Ultra-high pressure homogenization treatment combined with lysozyme for controlling Lactobacillus brevis contamination in model system

Abstract

Abstract It was studied the reduction of a population of Lactobacillus brevis in phosphate buffer by the combination of ultra-high pressure homogenization (UHPH) treatment and the use of lysozyme as antimicrobial. The minimum inhibitory concentration (MIC) of lysozyme against L. brevis was 50 mg.L − 1 . The observed inhibition was transitory and the growth curve showed that lysozyme addition was able to delay the L. brevis growth for 2 days. Lysozyme added at MIC concentration to a suspension of L. brevis caused a reduction of 1 logarithmic cycle after two hours of contact. The UHPH treatment against L. brevis resulted in a reduction of 7 log cycles at 200 MPa. Lysozyme was resistant to UHPH (200 MPa), without loss of muramidase activity or significant loss of antimicrobial power. A combined treatment was applied using 50 mg.L − 1 of lysozyme and pressure between 150 and 170 MPa; the combined effect showed a reduction of about 6 logarithmic cycles and the unaltered count of L. brevis after pressure treatment for a week, with the samples stored at room temperature (25 °C). Industrial relevance Ultra-high pressure homogenization is an alternative process for cold pasteurization that can be used to inactivate the common spoilage microorganisms of the juice and beer industry, for example, L. brevis . Combined treatment with lysozyme increases the pressure effect and, consequently, reduces the level of pressure required for treatment. The possibility of operating with lower pressures requires less robust equipment, which makes the utilization of lower-cost equipment possible.