Fermentation process monitoring of Japanese sake by dielectric measurement

During the fermentation of an alcoholic beverage, the water/alcohol ratio changes with time, and it is expected that the process can be monitored by the dielectric measurement. We have developed a complex permittivity measurement system of a liquid or gel specimen of 1 mm³ order volume by using a waveguide and a capillary and observed complex permittivity of a Japanese alcoholic beverage sake specimens extracted during the fermentation process. Experimental results in the frequency range of micro- and milli-metre wave suggested that the peak shift in the dielectric loss indicates the increase of alcohol content, and may have relationship with aroma contents of sake. This work will contribute to the on-line monitoring of fermentation process of various food products.