The Effect of High Pressure on Levilactobacillus brevis in Beer—Inactivation and Sublethal Injury

Abstract

Beer, with its low pH, presence of hop acids, alcohol content, and limited nutrient availability, presents a hostile environment for most bacteria. However, Levilactobacillus brevis remains a significant spoilage organism in the brewing industry. This study examines the impact of high hydrostatic pressure (HHP) on the inactivation and sublethal injury of Lb. brevis KKP 3574 in beer and wort. The results indicate that applying HHP at 400 MPa for 5 min effectively inactivates Lb. brevis, achieving up to a 7 log CFU/mL reduction in bacterial counts in beer, with no detectable sublethal injuries in beer samples. In contrast, in 10% wort, a sublethal injury level of 1.1 log CFU/mL was observed following the same HHP treatment. Furthermore, this study reveals a differential response of Lb. brevis cells depending on their growth phase; cells in the logarithmic growth phase are more susceptible to HHP, showing greater reduction in viability compared to those in the stationary phase. The survival dynamics of sublethally injured cells during refrigerated storage are also explored, with no regeneration observed in beer samples treated at pressures of 400 MPa or higher. These findings underscore the potential of HHP as a robust method for enhancing the microbiological safety and stability of beer while minimizing the risk of spoilage due to sublethally injured bacterial cells. This study provides crucial insights into optimizing HHP parameters to ensure product quality in the brewing industry.