Bread is a baked food made from a dough of ground or milled cereal grain, usually wheat flour, and leavened by chemical or microbiological action.
Because of the leavening process, the making of even the simplest kind of bread is a fairly complicated procedure. Only wheat flour contains gluten, a substance that supplies the structure needed for leavening. Many non-wheat-growing cultures have never known bread.
Bread making may have originated in Egypt. Archaeologists have found pieces of bread that show clear evidence of leavening action in deposits dating from about 3500 BC. The "sun bread" of Upper Egypt, made today by a method that must be very old, is prepared from a thick batter that is placed in the sun to leaven and partially dry before it is baked into a hard-crusted loaf with a sweet, soft interior. By the dynastic period, loaves of special shapes and sizes were made for religious purposes and for consumption by different social groups.
Bread was a common foodstuff in Rome, and a sophisticated baking industry developed, using mechanical kneading devices. During the early Middle Ages, baking technology regressed; although eventually the growth of bakers' guilds resulted in improvements in techniques and tools. During the Industrial Revolution, an acceleration occurred in the development of baking technology, and today the making of bread is a highly mechanized process in most Western countries.
LEAVENING
Dough was originally leavened by adding sourdough left over from a previous day's bread production. The relative acidity, alcohol content, and low oxygen tension in the interior of a sourdough mass tend to inhibit the growth of molds and undesirable bacteria while allowing preferred strains of yeast to proliferate. The results are unpredictable, however, because varying amounts and types of yeast can develop in the sourdoughs. An improved method of ancient origin uses the relatively pure yeast that settles out from beer or wine.
   Yeast
Today bread is leavened with yeast manufactured by inoculating pure cultures of the selected strain of microorganism into carefully formulated and sterilized liquid media. The yeast cells multiply under controlled conditions; they are harvested by centrifugation and filtering, washed free of media, and packaged for delivery. Bakers' yeast is composed of the living cells of Saccharomyces cerevisiae, a unicellular microorganism.
Yeast performs its leavening function by fermenting carbohydrates such as glucose, fructose, maltose, and sucrose. (It cannot metabolize lactose, the predominant carbohydrate in milk.) The principal products of fermentation are carbon dioxide, which produces the leavening effect, and ethanol. Yeast also produces many other chemical substances that flavor the baked product and change the dough's physical properties.
Although most breads and rolls are leavened by yeast, some breadlike products (Irish soda bread, corn bread, certain kinds of muffins) are leavened by chemical systems such as baking powder.
INGREDIENTS OF BREAD
Bread can be made using only flour, water, salt, and leavening. This simple recipe is used for the popular Italian and French breads, which are light in color and have a crisp crust and coarse, relatively tough crumb. The flavor and the texture of both crust and crumb deteriorate rather quickly, however. Other ingredients must be added to improve storage stability.
Bread flour is usually made from hard wheat, which produces a dough that is elastic enough to hold the gas produced during fermentation.
Nonfat dry milk is often added to improve the flavor and enhance the nutritional quality of commercial bread. Shortening improves the texture of the crumb and increases shelf life. It also makes the dough easier to handle. Some types of shortening, such as butter, contribute significantly to the flavor of the finished loaf. Eggs contribute their characteristic color and flavor to the bread, and their natural emulsifiers improve the handling properties of the dough and make the crumb softer. Sugar and corn syrup make the bread sweeter and supply fermentable carbohydrates for the yeast to metabolize. Molasses and honey add their typical flavors as well as sweetness. Most consumers prefer slightly sweet bread.
Other ingredients sometimes added to commercial bread and rolls include dough improvers (to adjust handling properties), yeast foods, mold inhibitors, vitamins, and minerals.
   Whole Wheat Bread
Whole wheat bread is made from a meal that contains essentially all of the components of the cleaned wheat kernel in the same proportions as they are found in the grain. The loaves are dense, firm, dark in color, coarse in texture, and strong in flavor. Wheat and part-whole-wheat breads contain a mixture of whole grain meal and enough white flour to assure good dough expansion and a lighter color and density.
   Pumpernickel and Rye Bread
Pumpernickel, a dark, tough, and close-textured loaf, is made from crushed or ground whole rye kernels, without the admixture of wheat flour. Rye and wheat flours are added to produce rye bread, which has a better texture, lighter color, and milder flavor than pumpernickel. Caramel coloring and caraway seeds are often added to rye bread.
