How Baking Works

Copyright © 2000 Sarah Phillips Sarah Phillips, Inc. All rights reserved. 

In general, baking ingredients can be divided into two types, "tougheners / strengtheners" (flour, eggs) and "tenderizers / weakeners" (fat, sugar), sometimes overlapping. In order for a recipe to bake with all of the qualities we like, such as being tender, fluffy, moist, chewy, dense, etc, there needs to be a balance between the two. If one is increased, the other must be decreased, but there's more to it than that.

Recipes also vary by the amounts of each ingredient and the mixing techniques used to combine them. Professional baker's use Baker's Percentages to express their relationship to one another, where home bakers use recipes with ingredient amounts. Cooking temperatures and times also affect the final baked good. These relationships affect the color, flavor, texture, shape and volume.

Each ingredient in a recipe contributes to the final baked good. 
The taste and texture of breads, pasta, and pastries depends upon the makeup of the batter or dough. Batters and doughs are made up of water, gluten proteins, and starch granules. Glutens are chains of proteins, and when they are dry, the gluten protein chains don't react or move. When the gluten protein chains come in contact with water, however, they work together and can change their shape, either forming longer chains or breaking into smaller chains. This results in a substance that is both plastic (can change its shape) and elastic (bounces back and returns to its original shape).

Though the dough can change its shape, it resists the change and tries to move back to its original shape. Gluten and water forms the network that gives bread its shape. Starch is also very important when making bread, for several reasons. It holds onto water and gives volume and structure to bread. It also makes its way through the bread and breaks up the gluten network, tenderizing it and giving it that light, delicate texture. 

Shortening tends to make dough more easily workable and the final product more tender, while also, in many cases, adding flavor. To make bread, you add water to flour to create a cohesive mixture of gluten and starch. In the case of a pastry, however, you add large amounts of fat to coat and separate the flour particles from each other, but you then add just enough water to make a dough. Since much of the starch in the flour is not in contact with any of the water, the resulting cooked dough is crumbly and flaky. The role of the fat in making a pastry is to give texture to the final product. Depending on the kind of fat used, the pastry will also have a certain flavor.

Eggs are binders which help hold all the ingredients together. Eggs contribute liquid to a recipe and thus serve as a toughener, especially the egg white portion. Egg whites, as mentioned, are often used to produce a light, airy texture, and yolks contribute to the color, flavor, and texture of baked products. But, too many egg whites, such as in a reduced-fat cake recipe make it dry. Including at least one whole egg helps to tenderize. Eggs can also act as leaveners especially when egg whites are beaten separately. The yolk functions to emulsify fat and liquids due to its lecithin content.

In a cake recipe, for example, butter and shortening are tenderizes because they help make it tender and moist. Leaveners can also weaken a baked goods' structure. The expanding air bubbles weaken and disrupt the gluten network, formed by the wheat flour when combined with liquid, during baking. If your cake dips slightly, it has too much leavening, so reduce the baking powder by 1/4 teaspoon; if baking soda by 1/16 teaspoon. If the cake domes, do the opposite - increase the baking powder by 1/4 teaspoon; if baking soda by 1/16

Sugar tenderizes (and of course makes it sweet) because it prevents the flour from forming gluten (gluten is formed when wheat flour is mixed with water or moisture). Sugar competes for water with the flour and wins, making less available. Buttermilk, an acidic ingredient, also tenderizes.

Liquids bridge both categories as a toughener or a tenderizer. Water and milk enhance the development of gluten and/or gelatinization of starch in the flour or the setting of the structure (baking) and thus serve as a toughener. Milk is used for flavoring, and sugars to sweeten and to aid fermentation. Milk also contains proteins which act as a structural enhancer. But, too much liquid will cause a baked good to collapse or the batter to become too thin, with the final baked good too heavy. The perfect balance of liquid offers both structural support and moistness which is perceived as tenderness.