Starch is a carbohydrate composed of multiple glucose (sugar) units fused together by glycosidic bonds. A staple in the human diet, it is often extracted from rice, corn, potatoes and cassavas to produce white paste or powder. The most common use for starch is in food processing, where it is incorporated as a binder and thickener. Starch also has non-food-related purposes; it is a key ingredient in glue, laundry supplies and paper making.
One of the smaller granules of starch, rice starch is often used for the laundering of clothes and paper making. The starch is extracted from rice grains by steeping them in a mixture of water and caustic soda, also known as lye. The lye helps to break down the rice into a starchy mass, which is put through a centrifuge to separate the rice starch from its other components. Water is added at the end to hydrate the rice starch, creating a paste that is the basis for clothing starch and the starch used for paper making.
Corn starch is often used as a thickening agent for gravies, syrups and custards. Extracting the starch from the corn requires that the kernels be soaked in water for up to 48 hours. Soaking allows the corn to ferment, which helps to separate the grain from the endosperm, making it easier to release the starch. The starch is drained and then put through a centrifuge to remove the gluten. Afterward, it is dried, producing a very fine powder. Corn starch powder is also a common ingredient in baby powder.
The starch extracted from potatoes creates a powder that is neutral in taste and has high binding abilities. To extract the starch, the potatoes are crushed to release the white filmy starch, which is drained from the vegetable and dehydrated to produce a white powder. Potatoes produce large oval-shaped granules that have a neutral taste and do not alter the color of the food into which it is incorporated. These qualities make potato starch the perfect candidate for processed foods, from pastries to kosher hot dogs.
Cassava, also known as yucca, is a root vegetable native to subtropical areas. The cassavas are crushed or milled into a pulp, which helps to release the starch. Similar to potatoes, the cassava pulp is soaked in water before the starchy liquid is drained and dehydrated to produce granules. Cassava starch granules are also bland in taste and are often used as a thickener in processed foods. The powder is also used in glues and as a binding ingredient in pharmaceuticals.