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

Abstract

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.

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

“…Sound velocity ( USV ) course over process time for (a) VPS 1 trial1 (cylindrical trial fermenter) and (b) VPS 7 trial3 (cylindrico‐conical tank); USV WME … USV as it was expected according to temperature and component concentration (Hoche et al ., ), USV US … USV determined from TOF and temperature‐dependent sound propagation path, USV US c … CO 2 corrected USV US .…”

“…Reflection coefficient, density and component mass fractions determined by the introduced sensor and the USV ‐ T ‐ ρ model for (a) VPS 1 trial1 (cylindrical trial fermenter) and (b) VPS 7 trial3 (cylindrico‐conical tank); r, reflection coefficient, c, mass fraction, rho, density; indices: l, laboratory results, US , measured via ultrasound sensor, theo, theoretical value according to laboratory reference and (Hoche et al ., ), E, ethanol, M, sugar.…”

“…Nevertheless, the existing data (Hoche et al ., ) – altogether a systematic study of 271 different combinations of maltose concentrations, ethanol concentration and temperature including 100 values of all relevant variables at each combination – still provide several opportunities to realise a sugar and ethanol estimation model. Basically, it is assumed that the main sugar type (maltose) governs the property behaviour of malt‐based sugar solutions (wort).…”

“…A detailed overview of the applied statistics is given in the evaluation of the CPPs by Hoche et al . (). The database was split into a calibration and a validation data set and each model was analysed with regard to the following presented quality indicators to evaluate the model suitability to represent the data:…”

“…In the same way, the results of Hoche et al . () show that a unique interpretation of sugar and alcohol content of sufficiently pure mixtures is possible via the USV‐ T ‐ ρ relationship, and they also clarify that the relation between USV and the two component concentrations at a certain temperature is undetermined. But, regarding the fact that only specific substrate–product combinations come into consideration during the anaerobic batch fermentation with yeast ( Saccharomyces cerevisiae ) might turn the USV‐ T combination to applicable estimation parameters.…”