In the Thick of it
FOOD FOR THOUGHT - April 20, 2005
Mark R. Vogel - [email protected] - Archive of other articles by Mark Vogel
Sauces come in a seemingly infinite number of styles. The ingredients, methods, and applications for sauces almost know no bounds. And while sauces certainly vary in terms of their viscosity, thickening them is an oft-needed necessity. This is due to the fact that many sauces are based on aqueous liquids, e.g., water, stock, broth, wine, etc. A sauce with greater body will adhere better to the food and thus create a more noteworthy flavor sensation. The procedures for concentrating sauces fall into one of two categories: condensation or addition of a thickening agent.
The simplest and most straightforward method of thickening a sauce is to reduce it over high heat. Unlike any of the ensuing methods to be discussed, this has the added benefit of intensifying the flavor by evaporating the excess water. This technique is almost always employed whenever wine or liquor is added to a sauce in order to vaporize the alcohol. But alcohol or not, any sauce that can be cooked can be reduced. How much to reduce a sauce will depend on the specific recipe. Generally speaking, when the sauce has congealed enough that it can coat the back of a spoon without running off, (known as “nappé”), it is completed. Remember that when a sauce is reduced it will naturally become saltier. Thus, hold off seasoning until it is finished or near done to prevent over seasoning.
The most common thickening agents are starch-based thickeners, namely flour, cornstarch and arrowroot. Less common are potato starch and rice flour. Starch is simply chains of glucose molecules, a type of sugar produced by plants through the process of photosynthesis. When added to sauces and heated, the long chains of glucose molecules unwind, bond to the water’s hydrogen molecules, and thus gelatinize the sauce. This would be analogous to tying everyone’s hands together at a cocktail party. The individuals, (water molecules), would not be as free, (or as “fluid”), to move around the room, since the rope, (starch molecules), are holding them together.
Starches cannot just be directly added to a sauce. Doing so would cause dreadful lumps that will never incorporate into the surrounding liquid. They must be prepped first. Flour is almost always mixed with butter, (or some other form of fat), before being introduced into a sauce. Take an equal amount of flour and softened butter and knead them together until a pliable, but not melted paste is achieved and you have what the French call beurre manié.
To employ beurre manié as a thickener, bring the sauce to a simmer, and whisk it in one piece at a time, waiting for the previous one to melt before adding the next. When all of the beurre manié is incorporated, bring the sauce to a near boil and simmer for three minutes.
If you were to cook the flour and butter together first, then you would have a roux. Melt the butter in a skillet or saucepan over low to medium heat; add an equal amount of flour and cook, stirring constantly until the desired degree of doneness. The longer you cook roux the darker it will become. If you do not wish to darken your sauce but merely want to cook out the raw, floury taste of the roux, cook for just a few minutes. You can add the roux to the sauce or vice versa but they must be at different starting temperatures, (at the very least, one room temperature and one hot). You must also gradually add one to the other and whisk incessantly. All of these steps help prevent lumping.
Employing a roux is the premier method for making gravy for your chicken or turkey. After the bird has roasted, add flour to the drippings in the roasting pan, cook for a few minutes, and then gradually whisk in chicken stock. Bring to a near boil, simmer to the desired consistency, and season with salt and pepper.
Cornstarch and arrowroot will thicken more efficiently than flour since they contain no protein. They have 50 to 100% more thickening power than flour and thus, less of them is needed. They also thicken at a somewhat lower temperature and do not need to be pre-cooked, like roux. However, they do need to be dissolved in fluid first. Mix the cornstarch or arrowroot in just enough cold water to form the consistency of heavy cream. This is called a slurry. Add it to your simmering sauce, bring to a near boil and then simmer for only a minute or two. Extended cooking will reverse the thickening process.
Every chef in the world will tell you to bring your roux or cornstarch/arrowroot thickened sauce to a full boil to achieve its maximum thickening potential. This is not scientifically correct. Beyond 200-205 degrees (boiling is 212), the starch will begin to break down. Thus, bring it to almost a full boil, immediately reduce to a simmer, and stir gently.
Finally, sauces can be thickened by adding a liaison, (a mixture of cream and egg yolks), butter, gelatin, and pureed vegetables or fruits. Which of these are utilized will depend on the type of sauce and it’s specific recipe.