Rye bread can be made by the sourdough method, where leavening and flavor result from the addition of a small amount of old dough in which lactic-acid-producing bacteria have developed. These microorganisms ferment some of the carbohydrates in the fresh dough batch, producing characteristic sour tastes and odors.
   Salt-Rising Bread
Salt-rising bread is made with a sourdough high in salt. The salt limits the growth of common bakers' yeast while creating a more favorable environment for growth of bacteria that influence the flavor.
PRODUCTION METHODS
All conventional bread production involves measuring the ingredients; mixing and kneading the ingredients to form an extensible dough; allowing the dough to ferment under controlled conditions; kneading the fermented dough; forming the dough piece; proofing, or allowing the dough piece to ferment; and baking. There are many variations of this simple scheme.
Mixing and kneading the ingredients to form a soft, elastic mass (called developing the dough) is a critical part of the baking process. Unless the proper physical properties are obtained at this stage, the dough will be very difficult to manipulate, either by hand or by machinery, and will not produce bread of optimal volume and texture. An adequately developed bread dough will exhibit a slight sheen on the surface but will be only slightly sticky to the touch. When the dough is stretched out to a thin film, it will not tear readily and will have a translucent, webbed appearance when viewed against the light.
The second kneading process collapses the expanded dough piece so that most of the leavening gas is pressed out of it. This is done to prevent the formation of large gas bubbles, which mar the appearance of the loaf and reduce the quality of the bread.
After the initial fermentation, the bulk dough mass is cut into pieces calculated to yield the desired size of roll or loaf. In one type of bread making, the dough is deposited into the pans immediately after it has been mixed. The panned or rounded dough pieces then undergo a second, and sometimes a third, fermentation, during which the leavening gas generated by the yeast causes them to expand considerably.
Bread and rolls can be baked in pans or on sheets; the latter method produces the so-called hearth breads. Most commercial ovens for large-scale production are of the tunnel type, in which multiple assemblies of loaf pans or sheets are carried through long baking chambers indirectly heated by gas, oil, or electricity.
NUTRITIONAL QUALITIES
Most white bread sold in the United States is enriched. Federal standards require that enriched bread contain not less than 1.8 mg of thiamin, 1.1 mg of riboflavin, 15 mg of niacin, and 12.5 mg of iron to a pound. It may contain enough added calcium to bring the total calcium content of the bread to 600 mg a pound. When so enriched, bread can supply significant percentages of the daily requirements of these and several other essential nutrients. (Nutrient amounts and percentages are those used by the U.S. Department of Agriculture.)
A serving of bread will vary in size depending on the desires of the individual consumer, but an average portion is generally considered to be 1 ounce, or about one slice. Consuming two slices of enriched white bread made with 4 percent nonfat dry milk at each of three daily meals will supply the nutrients shown in the tables at the end of this article.
SPECIAL DIETARY BREADS
To meet the needs of people who experience adverse physiological reactions to some ingredients of bread, bakers have developed special products that do not contain the offending ingredients. A few bakers produce bread containing less than 5 mg of sodium per slice. Although this bread is not as palatable as the regular product, it can be helpful in the diets of persons with edematous conditions, certain hypertensive states, and nephritis.
Gluten bread contains reduced amounts of starch and a higher percentage of protein than regular white bread. Persons who react adversely to the consumption of wheat starch can usually eat this food without developing symptoms. It is also recommended for high-protein, low-calorie diets.
Wheat gluten, as well as some other proteins, can cause celiac disease, a debilitating intestinal disorder affecting susceptible infants and small children. Foods resembling bread can be made for these patients from starch and a texturizing agent such as egg whites.
Samuel A. Matz
Bibliography: Beard, James, Beard on Bread (1977); Clayton, B., Jr., The New Complete Book of Breads (1987); Hensperger, Beth, Baking Bread: Old and New Traditions (1992); Johnson, E. F., The Bread Book: A Baker's Almanac (1994); Jones, J. and E., The Book of Bread (1986); Matz, S. A., Ingredients for Bakers (1987; repr. 1990); Miller, B., Variety Breads in the U.S. (1981); Pomeranz, Y., and Shellenberger, J. A., Bread Science and Technology (1971).