Changes in color of Japanese sakes brewed in Hiroshima Prefecture were monitored under fluorescent light for 6 months. Nine samples of regular type sakes in brown bottles were under a ceiling lamp at room temperature, and twelve samples of Junmai type sakes -- seven samples in green bottles and five samples in brown bottles -- were directly lighted with fluorescent lamps at 10~15℃ in a refrigerator. None of regular type sakes showed any distinct increase in color during the storage. On the other hand, some samples of Junmai type sakes clearly showed an increase in color. None of the Junmai type sakes in brown bottles showed much increase in color. For the Junmai type sakes in green bottles, a difference could be observed in the extent of the increase of the color between the samples. It was found that there is a negative correlation between the amount of increase for the color during storage and the Fe ion content of the Junmai type sakes in green bottles. With experiments of adding Fe ion to a Japanese sake of the Junmai type, it could be observed that Japanese sakes containing more Fe ion showed less increase in color. It was suggested that Fe ion might reduce the increase in color of some Japanese sakes under fluorescent light, although it was well known that Fe ion itself causes a coloring of Japanese sakes after reacting with deferriferrichrysin..
In this study, we examined the current production methods and the aroma characteristics of aochu, which is a kind of shochu made on Aogashima Island. It was confirmed from a field survey that there were eight aochu manufacturers. Five of them made koji by individually, while the rest jointly made koji. The preparation of moromi, distillation and bottling were done in one place. Some manufacturers inoculated the steamed materials with tane-koji and tomo-koji while others used the leaves of Asplenium antiquum Makino and utilized wild microorganisms. One manufacturer added cultured yeast to the moromi. The aroma characteristics of twelve samples of aochu and six samples of control-shochu produced in Kyushu were examined. The acidity, ultraviolet absorption, and thiobarbitur acid value in aochu were higher than those of the control-shochu. Consequently, 69 aroma components were determined in the GC-MS analysis. When compared with the control, ethyl isobutyrate, ethyl isovalerate, ethyl benzoate, isovaleraldehyde, 2-methylbutylaldehyde, isovaleraldehyde, pentanal, hexanal, heptanal, 2-octenal, benzaldehyde, 2-nonenal, hexanol, 1-octen-3-ol, caproic acid, caprylic acid, capric acid, furfural and DMTS were higher in aochu. Finally, the principal component analysis performed on the 69 quantified aroma components found that clusters were formed for each koji making method. Sensory evaluation revealed that the characteristic aromas of aochu were “grassy” and “a sour smell.”