Kitchen Techniques: Thickening

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If you’ve ever tried to learn to draw from a book, you’ve probably encountered something like this:
lutz - public domain drawing book
(E.G. Lutz; 1913)
This is useful if, and really only if, you’re interested in drawing a crane. If you follow enough of these little exercises, perhaps you’d learn something about the way a draughtsperson thinks about drawing — if you really paid attention.
I feel the same way about recipes. A recipe really only tells you how to make one dish. I thought it might be fun to look at some more general-purpose cooking techniques.

Today’s topic: thickening. Soups, puddings, gravies, and sauces: all of these dishes are distressing if they’re watery when they shouldn’t be. So we thicken!

     Thickening agents almost all work the same way: they start as long, long molecules all wadded up in little balls. When you activate the thickener, the balls unwind, and neighboring molecules tangle up with one another, forming a big, slow-flowing net. The net traps the liquid you want to thicken, and slows it down, too.
     Sometimes those molecules are starchy carbohydrates, and sometimes they’re proteins  but the action is the same: spread out and tangle up. This means that they all have the same potential problem: clumping. If the thickener tangles up too quickly, all it will trap inside its net is more thickener! Scientists refer to this as OH NO LUMPS. Each of the different techniques for using specific thickeners amount to three facts:
  • How do you activate the thickener (make it spread out and tangle up)
  • How do you deliver the thickener to the sauce,
  • How do you prevent lumps?

So with that in mind, let’s talk about specific thickeners.

Flour:

Flour is a starchy carbohydrate. It’s activated by water, so we don’t want it to get wet until it’s actually in the sauce — we’ll deliver it using butter. There are two ways to get a butter-flour mixture.
You can melt the butter in a pan, and add flour until it makes a smooth paste. You’re probably familiar with this: it’s called a roux (“You’ll rue the day”).
You can also knead the flour into cold butter, making little balls of flour-butter. Chefs call this beurre manie (pronounced “bare manYAY” and remembered by imagining someone excited to see a naked gentlemen.)
The problem with flour is that it tastes of flour. Roux avoids the floury taste by cooking the flour. You’ll hear talk of the varying colors of roux, ranging from blond to dark brown. Each tastes a little different, because as the flour cooks more, the roux gets darker. Blond roux is the most useful for straight-up thickening.
Buerre manie lets you take the opposite approach: you drop those suckers in during the final minute, and don’t let it cook at all. You can also cook the sauce for an extended period (like, 30 minutes) after you drop em in.  — what you don’t want to do is let the flour heat up a little but fail to get truly cooked. Then it will taste of flour.
Generally, you start a sauce with a roux, but you end a sauce with buerre manie.
Add milk to your roux, and you have a white sauce. Add cheese, and you’ll have an amazing cheese sauce for home-made mac-n-cheese.

Corn starch:

We’ll activate corn starch with heat, so we can deliver it using water. If you drop it straight into your sauce, you won’t be able to blend out the lumps fast enough (if ever) so add a little corn starch to a little cold water and mix it into a slurry (thinner than a paste) and only pour it into your sauce once its smooth.
Bring the sauce back up to a bare simmer (adding the cold water mixture will have dropped the temperature . It will thicken as it heats, and thicken further once you take it off the heat.
Don’t forget to re-season — you’ll have diluted the flavor, some.

Arrowroot:

If you’re a Yankee who can digest gluten, you probably don’t have any of this hanging around. If you do, use it just like corn starch — it will thicken at a lower temperature, and remain clear.

Egg yolk:

We activate egg yolk with heat, too — but unlike the starches, we must heat egg yolks slowly (slowly!) to make sure it distributes evenly. Egg yolk lumps mean having scrambled egg in your still-watery sauce. Eugh.
The best way to do this is to plop your yolk into a bowl, and spoon a little of your warm sauce into the bowl with it. Mix slowly and gently, until it’s smooth. Then add another spoonful of the warm stuff. Cooks call this process ‘tempering’ your egg, and it’ll bring it up to temperature without letting it scramble: you’ll have a custard!
If you don’t have a sauce already (perhaps you’re making a hollandaise) you should bring your egg to temperature in a double boiler.

Potato flakes:

Activated by heat, deliver by pouring ’em straight in. This is pretty much only for when you’re desperate. Not a great texture.

Peanut butter:

No activation needed; heat is useful for melting it enough to blend it in properly. Just mix in a spoonful, check your seasoning, and serve. Very fast. Great for faux-asian sauces over stir-fry or egg rolls; you’ll taste the peanut.

Reduction:

If your sauce already has some starches or proteins or other long molecules hanging around, you can always let it simmer, and let the excess water evaporate. Once those molecules are close enough, they’ll start interacting and produce a thicker sauce — just less of it.

There are plenty of unusual thickeners in the world, but to add a new thickener to your arsenal, all you need to learn is how to deliver, how to activate, and how to prevent lumps.

Ooze forth, my friends. Thickly.

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