Why do you cook a roux?

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LOVE that question, reader Molly. Indeed, a mixture of melted butter and flour should in theory have plenty of thickening power just the way it is. Why bother to cook it? The primary reason is texture. An uncooked roux yields a thick sauce, but one that has a vaguely mealy mouthfeel. That’s the result of the flour granules in the mix, which are big enough that they register on our tongues. The result is sometimes described as a “starchy” taste. A few minutes’ exposure heat causes the flour particles, which are nothing more than bundles of stick-like starches, to start shedding molecules. As that happens they reduce in size to the point that we can no longer detect them.

The interesting thing is that as you continue to cook a roux, and the flour granules get ever smaller, the thickening power of the roux goes down (for reasons that are explained here). Still those styles of roux have uses, especially in the world of New Orleans creole cooking, which sometimes calls for roux that’s cooked to near blackness. I don’t know what purpose those deep dark things serve, but I’m sure someone somewhere out there will enlighten me. Thanks again for the question, Molly!

6 thoughts on “Why do you cook a roux?”

    1. Hi Sonya!

      Sorry for the very late reply. The answer is that it depends on how long you cook a roux. The longer it cooks the weaker it becomes as a thickener, however it takes longer to weaken in a roux because the medium is fat rather than water. The granules don’t come apart nearly as readily.

      Cheers,

      – Joe

  1. The uber-dark Cajun rue becomes a flavoring agent as much as a thickener (this is why additional thickeners were used , such as okra or fíle in gumbo, for instance). I was taught by my Mammaw that the rue should look like chocolate…preferably dark chocolate, but milk chocolate for some dishes (like brown gravy).

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