Carbs in Cornstarch for Thickening Soups and Sauces

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Cornstarch in a pile with a wooden spoon
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Thickening a sauce, stew, gravy, or soup can be tricky when you are limiting carbohydrates. Knowing the number of carbs in cornstarch compared to the alternatives will help you choose the thickener best suited to your diet, as well as guide how much of an agent you'll need to use.

Traditional thickening agents such as flour or cornstarch may work if you only need a small amount, but a lower-carb starch alternative may be preferable when a recipe calls for more thickener or contains other carb-heavy ingredients.

No matter what your carb intake goals are, there is a thickening agent that will work for any dish you're preparing.

White or Whole Wheat Flour

White flour is the most common thickener used in sauces. There are 6 grams of carbohydrates per tablespoon of white flour, which will thicken one cup of a gravy (which has some thickeners from the meat) or a thin sauce.

Keep in mind that you'll need to add more flour, and therefore carbs, for thicker recipes: You'll need two tablespoons of flour to thicken a sauce to medium thickness, and three for a thick sauce.

A tablespoon of whole wheat flour has 4.5 grams of carbohydrates. Be aware that it usually takes a little more wheat flour than white flour to thicken a sauce, and it may slightly alter the flavor of the dish you add it to.

Gluten-free flours such as rice flour work the same way as wheat flour when it comes to thickening sauces, and have approximately the same amount of carbs.

When you use flour to thicken a sauce, you cannot add it directly as it will create lumps. The best way to add it is in a roux—heat it with a fat, like oil or butter, and cook it for a minute or two (stirring constantly) to get rid of the raw flour taste. Then, whisk in the liquid.

A roux will slowly get darker the longer you cook it. Some recipes will call for a darker roux, but the thickening power of flour decreases as the roux cooks, so for low-carb purposes, a white roux is best.

Cornstarch

Cornstarch has 7 grams of carbs per tablespoon, but more thickening power than flour, so you can often use less than what the recipe calls for. According to cornstarch manufacturers, you only need half as much cornstarch as flour to achieve the same thickening results, though some cooks may question this claim.

If your recipe only calls for one tablespoon of a thickener, cornstarch can be a low-carb option.

Sauces thickened with cornstarch are less opaque and will be glossier than ones with flour. Cornstarch is generally added to cold water and then to the sauce (whisk or shake in a small container to combine), and you do not have to worry about cooking it first.

Arrowroot Flour

If you are looking for an easy way to thicken a sauce without changing the taste of your food, turn to arrowroot flour instead of cornstarch, which can leave foods tasting chalky if undercooked.

Arrowroot flour is a fine white powder made from dried tubers. It is similar to cornstarch in the number of carbs it has and is used the same way, except it has a glossier appearance. It also stands up to acidic liquids better than cornstarch does.

When used in cooking, arrowroot flour has twice the thickening power of wheat flour, but unlike wheat flour, it does not alter the flavor of the food.

Use arrowroot flour to thicken sauces that should remain clear. Note that while it freezes well, it does not reheat successfully and cannot be used at high temperatures or in recipes that involve long cook times.

Alternatives to Starch

If you want to avoid using starches as thickening agents altogether, there are a few alternatives, like vegetables, dairy products, eggs, nuts, and seeds. The choice of alternative you can choose depends on what you need to cook and any other dietary restrictions.

Vegetable Gums

With names like guar gum and xanthan gum, vegetable gums may not sound appetizing, but don't let that scare you. Both thickeners are made from vegetable fiber that absorbs water to make a gel-like, viscous consistency.

Most brands of guar and xanthan gum have between 6 to 9 grams of carb per tablespoon.

Depending on what your recipe calls for, you may not even require a full serving.

For example, to use vegetable gums to thicken sauces, you only need to sprinkle a small amount into the sauce while whisking. Go slowly, because too much will over-thicken the sauce and leave a slick feel to the food.

Unlike flours, vegetable gums are gluten-free and are often used as thickeners in commercial products. You can buy them in health food stores and online.

Pureed Vegetables

Pureed vegetables are especially good for creamy soups and also work well for sauces. Almost any cooked vegetable can be blended and used to thicken a soup or sauce, but consider how the flavors will work together; for example, pureed broccoli would probably taste good as a thickener for pumpkin soup.

Other pureed veggies you can use include:

Dairy Products

Cream thickens as it reduces, so if you add cream to a sauce and boil it, the sauce will thicken more than it will if reducing without the cream.

Sour cream is an already thickened version of cream and can be easily whisked into a sauce. One tablespoon of sour cream adds just 0.3 grams of carbs to a dish.

Cream cheese, which is thicker than sour cream, can also be used as a thickener, although it imparts a distinctive flavor. One tablespoon of regular cream cheese has 0.6 grams of carbs.

You can also add cold butter at the end of cooking a pan sauce to achieve a thickening effect. While butter won't add any carbs, it does add fat and calories.

Eggs

One large egg has about 0.6 grams of carbs. Egg yolk mixed with fat is an effective thickener; imagine the consistency of mayonnaise or hollandaise, which are made with oil or butter and egg yolk.

As a rule, do not add yolk directly to a hot sauce or it will scramble. To avoid this, temper the yolk by adding a small amount of the sauce to it to gradually bring it up to temperature. Then, add the tempered yolk to the sauce.

Nuts

Ground-up nuts have long been used to thicken sauces, and the traditional technique is effective. Nut butter, like peanut and almond, also work well.

A tablespoon of peanut butter adds about 8 grams of carbs. For fewer carbs, try almond butter, which adds just 3 grams of carbs per tablespoon.

Coconut butter is another option. It won't add any carbs to your dish and you can buy jars or cakes of concentrated coconut cream to use as a thickener.

Be careful not to confuse coconut butter with similarly-named coconut drink mixes, as they have added sugar.

Seeds

Flaxseed meal and chia seeds expand and thicken liquids, but they can be grainy, so they typically don't work for sauces. They work best to thicken drinks, turning juices into shakes.

While chia seeds add about 6 grams of carbs per tablespoon, one whole cup of flaxseed meal only adds around 1.5 grams.

A Word From Verywell

With a few new kitchen tricks, you will be able to enjoy sauces, soups, and gravy that are lower in carbohydrates but retain the thick consistency you're looking for. You may even discover you enjoy these variations more than the traditional methods!

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