Tapioca comes from the cassava root. Tapioca starch is a thickening agent often used in pie fillings, puddings, soups and sauces. It helps bind the ingredient together so the final product isn't syrupy or watery.Tapioca also provides a sheen to the cooked food, which gives cherry pie filling or a chocolate pudding its glossy appearance.apioca starch is a thickening agent often used in pie fillings, puddings, soups and sauces. It helps bind the ingredient together so the final product isn't syrupy or watery. Tapioca also provides a sheen to the cooked food, which gives cherry pie filling or a chocolate pudding its glossy appearance.