Quantification and Odor Contribution of Volatile Thiols in Japanese Soy Sauce

Three compounds of volatile thiols, 2-furanmethanethiol (2FM) with a strong roast coffee aroma, benzenemethanethiol (BM) with a strong empyreumatic aroma reminiscent of smoke and ethyl 2-mercaptopropionate (ET2MP) with a tropical fruit-like aroma, were identified for the first time in four types of heat-treated soy sauce and raw soy sauce. 2FM, BM and ET2MP were present in these soy sauce samples at considerably higher concentrations than their perception thresholds. Their concentrations also increased when the raw soy sauce was heated for pasteurization. A triangle test on the raw soy sauce and heat-treated soy sauce showed that the aroma of the raw soy sauce became similar to that of the heat-treated soy sauce after the addition of the three volatile thiols to the raw soy sauce. The volatile thiols thus contributed to the aroma of heat-treated soy sauce.