Disinfection of Bacillus cereus biofilms on leafy green vegetables with slightly acidic electrolyzed water, ultrasound and mild heat

Abstract

This study aims to examine the disinfection kinetics of slightly acidic electrolyzed water (SAEW) with mild heat and ultrasound on Bacillus cereus biofilms on green leaf surfaces. Biofilms of two B. cereus reference strains (ATCC 10987 and ATCC 14579) were grown on spinach, beet and lettuce leaves. Biofilm formation was quantified using crystal violet (CV) assays and cell enumeration. Established biofilms were treated with SAEW with heat (60 °C) and ultrasound, and the surviving populations were measured. Obtained inactivation kinetics data was determined by Weibull model. Based on the CV assay, both strains formed biofilms on leaves. During disinfection, SAEW with 80 mg/L treatment for 15 min resulted in a reduction of ~3.0 and ~3.4 log CFU/cm2 for ATCC 10987 and ATCC 14579, respectively. A combination of SAEW with mild heat and ultrasound showed additional reductions for both of the strains, and the TR (4 log/cm2 reduction) values ± 10.32 min were obtained for the ATCC 10987 biofilms. These data suggest that SAEW with ultrasound and mild heat may provide better cleaning strategies to remove B. cereus biofilms from green leaves.