A colorless and tasteless thickening agent, unflavored gelatin is used to give body to chilled aspics, gelatin salads and molded desserts. Originally obtained from natural sources, such as calves' feet, now it is commercially made. Most gelatin is granulated, although it is available in sheets (known as sheet or leaf gelatin) in some gourmet shops. A 1/4-ounce envelope of unflavored gelatin contains 1 tablespoon, which is enough to gel 2 cups of most clear liquids. Certain raw foods contain an enzyme that prevents gelatin from thickening. These include figs, ginger root, guava, kiwifruit, papaya and pineapple. Cooking and canning destroys the enzyme. Sweetened, flavored gelatin mixes are also readily available.

Before using, unflavored gelatin must be softened. To soften, place 1/4 cup of the cold liquid used in the recipe in a small bowl or saucepan and evenly sprinkle the liquid with 1 tablespoon gelatin. Let it stand for 5 minutes. To dissolve gelatin, place the bowl in a larger container of hot water. Let it stand until all the crystals have dissolved. Softened gelatin can also be added to a hot mixture or heated in a saucepan over very low heat until dissolved. Do not let the softened gelatin boil, because this will destroy its thickening powers.