Cornstarch, sometimes referred to as cornflour, is a carbohydrate extracted from the endosperm of corn. This white powdery substance is used for many culinary, household, and industrial purposes. It was developed in 1844 in New Jersey and is produced today in corn-growing countries like the United States, China, Brazil, and India. In the kitchen, cornstarch is most often used as a thickening agent for marinades, sauces, gravies, glazes, soups, casseroles, pies, and other desserts. It's found in cuisines throughout the world, with North America and Asia leading both production and use.
- Primary Use: Thickener
- Other Names: Cornflour (U.K.), corn starch
- Storage: Airtight container in a cool, dry place
- Shelf Life: Indefinite
Cornstarch vs. Flour
Flour is typically made from wheat. Cornstarch is made from corn and only contains carbohydrates (no protein), so it is a gluten-free product. For this reason, cornstarch is an excellent gluten-free alternative to flour thickeners in gravy and sauce recipes. It's often preferred over flour as a thickener because the resulting gel is transparent, rather than opaque. It is also relatively flavorless in comparison and provides roughly two times the thickening power.
Either flour or cornstarch can be used for fried food batters. The two may be used together in baked goods like cake because the cornstarch will soften the flour to create the perfect texture and crumb. You would not simply use the same amount of cornstarch as flour in recipes that rely on a large amount of flour, though. Instead, in gluten-free recipes, cornstarch is often paired with non-wheat flours.
In the U.K., cornstarch is often called cornflour (most often one word). This is different than corn flour (often two words) as used in the Southern U.S., which refers to finely ground cornmeal.
Cornstarch is prized for its thickening properties. It is comprised of long chains of starch molecules, which when heated in the presence of moisture, will unravel and swell. This swelling action, or gelatinization, is what causes the thickening to occur.
You can also use cornstarch to coat the fruit in pies, tarts, and other desserts before baking. The thin layer of cornstarch mixes with the fruit juices and then thickens as it bakes. This prevents pies and other desserts from having a watery or runny texture.
Cornstarch is useful as an anti-caking agent. Shredded cheese is often coated with a thin dusting of cornstarch to prevent it from clumping in the package. The cornstarch will also help absorb moisture from condensation and prevent a slimy texture from developing. A small amount of cornstarch is often mixed with powdered sugar for the same purpose.
How to Cook With Cornstarch
Cornstarch should not be added straight into a hot liquid as this can cause it to form lumps. Instead, mix cornstarch into a room temperature or slightly cool liquid to form a slurry, and then stir it into the hot liquid. This will allow for even distribution of the cornstarch molecules before they have a chance to swell and gelatinize.
Mixtures containing cornstarch should be brought to a full boil before cooling. The mixture may appear thickened after slight heating, but if the starch molecules are not fully gelatinized, they will release the moisture once cooled and become thin.
Sauces and other mixtures thickened with cornstarch should not be frozen. Freezing will break down the gelatinized starch matrix, and the mixture will become thin after thawing.
You can use a variety of things as a cornstarch substitute. Flour is a good all-purpose substitute for sauces, you will just want to use twice the amount. Arrowroot is an equal substitute, as is potato starch, though with this one you will need to whisk it more to prevent clumping. Tapioca starch (or flour) is an excellent substitute; use 2 tablespoons for 1 tablespoon of cornstarch. Rice flour is another option and you'll need to use 3 tablespoons for every tablespoon of cornstarch.
Gravy, sauce, chowder, custard, and pudding all benefit from cornstarch's thickening properties. It's also common in Asian stir-fries and meat marinades. Pies, fruit desserts, and cakes can put cornstarch to good use as well.
Where to Buy Cornstarch
Any grocery store or supermarket should stock at least one canister of cornstarch in the baking aisle. The average 16-ounce container generally costs just a couple of dollars. Bulk quantities are available, but a tablespoon or two is the most you'll use for recipes, so that's unnecessary for most home cooks. You can find cornstarch made from non-GMO corn as well and it will be clearly marked.
If you're following a gluten-free diet, read the packaging carefully. Make sure your cornstarch has not been produced in a facility that also processes wheat products in order to prevent the possibility of cross-contamination.
Cornstarch is designed to absorb moisture, so it is critical to keep it in an air-tight container where it will not be exposed to ambient humidity. Keep it away from extreme heat. A cool, dry place, such as a pantry, is best. When stored properly, cornstarch will last indefinitely.