IDENTIFICATION OF ENZYMATIC DIGESTION AND FERMENTATION RATES IN SAKE MASH USING THE EXTENDED KALMAN FILTER METHOD

Enzymic digestion and fermentation rates are identified for 19 examples of actual sake mash processes in Akita prefecture using the extended Kalman filter method. As well as the digestion and fermentation rates, their temperature coefficients are also identified so that the estimated mash processes can agree better with the actual ones. The digestion rates are about 3 percent per 100 percent of raw materials per day. The temperature coefficient of the digestion rates differs according to the kind of raw material used. The temperature coefficient is smaller in the case of using what is termed "rice suitable for making sake" than it is when using what is designated as "rice for eating". The digestion rates at the maximum temperature in sake mash processes are also lower in the case of the former. It is thus noted that mash processes with the "rice suitable for making sake" should be controlled at a lower temperature state for a longer period. The fermentation rates are about 1 percent per 100 percent of digested materials per day. The temperature coefficient of the fermentation rates does not differ with different kinds of "kobo", while the fermentation rates at the maximum temperature in sake mash processes are low, increasing in the order of Akita Hana kobo, Kyokai No. 9 kobo and kyokai no. 7 kobo. It is further noted that the fermentation process using the so-called "Ginjoh kobo" is much slower under the condition of what is known as "Ginjoh sake making".