From the results of Experiment 69 we know that an increased quantity of baking soda will not produce satisfactory results. Hence more carbon dioxide gas must be obtained by other means. Since baking powder consists of both baking soda and an "acid" material, it makes a desirable substance for additional leavening. A combination of baking soda, sour milk, and baking powder is therefore used for leavening some quick bread mixtures, especially those that contain only a small quantity of sour milk and no eggs. This involves a double reaction:
(a) Baking soda + sour milk —> neutral material + carbon dioxide gas + water.
(b) Baking powder (moistened and heated) —> neutral material + carbon dioxide gas + water.
About 1/4 of baking powder is baking soda. Hence 1/4 teaspoonful of baking soda (with the necessary quantity of "acid" material) is equivalent to 1 teaspoonful of baking powder in leavening. If 2 teaspoonfuls of baking powder are used to leaven 1 cupful of flour, 1/2 teaspoonful of baking soda (with the necessary quantity of "acid" material) should be used to leaven 1 cupful of flour.
Two thirds teaspoonful of baking soda (with the necessary quantity of "acid" material) should be used to leaven 1 cupful of coarse flour or flour or meal other than wheat.
In determining the quantity of baking powder to use in materials leavened with sour milk and baking soda, note the quantity of baking soda and flour. Assuming that 1/2 teaspoonful of baking soda (with "acid") or 2 teaspoonfuls of baking powder leavens 1 cupful of flour, determine the amount of flour that the given quantity of baking soda (with "acid") will leaven and then use sufficient baking powder to leaven the remainder of the flour. For example, if a recipe states (among other ingredients) 1/2 teaspoonful of baking soda and 2 cupfuls of flour, the baking soda (with "acid") will leaven 1 cupful of flour. Hence baking powder sufficient to leaven 1 cupful of flour (i.e. 2 teaspoonfuls) should be used. Again, if a recipe states that 3/4 teaspoonful baking soda and 2 cupfuls of flour, the baking soda (with "acid") will leaven 1 1/2 cupfuls of flour. Hence baking powder sufficient to leaven 1/2 cupful flour (i.e. 1 teaspoonful) should be used.
SOUR MILK GRIDDLE CAKES (without eggs)
2 cupfuls flour 1/2 teaspoonful salt 1/2 teaspoonful baking powder 7/8 teaspoonful baking soda 1 3/4 cupfuls sour milk 3 tablespoonfuls fat
Turn the sour milk into a mixing bowl. Melt the fat and add it to the sour milk. Add the dry ingredients (through a sifter) to the mixture. Mix thoroughly. If more moisture is needed, add water.