The Gastronomer

Onions That Don't Bite Back

By Andreas Viestad
Special to The Washington Post
Wednesday, April 16, 2008

It could happen to the best of us at the best of times. Instead it happened to me, on an ordinary Tuesday when I was in a hurry to feed my family. For the second time in just minutes, my eyes filled with tears. The chopped onions I had thrown into the pan at the last moment to accompany a main course that needed some support were just the opposite of what I wanted them to be. They were bitter and charred on the outside, still raw and sharp within.

It was a disaster of microscopic proportions, I admit. In my fridge I keep an arsenal of French pâtés and preserves that I turn to when all else fails. And even if I hadn't had backup, the worst that could have happened was that my wife and son would have had to suffer through a meal that just wasn't much fun. Still, I was upset. What made it so disturbing was the everydayness of the situation: that I had failed in the most basic of tasks, browning onions in the pan.

Onions are one of the most important building blocks of cooking. They are an essential part of salads and sauces, stews and savory pies. They give us depth of flavor, a hint of sweetness, a blast of pungency. But to most of us they are also a mystery. They are just there, quietly fulfilling the task we want them to. We don't notice or appreciate them until something goes wrong. Then we realize that we don't really know them at all. And that's just a crying shame.

Most recipes call for cooking onions slowly, and it was by doing no such thing that I went wrong. Even my grandmother could have told me that nothing good comes of rushing an onion. "It is done when it is done," she used to say, echoing Yogi Berra.

Kent Kirshenbaum, an assistant professor of chemistry at New York University, is also somewhat philosophical when discussing onions and why they act as they do. "The browning reaction is a marvelous and fascinating thing," says Kirshenbaum, who co-founded the Experimental Cuisine Collective to explore how science can improve cooking. "But it is often poorly understood."

When onions are transformed from white, pungent and angry to golden brown and sweet, several things are happening: The vegetable's sulfurous compounds are neutralized as they react with each other and form other, less aggressive flavor compounds. The sugars break down, caramelize and react with amino acids to become rich and sweet-tasting. Those processes, Kirshenbaum tells me, require a moderate amount of heat and a generous amount of time. They are also helped along with the use of an iron or copper pan.

Some recipes call for salting onions before cooking. In a recent experiment at his Paris lab, French food scientist Hervé This confirmed that salting does lead to better browning, though he was not able to determine why it works. Perhaps it's because the salt draws water from the onion, and that water contains sugars.

After my own failure I have been quite anxious to prove myself as master -- not victim -- of the onion. For several nights in a row I have done everything by the book. I have pre-salted my onions and cooked them slowly in an iron pot, shunning the convenience of my nonstick skillet. The result has been consistently good enough for me to regain confidence. So much so that I have, once again, started to experiment: I have found that adding a small amount of sugar will give an even richer caramelization than salt alone.

I have always used a generous amount of fat when cooking onions -- far more than what most recipes call for. Despite what a nutritionist might advise, there is something special about the sweetness of onions blended with the richness of butter, bacon fat or -- heaven on earth -- duck fat. Fat, I am told by This and Kirshenbaum, also makes the heat distribution more predictable when cooking and therefore makes charring less likely. But if you understand the difficulties and dangers of fat-free caramelization, it is perfectly possible to get a good result: light brown, surprisingly sweet and containing only the minuscule amount of fat found in the onion itself.

The knowledge given us by food science can make cooking more predictable. It can also make it fun. Recently chef Michel Richard served an onion tarte tatin for dessert at his Georgetown restaurant, Citronelle. It takes some imagination from the chef and guests in almost equal measure. But if you know that the onion is really quite sweet, not just pungent, and that the caramelization of the sugars happens regardless of whether the onion is destined for a dessert or a savory dish, it doesn't seem all that strange.

The science that leads to such understanding is all the rage. Time magazine, for instance, recently named kitchen chemistry among "10 Ideas That Are Changing the World." As No. 5 on the list, it is slightly less important than a new strategy in the war on terrorism and slightly more important than a new strategy against global warming. (Is saving a mayonnaise more important than saving the planet?) As one who has long been interested in the science behind cooking, I am excited that molecular gastronomy has been elevated from fringe phenomenon to important contribution.

But I am less enthusiastic about the rationale for exclaiming that "a revolution" is on the way: "You have been cooking like an idiot," says the article in Time. "If people made medicine this way, we'd all be dead." Predicting the end of old-fashioned cooking is as misguided as the futurists who in the 1980s prophesied a "paperless society." The point is that in most cases you might have been cooking in the dark, but not like an idiot.

And you might have been doing the right thing all along. Kirshenbaum knows that, which is why when I ask him how best to cook an onion, he puts the chemistry aside.

"I seriously could give you a huge equation that describes the quadratic response of the browning to variations in time, temperature and water activity," he says. "Instead, I'll just recommend what my mother used to do when starting her sugo: She would put her chopped onions in a big iron pot on the stove with the flame just barely on and leave it overnight. If the flame didn't blow out in our drafty old house, I would wake up in the morning to a beautiful aroma, knowing that her sauce would be ready the following day. Despite all our advances in gastronomic science, maybe some things can't be rushed."

Andreas Viestad is the author of "Kitchen of Light" and "Where Flavor Was Born," the host of the public television series "New Scandinavian Cooking" and co-host of the forthcoming series "Perfect Day." He can be reached at or His Gastronomer column appears monthly.

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