What is the purpose of a roux?

The purpose of a roux is to thicken liquids such as soups, sauces, and gravies. A roux is a mixture of equal parts flour and fat (commonly butter) that is cooked together until it forms a paste. The cooking process helps to eliminate the raw flavor of the flour, and as it is combined with liquid, it thickens that liquid, giving it a smooth and creamy texture. This technique is foundational in classical cooking and is widely used in French cuisine, as well as in many other culinary traditions.

When a roux is cooked longer, it develops a deeper color and richer flavor, which can enhance the overall taste of the dish. The thickening process occurs because the starches in the flour swell and absorb the liquid when heated, creating a stable and cohesive mixture. This versatility makes roux an essential component in various recipes, such as gumbo, béchamel sauce, and many gravies.

The other options describe different culinary techniques or preservation methods that do not relate to the primary role of roux in cooking.