Acrylamide: an update

Acrylamide is the industrially useful but toxic chemical that reared its ugly head among our potato chips and fries in 2002, when Swedish food chemists first thought to look for it in foods. Acrylamide is known to cause cancer and other illnesses in animals, and nerve damage in humans. It's suspected to be a human carcinogen as well. Acrylamide concentrations in drinking water are regulated by the Environmental Protection Agency, and the Swedish chemists found food levels hundreds of times higher than the EPA limit.

Since 2002, we've learned a lot about acrylamide in food.

It's formed in both food manufacturing and in our kitchens during the heating of carbohydrate-rich foods (potatoes, grains and their products) at temperatures high enough to cause browning and the development of the desirable flavors typical of browned foods (above about 250 degrees F, 120 degrees C). It arises from the reaction of a particular amino acid, asparagine (the major amino acid in potatoes), with glucose and other sugars. Among the foods that contribute most to our daily intake of acrylamide are french fries and potato chips, breakfast cereals, cookies, and coffee. Breads, toast, pies and cakes, and corn snacks are also significant sources. Recently acrylamide was even detected in Japanese green teas, which contain asparagine and are finished by roasting at 250-280 degrees F, 120-140 degrees C.

Food chemists are coming up with a lot of new information about acrylamide levels in foods and ways to minimize them. Here are some recent findings.

A study from Donald Mottram and colleagues at the University of Reading shows that the addition of a little citric acid and the amino acid glycine reduces the acrylamide levels on cooked potatoes without reducing flavor.

Mottram and others have also found that the asparagine content of wheat flours, and their tendency to form acrylamide, depend strongly on the wheat variety, growing conditions, and farming methods. Inadequate sulfur nutrition can increase acrylamide production by a factor of 5. Less refined flours with more of the outer protein-rich aleurone layer produce more acrylamide, as do flours made from sprouted wheat.

Felix Escher and colleagues at the ETH in Zurich have found that during the last stage of potato frying, when the moisture content of the potato falls below 20%, the energy required for acrylamide production increases, while flavor production continues unaffected. This means that acrylamide levels can be minimized by lowering the oil temperature toward the end of the frying process.

What we don't yet know about acrylamide is the actual risk that it poses in our current diet. That bottom-line question is under active investigation by scientists in several countries. The fact that coffee consumption isn't associated with a higher cancer risk suggests to me that other protective factors in food compensate for its presence. But until we know for sure, it's prudent to go easy on fries and packaged snacks.

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Mizukami, Y., et al. Analysis of acrylamide in green tea . . . . J. Agric. Food Chem. 2006, 54, 7370-77.

Low, M.Y. et al. Effect of citric acid and glycine addition on acrylamide and flavor in a potato model system. J. Agric. Food Chem. 2006, 54, 5976-83.

Muttucumaru, N. et al. Formation of high levels of acrylamide during the processing of flour derived from sulfate-deprived wheat. J. Agric. Food Chem. 2006, 54, 8951-55.

Claus, A. et al. Influence of agronomic factors and extraction rate on the acrylamide contents in yeast-leavened breads. J. Agric. Food Chem. 2006, 54, 8968-76.

Amrein, T.M. et al. Influence of thermal processing conditions on acrylamide generation and browning in a potato model system. J. Agric. Food Chem. 2006, 54, 5910-16.