Aroma and Flavor of Japanese Soy Sauce

Abstract

This chapter discusses the flavor substances of true Japanese soy sauce produced by the traditional fermentation method. The chemistry and composition of Japanese soy sauce has been reviewed, with emphasis on the flavor and aroma constituents. Over 90% of Japanese soy sauce is the koikuchi type, containing about equal amounts of fermented sauce and a chemical hydrolyzate, obtained from defatted soybeans. The volatile compounds in raw soy sauce and in soy cake are classified as: aliphatic carbonyl series; aliphatic esters, alcohols, and acids; sulfur-containing compounds; phenols; and other aromatic compounds. The specific aroma of soy sauce is due to sulfur-containing compounds. However, most of the aroma and flavor of soy sauce exists in the acid fraction. Tyrosol or p-hydroxyphenylethyl alcohol is found in commercial soy sauce and is associated with the bitterness of soy sauce. The characteristic flavor ingredients produced by cooking soy sauce are the guaiacyl compounds such as: vanillin, vanillic acid, ferulic acid and 4-ethylguaiacol. Among these, vanillin was the most aromatic. The factors related to the aroma and flavor of soy sauce that have been discussed in this chapter include raw materials; condition of fermentation, especially the volume of salt water relative to koji, salt concentration and aging period; and microorganisms involved in digestion and fermentation.