Liquid or "wet" ingredients are a necessity in making any baking recipe a success. Each liquid functions in a different way, depending on the item you're baking, so read all recipes carefully and make an effort to follow the instructions as they are written and to use the ingredients recommended. As you become a better baker and learn more about what each ingredient does, you can attempt substitutions and alterations to existing recipes.
Water is the most vital liquid ingredient in many baked goods, particularly bread. The right amount of water helps dissolve the yeast in bread and encourages it to become active, and it combines with flour and the other dry ingredients to form a smooth, workable dough. In that way, water acts as a binding agent for the bread. In other baked goods, water helps provide needed moisture without affecting the final flavor of the product.
Milk and Cream
Milk and cream, like water, moisten dough and batters. Unlike water, they add a slight flavor to the final baked good and increase its richness. Depending upon the fat content of the milk or cream--skim, 1 percent, 2 percent, whole, half and half, or heavy whipping--it's possible to impart varying degrees of richness to the dough or batter you're making with it. Milk and cream also create a fuller, moister texture in baked goods and help them brown on the surface.
Yogurt and Sour Cream
Yogurt and sour cream make the dough moist but impart a sharper, more tart flavor than milk or cream. They can also work as binding agents in quick bread or muffin batters, cutting off some of the sweetness from added sugar while adding structure and helping the crumb in the product develop well.
Oil is sometimes used as a substitute for butter in recipes, although it does not have the same flavor and doesn't always function in the same way. For quick breads, muffins and other recipes in which the oil isn't meant to impact the final flavor, bakers should choose canola oil or vegetable oil as ingredients. Oil adds structure and moistness to a baked good and boosts its flavor.
Eggs are a binding agent that helps finished baked goods stick together and rise well. They also enhance texture and produce a moister final product. The yolks of eggs add fat to recipes, resulting in greater flavor. Because of these varied properties, it can be difficult to substitute other ingredients for eggs in a recipe.
Sugars and Extracts
Liquid sugars, such as corn syrup, honey, molasses or maple syrup, sweeten baked goods and give them a pleasant flavor. Vanilla extract and other liquid flavorings can help enhance and adjust this sweet flavor.