Powdered, unflavored gelatin is tasteless and virtually colorless and derived from animal collagen. It can be used as a thickening agent for savory sauces, like a rich, meaty demi-glace, or in a sweet berry sauce. In classic French cooking, powdered gelatin is used in chaud-froids. Chaud-froid translates literally as "hot-cold," and these shiny, glazed sauces are prepared hot then chilled to set. Gelatin is protein-based and thickens as it cools, in contrast to starch thickeners, like flour or cornstarch, which thicken when heated. Gelatin is a suitable substitute thickener for gluten-free, low-carb and grain-free diets.
Add about 2 tablespoons of cold water to a small bowl. Measure out the powdered gelatin. Use 1 1/2 teaspoons of gelatin for every 1 cup of sauce liquid for thin sauce, and up to 4 1/2 teaspoons of gelatin per 1 cup for thick sauce. Sprinkle the powdered gelatin over the surface of the water.
Whisk the gelatin and water together. Allow the gelatin and water mixture to sit for a few minutes to hydrate the gelatin powder.
Pour the mixture into your simmering pot sauce. Stir the sauce for about one minute to integrate the gelatin with the sauce. Do not allow the sauce to boil after you've added the gelatin.
Remove your pot of sauce from heat. Allow the sauce to cool at room temperature until it begins to thicken slightly, then serve warm. Finish sauces that are meant to be served cold by placing the saucepot in a large bowl filled with ice. Stir the sauce constantly until it has cooled to the desired temperature.