. Use a bit of soft paper or a brush for greasing the pan and ordinarily an inexpensive fat, reserving b.u.t.ter for delicate cake. Flour sprinkled on a pan is sufficient for biscuit and cookies. Line a pan for loaf cake with white paper, and grease the paper.

See that the oven is ready before the mixing begins. We shall not be able to bake accurately until our ovens are equipped with thermometers. In the meantime we must use some simple oven test. The indicators on the doors of some ovens are a guide, although they are not really accurate according to the scale of the thermometer. A gla.s.s door is also a convenience.

A loaf should be baked at a lower temperature than a biscuit or m.u.f.fin.

Why?

_For loaves_, 380 F. Test by the hand, counting fifteen slowly, fifteen seconds. A piece of white paper will become a delicate brown in five minutes.

_For biscuits, m.u.f.fins_, and _small cakes_, 425 to 450 F.--Test by the hand, a count of ten. A piece of paper becomes a deeper golden brown in five minutes.

Any mixture containing baking powder may stand some little time before it is put in the oven, provided it is kept cold. The action of the baking powder is not immediate, and is very slight at a low temperature.

The stages of the baking are first, the rising; second, the crusting over; third, the baking of the interior; and last, a shrinkage of the whole.

Many ovens bake unevenly, and pans must be shifted. This should be done with care and not before the third stage of the baking. It is often well to cool off the oven the latter part of the time. An oven that is too hot may be cooled by a pan of water. Paper may be laid over the top of the cake if the browning has been too rapid. These are all makeshifts, and indicate a poor oven, or poor management of the fire. Do not look into the oven for the first ten minutes of baking, and always close the oven door gently.

When we are privileged to have electric ovens, with gla.s.s doors, and an accurate thermometer, baking will be an easy and accurate process.

EXPERIMENTS AND RECIPES

_A. Experiments with baking powder._

1. Dissolve half a teaspoonful of baking powder in two tablespoonfuls of water and heat in a test tube, or saucepan, over a flame; notice the effervescence when the bubbling is at its height, and hold a lighted match in the mouth of the tube. This is a simple test for carbon dioxide.