What is a Thickening Agent and How to Use it

Using a thickening agent can instantly add a creamy and flavorful texture to any savory or sweet recipe. Here’s a helpful guide to understanding the process of how cooking starches and gums to a gel-like consistency helps to thicken sauces, stews, and fillings. 

Spoon testing lifting a sauce out of the pan to test its thickness

Plants naturally contain starches as an energy source, which can be extracted and used for adding thickness to food. Starch gelatinization is vital for developing thicker sauces as the properties of the ingredients change when heated.

There are many types of thickening agents to choose from. Examples of plants that contain starches for cooking applications include; corn, rice, wheat, barley, spelt, oat, beans, peas, potatoes, tapioca, arrowroot, green bananas, plantains, gums, and pectin. Let’s take a closer look at the science behind ways to create a delicious sauce using a thickening agent, and the most common types to have stocked in the pantry.

What is a Thickening Agent?

Starch-based thickening agents are polysaccharides. Large molecular weight carbohydrates which interact and form gels or thickened dispersions when in contact with water. Amylose and Amylopectin are two major polysaccharides in starches that are responsible for thickening foods.

The structures of these polysaccharides are dependent on the plant source. The ratio of amylose to amylopectin impacts their thickening properties. In general, the thickening power, clarity, and stickiness of a starch paste are most significant with cereal grains, roots and then tubers like wheat, corn, arrowroot, and potatoes.

Compilation of four photos showing the process of using a thickening agent

How A Thickening Agent Works

By applying heat to the starch and water mixture, the viscosity increases due to initial swelling and dissolution.

Two stages of swelling for starches to thicken

  • Gelatinization: Heat irreversibly disrupts the semi-crystalline structure of the uncooked starch granule. This process allows amylose and amylopectin starch granules to solubilize and absorb the water and begin swelling. The temperature needed for gelatinization happens over a range and is starch dependent.
  • Pasting: To achieve maximum thickness, the second stage requires the starch slurry to be heated a few degrees higher than the gelatinization temperature. Agitation is also needed by whisking the sauce to prevent lumping. This process allows the starches to swell independently from each other while the heat reaches the endpoint cooking temperature for the greatest thickness capability of a sauce.

How to Tell When Thickening is Complete

  • Taste & Consistency: Once the sauce has thickened, there should be no raw flour or starchy taste. The product should have a smooth texture and consistency that can coat the back of a spoon. This quick test indicates that it will cling to food when poured or mixed.

Starches Can Breakdown

  • Breakdown: If you hold the starch paste too long or too high at its endpoint temperature, you will notice the viscosity starts to thin, this is called breakdown or shear thinning. This is why some starches like arrowroot or cornstarch should not be reheated.

Substituting Starches

  • A general rule of thumb to substitute starches: 2 tablespoons wheat flour = 1 tablespoon cornstarch = 1 tablespoon tapioca = 4 1/2 teaspoons arrowroot = 1 1/2 tsp. potato starch (Source: Fine Cooking). For a medium consistency sauce, add the amount of desired thickening agent listed, to thicken 1 cup of liquid. Depending on the desired thickness of the product and use (sauce, filling, or baked), these amounts may vary.

Common Types of Thickening Agents:

Here is a list of the most common starch and gum food thickeners.

Wheat Flour

Wheat flour in a wooden spoon

Wheat flour is the thickening agent to make a roux. A roux is a mixture of flour and fat and is a classic way to thicken soups, gravies, and sauces like bechamel or stews like gumbo. Equal parts of wheat flour and typically butter are cooked in a heated vessel, forming different colored pastes depending on use.

Roux made from wheat flour is classified into white, blond and brown varieties. The cooking allows the fat to effectively coat the flour to prevent clumping, once whisked with a liquid. To prevent a lumpy sauce either add cool roux to a hot stock, or cool stock to a hot roux.

