I rarely have butter in the house. Can you tell me what will happen if I use margarine in a recipe that calls for butter? Thanks for your help! —M.H., New Castle, PennsylvaniaOur Test Kitchen home economists use butter in recipes for a variety of reasons. In some recipes, we felt that butter adds a rich flavor that margarine would not achieve. Also, because labeling laws have changed, there’s some confusion on the part of consumers as to how margarine is defined. Both butter and margarine contain 80% fat. Margarine is a butter substitute made with vegetable oils and is available only in stick form. It can generally be used in place of butter unless the distinct flavor of butter is key to the recipe, as with butter cookies.Vegetable oil spreads are products that contain less than 80% fat (water has been substituted for some of the fat). Using spreads in place of butter or margarine will affect the texture and quality of baked goods and candies. Often, it is clearly stated on the package that a vegetable oil spread is not suitable for baking or frying. Another way to determine whether a product is margarine or a vegetable oil spread is to look at the Nutrition Fact label on the package. Both margarine and butter contain 11 grams of fat per tablespoon. Spreads contain less fat and therefore should not be substituted for butter or margarine. Hope this helps!