Pure Gluten Free Potato Starch Flour 500g Potato starch is a fine, white powder made from potatoes. The potatoes are crushed & then the starch grains washed out & dried into a powder. Thanks to its low protein & low fat contents potato starch is virtually flavourless, has a good binding strength & high swelling power. This makes it a good thickener for soups & it helps to keep cakes moist & give them a soft texture when used in baking.