Out of 40 soy sauce and seasoning samples, some of which were well-known brand names, 11 contained traces of 4-methylimidazole, 10 were substandard, eight contained heavy metals and two had excess levels of monosodium glutamate.
The carcinogen was found as a contaminant byproduct in Caramel III and IV. Indicated as 150c and 150d on pre-packaged food labelling, these additives are often used to enhance colour intensity in soy sauces.
Though classified by the World Health Organisation as a possible human carcinogen, 4-methylimidazole is unlikely to be harmful to humans in small quantities. In some American states, including California, manufacturers are required to notify consumers if their products could cause exposure to more than 29 micrograms per day of the compound.
The Consumer Council test found that 11 samples contained 4-methylimidazole at a concentration of up to 15.9ppm—equivalent of 31.8 micrograms per standard soy sauce serving.
As there is currently no standard for the safety and quality of soy sauces or seasonings in Hong Kong, manufacturers are not required to warn consumers of the presence of 4-methylimidazole.
In its testing, the Consumer Council used mainland Chinese and Taiwanese standards as benchmarks, along with relevant Hong Kong food regulations and guidelines to assess the condiments.
The results also showed that eight samples contained arsenic or lead, though in quantities far below the limits set by the mainland’s National Food Safety Standard.
To assess the quality of the samples, the testers used Taiwan’s system of grading soy sauces into three categories according to their salt-free soluble solids, total nitrogen and amino nitrogen contents, with Grade A being the best.
The results showed that 10 of the samples met the Grade A level, though six were classed as Grade B and 12 fell under Grade C.
The remaining 10 samples did not meet any grading criteria, showing either that their standards for manufacturing were poor, or improvement was required on their formulations, the Consumer council said.
Hong Kong’s food safety inspector, the Centre for Food and Safety, said it was studying the soy sauce samples from the survey, and would follow up with the manufacturers of those that failed to comply with current regulations.