Gelatin is used in molded desserts and salads and to thicken cold soups. The raw material for gelatin is the naturally occuring protein, collagen, which is commercially obtained from the meat industry (pure protein derived from beef and veal bones, cartilage, tendons, skin and connective tissue). Most commercial gelatin is produced from pig skin. The cleaning and processing of collagen results in a pale yellow dry powder -- an odorless, tasteless thickening agent. When dissolved in hot water then cooled, it forms a jelly. Granulated gelatin is the most common form of unsweetened gelatin. Unsweetened gelatin is typically soaked in a cold liquid for 3-5 minutes before dissolving it. This softens and swells the granules so they will dissolve smoothly when heated. Leaf or sheet gelatin is also available, although not as common as the granulated form. Leaf gelatin requires a longer soaking time than granulated gelatin. Sweetened gelatin dessert mixes, such as the popular Jell-O brand, are available in many artificial fruit flavors.
Professional cooks often use leaf gelatin because it makes a clearer gelatin with purer flavor. Many European recipes call for leaf gelatin. You can successfully substitute powdered gelatin for leaf gelatin in any recipe. One package (1 tablespoon) of powdered gelatin equals 4 sheets. One package of gelatin is enough to jell 2 cups of liquid. Vegan/Vegetarian: Alternative choices include Agar-Agar, which is derived from seaweed. Agar-Agar is sold in noodle-like strands, in powdered form or in long blocks. Other options are arrowroot, guar gum, xanthan gum, pectin and kudzu.
4 sheets leaf gelatin = 1 (.25 oz) envelope granulated gelatin = 1 tablespoon granulated gelatin; Agar-Agar, which is an algae based gellifying agent