Thermosonication and inactivation of viable putative non-culturableLactobacillus acetotoleransin beer

Abstract

This work compares the inactivation by thermosonication of exponentially growing Lactobacillus acetotolerans cells with viable putative non-culturable (VPNC) cells in beer. The critical process parameters were optimised using response surface methodology using a three-factor three level Box–Behnken design. The three independent variables were volumetric power (2.7, 5.8 and 8.9 W/mL), temperature (40, 50 and 60°C) and treatment time (2, 4 and 6 minutes) with the output of log reduction in viable cell number of L. acetotolerans cells growing exponentially or in the VPNC state. The results showed that under different conditions of volumetric acoustic power–temperature–time combination, cells of L. acetotolerans in the VPNC state were more resistant to thermosonication than exponential cells. This insight will be of value to the design of appropriate thermosonication conditions to pasteurise beer and other beverages. © 2018 The Institute of Brewing & Distilling