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the process of using heat to prepare foods for consumption.
Many common cooking methods involve the use of oil. Frying is cooking in hot oil; sautéing is cooking in a small amount of oil; stir-frying
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the process by which bread products are produced from dough. The principal raw materials in baking are wheat and rye flours of various grades, water, bakers’ yeast, and salt. Supplementary ingredients may include sugar, starch syrup, shortening, liquid and dry milk, whey, eggs, poppy seed, and spices. The major steps in baking are reception and storage of ingredients; preparation, dividing, and proofing of the dough; and baking, cooling, and, sometimes, packaging of the bread.
Flour is usually delivered to bakeries in the tanks of flour trucks, from which it is pumped under pressure through pipes to hoppers located in storerooms. Before the flour is mixed with the other ingredients, it is sifted and freed of ferromagnetic impurities with magnets. During storage various biochemical changes occur that improve the flour’s baking qualities.
The preparation of dough consists in mixing the flour, water, salt, and yeast, a leavened dough (sponge), or a ferment, together with any other ingredients. Salt and sugar are measured out in the form of filtered aqueous solutions, the yeast in the form of an aqueous suspension, and the shortening in a melted state. During preparation of the dough the flour particles expand as the water combines with albumins, starch, and pentosans; lactic and other organic acids accumulate as a result of the activity of lactic acid bacteria, and the yeast cells are activated (the fermentation activity is increased) and multiply. The hydrolytic action of the enzymes in the dough increases the amount of sugars and water-soluble albumins. The expansion of the flour particles enables the dough to retain its shape and the gas produced by the yeast. The organic acids give bread a slightly sour taste. The yeast cells in dough give rise to alcoholic fermentation with the formation of ethyl alcohol and carbon dioxide gas; the carbon dioxide bubbles expand the dough and ensure a porous structure in the crumb.
The traditional methods of preparing wheat dough are the sponge-and-dough (batch) and straight-dough methods. In the latter, all the ingredients are mixed at one time, and the dough is ready after two or three hours; in the sponge-and-dough method, a sponge is first mixed to produce a more liquid dough from 50–70 percent of the total amount of flour and the entire amount of yeast. After four to five hours the remainder of the flour, water, and other ingredients are added to the fermented dough, which is then mixed to proper development and left to ferment for one or two hours. Somewhat less yeast (approximately 1 percent) is required for this method than for the straight-dough method (1.5–3 percent).
In a new method that shortens the bread production cycle and facilitates mechanization and automation of the process, the dough is prepared as a liquid sponge mixed from approximately 30 percent of the total flour. As a result, the lactic acid fermentation processes and the activation and multiplication of the yeast occur in a liquid sponge, which accelerates fermentation and facilitates transportation and metering of the sponge. The accelerated effect may also be obtained by a separate preparation of 5–15 percent of the flour with a lactic acid ferment or a semifinished product for activation of the yeast. The new method makes it possible to optimize the basic maturing processes for the dough and reduce the volume of equipment needed. If the dough is prepared by mixing all ingredients at one time together with food acids (lactic, citric, and malic) or whey (liquid, concentrated, or dried) in quantities sufficient to create the required acidity in the bread, the process can be accelerated to a still greater degree. All the accelerated methods are economical. They are characterized by intensification of the biochemical, microbiological, and colloidal processes in the dough; for example, the fermentation time is no more than 30–40 minutes.
Preparation of the dough can also be accelerated by adding amylolytic and proteolytic fermentation preparations, ameliorators of the oxidizing processes (ascorbic acid, potassium bromate, or potassium iodate) and reducing processes (cysteine and sodium thiosulphate), and surface-active agents (monoglycerides and diglycerides, lecithin, and glycolipides).
Rye dough and dough made of a mixture of rye and wheat flours may be prepared in either thick or liquid ferments. The production properties of rye flour are responsible for the higher acidity and moisture of the dough compared with wheat dough.
The readiness of the sponge, ferment, and dough is determined by the final acidity, or pH value, of the medium and by the fermentation activity. The acidity and moisture content of a dough and of the resulting bread are a function of the grade of wheat or rye flour, the recipe, and the type of bread product produced.
The dividing of wheat dough actually comprises the individual operations of dividing, rounding, intermediate proofing for several minutes (the internal stresses in the dough are resorbed and the structure is partially restored), molding, and final proofing. For dough made of rye flour, the process is restricted to dividing, molding, and final proofing. The final proofing of pieces of dough is accompanied by a fermentation process, which makes it possible to obtain bread with a well-aerated crumb. The duration varies widely—from 25 to 120 minutes. The readiness of a piece of dough is judged by the dough’s volume, aeration, and elasticity.
Bread is baked in baking ovens. The dough may rest in metal pans (pan bread) or lie directly on the oven hearth (hearth bread). The heating forms a crust on the surface of the dough; at the same time, the albumins inside the dough are denatured, and the starch is partially converted to a paste to form the crumb. The temperature in the middle of the crumb during baking rises to 92°–98°C, and the crust is heated to 140°–175°C. The ferments in the dough cause hydrolytic decomposition of the starch during baking, with an increase in the amount of water-soluble carbohydrates. In addition, in rye bread there is a partial acid hydrolysis of the starch.
The higher temperature in the crust causes almost all moisture to be lost and results in dextrinization (partial disintegration) of the starch. In addition, processes of oxidation and reduction occur in the unfermented sugars and in the products from the proteolysis of the albumins in the dough; in the latter case, melanoidins are formed, which color the crust golden to brown. A group of intermediates and by-products is also formed—primarily volatile substances (over 200)—which together provide the distinctive aroma of bread. Substantial humidification of the steam-air medium in the baking chamber during the initial baking period increases the volume of the bread and makes the surface of the crust glossy. During baking, the dough loses part of the water, ethyl alcohol, and volatile substances. The difference between the weight of the dough that enters the oven and the weight of the bread removed depends on the initial weight and the shape and ranges from 6 to 14 percent.
After it is removed from the oven, the bread is cooled on trays in storerooms and dispatching rooms; it is then shipped to market. During cooling and storage, bread loses between 1.5 and 5 percent of its weight, primarily through moisture loss.
The future development of baking calls for expansion of the variety of breads offered; improvements in the taste, aroma, and appearance of the products; and an increase in the output of enriched baked goods with more albumins, essential amino acids, and vitamins. Baking can be made more efficient by intensification and modernization of the control methods used in the production processes and by the development and introduction of integrated mechanization and automation for baking enterprises.
REFERENCESKoz’mina, N. P. Biokhimiia khlebopecheniia. Moscow, 1971.
Auerman, L. Ia. Tekhnologiia khlebopekarnogo proizvodstva, 7th ed. Moscow, 1972.
Spravochnik po khlebopekarnomu proizvodstvu, vols. 1–2. Moscow, 1972.
Shcherbatenko, V. V. Regulirovanie tekhnologicheskikh protsessov proizvodstva khleba ipovyshenie ego kachestva. Moscow, 1976.
V. V. SHCHERBATENKO