School and Home Cooking

by Carlotta C. Greer

LESSON CX

LEAVENING WITH BAKING SODA AND SOUR MILK: SPIDER CORN BREAD

Besides the air that is beaten into the eggs and into the combined ingredients of quick bread mixtures, a gas—carbon dioxide—is often introduced into such mixtures. To find how this gas may be formed, try the following:

EXPERIMENT 67: ACTION OF BAKING SODA ON SOUR MILK.—Place a teaspoonful of sour milk in a test tube and add a pinch of baking soda. Do you notice any change in the ingredients? Apply heat to the contents of the tube. What kind of material (solid, liquid, or gas) is indicated by the bubbling (see Experiment 7)? What does this experiment teach with regard to the use of baking soda and sour milk, for lightening a mixture?

EXPERIMENT 68: CHEMICAL CHANGE.—Measure 1/4 cupful of thick sour milk. [Footnote 78: The amount of acid in sour milk varies slightly.] Dip the end of a piece of blue litmus paper in it. What change in color takes place in the paper? When blue litmus changes to pink, an acid is present. The sour milk therefore contains acid. Measure 1/8 teaspoonful of baking soda. Mix this with a little water. Test with pink litmus paper. When pink litmus paper changes to blue, an alkaline substance is present. Baking soda is therefore alkaline in reaction.

Pour the milk into a saucepan, add about 3/4 of the soda mixture, stir and heat until effervescence (bubbling) has ceased. Test the mixture in the saucepan with blue litmus paper. If the blue litmus paper changes color, carefully add a little more of the soda solution. Test with litmus again. If there is still a change in color, add soda solution until the litmus does not change. Then test with pink litmus. When neither pink nor blue litmus paper changes color a neutral substance is present, i.e. a substance neither acid nor alkaline.

When this occurs, the mixture in the pan is no longer acid in reaction. Neither sour milk nor baking soda exists in the pan. A chemical change has taken place. From the union of sour milk and soda, entirely different materials are formed; one is the neutral substance in the pan; another is the carbon dioxide gas which has escaped, and the third is water. When an acid and an alkaline material are mixed, a chemical change always occurs. Chemical changes are constantly taking place when certain food mixtures are cooked and digested.

EXPERIMENT 69: QUANTITY OF BAKING SODA TO USE WITH SOUR MILK.—To the contents of the saucepan of Experiment 68, add 1/8 teaspoonful more of baking soda. Stir, heat, and test with pink litmus. What is the reaction— acid or alkaline? Has the last quantity of soda been neutralized as was the first quantity? Explain.

If more baking soda than is necessary to neutralize the acid of the sour milk is used, some unneutralized soda will remain in the mixture. This is undesirable, since soda has a "bitter taste." An excessive quantity of unneutralized soda also discolors the mixture.

Experiments 68 and 69 indicate that the approximate proportion of baking soda to sour milk is: 1/2 teaspoonful of baking soda to 1 cupful of thick sour milk.

The following "equations" indicate the importance of using the proper amount of baking soda to neutralize the acid materials:

1 cupful of sour milk + 1/2 teaspoonful of baking soda —> [Footnote 79: The plus sign is read "with"; the arrow is read "yields.">[ water + carbon dioxide gas + neutral material.

1 cupful of sour milk + 1 teaspoonful of baking soda —> water + carbon dioxide gas + neutral material + unneutralized "soda."

SPIDER CORN BREAD

3/4 cupful corn-meal 1/2 teaspoonful baking soda 1/4 cupful flour 1 egg 1 tablespoonful sugar 1 cupful sour milk 1/2 teaspoonful salt 1 tablespoonful butter or substitute

Mix the dry ingredients. In a mixing bowl, beat an egg, add the sour milk, then the dry ingredients. Beat the mixtures until the ingredients are well blended.

Melt the butter or substitute in a hot "spider" or frying pan. Pour the corn-meal mixture into it. Bake in a hot oven until sufficiently baked, usually about 20 minutes (see tests below). Serve hot.

TESTS FOR SUFFICIENT BAKING OF QUICK BREAD.—Quick Bread is usually sufficiently baked: (a) when it is a golden brown in color; (b) when the mixture shrinks from the pan; (c) when the crust springs back into place, if pressed gently with the fingers; or (d) when no batter or dough clings to a wire skewer or knitting needle (see Figure 1) that has been inserted. Usually it is not necessary to apply this last test, unless the quick bread is baked in a loaf or in a very thick layer.