Quantifying trace amounts of carcinogens in acid-hydrolysed soy products

In ancient times, soy sauce was produced by mixing soy beans, malts and other materials together and bacterially fermenting the mix for three months. Today, vegetable proteins are subjected to acid hydrolysis to produce artificial soy sauce with acids added to the raw material mixture to breakdown the soy proteins. Artificial flavouring is added to mimic the taste of soy sauce.

In recent studies, carcinogen 3-monochloropropanediols (3-MCPD) has been found in acid hydrolysed soy products. In laboratory animal and toxicology testing, 3-MCPD is reported to be carcinogenic and toxic to both kidneys and reproductive organs.

The traditional method for 3-MCPD quantification is chromatographic separation. The standard derivatisation agent used to derivatise 3-MCPD is heptafluorobutyrylimidazole (HFBI). However HFBI is very moisture sensitive, expensive and must be kept at -20°C. The derivatisation process has to be conducted in a heated oven and an inert environment.

University of Malaya researchers have found an alternative, more laboratory friendly derivatising agent for 3-MCPD. Hexamethyldisilazane (HMDS) is less sensitive towards moisture at room temperature, making storage easier. It will only derivatise 3-MCPD when a suitable catalyst (trimethylsilyl trifluoromethanesulfonate, TMSOTf) is added into the reaction system. Further, the activation of HMDS by catalyst is an exothermic process; this removes the need of an oven to initiate the derivatisation. As an added benefit, HMDS costs around 100 times less than HFBI.