Studies on the acetic acid bacteria and their utilization

(part 4) Application of diethylpyrocarbonate as a bactericide (DEPC) for vinegar production

Abstract

In order to utilize diethylpyrocarbonate (DEPC) for vinegar production, following experiments were carried out.
DEPC was used for pasteurization of fermenting materials of vinegar, together with acetic acid. When 25ppm DEPC and 0.5% acetic acid were used at the same time, it was possible to kill microorganisms existed in the sake cake extraction as much as 10⁶/ml. When the materials were sterilized by both DEPC and acetic acid, the batch and semi continuous fermentations progressed satisfactorily.
In order to repair an abnormaly fermenting moromi and to keep some extract in the fermented moromi, DEPC was applied to stop the fermentation at an intermediate period. The fermentation, was stopped by addition of 100 ppm DEPC at the strongly fermenting period, addition of 50 ppm at the early or later period of the fermentation was enongh. However, addition of 300 ppm DEPC was, needed to stop the fermentation of the moromi containing more living cells as in case of shaked culture.
DEPC was decomposed completely in vinegar before eight hours, when added as much as 200 ppm.
When the DEPC was added to fermenting materials containing alcohol, diethylcarbonate (DC) occured in the moromi mash. DC hindered the acid formation in the moromi-mash at an early period but did not at the later period.