Various other foods can substitute for butter when you are baking a cake. There are limitations to what you can achieve, though, because food substitutions create a different texture as well as flavor. For this reason "Cooking Light" magazine refuses to make butter substitutions. Other cooks are willing to experiment, often with good results. Several natural ingredients can be substituted, although each has its own characteristics.
What Butter Does
The chemistry of baking is complex. According to “Cooking Light” magazine, butter has three roles in cakes -- to carry rich flavors, to make cakes tender by coating flour protein to prevent gluten formation and to make them delicate and light by holding the air bubbles that leavening agents produce. Changing ingredients changes taste and texture so “Cooking Light” doesn’t make butter substitutions. They “lighten up” by cutting fat quantity instead. “Cooking Light” also refuses to make substitutions for sugar, because sugar acts as a chemical “tenderizer” and in that way can help replace missing fat in reduced-fat recipes.
Lard or shortening like palm shortening – solid natural animal or vegetable fats – both cream well and are even better than butter at moisturizing cake, but don’t add flavor or carry flavors well. Semisolid natural dairy products including cream cheese, sour cream and yogurt can also substitute 1:1 for butter, depending on the recipe. Pureed silken tofu easily substitutes for half of the butter in a recipe, for a nutty flavor, with something moister making up the other half. Other vegan options for natural butter substitutes include coconut cream -- the thick section you skim off the top of whole fat coconut milk – and natural bean puree.
Fruit & Vegetable Purees
If reducing or eliminating dairy or fat is your aim, natural fruit and vegetable purees can make that possible. Substitute applesauce on an equal basis, 1 cup of applesauce for 1 cup of butter, for a very moist cake -- so moist you may want to reduce other moisture in the recipe. Mashed bananas are also good, though they lend a strong, distinctive flavor. Pureed prunes also make a good substitute but a dry one, so replace just half the recipe’s butter with prune puree for best results, using applesauce, yogurt or other “wet” substitute for the rest. Also good but lending distinctive color is pureed pumpkin. If your intention is to make a more healthful cake, though, note the high sugar content of the fruit substitutes; when it comes to cake, it appears you really can't have it and eat it too.
Substituting natural vegetable oils for butter in recipes can work but it can pose a challenge, because oil is too liquidy to hold air in the cake during creaming, which changes cake texture. To use oil in cake try a light-flavored olive oil first, because it is high in natural emulsifiers and blends well with other ingredients for a moist cake. Olive oil also enhances other natural flavors. Using oil works best for denser cakes, and you need to use less oil than butter. For every cup of butter called for, use 3/4 cup of olive oil. Even in cake recipes where lightness, or the batter’s ability to aerate, is important, inventive cooks have found ways to make oil work. The most common technique is to separate eggs and beat air into the egg whites to create a meringue-like volume of egg and air, which is folded into the batter after other ingredients.