David Nelson, age 14, of Sullivan, Wis., for his question:
HOW DOES BAKING POWDER WORK?
Bread is called the staff of life since it is one of the world's most widely eaten foods. Wheat flower is used chiefly, although barley, corn, oats, rice and rye grains are milled in all parts of the world to be used for bread. In the United States, Canada and Europe, most bread is light and airy, but flat bread is enjoyed in many parts of the world.
There are basically three kinds of bread: yeast bread, flat bread and quick bread. Quick bread is the type that is made most often at home and includes muffins, corn bread and fluffy biscuits. Most quick breads call for the addition of baking powder to its ingredients.
Baking powder is a white powder used to make biscuits and cakes leaven, or rise. Added to flour when you're baking at home, baking powder produces a chemical reaction when air and either water or sweet milk are mixed in. Bubbles of carbon‑dioxide gas form and they become trapped in the flour mixture. When the mixture is heated in the oven, the bubbles will expand and make the entire mixture rise.
Baking powder contains starch, sodium bicarbonate (which is baking soda) and other acid‑forming ingredients. The starch keeps the powder dry and prevents it from going through its magic act until liquid is added.
Different speeds of reaction are obtained by different types of baking powders. Sulfate powder is the slowest since it does not react fully until heated. Tartrate and phosphate powders are the fastest since they act as soon as they are mixed with a liquid.
Double‑action or combination powders are also widely used. This type reacts well in both mixing and baking processes.
Tartrate baking powders contain cream of tartar and tartaric acid, while phosphate powders use calcium dihydrogen phosphate. Sulfate powders contain sodium aluminum sulfate, or alum, while double‑action or combination powders have both phosphate and sulfate.
Baking soda and sour milk have the same rising effect on flour mixtures as baking powder and sweet milk.
About 99 percent of all commercial bread is of the yeast type. Baking powder is not used here. Rather, as the name clearly tells you, yeast is used as the raising ingredient.
Flat bread, which includes matzo and tortillas, uses little or no leaven.
Nutritionists say that unenriched white bread is a poor source of vitamins and minerals. Enriched white bread, however, provides important amounts of protein, starch, iron and three B vitamins. Many recommend whole‑wheat bread, however, since it provides almost all the natural vitamins and minerals of wheat including niacin, riboflavin, thiamine, vitamin E, iron and calcium. Whole‑wheat bread also contains fiber, an important diet ingredient.