Effect of Maturation Time on Koji-like Smell and Volatile Compounds of Barley Miso (Japanese Soybean Paste) during Fermentation

Barley miso (Japanese soybean paste) is generally classified into either the light-colored type or the red type based on a short or long maturation time, respectively. In this study, we characterized barley miso with a focus on its koji-like smell. Sensory evaluation showed that koji-like smell was significantly reduced during the maturation process, especially after two months. However, comprehensive analysis of volatile compounds indicated that known constituents of koji-like smell, 1-octen-3-ol and phenylacetaldehyde, were present in similar and lower concentrations, respectively, in the light-colored barley miso compared to the red barley miso. In addition, most compounds, such as aldehydes and esters, were found in larger concentrations in the red barley miso than in the light-colored barley miso. These results suggest that maturation time has an important role in koji-like smell, and the contributions of decreases in 1-octen-3-ol and phenylacetaldehyde to koji-like smell during the maturation process remains unclear.