Cornstarch vs. Flour vs. Arrowroot—When Should You Use Which Thickener?

Confused about the difference between the thickeners? We make it easy to know when to choose cornstarch vs. flour and more.

Organic wheat flour in wooden spoonShutterstock / Sebastian Studio

Starches are a beautiful thing—they thicken sauces, provide body to our best pie fillings and transform soups and stews from loose and watery affairs to thick and creamy meals. The only problem? There are a few different options when it comes to thickeners, and while they all thicken liquids, they also vary in their final look and feel. While you can substitute one for the other in many recipes, it’s important to know why you choose one thickener over the other. Let’s dive in!

Flour

All-purpose flour is a traditional thickener in classic French cuisine. Many soups and sauces begin by making a roux—a cooked combination of flour and fat, cooked lightly to remove the taste of flour or for a long time to make a dark roux for gumbo. Or, you can dredge stew meats in flour before browning them, which will thicken the liquid as they cook.

Using flour as a thickener makes sauces cloudy, so it’s perfect for dairy-based sauces (think biscuits and gravy) or other thick stews and gravies. It’s also great for sauces that you want to thicken from the beginning, as flour can be simmered for hours without losing its thickening power.

How to substitute: Flour won’t thicken as well as cornstarch, so use twice as much flour as cornstarch. For best results, use all-purpose flour as opposed to whole-wheat flours because of their higher starch content.

Cornstarch

Cornstarch is a pure starch derived from the endosperm of the corn kernel. It’s a very effective thickener that doesn’t require much cooking time. To avoid creating a clumpy situation, first make a slurry by combining equal parts cold liquid with the cornstarch. Add the slurry to a hot, simmering sauce and cook briefly to activate the thickening power. If it’s cooked for too long it will break down, causing your sauce to thin out.

Cornstarch has a glossy appearance when added to sauces, making it ideal for stir frys (these are our favorites!), sweet sauces and pie fillings. It’s perfect for dishes cooked at high temperatures but acidic ingredients (like lemon, vinegar or tomatoes) can affect the cornstarch’s ability to thicken. It should never be used for dishes you intend to freeze, as it will turn spongy when thawed.

How to substitute: As a general rule of thumb, use half as much cornstarch as flour when making substitutions.

Arrowroot

Arrowroot is a root starch made from a West Indian plant in the Marantaceae family. This starch has become a go-to for gluten-free cooking and it’s also naturally GMO-free. Like cornstarch, you need to make a slurry before using arrowroot, but it doesn’t need to be cooked for nearly as long so it can be added to a simmering sauce at the end of the cooking process.

Arrowroot is an ideal substitute for cornstarch in sauces that have acidic ingredients or that you intend to freeze. It can be used in any pie filling as a substitute for cornstarch. In most situations, arrowroot creates a glossy texture and a silky mouthfeel. However, you should avoid combining arrowroot and dairy because it creates a slimy texture.

How to substitute: Arrowroot can be substituted in equal parts as cornstarch.

Flax seeds

Flax seeds are naturally high in fiber, so they make an excellent thickening agent. They can be used as a flour substitute in roux when ground into a very fine powder. This fine powder will burn very quickly, so you won’t need to cook your roux for more than a minute to achieve maximum thickening power.

Flax can also be combined with water to create a gel, making it great for smoothies and a good substitute for cornstarch. It can be a bit grittier than cornstarch, though, so your sauce may not be as smooth.

How to substitute: To use flax as a flour substitute in a roux, use twice as much flax as flour. To substitute for cornstarch, use half as much flax as cornstarch.

Now that you know your arrowroot from your cornstarch, you can start substituting and creating all sorts of dishes worry-free. Maybe start with one of our favorite potpies.

Get cooking!
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Lindsay D. Mattison
After years of working in professional kitchens, Lindsay traded her knives in for the pen. While she spends most of her time writing these days, she still exercises her culinary muscles on the regular, taking any opportunity to turn local, seasonal ingredients into beautiful meals for her family.