Improvements in Flavor, Color, and Dispersability

Appears in
On Food and Cooking

By Harold McGee

Published 2004

  • About
In addition to coating the flour particles with fat and making them easier to disperse in a hot liquid, roux making has three other useful effects on the flour. First, it cooks out the raw cereal flavor and develops a rounded, toasty flavor that becomes more pronounced and intense as the color darkens. Second, the color itself—the product of the same browning reactions between carbohydrates and proteins that produce the toasty flavor—can lend some depth to the color of the sauce.

Finally, the heat causes some of the starch chains to split, and then to form new bonds with each other. This generally means that long chains and branches are broken down into smaller pieces that then form short branches on other molecules. The short, branched molecules are less efficient at thickening liquids than the long chains, but they’re also slower to bond to each other and form a continuous network as the liquid cools. The sauce is therefore less prone to congeal on the plate. The darker the roux, the more starch chains are modified in this way, and so the more roux is required to create a given thickness. It takes more of a dark brown roux than a light one to thicken a given amount of liquid. (The industrial version of roux making to make a starch more dispersable and stable to cooling is called dextrinization, and involves heating dry starch together with some dilute acid or alkali to 375°F/190°C.)