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Science of Cooking: Polenta

Polenta is a much beloved dish both here in the United States as well as in its birthplace, northern Italy. At one time it was considered to be a staple of the Italian diet, even more so than pasta, which only took over its place in the 20th Century (O’Neill). The origin of the word polenta dates back to the late 16th Century from Latin, meaning pearl barley (Oxford American Dictionary).

It is indeed a very simple and humble dish made from ground cornmeal, which would be otherwise not very easily digested by humans. Historically, polenta has been cooked by taking coarsely ground cornmeal and pouring it over boiling salt water, then stirring for up to one hour. The stirring is a very important part of the process because the cornmeal forms thick lumps that are nearly impossible to break after it starts getting very hot.

Starch gelatinization is the villain when it comes to polenta lumps, though it is also the reason why it can achieve its creamy texture. Gelatinization is the “thermal disordering of crystalline structures in native starch granules” (Tester and Morrison 551). Basically what this means is that the two polymers which make up starch, amylose and amylopectin, break down when the corn comes in contact with the hot water, causing it to eventually gelatinize (Farhat, Belton, and Webb 142). As can be seen by the diagram below, the starches located in the endosperm, are not readily accessed by the hot water. The gelatinization process begins with the corn absorbing water, swelling, and then bursting, hence exposing its starches. This process begins at a temperature of 50°C when the hydrogen bonds start to weaken and water is absorbed, up to 80°C when the granules completely lose their shape (Farhat, Belton, and Webb 142). The amylose is the gelatinization agent.

The process has a range of 30°C from start to finish, which is why typical recipes require constant stirring. If the polenta is not being stirred at all the times some areas of the pan will reach gelatinization faster than others, causing unbreakable lumps due to the amylose’s strong bonds.

The authors of Cook’s Illustrated came up with a foolproof recipe in order to cut down the stirring time. They opted for a coarsely ground cornmeal, which ensures a rich flavor that could not be attained with an instant form of polenta. In order to have the water reach the starch faster and more evenly in all the kernels, a pinch of baking soda was added to the water before the corn was introduced. What the baking soda does is replace some of the calcium and magnesium ions, present on the outside of the starch granule, with its own sodium ions. This weakens the outer layer of the starch granule allowing faster release at the beginning, thus avoiding the one hour cooking time filled with stirring (“No-Fuss Creamy Polenta”).

Below is the full “Cook’s Illustrated” recipe, hope you enjoy it as much as I did. 

“Italian Comfort Classics”

Ingredients: 7 ½ cups water 1 ½ teaspoons table salt Pinch baking soda 1 ½ cups coarse-ground cornmeal 2 tablespoons unsalted butter 4 ounces good-quality Parmesan              Cheese, grated (about 2 cups), plus extra for serving Ground black pepper

Instructions:

1. Bring water to boil in heavy-bottomed 4-quart saucepan over mediumhigh heat. Stir in salt and baking soda. Slowly pour cornmeal into water in steady stream, while stirring back and forth with wooden spoon or rubber spatula. Bring mixture to boil, stirring constantly, about 1 minute. Reduce heat to lowest possible setting and cover. 2. After 5 minutes, whisk polenta to smooth out any lumps that may have formed, about 15 seconds. (Make sure to scrape down sides and bottom of pan.) Cover and continue to cook, without stirring, until grains of polenta are tender but slightly al dente, about 25 minutes longer. (Polenta should be loose and barely hold its shape but will continue to thicken as it cools.)

3. Remove from heat, stir in butter and Parmesan, and season to taste with black pepper. Let stand, covered, 5 minutes. Serve, passing Parmesan separately. For your reference: 1. Farhat, Imad A., P. S. Belton, and G. A. Webb. "MRI Study of Polenta Gelatinization During Cooking." Magnetic Resonance in Food Science: From Molecules to Man. Cambridge: RSC Pub., 2007. N. pag. Print. 2. "Italian Comfort Classics." America's Test Kitchen. PBS. 2010. 2012. Web. 3. "No-Fuss Creamy Polenta." Cooks Illustrated. N.p., 1 Mar. 2010. Web. 24 Feb. 2013. 4. O'Neill, Molly. "From Pot To Plank: Polenta Eaten Off The Table." The New York Times. The New York Times, 18 Mar. 1998. Web. 25 Feb. 2013. 5. "Polenta." Oxford American Dictionaries. N.d. Web. 6. "Preserving Value." Tate & Lyle Annual Report 2009. N.p., 2009. Web. 25 Feb. 2013. 7. Tester, Richard F., and William R. Morrison. "Swelling and Gelatinization of Cereal Starches. I. Effects of Amylopectin, Amylose, and Lipids." Cereal Chemistry 67.6 (1990): 551-57. Web. 8. Image: http://www.morguefile.com/archive/#/?q=polenta