4-Methylimidazole (4-MEI) in Soy Sauce


Food culture in China has a long-standing history, with soy sauce (also called soya sauce) already over a thousand years. In the contemporary world, soy sauce manufacturers add caramel colouring in the production process to enhance its colour intensity. This food colour is further classified into Caramel I, II, III and IV whose INS (International Numbering System) numbers are 150a, 150b, 150c and 150d respectively. Yet in the manufacturing process of Caramel III and IV, 4-Methylimidazole (4-MEI) may be formed, a by-product that is possibly carcinogenic.


The International Agency for Research on Cancer of World Health Organization has classified 4-MEI as Group 2B compounds, which are “possibly carcinogenic to humans”. Its classification is based on the adequacy of scientific evidence and not the strength of carcinogenicity. The intake of 4-MEI through consumption of food containing Caramel III and IV is unlikely to cause health impacts.


Advice to the Trade:

  • Where it is technically practicable, manufacturers of caramel colouring should reduce levels of 4-MEI to a minimum;
  • Food manufacturers should minimize the use of food colourings, at a level not higher than that is necessary to achieve the intended colour enhancement.


Advice to the Public:

  • Before making choices, read the food label for content of caramel colouring, particularly for Caramel III and IV or their identification numbers (150c and 150d);
  • Always purchase food products from reputation shops in good hygiene condition;
  • Read the food label on the package carefully and take note of the expiry date;
  • Check whether the packaging is intact and without damage;
  • Follow the instructions on the food label by keeping the food product in a cool and well-ventilated place or under cold storage to maintain its freshness;
  • Do not buy or use soy sauce product of abnormal taste or with pungent smell;
  • Be a smart consumer. Do not buy or consume any soy sauce product if doubtful about its safety.