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

Abstract

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.

Effect of Peony (Paeonia ostii) Seed Meal Supplement on Enzyme Activities and Flavor Compounds of Chinese Traditional Soybean Paste during Fermentation

“…Phenylacetaldehyde, for instance, can be generated through the metabolic processes of amino acids and undergo oxidation-reduction reactions to form corresponding acids and alcohols [32]. These compounds can then participate in esterification reactions, producing esters, which are recognized as crucial flavor compounds in soybean paste [33].…”

Carbon stable isotopes of glucose during the degradation of rice by the koji fungus Aspergillus oryzae

“…During koji production, A. oryzae grows on steamed rice ( Oryaze sativa ) and secretes hydrolytic enzymes, including α-amylase and glucoamylase, that degrade starch into fermentable sugars [ 6 , 7 ]. This process is essential for generating the glucose required for making numerous traditional Japanese fermented foods, such as sake [ 8 , 9 ], sparkling sake [ 10 ], amazake [ 11 , 12 ], shochu [ 13 ], vinegar [ 14 ], mirin [ 15 , 16 ], miso [ 17 , 18 ], and shoyu [ [19] , [20] , [21] ]. The saccharification of rice starch into glucose is critical in sake production, as this sugar is the primary carbon source for sake yeast ( Saccharomyces cerevisiae ), which converts the glucose into ethanol via alcoholic fermentation [ 22 , 23 ].…”