cornstarch or custard powder

Cornstarch is a fine, white powder derived from the endosperm of corn kernels (Zea mays), extracted through wet milling to isolate the starch granules. It is nearly pure carbohydrate with minimal protein, fat, or fiber. Custard powder, by contrast, is a British invention consisting primarily of cornstarch blended with flavorings (typically vanilla, turmeric for color, and annatto), along with small amounts of milk solids and other ingredients. The key distinction is that cornstarch is a pure ingredient used as a thickening agent, while custard powder is a ready-mixed dessert ingredient designed specifically for making custard sauce. Both are white to pale yellow in color with a smooth, talc-like texture that readily disperses in liquid.

Cornstarch functions as a primary thickening agent in sauces, gravies, soups, and desserts, where its starch granules gelatinize when heated with liquid to create a glossy, smooth texture. It is also used in baking to reduce gluten development in cakes and pastries, and as a coating for fried foods to create crispness. Custard powder is used specifically to prepare custard sauce by whisking with milk and sweetener; it is less versatile than cornstarch but provides consistent flavor and texture. Both are essential in Asian cuisines, where cornstarch is a standard thickening agent in stir-fries, and in French and British cuisines for desserts and sauces.