In Chinese culinary culture, soy sauces and seasonings are common condiments that, with an appropriate amount added, can bring out the umami in food. The Consumer Council tested 40 soy sauce and seasoning samples. It was found that 11 samples have traces of possible carcinogenic 4-methylimidazole and the aerobic colony count of 1 sample has greatly exceeded the limit under the Mainland standard. 2 samples have high monosodium glutamate (MSG) content and the quality of 10 samples fail to meet the quality grading standard. As some of the brands are well-known by consumers, this gives rise to great concerns.
Among the samples tested, 38 are soy sauces while the remaining 2 are seasonings. Currently, there is no standard for the safety and quality of soy sauces or seasonings in Hong Kong. Therefore, the Council made reference to both Mainland and Taiwan standards, as well as relevant Hong Kong food regulations and guidelines in conducting microbial, chemical safety and quality tests to help consumer choose value-for-money soy sauces.
Chemical Safety Tests
Manufacturers add caramel colourings to soy sauces to increase their colour intensity. However, Caramel III and IV (indicated as 150c and 150d in the ingredient list of pre-packaged food) contain a contaminant 4-methylimidazole. The World Health Organisation classified 4-methylimidazole as a possible human carcinogen. The permitted concentration of 4-methylimidazole in food is not specified in Hong Kong regulations while in California, USA, businesses are required to put warning on product packaging if the products cause exposures to 4-methylimidazole of more than 29ug per day. In this test, it is found that 11 samples contain 4-methylimidazole with an amount between 0.1ppm and 15.9ppm. Taking the sample with the highest concentration of 15.9ppm as an example, consuming 2ml (less than 1/2 teaspoon) of this product means an intake of 31.8ug of 4-methylimidazole; consuming 7ml of the sample with second highest concentration of 4.2ppm means an intake of 29.7ug of 4-methylimidazole, both exceeded the limit for warning set in California. As there is no regulatory requirement in Hong Kong, no warnings are found on these products.
The test results also show that 8 samples contain heavy metals arsenic or lead. However, the amount is far below the limit stated in the Mainland’s National Food Safety Standard. In addition, contaminants such as 3-monochloropropane-1,2-diol (3-MCPD) and Aflatoxin B1 which induce acute liver damage, cirrhosis and tumour, were not detected in any of the samples tested and the outcome is satisfactory.
Quality Tests
The general requirement for soy sauce under Taiwan Soy Sauce Standard grades soy sauce into Grade A, B or C according to their salt-free soluble solids (soluble substances other than salt, such as protein, sugar and amino acid), total nitrogen and amino nitrogen contents, with Grade A being the best. The results show that among the 38 soy sauce samples tested, 10 samples met the Grade A level, 6 samples fell under Grade B and 12 fell under Grade C. The remaining 10 samples (over 25% of the total) did not meet the grading level, showing either their production standards are poor or improvement on product formulae are required.
Soy sauces are classified as brewed or blended according to their manufacturing process. Brewed soy sauces, using soy and/or defatted soy, wheat and/or wheat bran as raw materials, are produced via microbial fermentation. Blended soy sauces are manufactured by combining brewed soy sauces with ingredients containing acid hydrolysed vegetable proteins and other food additives.
Currently, quite a number of soy sauces in the market claim themselves to be naturally brewed. If manufacturers want to shorten the production time of soy sauces, hydrochloric acid-hydrolysed soya protein (acid hydrolysis) will be added which may produce levulinic acid during the process. For naturally fermented soy sauces, there should be no or only trace of levulinic acid. Therefore, the amount of levulinic acid can be used to assess whether a soy sauce is a blended one. According to Taiwan Standard, levulinic acid content in brewed soy sauces should not exceed 0.1%. Among the 21 samples claiming to be naturally brewed, 3 are found to contain levulinic acid ranging from 0.2% to 0.331% which exceeded the amount indicated in Taiwan standard.
Some manufacturers manually add flavour enhancer to improve the "umami". Results also showed that all samples contained MSG. 2 samples reaching Grade A under Taiwan Soy Sauce Standard are found to have MSG content as high as 10.41% and 9.4% respectively. 1 sample, considered as not meeting the grading level, contains the lowest MSG level of 0.048%. Consumers resist having MSG should take note that although some people will experience temporary discomforts such as headache, thirst and muscle tension after consuming food with MSG, there is currently insufficient evidence linking the above symptoms directly with MSG.
In terms of sodium content, 39 out of 40 samples contain a high level of 2,600 to 9,970 milligram (mg) sodium in every 100ml. Only 1 sample had a relatively low sodium content of 814mg. By consuming 20ml of the highest sodium content sample, one will reach the recommended daily sodium intake limit. Consumers should note their intake amount as excessive sodium intake can increase the risk of hypertension, cardiovascular disease, stroke and coronary heart disease.
The Council also studied the storage methods labelling of the samples. 6 samples have not labelled any storage method, 30 with general descriptions only or just state storage method before or after opening. Only 4 samples carry storage advice for both before and after opening in their labels. The overall condition requires improvement.
Regarding the aerobic colony count (ACC) test, 1 soy sauce sample is found to contain 13 million colony forming units per millilitre (cfu/ml), far exceeding Mainland's standard of <30,000cfu/ml for ready-to-eat table soy sauce. The case was referred to Centre for Food Safety to follow up. ACC at a level exceeding the limit only reflects the sanitary conditions of the products, types and quality of the raw materials used, or the extent of processing in prepackaging procedures such as thermal sterilisation, but does not mean there will be food safety issues upon consumption.
The test results also show that 1 sample contain Bacillus cereus at 2,400 spores per millilitre. Although the result is considered as "fair" according to the Hong Kong Microbiological Guidelines for Food, the Council suggests the manufacturer investigate into the reason and improve the situation. For the remaining 39 samples, Bacillus cereus level are detected between less than 10 and 100 spores, the result is satisfactory. Bacillus cereus is ubiquitous in the environment and unsatisfactory sanitary conditions during manufacturing, transportation or storage of food can lead to its growth and reproduction. Consumption of food with excessive Bacillus cereus can cause stomach upset.
- Good soy sauce should be reddish-brown or brown in colour and glossy; seasoning should be a transparent brown liquid which may have a small amount of aggregates or sediment;
- Better choose naturally brewed products with soybean, wheat, bran listed as the first few ingredients in the labels and pay attention to raw materials, colourants and other additives used;
- Purchase products with low sodium content. Maintain a balanced diet, pay attention to amount used, and avoid excessive intake of sodium;
- Store the products according to the methods recommended in the packaging, particularly after opening, to reduce the possibility of spoilage. Use before the expiry date.
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