Cornstarch, Arrowroot, & Starches: What's the Difference?



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What's The Difference Between These Cooking Thickeners?

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Summer’s extreme heat may take the starch right out of you. But it’s the time of year to reach for one of the common cooking starches—cornstarch, arrowroot, tapioca, or potato starch—to thicken your berry pies, crisps and cobblers, garden-vegetable stir-fries, and other foods. Why might you choose to use one kind of starch over the other?

What is a Starch?

Just a few teaspoons of any cooking starch will thicken loose puddings and sauces. 

All starches work when the starch molecules absorb and trap liquid, then swell as they’re heated. The amount of starch used determines the degree of thickening. 

To prevent any of these powdery starches from lumping and clumping in a sauce, stir the starch first into a little cool liquid until it’s smooth, then add the slurry slowly to your sauce or filling and whisk it in as it heats. For a pie filling, pudding, or other recipe calling for sugar, mix the powdered starch with the sugar before adding it to distribute the starch evenly throughout the mixture.

We tend to think of common kitchen starches as roughly interchangeable, but their different molecular structures give them different cooking properties. That’s why it’s a good idea to keep small amounts of each on hand.

You can divide cooking starches into two main groups:

  1. Grain starches (wheat, corn, oats)
  2. Root starches (arrowroot, potato, tapioca)

We’ll focus on the four types of cooking thickeners: cornstarch, arrowroot, potato starch, and tapioca. All are gluten-free. 


Cheap and available in most American supermarkets, cornstarch is made from corn (maize) grain. Specifically, it’s obtained by removing and refining the endosperm from corn kernels. 

Besides showing up in the familiar box in the baking aisle, you’ll find it (sometimes in “modified” form) as an ingredient in commercial baked goods, frozen foods, ice cream, salad dressings, low-fat meats, and more. Half of the billions of pounds of cornstarch produced each year goes into the manufacture of corn syrup. It’s also used in paints, pharmaceuticals, adhesives, medical products, building materials, cosmetics, and textile and paper manufacturing, among tens of thousands of other industrial uses.

As a thickener, cornstarch is the go-to for many recipes.

  • It holds up to simmering and thickens at a higher temperature than the root starches. 
  • Cornstarch is usually used to thicken at the beginning of cooking—as you would do with a macaroni & cheese or a traditional beef stew.
  • It’s especially good at thickening dairy products—it doesn’t turn slimy in cream sauce or cheese sauce.
  • It’s clear when hot but opaque, matte-like, and cloudy when cold. This is problematic with berry pies because the sauce needs to be clear, whether hot or cold.
  • However, cornstarch would be great for a stir-fry because it’s clear when hot. 
  • Don’t use cornstarch in recipes that contain acidic ingredients (lemon juice, vinegar, citric acid, wine), as the acid may break down the starch molecules, leaving a thin, watery sauce.
  • Don’t use cornstarch in dishes you plan to freeze and reheat because the food turns spongy (Use one of the root starches below if you plan to freeze your food).
  • Cornstarch can lend a “starchy” cereal-like taste. Keep stirring and bring the sauce to a full boil, then lower the heat and allow it to simmer for a couple of minutes to allow the cornstarch to lose its starchy flavor. If you need to reheat a sauce made with cornstarch, do it slowly over low heat.

See 15 surprising uses for cornstarch around the house!

Root Starches

Arrowroot, made from the rhizomes (tubers) of tropical plants, has almost no flavor of its own and thickens at a much lower temperature than cornstarch.

  • Root starches do not hold up at high temperatures, so they are best used to thicken sauces toward the very end of cooking.
  • Arrowroot starches work well with pie fillings and sauces, adding a crystal clear, shimmering sheen and a silkier mouth feel.
  • However, arrowroot does not thicken like cornstarch, so it should not be used in a pie that needs to be thick enough to slice (e.g., coconut cream pie).
  • Arrowroot freezes and thaws without change, unlike cornstarch.
  • Arrowroot has a more neutral taste; it doesn’t taste “starchy” like grain starches (cornstarch, flour).
  • Don’t use it for dairy-based sauces—it turns them slimy.
  • Choose arrowroot if you’re thickening an acidic liquid. 
A root starch like tapioca or arrowroot would provide a clear, thick sauce for your berry pies.

Potato starch has many of the same benefits as arrowroot. As its name implies, potato starch is refined from potatoes, often those culled from sorting and processing operations, but sometimes from varieties bred especially for their starch content.

Potato starch won’t impart a starchy flavor to your finished product. It’s also a very refined starch with minimal protein or fat, a neutral taste, and a clear color. Like arrowroot, potato starch products have a very silky and glossy appearance.

Add it toward the end of cooking a sauce as well, since it doesn’t stand up well to long stovetop heating. It’s a great last-minute addition if your sauce is too thin.

Potato starch is used in soups, gravy, cakes, pastries, and pasta. It keeps very well for long periods of time. Store in an airtight container in a dark, dry, and cool place (no refrigeration is required).

Tapioca is refined from the cassava root (Manihot esculenta), which is cultivated globally in subtropical regions. Although it’s usually sold as “tapioca pearls,” turning it into a fine powder is easy in a spice grinder (or a second bowl of a coffee grinder).

Tapioca thickens quickly, so it’s also a good choice for adjusting a too-thin sauce toward the very end of cooking; however, like other root starches, it doesn’t stand up well to long stovetop cooking.

Because it absorbs and thickens quickly, tapioca is a favorite for juicy pies and cobblers. It also stands up well to freezing and thawing.

Resistant Starches

You may have heard of another type of starch called “resistant starch.” As its name implies, resistant starch resists digestion in the stomach and small intestine. Resistant starch moves into the colon, where it feeds beneficial gut bacteria, conferring health benefits such as lower blood sugar levels, reduced appetite, and improved colonic function. Resistant starch is a complicated topic, worthy of a post or two itself.

Maybe later, though. Berries are ripe. Time to make a cherry pie!

About The Author

Margaret Boyles

Margaret Boyles is a longtime contributor to The Old Farmer’s Almanac. She wrote for UNH Cooperative Extension, managed NH Outside, and contributes to various media covering environmental and human health issues. Read More from Margaret Boyles

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