GC-Olfactometry analysis of the aroma components in sake koji

Abstract

In order to clarify the aroma compounds responsible for the aroma of sake koji, we identified these and examined the contribution of each aroma compound to the whole aroma. First of all, the intensity of koji aroma was evaluated by sensory analysis. Employing GC-Olfactometry (GC-0) and GC-MS analysis using a head space sorptive extraction (HSSE) method, we found novel 5 compounds: 1-octen -3-one (mushroom-like), 2-methyl-2-hepten-6-one (nut-like), methional (potato-like), phenylacetaldehyde (rose-like) and (Z) 5-octadien-3-one (geranium-like) besides isobutyraldehyde, isovaleraldehyde, and 1-octen-3-ol in sake koji. The concentrations of 1-octen-3-one, 1-octen-3-ol, and phenylacetaldehyde were higher in strong-smelling koji than in weak ones. The flavor dilution factors (FD) of 1-octen-3-one and methional were highest (FD 125), and those of 2-methyl-2-hepten-6-one, Phenylacetaldehyde, and (Z)-1, 5-octadien-3-one were second (FD= 25). It was possible to reproduce the aroma of koji by blending 2-methyl-2-hepten-6-one, methional, 1-octen-3-one, 1-octen-3-ol, and phenylacetaldehyde. It was concluded that methional, 1-octen-3-one, and phenylacetaldehyde were important for the aroma of koji.