Definition of 'optimum'. optimum (ÉptÉªmÉm ) or optimal. The optimum or optimal level or state of something is the best level or state that it could achieve. Aim to do some physical activity three times a week for optimum health. ...regions in which optimal conditions for farming can be created.
Use Tapioca Flour. Also know as tapioca starch, it's a great substitute. You'll want to use 2 tablespoons for every 1 tablespoon of cornstarch. Use Rice Flour. Rice flour thickens up like regular flour so use the same proportion: 3 tablespoons for every 1 tablespoon of cornstarch.
Check out the figures below. You will see that the starch is just a big list of zeroes when it comes to vitamins and minerals. Notice that corn flour has 16 times the amount of protein, infinitely more of most of the vitamins (since corn starch has ZERO) and many times the amount of the minerals.