1989 Volume 36 Issue 3 Pages 237-244
The role of floating rice koji in the manufacture of pot vinegar was investigated using the mash prepared on an industrial scale at Fukuyama, Kagoshima Prefecture. The results were as follows: (1) Effects of the addition of floating rice koji: without addition of floating rice koji, alcohol fermentation occurred significantly at the early stage and delayed the start of acetic acid fermentation, resulting in the prolongation of the fermentation period. These results revealed that surplus alcohol content hindered acetic acid fermentation even in the presence of acetic acid bacteria. (2) Effects on the formation of organic acids except acetic acid: lactic acid was the most dominant in both samples. The amount of lactic acid produced was high in the pot vinegar added with floating rice koji. The other acids detected were succinic, pyroglutamic, pyruvic and malic acids. (3) Effects of the time of adding floating rice koji: delayed addition of floating rice koji onto the mash caused higher level of alcohol production, resulting in the reduction of acetic acid fermentation. (4) Effect of the addition of starters including yeast immediately after the mash preparation: addition of a high inoculum size of yeast cells resulted in a high production of alcohol and hindered the acetic acid fermentation. Addition of acetic acid bacteria after alcohol fermentation without the addition of yeast showed no significant difference from the sample without the addition of acetic acid bacteria. From these results, it was revealed that addition of floating rice koji immediately after the preparation of mash in the manufacture of pot vinegar, played an important role to help smooth acetic acid fermentation after alcohol fermentation.