Cornstarch

Cornstarch in a wooden spoon

The corn endosperm is ground, washed, dried to a fine powder. This gluten-free thickening agent can be used to give sauces more viscosity and sheen rapidly. Cornstarch is often used in Chinese cooking for stir-fry sauce. It has twice the amount of thickening ability compared to flour, but if heated too long can break down and lose some of its consistency.

The key to incorporating cornstarch into hot or cold liquids is to make a slurry. Typically 2 parts cold water is mixed with 1 part cornstarch until an opaque mixed is formed. For example, 1 tablespoon of cornstarch with 2 tablespoons water to thicken about 2 cups of hot liquid. More slurry can be added for a thickened sauce.

Arrowroot

Arrowroot in a wooden spoon

Arrowroot starch is extracted from the tubers of the tropical plant, Maranata arundinacea. A very fine white powder with similar thickening to cornstarch. Arrowroot powder is neutral in taste and keeps sauces clear.

A slurry should be made before adding, 2 parts room temperature water to 1 part arrowroot powder into a hot liquid. Do not reheat sauces made with arrowroot. An excellent option for grain-free, gluten-free diets, and very popular in Whole30 and Paleo lifestyles.

Tapioca Starch

Tapioca starch in a wooden spoon

Tapioca starch is made from the South American cassava plant or yuca. The fine white powder has a slightly sweet flavor but does not add a noticeable flavor. It’s most often used for fruit pie fillings because it thickens quickly and reheats and freezes well. It does not work as well for sauces like gravies that requires a lot of stirring.

The advantages of using tapioca starch are that it does not discolor when cooking, is gluten-free, and does not separate or clump when refrigerated or frozen. When replacing cornstarch, it requires 2 times as much. For example, use 2 tablespoons per 1 tablespoon of cornstarch.

Xanthan Gum

Xanthan Gum in a wooden spoon

Xanthan Gum is a microbial polysaccharide made from fermenting sugar with a bacteria called Xanthomonas campestris, which creates a gel that is dried and milled into a powder. The neutral-tasting gum acts as a powerful thickening, emulsifying, and stabilizing agent. It’s most often used for thickening and stabilizing gravies, sauces, dressings, and non-dairy milk and ice creams as it adds a creaminess and richness to those recipes.

It’s also a great binder for gluten-free baking because it mimics the gluten function in dough to give elasticity and viscosity. Xanthan Gum is unique in that it can thicken at a range of temperatures very quickly, so it does not need to be heated. Only a very small amount is needed to thicken a mixture, about 0.1% to 1% weight ratio.

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Jessica Gavin

I'm a culinary school graduate, cookbook author, and a mom who loves croissants! My passion is creating recipes and sharing the science behind cooking to help you gain confidence in the kitchen.

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8 Comments Leave a comment or review

  1. Anushi Patel says

    This was so helpful!
    I have a bit of a complicated question-
    I’m trying to make a vegan hollandaise sauce with coconut oil, I’m adding my starch slurry into my soy milk with a little xanthan gum and gently heating it up while whisking, I then stream my coconut oil into the mix and sometimes it emulsifies beautifully, sometimes it doesn’t and I have to wait for it to cool down and blend it.

    I’m not sure if i can just add my oil along with the slurry and gum? will it prevent the starch and gum from hydrating? i will try it out but wanted to know if you have nay experience with something like this.

    Thanks!

    • Jessica Gavin says

      Hi Anushi- I have not made vegan hollandaise yet, however, based on what you describe, I would wait to add the coconut oil. The oil could coat the starch granules and prevent it from hydrating and thickening as you suggested. Just a hypothesis 🙂 let me know how it goes!

  2. Sandra says

    Great website and information, Jessica, thank you! I’ve been working on a sugar-free caramel using coconut palm sugar, cream, and butter. The taste is wonderful and much better than sugar. Although it is perfect in any dessert that uses caramel, it is too soft for a caramel apple and just drips off, leaving only a very light and translucent coating. When I reduce the proportions of cream and butter, it is thicker, but becomes too hard to bite into. I am familiar with cornstarch, arrowroot and xanthan gum, but can you recommend anything else for this particular application?

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