Combined treatment of nut by-product extracts and peracetic acid against Listeria monocytogenes on red mustard and kale leaves

Abstract

In this study, the antibacterial activities of nut by-product extracts (NBE), such as peanut skin or hull and walnut shell, against Listeria monocytogenes were examined. The applicability of a combined treatment using NBE and peracetic acid (PAA) for washing fresh-cut red mustard and kale leaves was also evaluated. Minimum inhibitory concentration and minimum bactericidal concentration tests indicated antimicrobial activities of NBE against L. monocytogenes. In addition, intracellular compound leakage and scanning electron microscopy images revealed that NBE caused bacterial cell death by disrupting cell wall and membrane permeability. Antibacterial activities against L. monocytogenes on red mustard and kale leaves established the effectiveness of an NBE treatment combined with PAA regardless of the fresh-cut produce type. In particular, the combination of 0.1% peanut skin extract and 80 mg/L PAA showed 1.6–1.9 log reductions in L. monocytogenes populations on vegetable leaves compared to water washing, showing higher microbial reduction than 200 mg/L of sodium hypochlorite washing. Furthermore, the combined treatment did not change the physicochemical properties of red mustard and kale leaves during storage. These results suggest that NBE is a good antimicrobial agent against L. monocytogenes and that a combined washing treatment with PAA is potentially efficient for disinfecting fresh-cut vegetables.