Sugar in Bakery Foods
During the mixing process, sugar acts as a tenderizing agent by absorbing water and slowing gluten development.
During the mixing of batters and doughs, flour proteins are hydrated (surrounded with water) forming gluten strands. The gluten forms thousands of small, balloon-like pockets that trap the gases produced during leavening. These gluten strands are highly elastic and allow the batter to stretch under expansion of gases. However, if too much gluten develops, the dough or batter becomes rigid and tough.
Sugar competes with these gluten-forming proteins for water in the batter and prevents full hydration of the proteins during mixing. As a consequence, less gluten is allowed to “develop,” preventing the elastic dough or batter from becoming rigid. With the correct proportion of sugar in the recipe, the gluten maintains optimum elasticity, which allows for gases to be held within the dough matrix. These gases, from leavening agents and mixing, expand and allow the batter or dough to rise. By preventing the gluten development, sugar helps give the final baked product tender crumb texture and good volume.
Sugar increases the effectiveness of yeast by providing an immediate, more utilizable source of nourishment for its growth.
Under recipe conditions of moisture and warmth, sugar is broken down by the yeast cells, and carbon dioxide gas is released at a faster rate than if only the carbohydrates of flour were present. The leavening process is hastened and the dough rises at a faster and more consistent rate.
Sugar crystals become interspersed among the shortening molecules when shortening and sugar are creamed together.
In cakes and cookies, sugar helps promote lightness by incorporating air into the shortening. Air is trapped on the face of sugar’s irregular crystals. When sugar is mixed with shortening, this air becomes incorporated as very small air cells. During baking, these air cells expand when filled with carbon dioxide and other gases from the leavening agent.
Sugar serves as a whipping aid to stabilize beaten egg foams.
In foam-type cakes, sugar interacts with egg proteins to stabilize the whipped foam structure. In doing so, sugar makes the egg foam more elastic so that air cells can expand and take up gases from the leavening agent.
Egg Protein Coagulation
In unshortened cakes, sugar molecules disperse among egg proteins and delay coagulation of the egg proteins during baking.
As the temperature rises, egg proteins coagulate, or form bonds among each other. The sugar molecules raise the temperature at which bonds form between these egg proteins by surrounding the egg proteins and interfering with bond formations. Once the egg proteins coagulate, the cake “sets,” forming the solid mesh-like structure of the cake.
During baking, sugar tenderizes by absorbing liquid and delaying gelatinization.
In cakes, the heat of baking causes the starch in flour to absorb liquid and swell. This process is called gelatinization. As more liquid is absorbed by the starch, the batter goes from a fluid to a solid state, “setting” the cake. Sugar acts to slow gelatinization by competing with the starch for liquid. By absorbing part of the liquid, sugar maintains the viscosity of the batter. As a result, the temperature at which the cake “sets” (turning from liquid to solid state) is delayed until the optimum amount of gases are produced by the leavening agents. Carbon dioxide, air and steam produced from leavening agents, heated water and air become entrapped and expand in the air cells. The result is a fine, uniformly-grained cake with a soft, smooth crumb texture.
As described above, sugar is effective in delaying starch gelatinization in cakes and provides good texture and volume. Little data is available concerning sugar’s function in delaying gelatinization in breads; therefore its influence on gelatinization in yeast-leavened breads is less clear. In theory, as breads with higher sugar content bake, gelatinization is delayed by the same mechanism described above in cakes. A bread with more tender crumb texture results.
Sugar caramelizes when heated above its melting point, adding flavor and leading to surface browning which improves moisture retention in baked products.
At about 175°C (or 347°F), melted dry sugar takes on an amber color and develops an appealing flavor and aroma. This amorphous substance resulting from the breakdown of sugar is known as caramel. In baking a batter or dough containing sugar, caramelization takes place under the influence of oven heat, and is one of two ways in which surface browning occurs. The golden-brown, flavorful and slightly crisp surface of breads, cakes, and cookies not only tastes good but helps retain moisture in the baked product.
At oven temperatures, sugar chemically reacts with proteins in the baking product, contributing to the food’s browned surface.
These Maillard reactions are the second way in which bread crusts, cakes, and cookies get their familiar brown surfaces. During baking of breads, cakes, and cookies, Maillard reactions occur among sugar and the amino acids, peptides or proteins from other ingredients in the baked products, causing browning. These reactions also result in the aroma associated with the baked good. The higher the sugar content of the baked good, the darker golden brown the surface appears. As described above, these browned surfaces not only taste good but help retain moisture in the baked product, prolonging freshness.
Sugar helps produce the desirable surface cracking of some cookies. Because of the relatively high concentration of sugar and the low water content in cookies, sugar crystallizes on the surface. As sugar crystallizes, it gives off heat that evaporates the water it absorbed during mixing and baking. At the same time, leavening gases expand and cause cracking of the dry surface.
Other Sugar Resources
- Calories in Sugar
- Sugar and Your Diet
- Frequently Asked Questions
- How We Get Sugar
- Types of Sugar
- Other Caloric Sweeteners
- The Other 26 Sweeteners
- Why Sugar is in Food
- Sugar in Jellies and Preserves
- Sugar in Canning and Freezing
- Sugar in Non-sweet Foods