I discovered something particularly fascinating the other day. But first, a little background information. I happen to be a chef instructor at Le Cordon Bleu Chicago who is very interested in the science behind cooking; the how's and why's concerning the changes that are taking place as we process raw ingredients into finished dishes. It pretty much goes without saying that I spend at least a little bit of time every day reading from Harold McGee's food-science bible, On Food and Cooking.
Earlier this week, I spent an evening with my class talking about the composition of rice and how different types of rice react differently to various cooking techniques. We focused mainly on using the variety of rice known as Arborio to make a simple but classic (and much beloved) Italian rice dish called risotto.
While researching for my lecture on rice, I came upon a piece of information of which I was previously unaware. All along, I was under the impression that it was solely the higher levels of amylopectin starches in the medium grain Arborio rice that give a finished risotto its characteristic creamy consistency. The starch is released into the broth during the almost continuous stirring of the dish while it simmers, and while this indeed is an important contributor to the wonderful richness and full mouth-feel of the finished dish, it's apparently not the only one.
As it turns out, as the starches in the rice kernels begin to heat up, they are drawing in water and swelling to many times their normal size. Because they are drawing in water from the meat-based stock or broth being used to cook the rice, the remaining stock that's left simmering around the kernels becomes highly concentrated with gelatin molecules. The high concentration of gelatin is apparently just as important as the release of starch when it comes to the smooth, saucy, velvet-like consistency of the liquid surrounding the tender rice kernels in a finished risotto. Amazing! Of course, the chunk of butter and the handful of grated parmesan cheese that go in at the end don't hurt, either!