An expert system applied to the physiological analysis of early stage of beer fermentation.

A fuzzy expert system was applied to the knowledge analysis of yeast physiology in the early stage of beer fermentation, when the wort was aerated. We used ergosterol and glycogen concentration in the wort as a suitable marker of physiological state of the cell population. The amount of both compounds influences the rate of fermentation, cell growth and the final taste of beer. The concentrations of ergosterol and glycogen including the number of cells can not be measured immediately during the relatively short aeration period, and incomplete experimental data are therefore found in laboratory logbooks. We therefore suggested that the fuzzy relation between the directly measurable dissolved oxygen concentration and the rate of ergosterol or glycogen formation should be identified and a fuzzy expert system should be used to analyze the behavior of the yeast.