What is the main purpose of using a roux in cooking?

The main purpose of using a roux in cooking is to thicken sauces. A roux is a mixture of equal parts flour and fat, typically butter, that is cooked together. This process helps to create a base that, when combined with liquids, forms a sauce or soup that achieves the desired consistency. The starches in the flour gelatinize as they heat, which effectively thickens the liquid when it is incorporated.

While a roux can add some flavor and a subtle nuttiness depending on how long it’s cooked, its primary function is to serve as a thickening agent. Roux is fundamental in classic recipes, such as béchamel and gumbo, where a smooth, velvety texture is essential. The choice to categorize it as a thickening agent highlights its essential role in developing the texture of a dish rather than merely enhancing flavor or serving other culinary functions.