Cooks may find that the corn flour they purchased to use in a recipe calling for cornstarch does not produce the same effects as the starch. Cornstarch and corn flour are both produced by drying and grinding corn, but the handling of each can differ. Additionally, the naming of each in different regions can add to the confusion.
In the U.S., cornstarch and corn flour are not synonymous. Cornstarch is a finely ground, silky, white powder made from the endosperm, or inner tissue, of dried corn kernels. The powder is used as a thickening agent in certain foods, providing twice the thickening power of corn flour. When heated, cornstarch's molecular chains unravel, causing them to link with other starch chains and gel.
Corn flour refers to a ground powder in the U.S. Unlike cornstarch, which is ground from the endosperm, the entire dried corn kernel is ground to make corn flour. Corn flour's consistency lies somewhere between cornmeal and cornstarch. One example of corn flour is masa harina, which is used to make tortillas and the outer, breaded layer of tamales. Corn flour also can be used in breaded coatings, as with fried chicken or fish.
In the U.K.
One reason for the confusion between cornstarch and corn flour is that United Kingdom and Commonwealth recipes use the term corn flour for cornstarch. Americans cooking from a recipe in a British cookbook, for example, have to assume a reference to corn flour is a call for cornstarch.
Uses for cornstarch
Cornstarch is used as a thickener for gravies, fruit dessert fillings and sauces. Some biscuits and breads also call for cornstarch. Since cornstarch is pure starch, it doesn't contain gluten, as wheat flours do, and can help lower the gluten level of baked goods. This lack of gluten is beneficial as a tenderizer. Some baked goods, such as shortbread, can be overworked, overdeveloping the gluten in wheat flour, and become tough. Cornstarch helps offset that toughness.