Photograph by Beth Wald, Nat Geo Image Collection
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Freshly barbecued meat at the Explora Quincho, outside of Torres del Paine National Park, Chile
Photograph by Beth Wald, Nat Geo Image Collection
The Plate

The Chemistry of Barbecue and You

According to the Hearth, Patio, and Barbecue Association (HPBA), about 80 percent of American households own barbecue grills. Most popular days for grilling, says the HPBA, are Labor Day, Memorial Day, and the Fourth of July—though a good 60 percent of grill owners grill steadily year-round, undeterred by snow, rain, heat, or gloom of night. Real enthusiasts even cook their Thanksgiving turkeys and Christmas dinners on the barbecue grill. And Americans are not the only ones who love a flame-broiled meal (see Getting Our Global Grill On.)

So what is it about grilling that makes food so yummy? Why is boiled beef so blah, but its grilled cousin so brown, aromatic, tasty, and generally delicious? It’s all in the chemistry.

The answer lies in the Maillard reaction, discovered in 1912 by French chemist Louis Camille Maillard, who thought that the compounds produced when food browns might just possibly help cure diabetes. He missed the boat there, but his eponymous reaction—which nobody clearly understands to this day—has fascinated food scientists ever since.

The Maillard reaction not only puts the flavorful pizzazz in seared steak, broiled burgers, and sizzling bacon, but is responsible for the unique tastes and aromas of fresh-baked bread, crunchy toast, French fries, fried onions, beer, chocolate, and coffee. The root of this versatile reaction is the interaction of amino acids (the building blocks of proteins) with sugars at temperatures upwards of 230 degrees Fahrenheit.

The resultant products, called Amadori compounds, then rearrange, reshuffle, and interact in turn in what amounts to a complex chemical feeding frenzy, eventually generating hundreds of different organic molecules. Since each food starts out with its own unique battery of proteins and sugars, the Maillard reaction can churn out a wide range of different flavor profiles. Different batches of Maillard end-products are the reason that grilled steak doesn’t taste like grilled hotdog, and neither tastes like a baguette.

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Maillard himself never realized that his browning reaction had anything to do with flavor. That discovery can be attributed to disgruntled soldiers in World War II, who complained that the powdered eggs in their ration packets were turning brown and tasting unusually awful. Analyses showed that the gicky-tasting eggs contained high enough concentrations of amino acids and sugars to undergo a species of Maillard reaction, even at room temperature. (For more on the evolution of military food, see Feeding the Troops.)

While the results of the Maillard reaction are more likely to be delicious than disgusting, some of its offshoots have been deemed worrisome, if not downright dangerous. In 2002, a much-publicized paper in the prestigious science journal Nature showed that acrylamide, a possible carcinogen, was a common Maillard reaction product, particularly prevalent in such fried foods as French fries and potato chips. An even worse culprit, acrylamide-wise, is coffee, said to account for 20 to 40 percent of our acrylamide uptake. This last revelation promptly led California’s Council for Education and Research on Toxics to sue Starbucks and other large coffee companies, demanding that cancer-warning labels be affixed to every bag of beans and cup of mocha latte.

While studies have shown that acrylamide, administered in mega-quantities, does cause cancer in mice and rats, researchers to date haven’t confirmed carcinogenicity in humans—at least not at the tiny levels ordinarily consumed in food. Stanley Omaye, professor of nutrition and toxicology at the University of Nevada, points out that you’d have to chug 100 good-sized cups of coffee a day to get anywhere near a dangerous dose. (Of more concern is the level of acrylamide in cigarette smoke, which is at least three times greater than that found in food.)

The consensus nowadays, however, is that dietary acrylamide shouldn’t be high on our worry list. For the cautious, food safety experts point out that acrylamide levels rise the longer you cook something at high heat. Thus they recommend not burning your toast, charring your bacon, or serving your steak well-done.

And finally, the barbecue grill, the frying pan, and the oven aren’t the only places where Maillard’s famous reaction takes place. It also occurs very slowly in the human body, where it may be a factor in cataract formation and atherosclerosis.

In other words, in one way or another, we’re all cooking.