Onions!

Everyone knows that onions make you cry. Most people have at some point looked up why. Basically, when you cut open the cells of the onion you're allowing enzymes alliinases to react with the sulfur containing compounds in the onion, to create sulfenic acids. Sulfenic acids decompose to syn-propanethial-S-oxide, which is volatile and binds to receptors in your eyes, creating the burning sensation. Fewer people know that to reduce this somewhat annoying proprty of onions, all you have to do is wash it periodically.

What's more interesting about onions is the vast number of different flavors they can produce. Off the top of my head, I can think of five good flavors and one bad flavor you can get with just onions: Raw, Sauteed, grilled, fried, carmelized, and burnt. What makes them so remarkable is the combination of the sulfur compounds with the natural sugars in the onion. Biting into a raw onion, you would never know that some varieties contain as much sugar as oranges and apples. On the other hand, if you try a good soupe d'oignon you'll know exactly what I'm talking about. There the onions are caramelized (medium high heat for a long time), which largely eliminates the harsh sulfur flavor and brings out the sugar.

If you're going for something simple and delicious, grilled onion skewers are the way to go. Basically, a very coarse chop of the onions minimizes the alliinases effect, so the onion remains largely sweet, except on the cut ends, where the exposed sugar caramelizes in the high heat of the grill.

On the other hand, if you forget about your grilled onions while they're cooking, you'll wind up with a burned tasteless mess. So, the point is this: it seems to me that most food chemistry is applied to either research on health benefits of food or to industrial applications like preservation and anti-caking. I could rattle off some of the compounds in onions with anti-bacterial, anti-cancer, or anti-fungal properties here, but I'm much more interested in the application of chemistry to making food taste good. And there's not nearly enough of that.

http://www.chm.bris.ac.uk/webprojects2001/gray/chemistry.htm


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