Food History - See also: Gumbo
It was during the middle of the 17th century that roux was introduced as a thickener and binder. In classic French cuisine, roux is a mixture of equal amounts (by weight) of flour and butter, cooked for a short time, both to rid the mixture of a 'raw' flour taste and to obtain the desired color. Cooking the flour with oil or fat also coats the starch and prevents it from forming lumps when added to a liquid. In French cuisine, roux is white, blonde or brown, depending upon the sauce it is to be used in. White roux is cooked just long enough to get rid of the raw taste (used for velouté, béchamel, etc.); blonde roux is cooked to a pale golden color; brown roux is cooked until a light brown color is obtained (used in demi-glace, Espagnole, etc.). Its purpose is to thicken.
Créole roux is basically the same, sometimes using bacon fat or lard in place of butter. Créole brown roux is cooked more than the French brown roux. It is used as a thickener, but because it is cooked longer, does add some flavor. Its color begins where French roux ends.
It is with Cajun cooking that roux really comes into its own. Cajun brown roux is made with lard, vegetable oils, bacon fat and even duck fat. Cajun roux can be from light brown to a very deep, dark, nutty brown. Roux is used in Cajun cuisine for flavor rather than for thickening. When the roux is cooked to a dark brown, it loses much of its thickening power, but gains a rich, deep nutty flavor. This dark brown, nutty roux is the basis for many classic Cajun dishes, adding a unique richness and depth. It is the secret ingredient in Cajun food.