抄録
Apparent extract concentration is a very important variable in beer fermentation processes, which indicates the fermentation degree according to the change of the total sugar concentration and the produced ethanol concentration. On the other hand, volatile compounds which are formed as by-products in yeast metabolism would cause undesirable flavor when their concentrations are over threshold values. The objective in this study is developing a system to control apparent extract concentration which should be decreased below the target value at the fixed time under the constraint for admissible amounts of production of volatile compounds. For this purpose, a sophisticated control strategy, which was developed, composed of the state estimation step of the fermentation degree and the determination step of brewing temperature profile for a simultaneous control of apparent extract and volatile compounds concentrations. For the estimation of apparent extract and volatile compounds concentrations, CO2 concentration in the exhaust gas was utilized. Temperature profiles were searched and determined by feeding back the information of fermentative activity of the yeast inoculated, which will bring the brewing process to the target value of apparent extract concentration and fewer amounts of volatile compounds than the threshold ones at the fixed time. The developed feedback control of brewing temperature profile was successfully applied to the brewing process, and apparent extract and volatile compounds concentrations at the fixed time have satisfied the desirable conditions.
