Cornstarch is a gluten-free flour used to thicken sauces, soups, or used as a batter for frying foods. With twice the thickening power of flour, use a ratio of 1:1 cornstarch to liquid. To prevent clumping, we suggest you make a slurry first to ensure smooth results. California Warning: Risk of cancer and reproductive harm from exposure to lead. See www.P65Warnings.ca.gov/food.