Empirical Kinetic Modelling of High-Temperature Vacuum Fermentation for Low-Alcohol Beer Production

Abstract

This study investigates the production of low-alcohol beer (LAB) through simultaneous fermentation and ethanol stripping using a custom-instrumented lab-scale system. Fermentation was conducted at an elevated temperature (40 °C) under vacuum pressure (~200 mbar) to facilitate continuous ethanol evaporation, addressing the rising consumer demand for high-quality LAB (0.5% to 1.2% v/v). A robust empirical kinetic model, based on a second-order polynomial, was developed to predict the time-dependent decay of the wort's relative density. These real-time density predictions were successfully integrated with highly validated linear correlations to determine instantaneous real extract and alcohol by volume (ABV) levels. The process demonstrated high efficiency: high-gravity wort (~18 °Brix) yielded a final beer with 1.9% ABV under vacuum conditions, representing a significant reduction from the 7.5% ABV observed in atmospheric control runs. Subsequent dilution of the vacuum-fermented base easily achieved the target low-alcohol concentration of 1.2 ± 0.5% (v/v). These results confirm the technical feasibility of this integrated approach and establish a predictive modelling framework for the precise, high-temperature vacuum production of low-alcohol beer.