Critical process parameter of alcoholic yeast fermentation: Speed of sound and density in the temperature range 5-30 °C

Summary: To implement process analytical technology in beer manufacturing, a systematic study of the ternary system water-maltose-ethanol with respect to the critical process parameters, density, speed of sound and temperature was performed. The results are presented in the form of temperature and mass-fraction-dependent polynomial expressions. On average, a variation of 1% mass fraction maltose results in variations of 3.548 m s^-1 ultrasound velocity and 0.0041 g cm^-3 density, whereas in the case of ethanol, the variations are 8.060 m s^-1 and -0.0018 g cm^-3. Indeed, the relations are strictly nonlinear. Nevertheless, the determined data show the feasibility to predict online, concentrations of multicomponent mixtures of polar liquids by determining density and ultrasound velocity. With <0.1% error, the measured data show excellent agreement with reference data of binary mixtures as given in literature.