More than 300 food samples have been tested for two types of chloropropanols and most are below the limit of detection, a Centre for Food Safety survey has found.

Only ready-to-eat seaweed and roast pork had a higher amount.

The Centre's Community Medicine Consultant Dr Ho Yuk-yin said today that the 318 samples covered eight major food groups - cereals and cereal products; vegetables and their products; fruit; fish, shellfish and their products; meat, poultry and their products; eggs and their products; dairy products; and snacks.

The results found 3-monochloropropan-1, 2-diol (3-MCPD) in most of the food samples, including vegetables, fruit, eggs and dairy products, was below the detection limit of 2.5 micrograms per kilogram. Ready-to-eat seaweed had the highest concentration at 56 micrograms per kilogram.

Various sources

"Chloropropanols can be present in foods for various reasons. Condiments such as soya sauce and oyster sauce, after going through an acid treatment, would contain 3-MCPD. Other food products, such as instant noodles and hamburgers, that used acid-hydrolysed vegetable protein as an ingredient, also contained 3-MCPD. Lipids and sodium chloride in foods also contribute to the formation of 3-MCPD during normal heat processing such as coffee roasting and bread-baking."

The presence of 3-MCPD in some foods might also be due to the use of certain types of sausage casings, tea bags and coffee filter paper, he added.

The study also found that 1,3-dichloro-2-propanol (1,3-DCP) in most food samples was below the detection limit of 0.5 micrograms per kilogram. Only fish, shellfish and their products; meat; poultry and poultry products were detected to have 1,3-DCP. Roast pork had the highest average level of 9.3 micrograms per kilogram.

However, it is still not known how 1,3-DCP is produced in foods.

According to the United Nations Joint Food & Agriculture Organisation, World Health Organisation Expert Committee on Food Additives, 3-MCPD is generally not genotoxic to humans. However, the genotoxicity of 1,3-DCP cannot be ruled out.

Health risks

The survey showed that daily dietary exposure to 3-MCPD for an average secondary school student falls well below the provisional maximum tolerable daily intake of 2 micrograms per kilogram in bodyweight a day. Cereal and cereal products, particularly instant noodles, are the largest contributor to total dietary exposure to 3-MCPD, with an average of 0.012 micrograms per kilogram in bodyweight a day.

"As for 1,3-DCP, the margin of exposure for an average secondary school student is of low health concern. Sausage was also found to be the largest contributor to total dietary exposure to 1,3-DCP, with an average of 0.002 micrograms per kilogram of bodyweight a day.

"Based on these assessments, chloropropanol exposure through normal food consumption should not pose any adverse health effects," Dr Ho said.

He called on the food trade to observe good manufacturing practices to reduce the levels of chloropropanols in food, while the public should maintain a balanced diet.