Good Eats Tapioca Starch is obtained from the cassava root and then ground into a powder. It can be used in a variety of baked goods such as pastries, cookies and cakes. It can also be used to thicken soups or sauces. Using tapioca starch is an excellent way to reduce carbohydrates in baking as well as replace gluten in your diet. Tapioca starch is a good source of fibre and iron.