Cornstarch is a gluten-free alternative to flour as a thickener in marinades, gravies, and sauces. Chinese cooks use corn starch to 'velvet' meat or seafood to keep protein tender and juicy and to make delicious stir-fries. To velvet, simply mix your sliced protein in water and soy sauce and set aside for 10 minutes. Add corn starch and vegetable oil and mix again until everything is well-coated. Set aside for 20 minutes. You are now ready to have a perfect stir-fry!