Ultrasound-based, in-line monitoring of anaerobe yeast fermentation: model, sensor design and process application

In order to implement process analytical technology in beer manufacturing, an ultrasound-based in-line sensor was developed which is capable to determine sound velocity and density via the multiple reflection method. Based on a systematic study of the ternary system water-maltose-ethanol, two models were established to estimate the critical process parameters: sugar and ethanol mass fraction. The sound velocity-based model showed unreasonable high errors although temperature variations and deviations due to dissolved CO2 were corrected. In contrast, the sound velocity-density-temperature model provided an average root mean square error of 0.53%g/g sugar and 0.26%g/g ethanol content for the main fermentation. Method, sensor and model showed the capability to capture the process signature which may be related to product and process quality.