When a baking recipe calls for sour cream, it's typically included to activate the baking soda in the recipe. When baking soda is mixed with a moist, acidic component such as buttermilk, sour cream, yogurt, molasses, brown sugar, chocolate, or non-Dutch-process cocoa, it creates carbon dioxide, which makes baked goods rise and gives them a light, airy texture. Greek yogurt is an excellent sour cream substitute for making cookies, provided it is plain and unflavored. Use the same amount of Greek yogurt as you would sour cream in recipes.
In addition to activating leavening agents, yogurt also adds rich moistness to baked goods. The bacterial benefits of yogurt dissipate when it's heated but it still provides important nutrients like protein and calcium when used in cooking and baking. Moreover, it has less calories and fat than buttermilk or sour cream. If you need to freeze plain yogurt to keep it from spoiling, you can still use it for baking and cooking although the consistency makes it unappealing to eat from the carton.
Cooking with Yogurt
Sour cream or heavy cream can be successfully replaced by yogurt in sauces and other recipes cooked on the stove top, using the same amount as the recipe calls for. However, if you add it to boiling or near-boiling mixtures, the bacteria will be destroyed and the mixture will probably curdle. For best results, mix a few tablespoons of the medium hot mixture into the yogurt and then slowly blend the yogurt into the remaining hot liquid.
Tips for Using Yogurt
Always add yogurt as close to the end of the cooking process as possible and gently warm it without letting it simmer. If you try to rush it, it will separate into curds and whey, giving the dish an unattractive appearance and texture. Bring the yogurt to room temperature before cooking with it. To use yogurt as a thickening agent, mix 1 or 2 tablespoons of cornstarch, arrowroot or flour with a cup of yogurt and a tablespoon or 2 of cold water. Avoid aluminum cookware when cooking with yogurt to prevent an adverse reaction with the metal, which often imparts food with an off-putting taste.
Other Sour Cream Substitutes
In addition to yogurt, there are other viable sour cream substitutes. Buttermilk is a good alternative, as is creme fraiche, both of which should be used in identical amounts as the quantities of sour cream the recipe calls for. You can also substitute 1 cup of sour cream with 1 cup of heavy whipping cream, with at least 35 percent butterfat content, combined with 1 tablespoon of lemon juice.