Shoyu flavor components

When Japanese rice wine (sake) is kept under unsuitable conditions, it develops an off-flavor with a burnt or soy-sauce (shoyu)-like odor. Takahashi al.(12) identified the main component as sotolon before our identification, and they claimed that the sotolon concentration was between 140-430 ppb in aged sake. This concentration is much higher than the threshold value of sotolon, and its aroma character would change from sugary to herbal or curry-like. The high sotolon content in aged sake could be a reason for the off-flavor defect. The formation of sotolon in aged... 

Nunomura N., Sasaki M., Asao Y. and Yokotsuka T. (1976) Isolation and identification of 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2//)-furanone, as a flavor component in shoyu (soy sauce). Agric. Biol Chem. 40, 491-5. 

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