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.

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Published:July 3, 2016


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