Cooking methods like boiling and steaming are among measures that help in curbing the formation of cancer-causing acrylamides in a wide range of foods from potatoes to rice, research shows.
Acrylamides form from a chemical reaction between sugars -- such as glucose and fructose -- and asparagins, a kind of amino acid, when they are heated to 120 degrees Celsius or higher. They occur easily in food products containing large amounts of carbohydrates, showing up in cooking that uses grains such as rice and wheat, as well as vegetables like bean sprouts, lotus root and cabbage. They can also be found in many processed products, like coffee, green tea, bread, fried potato snacks, and curry sauce.
Acrylamides form most easily from frying, grilling and stir-frying. Meanwhile, the temperatures of boiling and steaming usually don't reach 120 degrees Celsius, so hardly any acrylamides form through these cooking methods. Acrylamides also do not form much under microwave heating, which works by heating the water molecules found in food.
One main way to keep down acrylamides is to keep them from growing while foods are in storage. Potatoes, for example, become more sugary when stored for long periods in refrigeration. In an experiment, when potatoes that had been stored at room temperature and ones that had been refrigerated were stir-fried at 200 degrees Celsius for 10 minutes, the potatoes that had been refrigerated produced about twice the amount of acrylamides as the ones stored at room temperature.
Additionally, washing potatoes and other vegetables in water before cooking them at high temperatures results in lower acrylamide levels.
Based on various cooking experiments, the Ministry of Agriculture, Forestry and Fisheries' food safety policy division advises that potatoes not be stored in the refrigerator, but at temperatures of 8 degrees Celsius or higher. It also recommends washing foods in water to remove asparagins and sugars from their surfaces.
Another way of keeping down acrylamides is cutting down the amount of time that foods are subjected to high temperatures. The amount of charring on food can serve as a guide for its acrylamide level. The more black charring there is, the more acrylamides there are. To avoid this kind of charring, one can cook with a weaker flame and reduce the length of heating. It is also known that, when stir-frying multiple foods together, stirring them while they cook keeps the amount of acrylamides down.
Although vegetables can contain acrylamides, they are an important source of vitamins and minerals, and can also help prevent cancer and lifestyle diseases. Hiroshi Sato, head of the food safety commission, says, "It is impossible to reduce acrylamide intake to zero. It is good to eat a variety of foods, without excessively favoring a particular food or cooking method."
High-temperature heating of foods is not all bad either, with benefits like killing illness-causing bacteria and preventing food poisoning, and improving taste with the proper amount of charring. There is no need to be overly concerned about acrylamides, and the food safety policy division advises that people who eat a lot of stir-fried or fried foods should first try to eat a balanced diet, and then try to use cooking methods that keep acrylamides down as much as possible. The ministry has opened courses nationwide on how to cut down on acrylamides, and is calling on households to put these methods into practice.
Acrylamides are used as an industrial ingredient in products such as glues used in dam and tunnel construction. In 2002, the Swedish government announced that acrylamides form when foods are cooked at high temperatures, thrusting the chemical compound into the spotlight. According to the Food Safety Commission of Japan, the average acrylamide intake of Japanese people is 0.24 micrograms per kilogram of body weight per day, less than the averages for countries in the European Union, which ranged from 0.4 to 1.9 micrograms per kilogram of body weight per day. By food type, about 60 percent of the Japanese intake was from vegetables like bean sprouts, lotus root and potatoes that had been cooked at high temperatures. The remaining intake was from things like coffee, snack foods and bread.
The Food Safety Commission of Japan has put together a draft evaluation of acrylamides with the tentative conclusion that "we cannot say there is nothing to be concerned about," because the average Japanese acrylamide intake was relatively close to that of mice that, in an experiment, had a 10 percent increase in cancer.