Cornstarch is the starch of the corn (maize) grain. It is a fine, white powder made from the endosperm of the corn kernel. The starch is extracted from the kernels by a process of wet milling or dry milling. Cornstarch is used as a thickening agent in many food and industrial applications.
Cornstarch is composed of about 70% amylose and 30% amylopectin by weight. Amylose is a linear polymer of glucose molecules, while amylopectin is a highly branched polymer. The difference in structure affects the properties of cornstarch, with amylose being more soluble and having greater viscosity than amylopectin.
The majority of commercial cornstarch is produced from field maize, which has a higher percentage of amylose (about 20-25%) than waxy maize (which has only about 5% amylose). Waxy maize starch has fewer branches in its structure and so behaves differently when used as a thickener; it produces clear solutions rather than opaque ones, for example. For this reason, waxy maize starch is often used as an ingredient in “instant” or “quick” gravies and sauces.
Cornstarch can be used to thicken both acidic and basic (alkaline) liquids; however, it works best with neutral-pH foods such as milk or water. When added to cold liquid, cornstarch will first swell up and form clumps before dissolving completely; when added to hot liquid, it will dissolve more easily but may lose some of its thickening power if cooked for too long at high temperatures. For this reason, it’s generally recommended that you add cornstarch towards the end of cooking time if possible.
When mixed with water or another liquid,cornstarch forms what are called “linear chains” of glucose molecules known as dextrins . These dextrins are very efficient thickeners because they can interact with one another to form a three-dimensional network that traps water or other liquid within its structure . This trapping action gives cornstarch its characteristic ability to thicken liquids without changing their flavor . In addition , because these linear chains are relatively strong , they resist breakdown by enzymes , making cornstarch an effective thickener for both cooked and raw foods .
Cornstarch can also be used as a coating for fried foods . When combined with flour , it forms a crust that helps keep oil from penetrating the food being fried . This prevents sogginess and ensures that fried foods have a crisp texture .
It should be noted that although pure corn oil does not contain any cholesterol , almost all commercially available frying oils do contain small amounts of cholesterol due to impurities present in them . Therefore , using corn oil for frying may not be completely cholesterol – free unless special care is taken to remove all traces of impurities from the oil before use .