Low-Carb Thickeners

How To Thicken a Low-Carb Sauce

saffron cream sauce
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When making a white sauce or other sauce, stew, or soup requiring a thickener, many cooks who are trying to limit carbohydrate are unsure of the best approach, since traditional thickeners are starches such as flour. Sometimes if you are only using a little starch for a recipe that makes several servings, it may not matter. However, if you are cooking a thick sauce or soup, you might want to consider some lower-carb alternatives.

Here are some of the ins and outs of thickening sauces. Feel free to mix and match according to the effect and carb level you are going for.

Traditional Starch Thickeners

Regular Flour - White flour is the most common thickener used in sauces. In some recipes, you might be fine using it. There are 6 grams of carbohydrate per tablespoon of regular flour. This will thicken one cup of a gravy (which has some thickeners from the meat), or a thin sauce. It takes two tablespoons of flour to thicken a sauce of medium thickness, and three for a thick sauce. Whole wheat flour has 4.5 grams effective carbohydrate plus 1 gram fiber per tablespoon. It takes slightly more to thicken a sauce than white flour. 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 carb.

When you use flour to thicken a sauce, you can't add it directly, as it will create lumps.

The best way to add it is in a roux, where you 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, and some recipes will call for darker roux, however, their thickening power decreases as you cook them, so for low-carb purposes, a white roux is best.

Other ways to add flour to a sauce are a slurry, where you stir or shake up the flour with cold water and then add to the sauce, or a beurre manié, where you mix the flour and butter into a paste and add it bit by bit. You can also add the flour to vegetables or meat as you are browning or sauteing them.

Cornstarch - Cornstarch has 7 grams of carb per tablespoon, but more thickening power. According to the corn starch manufacturers you only need half as much cornstarch as flour, but experts seem to vary on this point. Sauces thickened with cornstarch are less opaque and glossier. Cornstarch is generally added to cold water and then to the sauce (whisk or shake in a small container to combine). You don't have to worry about cooking it first.

Arrowroot - Arrowroot is similar to cornstarch and used the same way, except it makes a totally clear sauce and lends a glossier appearance. Arrowroot stands up to acidic liquids better than cornstarch does.

Making a Low-Carb White Sauce

A traditional white sauce uses the same amount of fat as flour.  The two are cooked together, and then milk is added.  To make a low-carb white sauce (Bechamel sauce), try using half water and half cream instead of milk, (see carb counts), or unsweetened soy or almond milk (check the ingredients carefully to make sure no sweetener is added), with any of the thickeners on this page.

Alternative Thickeners

If you want to avoid starches altogether, there are quite a few alternatives. Which one you choose will depend a lot upon what you're making.

Reduction - Simply simmering the sauce until enough water evaporates that the sauce is thicker works in some cases (but the flavors and seasonings will also become more concentrated).

Vegetable gums - Yum! They may not sound really appetizing, but vegetable gums are just a type of fiber that absorbs water to make a sort of gel. They are often used as thickeners in commercial products. The most common are guar gum and xanthan gum, which can be purchased at most health food stores or online.

To use vegetable gums to thicken sauces, sprinkle them into the sauce while whisking. Often it only takes a small amount, so go slowly. Too much will overthicken and/or give the sauce a "slick" feel.

There are also commercial low-carb products which are usually a mixture of vegetable gums: one example is the​ Carb Counters brand.

Pureed vegetables - This is especially good for creamy soups, but works for other sauces as well. Almost any cooked vegetable can be blended and used to thicken a soup or sauce (think broccoli or pumpkin soup). Tomato paste is a great thickener. Eggplant, zucchini or other squash, cauliflower, or the lower carb root vegetables are all excellent choices when you don't want the vegetable to add too much flavor.

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

Sour cream is already thickened - whisk it into a sauce.

Cream cheese is thicker than sour cream, although it obviously has a distinctive flavor.

Butter - If you add cold butter at the end of cooking a pan sauce, it will have a thickening effect

Egg Yolk - Think of mayonnaise - at its heart, it's nothing more than oil and egg yolk. Or think of hollandaise sauce. An egg yolk can really bring the right kind of sauce together, especially if there is oil or fat in it. Don't add the yolk directly to a hot sauce or it will scramble. To avoid this, "temper" the yolk(s) by adding a small amount of the sauce to them to gradually bring them up to temperature. Then add the tempered eggs to the sauce.

How to Make Homemade Mayonnaise

Nuts and nut butters - Ground nuts were traditionally used to thicken sauces in olden times. Nut butters (peanut, almond, etc) work even better.

Coconut cream - I have not tried this, but you can buy jars or cakes of concentrated coconut cream that I hear are good for thickening some sauces (just don't get the drink mix with a similar name, which has sugar added).

Flax seed meal - Flax seed meal does thicken liquids, but it's so grainy that I haven't found it to work well in many sauces. I like it to thicken shakes, though.

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