Understanding & Applying Thickening Agents

Understanding & Applying Thickening Agents

Thickening agents are used in all types of cooking methods and there are a lot of different kinds of thickening agents you need to be aware of. Choosing the right type of thickening agent can make or break your dish and knowing the differences is useful in your journey in becoming a great cook.

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How Thickening Works

Almost all thickening agents with the exception of reduction use starch as its main thickening agent. There are many sources and combinations for proper starch thickening. Starch becomes gelatinous when it is cooked, producing a thickening property that blends well into many foods. Cooked properly, a gelatinized starch has a very neutral flavor and can be used in moderation with most foods to produce a thick product. Too much gelatinized starch causes food to take on the bland flavor and dilutes much of the flavoring you initially used.

Starches that aren’t thoroughly cooked properly have a very “starchy” flavor that can come through very prominently in your food. This is why it is important to continually taste your food to ensure the starch has been cooked.


A whitewash is a mixture of flour and water that has been combined and then added to a soup/sauce. While it works well, the combination of water and flour produce a very flavorless thickener. A whitewash also has a risk of separation with what it was thickening. A whitewash is best used when you need to thicken a dish that is to be served immediately and can withstand a hit in the flavor department. Overall, a whitewash is a cheap, fast solution for thickening that can be used in a pinch.

Cornstarch Slurry

A Thickened Sauce

A Thickened Brown Sauce

A slurry is the same as a whitewash, except cornstarch is used instead of flour. Never add dry cornstarch to a product that needs thickening, as you will produce lumps that will be next to impossible to use. The proper technique is to add a cold slurry to a hot liquid while stirring constantly. Starches begin to gelatinize around 60C (140F), so don’t be alarmed when you don’t notice immediate thickening action. A common mistake is thinking there isn’t enough slurry and adding more, resulting in an incredibly thick liquid once the starches do gelatinize.

A cornstarch slurry is preferable over a whitewash. The thickening power is more prominent which results in less flavor loss. Cornstarch slurries tend to separate from fats and other liquids if kept for long periods.

The Roux

Ah, now we get to the good stuff. A roux is your best friend for thickening. It is the almighty authority when it comes to thickening products. Always use a roux when you can, and learn how to properly cook with one too! Roux’s are the most finicky of the three major cooking thickening agents so care and attentiveness must be practiced when using a roux.

A roux is comprised of, by weight, 50% flour and 50% fat. It is always suggested you use butter as your fat, but you may also use canola/olive oil/other oils. Just remember, the oil you use will have an adverse impact your flavor. While I won’t get into using a roux here, it will be covered in later articles.

There are 3 stages of a roux.

  • White Roux
  • Blond Roux
  • Brown Roux

A white roux retains its initial color and is only cooked slightly to remove any starchiness from the roux. A blonde roux is caramelized slightly to give it a darker blonde color. A brown roux is cooked until almost burnt; highly caramelized, it also has a nice nutty flavor to it.

Deciding which roux to use depends on what you’re using it for. White roux are used for white sauces and cream soups. Blond roux’s for ivory colored sauces such as a veloute, or when a richer flavor is desired. A brown roux is used in brown sauces and dishes were a dark color is desired.

It is important to remember that cooking a starch without liquid breaks down the starch granules and prevents proper gelatinization from occurring.


Arrowroot Thickening Agent

Arrowroot Thickening Agent

An arrowroot thickener is derived from several tropical plants and is similar in texture, appearance and thickening power to cornstarch and is used in exactly the same way. Arrowroot is more expensive, but produces a clearer finished product and doesn’t break down as quickly as cornstarch would.

Beurre Manié

Beurre Manié is a combination of equal parts flour and softened butter. It is then kneaded together and formed into tiny balls to be dropped into sauces for flavor and thickening power. It is mainly used for quick thickening or thickening at the end of the cooking process. The butter adds shine and flavor as it melts.


Unlike most thickeners, a liaison doesn’t thicken by gelatinization. A liaison is a mixture of egg yolks and heavy cream that adds richness and smoothness with minimal thickening. It is important to ensure you prevent the egg yolks from coagulating when they are added to a hot liquid. Ratio is generally 3 yolks to 200ml (7 fl. oz) cream.


Reduction is the process of removing the water that is present in many ingredients leaving a more pronounced and concentrated flavor. A good example is a red wine reduction, in which wine is reduced with a simmer until by half or au sec. This produces much more concentrated flavor that can be added to sauces to make a delicious and high-end sauce.

Reduction is a useful method of thickening if it make sense to do so. You don’t want to reduce a soup to thicken it, because not only will you be waiting many hours but you’ll lose a lot of your yield. You must decide when it’s appropriate to reduce and when common sense dictates the use of a thickening agent.

Now that you understand the variations of thickening agents, you can confidently make an executive decision the next time you are wondering how to thicken your soup or sauce.

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