Sauce
How to make a roux (and why color matters)
A roux is flour cooked in fat. How to make one without lumps, what white, blond and brown roux are for, and why a darker roux thickens less.
Published
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What
A roux (say ‘roo’) is flour cooked in fat until it forms a paste, which then thickens a liquid. University of Wyoming Extension describes a range of cooking stages, from white to deep brown. University of Arkansas Extension calls roux both a seasoning and a thickener: the longer it cooks, the darker and more flavorful it gets.
How much fat to flour? Arkansas Extension adds as much flour as fat. Serious Eats describes roughly equal volumes. Start near equal and adjust by feel. Arkansas Extension says to add a little more fat if the paste is too thick to whisk, and a little more flour if it is too thin.
Color is the main choice you make with a roux. A darker roux brings more toasted flavor and less thickening.
| Color | What it looks like | Where the sources use it | Thickening |
|---|---|---|---|
| White | Cooked just long enough to lose the raw-flour taste, with no browning (Serious Eats) | Thickening milk for bechamel, a white sauce (Serious Eats) | Strongest |
| Blond | A light tan, just past white (Serious Eats) | — | Between white and medium |
| Medium brown | Coppery brown with a nutty taste and smell; about 15 to 30 minutes (Arkansas Extension) | Creole and Cajun cooking (Arkansas Extension) | Less |
| Dark brown | Looks like dark melted chocolate; usually 30 to 45 minutes (Arkansas Extension) | Traditional gumbo (Arkansas Extension) | Weakest: much of its thickening power is lost (Arkansas Extension) |
Serious Eats cooked four roux from the same flour and oil (white, blond, peanut butter-colored and dark brown), whisked each into the same amount of water, and found that the darker the roux, the thinner the result. Their explanation: long cooking breaks the starch down into shorter pieces that thicken less. A dark roux needs more of it to thicken the same pot. Cook times depend on the amount of roux and the heat (Arkansas Extension).
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Why (ELI5)
ELI5
Flour contains starch plus gluten, a protein. Illinois Extension explains that starch mixed with a liquid and heated gelatinizes, which thickens the sauce. Cooking the flour in fat first does two jobs, according to Serious Eats: it cooks out the raw-flour flavor, and it coats each starch granule in fat so the granules spread out in the liquid instead of sticking together. That is why dry flour dumped into hot liquid turns lumpy and a roux does not.
As the flour cooks longer it toasts, and Serious Eats credits that browning and flavor to the Maillard reaction, the same browning that gives seared meat its flavor. See the Maillard reaction ELI5.
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How
How to make a roux, step by step
- 01Heat the fat over medium heat. Butter, oil or animal fat all work (Arkansas Extension). For a dark roux, Serious Eats notes that many Creole and Cajun cooks use oil, because the milk solids in butter can scorch.
- 02Whisk in about the same amount of all-purpose flour until smooth. Arkansas Extension warns against self-rising flour: its leavening can make the roux foam and boil out of the pan.
- 03Cook, whisking constantly, until it reaches the color you want. For a light gravy roux, Wyoming Extension whisks until the mix looks like wet sand, then keeps stirring for about 1 to 2 minutes. To avoid lumps, it sprinkles the flour in through a fine-mesh sieve. Brown roux takes much longer (see the table above).
- 04Add hot liquid gradually. Wyoming Extension adds about half a cup first, whisks it smooth, then whisks in the rest slowly. Whisking constantly keeps lumps from forming.
- 05Bring it to a simmer and let it thicken. Check the thickness with a spoon, as in how to thicken a sauce.
Use a heavy pan over medium heat. Arkansas Extension suggests a heavy Dutch oven or cast-iron skillet. For managing the burner, see heat control.
How much roux for how much liquid
Amounts depend on how thick you want it and how dark the roux is: a darker roux needs more. For per-cup amounts, see how to thicken a sauce and how to make gravy. For a quick sauce in the skillet you just used, see how to make a pan sauce.
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