The basic recipe for cake frosting consists of creamed fat, powdered sugar and flavor extracts. Many recipes use shortening because it's less expensive and can withstand higher temperatures than the traditional butter. Shortening is partially hydrogenated vegetable oil and contains unhealthy trans fats; it also has a greasy, heavy mouth feel. If you want a healthier substitute for shortening, dislike the taste or have simply run out, you have several alternatives.
Replace shortening with butter and you'll have buttercream frosting with a rich flavor and creamy texture. Buttercream is softer than icing made with shortening and melts more easily if left in a warm place. For a healthier version, use a low-fat butter; however, keep in mind that your frosting needs some fat for quality results. Achieving a bright white frosting is also difficult due to the color of butter, but frosting whiteners are available at some cake supply stores.
Margarine or Spreads
Just like butter, margarine can be a substitute for shortening in frosting. Margarines can contain various vegetable oils, some butter, milk products or added health ingredients like omega fatty acids. The basic type usually includes an emulsified blend of vegetable oils and skim milk. Margarine is also usually less expensive and more stable at room temperature than butter. Some margarines contain hydrogenated oils and trans fats, just like shortening, so read the label carefully or look for brands that are specifically marketed as non-hydrogenated and trans-fat free.
Cream cheese contains less fat and more protein than shortening, especially when you use a low-fat variety. You will achieve the bright white color, but it does bring a different flavor. The tang of a cream cheese frosting adds complexity and complements most cakes very well, especially red velvet or chocolate. A basic recipe usually calls for cream cheese, powdered sugar and vanilla.
Sour Cream or Yogurt
Frosting made with sour cream or yogurt has less fat than the conventional kind, and if it's made with yogurt it's probably the healthiest version you can make. Greek-style yogurts are your best bet, because they have a thicker texture to begin with. It has a slight tart or tangy flavor. Frosting made solely with sour cream or yogurt has a thinner consistency and is much lighter in texture than frosting made with butter or shortening. You can also add sour cream or yogurt to the butter in buttercream frosting to give you the flavor without giving up that traditional creamy taste.
Other Nondairy Options
To make a vegan or nondairy frosting, use soy margarine or any nondairy milk like soy, rice or almond. You can also add soy milk powder to improve creaminess. You can make frosting with refined coconut oil, which comes in solid form, along with coconut milk for a real coconut flavor. Coconut oil has a low melting point, so keep it in a cool place. You can also use nut butters, like peanut, in frosting. Because of nut butters' thickness, many recipes call for the addition of another ingredient like cream or butter, in which case you can use a nondairy milk or cream.