Delicious Liasons — the Science and Art of Thickening
Liason. The very word conjures up images of entanglements, and well it should, since it comes from the French verb lier, to bind.
In cooking, a liason is something added to a liquid, like a sauce or a soup, to bind or thicken it.
There are two basic kinds of liasons–starches, like flour, and proteins, like egg.
Both work essentially the same way. Starches and proteins in their normal form are compact though complex molecules, because the sugar or amino acid molecules from which they are formed are twisted or folded together at the points where they are joined.
But when liquid and heat are added, these compact bundles start to unwind and lengthen. So, rather than compact little bundles of starch or proteins, you now have long strands of them. Since starches and proteins by their nature tend to attach to other starches and proteins, long strands of them results in thickening whatever they’re in, like weaving a net.
Throw some flour into a pan of warm milk and what do you get? Lumps, right? That’s because the starch in the flour is so eager to bind with other starches that as soon as it gets wet it does so quickly and forms a nearly impenetrable outer shell around the as-yet unaffected inner flour, hence the lump.
There are several ways around this. One is to disperse the flour over the surface of your liquid so that there isn’t enough flour in any one place to form a lump. (This method never works well for me.) Another is to make a slurry by adding just enough cold water to form a paste, though you still have to stir it with a fork to break up lumps before they get too solid.
A third way, and the one we’ll concentrate on for the rest of this post, is to make a roux, a mixture of flour and butter. The word roux also comes from French, buerre roux, or brown butter.
Most of us have seen the instructions for making a roux many times.
Melt butter in a pan. Add an equal amount of flour, stir until the flour is cooked to a light brown. Now you can add it to warm milk and no lumps. Why? Because the flour is fully coated with butterfat so its in less of a hurry to bind with other flour and form a lump.
As a general rule of thumb, one tablespoon of roux will thicken one cup of liquid. More on this later on.
A roux (butter and flour) and hot milk are the basic ingredients for a béchamel or white sauce, one of the ‘mother’ sauces in French cooking, as set forth by Marie-Antoine Carême in 1854. (Auguste Escoffier later removed one of Carême’s sauces from the list and added two more to get to the five mother sauces generally taught in culinary schools today.)
A béchamel sauce is very versatile, you can build many other sauces and even complete dishes from it.
Add some cheese and you have a mornay sauce, ready to put on your vegetables or on macaroni to make your own mac-and-cheese. Add some tuna and you have creamed tuna just waiting for the biscuits to get done, add chopped dried beef and spread it on toast and you have creamed chipped beef, known to soldiers as SOS. (But they love it!)
Add some sugar and flavoring to a béchamel sauce and you have pudding.
Add egg yolks, cheese and fold in whipped egg whites, bake it, and you have a soufflé.
Roux, Roux, Roux Debate
You can also make a roux with starches other than wheat flour. A few years ago, when we found out our daughter-in-law was having problems with wheat, I made up several batches of béchamel sauce, one using wheat flour, one using tapioca flour, one using potato starch, one using garbanzo bean flour, one using cornstarch, and one using rice flour.
In a blind taste test among the members of my family (rest assured my daughter-in-law didn’t get the wheat flour one), the garbanzo bean flour was judged to be the best tasting alternative to the classic wheat flour roux. The one made with tapioca flour was judged to be the best tasting overall, not surprising since it was essentially tapioca pudding. Cornstarch was deemed to have the least desirable taste. As my younger son put it, “No matter what you do to it, it still tastes like cornstarch.”
However, while you can make a roux with other starches, they don’t all have the same thickening power.
As it turns out, potato starch has the most thickening power and rice the least. It takes about half again as much additional garbanzo bean flour to equal the thickening power of wheat flour, and it takes over twice as much rice flour to equal the thickening power of wheat flour. Harold McGee’s On Food and Cooking gives a more detailed explanation and has a table of the effects commonly used starches have as a binding agent. (His table does not include garbanzo bean or rice as a binding agent.)
For those who are gluten free, or who have other dietary limitations, making a roux with other starches is a good way to adapt a recipe to your dietary requirements.
In Part 2 of our exploration of kitchen liasons, we’ll look at other ways to make a roux, and at a second mother sauce, velouté.
Home › Forums › Delicious Liasons — the Science and Art of Thickening
Tagged: bechamel, liason, mornay, roux, sauce, thicken