Glucono delta-lactone (GDL) is a lactone (cyclic ester) of D-gluconic acid, used as a food additive as a stabilizer and coagulant in silken & softer tofu, sausage; as preservatives: in seafood (fishes and shrimps) to keep fresh, as leavening agent: in baking powder to ferment; in pickling and curing meats and vegetables;
Used to make tofu: Mix 1 teaspoon of GDL with 1 quart of warm soy milk. It will set in about 1 hour.