Cornstarch

A fine, silky-white powder milled from the starchy heart of corn kernels — the go-to thickener that turns gravies glossy, pie fillings sliceable, and stir-fry sauces velvety. Flavorless and gluten-free, it does its work and disappears.

What it is

Cornstarch (called cornflour in the U.K. and much of the Commonwealth) is the pure starch extracted from the endosperm of corn kernels. It’s a very fine, bright-white, chalk-soft powder that squeaks between your fingers. On its own it has no flavor and no nutritional heft beyond carbohydrate — its value is functional. When heated in liquid, its starch granules swell and burst, a process called gelatinization that thickens the liquid into a smooth, often glossy, gel. It’s naturally gluten-free.

History & origin

Corn (maize) starch was first isolated industrially in the United States in 1842 by Thomas Kingsford, who developed a wet-milling process to separate the starch at a plant in New Jersey. Originally it was made for laundry starch and industrial uses, but by the later 19th century it had become a kitchen staple as a thickener and baking ingredient. Argo and Kingsford’s were early American brands; the process spread as corn wet-milling became a major agricultural industry.

Where it comes from today

It’s a commodity product of the corn wet-milling industry, with the U.S. as the dominant global producer thanks to its vast Midwestern corn crop; China and other large corn-growing nations also produce it in quantity. In the U.S. supermarket, Argo and Clabber Girl are common brands, along with countless store labels. The same corn wet-milling that yields cornstarch also produces corn syrup and other derivatives, so it’s woven into the broader food-industrial supply chain.

How it’s used today

It’s the workhorse thickener for gravies, sauces, and pan juices, prized because it thickens with a clear, glossy finish rather than the cloudy, pasty look of flour. It sets fruit pie fillings and puddings, and Chinese cooking relies on a cornstarch slurry (mixed with cold water) to give stir-fry sauces their signature velvety cling — plus a coating for velveting meat. It keeps powdered sugar free-flowing, crisps fried foods when added to batters, and lightens the crumb in shortbread and some cakes. Always mix it with a little cold liquid first; dumped into hot liquid it clumps.

Make your own

Unlike buttermilk or condensed milk, cornstarch isn’t something you make at home — it’s produced by industrially wet-milling and separating the starch from field corn, which requires steeping, grinding, and centrifuging equipment. For home cooks it’s strictly a buy-it item, though you can swap in other starches when you’re out.

Substitutes (if absolutely necessary)

• Arrowroot powder — use about the same amount (1:1) or slightly less; thickens clear and glossy and holds up better with acidic ingredients, but can turn slimy with dairy.
• Potato starch — roughly 1:1; thickens at a lower temperature and gives a clear finish, good for sauces but don’t boil hard or it thins out.
• Tapioca starch — about 1:1; glossy and freezer-stable, popular for pie fillings.
• All-purpose flour — use about twice as much (2 Tbsp flour per 1 Tbsp cornstarch); thickens but turns sauces cloudy and needs longer cooking to lose the raw-flour taste, and it isn’t gluten-free.

Where to find it

• Local store: the baking aisle near flour and leaveners (Argo, Clabber Girl, store brands); box or bag.
• Online: Amazon, Walmart, and grocery delivery carry it in bulk; look for cornflour if shopping U.K./Commonwealth listings.
• Make your own: not practical at home — it’s industrially wet-milled from corn; keep a box on the shelf or reach for arrowroot or potato starch instead.