Comparison of volatile components in soy sauce (Koikuchi shoyu) produced using Aspergillus sojae and Aspergillus oryzae

Volatile components contained in raw and pasteurized Japanese soy sauce of the koikuchi type (koikuchi shoyu) were compared among the products from nine different plants using two different koji molds, Aspergillus sojae No. 9 (A. sojae No.9) and Aspergillus oryzae S-03 (A. oryzae S-03). Identification of the volatile compounds in koikuchi shoyu and the quantitative comparison were carried out by GC, GC-MS analyses and the analysis of variance of the GC peak areas. Sixty-five compounds were identified or estimated as koikuchi shoyu volatile components, in which five compounds were newly confirmed or tentatively identified in koikuchi shoyu. The quantity of A. sojae No. 9 koikuchi shoyu volatiles was larger than that of A. oryzae S-03 koikuchi shoyu, and it increased when the koikuchi shoyu was heated. 2-Methyl-1-butanol, 3-methyl-1-butanol, ethyl lactate, acetic acid, and 2-phenylethanol, etc., besides ethanol, had large peak areas on the gas chromatograms of the koikuchi shoyu. Ethyl lactate, acetic acid, pyrazines, phenylacetaldehyde, phenol, and maltol, etc., were larger in A. sojae No. 9 koikuchi shoyu than those in A. oryzae S-03 koikuchi shoyu. On the other hand, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-phenylethanol, 2-methylbutanoic acid, 3-methylbutanoic acid, 5-methylthio-1-propanol, 2-ethyl-4-hydroxy-5-methyl-3 (2 H)-furanone, 4-ethylguaiacol, and 4-ethylphenol, etc., were found in abundance in A. oryzae S-03 koikuchi shoyu.