4.2: Roux and Thickening

Roux is a base sauce in international cuisines, originally French, composed of varying ratios of flour and fat (usually butter), useful for making sauces, and for thickening soups or gravies. The benefits of using a roux include the following: It does not have to cook very long to remove a floury taste, clumps of flour are removed, and it creates unique flavors. It can be cooked to different degrees:

• White roux
• Blonde roux
• Brown roux
• Dark Brown roux

Uses

Depending upon the intended use, and a darker roux (one that has been cooked longer) will also be thicker and have more flavor, but will have less thickening power.

The fat is most often butter in French cuisine, but may be lard or vegetable oil in other cuisines. The roux is used in three of the five mother sauces of classical French cooking: béchamel sauce, velouté sauce, and espagnole sauce.

In Cajun cuisine, roux is made with bacon fat or oil instead of butter and cooked to a medium or dark brown color, which lends much richness of flavor, but makes it thinner.

Methods

1. A basic roux may be composed of equal parts flour and butter by weight.
2. The fat is heated in a pot or pan, melting it if necessary.
3. Then the flour is added.
4. The mixture is heated and stirred until the flour is incorporated.
5. It is then cooked until at least the point where a raw flour taste is no longer apparent and the desired color is achieved.

The final color can range from nearly white to nearly black, depending on the length of time it is heated and its intended use. The end-result is a thickening and flavoring agent.

Roux is most often made with butter as the fat base, but it may be made with any edible fat. For meat gravies, fat rendered from meat is often used. In regional American cuisine, bacon is sometimes rendered to produce fat to use in the roux. If clarified butter is not available, vegetable oil is often used when producing dark roux, since it does not burn at high temperatures, as whole butter would.

Alternatives

Cooks can substitute for roux by adding a mixture of cold water and wheat flour to a dish that needs thickening, since the heat of boiling water will release the starch from the flour; however, this temperature is not high enough to eliminate the floury taste. A mixture of water and flour used in this way is colloquially known as “cowboy roux”, and in modern cuisine, it is called a white wash. It is used infrequently in restaurant cooking, since it imparts a flavor to the finished dish that a traditional haute cuisine chef would consider unacceptable. Corn flour (known as cornstarch in the United States) can be used instead of wheat flour. Since less is needed to thicken, it imparts less of the raw flour taste, and it also makes the final sauce shinier.

As an alternative to roux, which is high in fat and very energy-dense, some Creole chefs have experimented with toasting the flour without oil in a hot pan to use as an addition to gumbo. Cornstarch mixed with water (slurry), arrowroot, and other agents can be used in place of roux as well. These items do not contribute to the flavor of a dish, and are used solely for thickening liquids. More recently, many chefs have turned to a group of naturally occurring chemicals known as hydrocolloids. In addition to being flavorless and possessing the ability to act as a thickening agent. The resulting texture is thought by some to be superior, and only a small amount is required for the desired effect.

Notes, Tips and Variations

• Depending upon how you plan to use your roux, you may need to add the sauce's other ingredients before the roux is fully cooked.
• One way to use a roux is to add liquid to it, stirring it in as you go. Do not go the other way, adding the roux to the liquid, as you will get lumps. Once enough liquid has been added to the roux (you will know), you can safely add it back into another liquid.
• A good roux will have a slight shine to it, and neither the texture nor the taste of the flour will be apparent.
• When making a dark roux, switching from butter to an oil with a high smoke point (such as soybean oil or Canola oil) will allow for a higher cooking temperature, decreasing cooking time. Keep in mind that different fats will give the roux a somewhat different taste.

Thickening Agents:

There are many ways to thicken a soup, including flour and starches. Use the links bellow to learn more about theses agents and how they are best used:

• https://www.shiveshskitchen.com/2015/08/types-of-thickening-agents.html
• http://www.shiveshskitchen.com/2016/08/roux.html

Gelatinization:

Starches tendency to gel makes it a useful culinary tool in the creation of soups and sauces. Soups and sauces can either be thickened through the use of a roux (melted fat and flour) or by blending up starchy vegetables that have been simmered. The science behind this property is explained well here:

https://biologyreader.com/starch-gelatinization.html

Retrogradation:

Many starch containing foods are subject to the effects of retrogradation. Retrogradation is responsibile for mushy leftover pastas and even for causing bread to go stale. The following resource explains the topic very well: 

https://biologyreader.com/starch-gelatinization.html

Dextrinization:

Starches, when heated can take on a sweeter flavor than their non-heated counterparts. Consider the taste of bread and toast. Toast is often perceived to be sweeter and this is due to dextrinization. The flavor is not the only thing that changes however, and starches that have undergone dextrinization tend to be unable to act as a thickening agent. Simmering starches does not have this affect but starches cooked by dry-heat methods are subject to this change.

References

Auguste Escoffier (1907), Le Guide Culinaire "Roux Definition in the Cambridge English Dictionary". Dictionary.cambridge.org. Retrieved 2017-02-18.
Alton Brown (1999-08-25). "Gravy Confidential". Good Eats. Season 1. Episode 108. Food Network.