A Quick Comparison

• Bakers are often surprised to learn that corn oil, which, like other oils, is perceived as "light," actually contains more calories than a comparable quantity of butter. That's because butter is only about 80 percent fat, with the other 20 percent representing a mixture of water, proteins and other nutrients. That means butter improves the nutritional value of your baked goods as well as their flavor, but there is a price tag: Only about 12 percent of the fat in corn oil is saturated, but saturated fats account for a whopping 60 percent of the butter's fat. It's also high in cholesterol, so despite its virtues, butter should be used in moderation.

The Substitution

• A cup of corn oil is a simple thing, consisting entirely of fats. A cup of melted butter is only four-fifths fat, with the remainder -- about 1 1/2 fluid ounces -- consisting primarily of water. If you use melted butter as a straight one-to-one substitution for oil, it will often result in a slightly chewier texture. That's because fats soften the crumb of your baked goods, and you're adding less fat. The additional moisture also plays a part, helping the flour form more and stronger chains of gluten. You can resolve both problems by increasing the butter slightly, to provide more fat, and then reducing the other liquids in your recipe by a comparable amount.

Jazzing Up a Mix

• You can also use melted butter in place of the oil called for in boxed mixes for cakes, brownies and similar baked goods. Box mixes typically contain a number of emulsifiers and other ingredients to keep their batter smooth and texture soft, so the slight difference in moisture and fat levels won't be as evident. Still, depending on the individual mix, you might find it necessary to make small adjustments. Reducing the other liquids by a tablespoon or two, or adding an extra tablespoon or two of flour, will usually bring the mix back to its accustomed texture.

Specialty Butters

• Not all butters conform to the usual percentages, so it's important to pay close attention when you're choosing one to bake with. A few brands, usually described as "European-style," are higher in fat content. They also tend to have a stronger flavor, which can be a benefit in some cases but a flaw in delicately flavored cakes. Whipped butter has air beaten into it to increase its volume, so you might need to use twice as much or more. Melt it first, then measure it. "Light" butter spreads often contain additional water or oil. Melt the butter and measure just the fat, leaving the watery portion in your original cup.