Sweet tip on onions: Just let them burn

June 10, 1998|By Rob Kasper

LATELY I HAVE been burning onions, on purpose. They smell good and they taste even better.

It is a pretty simple procedure. I take an ordinary yellow onion and slice it in half, top to bottom. Then I put the onion halves over a medium-hot charcoal fire, and I leave them on the fire for 30 to 40 minutes.

That is when they burn, or char. The edges of the onion turn a forbidding shade of black. But the color is deceptive. Rather than tasting dried out and bitter, the charred onions develop a surprising sweet flavor. Other family members are horrified at the thought of eating black food. But I happily cut up the dark onions and add them to a grilled Italian sausage sandwich, or put them on the bottom of a hamburger.

Sometimes, if I am feeling ambitious, I also grill green peppers and slices of eggplant and mix them them with olive oil and end up with a dish of grilled vegetables.

But lately I have been feeling lazy, and have been content to merely burn the onions.

Onions are temperamental. Whole onions are as mild-mannered as a waiter angling for a big tip. Yet when sliced, onions turn as acerbic as a chef whose souffle has fallen. A cut-up onion can bring tears to your eyes.

I was curious about the chemical arsenal onions pack, so I looked up onions in "On Food and Cooking" by Harold McGee, a book that offers thorough, scientific explanations of food behavior. I read the passage on onions several times, slowly, before I was able to get a rough idea of how onions make me cry.

It works like this. The whole onion is sitting there minding its own business. But when a knife runs through it, its cells get all stirred up. Something called precursors behave pretty much like stable citizens when the onion is whole. But when the onion is chopped, the precursors get volatile, they collide with an enzyme or two, and this tangle produces disulfide compounds. These are, I gather, some of the bad boys of the onion arsenal, something you don't want to meet in a dark alley.

The culprit that makes our eyes water is called the lachrymator. When the onion is chopped, the culprit takes to the air. It floats up to our eyes and dissolves in the eye fluids, forming sulfuric acid. Lachrymations, or tears, result.

I got an image of onions behaving like thugs in bad B movies. When they get roused, they'll put acid in your eyes.

Over the years I have tried various onion-handling techniques to end the tears. Once, following advice I read in some cookbook, I tried sticking a piece of bread in my mouth as I chopped onions. The theory was that the bread would absorb the tear-producing fumes, preventing them from reaching my eyes. It didn't work. Instead I ended up looking like a sorrowful, stuffed turkey, bread sticking out of me, tears streaming from my eyes.

I now think the best way to subdue onions is to threaten them with fire. Cooking quickly brings them into line. The troublesome compounds, McGee reported, are driven off by high temperatures.

Moreover if you hold them close to the fire, another benefit ensues. Some of the once-obnoxious onion compounds are converted into molecules that, according to McGee, are 50 to 70 sweeter than table sugar.

I put in another way. To get an onion to behave, you burn it.

Pub Date: 6/10/98

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