Arrowroot powder can be used in place of cornstarch in recipes and has the advantage of being non-GMO (unlike most cornstarch), suitable for people with a corn allergy and extracted from the arrowroot without use of harsh chemicals. I keep a large bag of arrowroot in the freezer. Arrowroot tends to survive freezing better than cornstarch, and work well in acidic liquids (sauces, tomato based soups), but may break down after prolonged cooking/high heat. Available at most grocery stores in the specialty flour/baking area, but most reasonably priced when purchased online.
