Detection of acoustic emission during fermentation using an electret sensor

Abstract

In this study, we focused on acoustic emission (AE) as a method for quantitative evaluation of fermentation. Since bubbling in the culture medium and detachment of the medium during fermentation are considered to be phenomena similar to corrosion, AE could be expected to be detected. Therefore, we conducted AE measurements using ECS during fermentation of yeast in sucrose solution, fermentation of yeast during sake brewing, and fermentation of sawdust in a hot bath facility, and investigated the possibility of evaluation of fermentation process using electret sensor (ECS). AE was detected during the fermentation of yeast. The peak frequency of AE detected during yeast fermentation was widely distributed. Cumulative number of AE, however, showed a strong correlation with the decrease in sugar content during fermentation, indicating the possibility of quantitative evaluation of the fermentation state by AE measurement if a time lag is considered. In the measurement of AE from the fermentation of sake malt, a large amount of AE was detected from the lower part of the tank immediately after brewing, and the number of AE gradually increased in the upper part of the tank. These AE measurements suggested that even in top fermentation, the initial fermentation may occur in the lower part of the tank. In the fermentation and warm bath facility, AE during fermentation could be detected even in powdered media. Although the durability of the ECS needs to be improved under high temperature and high humidity conditions, it is expected to be able to monitor the fermentation process better than temperature measurements.