In April, Swedish scientists shocked the public with news that they had found a nerve poison and probable carcinogen, called acrylamide, in a range of fried and baked foods, especially potatoes. At the time, how the acrylamide got into plant-based foods was a mystery. Now, teams of scientists in the United Kingdom and Switzerland reporting in the 3 October issue of Nature have shown that the substance forms during cooking through a well-known chemical process called the Maillard reaction.
The Maillard reaction gives foods cooked at high temperatures (as opposed to boiled ones) their taste, aroma, and color. It explains the finger-licking goodness of fried chicken and the rich flavor of caramelized onions. The reaction is named for French chemist Louis Camille Maillard, who in 1912 observed that heating a mixture of amino acids and sugars turns it brown. Suspecting that the reaction might play a role in acrylamide formation, Richard Stadler and colleagues at the Nestlé Research Center in Lausanne, Switzerland, and Donald Mottram of the University of Reading and colleagues heated slurries of sugars and amino acids at temperatures hot enough to trigger the Maillard reaction.
As the researchers had theorized, one amino acid in particular, asparagine, generated significant amounts of acrylamide. Potatoes and some cereals contain lots of asparagine, and French fries, potato chips, and crackers figure prominently among foods with high acrylamide content. That suggests to the researchers that most of the acrylamide comes from frying and baking asparagine-rich starchy foods, although it is possible that other mechanisms contribute as well. But both teams caution that acrylamide is found in other foods that aren't fried or baked. Because the compound is probably produced in different ways in these foods, additional mechanisms need to be investigated.
Other experts call these first steps exciting. "This is what we have been waiting for," says Karl-Erik Hellenäs, a senior scientist at the National Food Administration in Sweden, adding that the results are in line with recent findings in the United States and Canada. Now his agency and others will proceed to experiment on a wide range of real foods. Scientists must also learn how acrylamide is metabolized in the human body and what health risk it poses. The ultimate goal, says Mottram, is to find ways of minimizing acrylamide while maintaining flavor and color.