Insights into Pathogen Inactivation and Shelf-Life Extension of Strawberries via Combined Ultrasound and Levulinic Acid Treatment

Abstract

This study investigated the bactericidal effects of levulinic acid (LVA) and ultrasound against Listeria monocytogenes and analysed its metabolic response posttreatment via nuclear magnetic resonance (NMR) spectroscopy. The results demonstrated that combined LVA and ultrasound treatment significantly affected amino acid metabolism, energy metabolism, and osmotic and oxidative stress defense mechanisms in L. monocytogenes. This finding was consistent with the results of the reactive oxygen species (ROS) and malondialdehyde (MDA) assays, which confirmed that the combined treatment intensified oxidative stress and lipid peroxidation, leading to disruption of membrane integrity. To assess the broader antimicrobial efficacy of this combination and its application potential in food systems, tests were conducted using Escherichia coli (ATCC 25922), E. coli O157:H7 (ATCC 35150), Salmonella Typhimurium (ATCC 14028), S. Enteritidis (ATCC 13076), MS2 (E. coli bacteriophage 15597-B1TM), and Tulane virus on fresh strawberries. Additionally, the application of ultrasound and LVA improved the physicochemical quality of strawberries during storage and significantly enhanced their antioxidant capacity. This study highlights the potential of this combined treatment approach as a promising disinfection and preservation method for fresh produce treatment.