Synergistic Bactericidal Efficacy of Combined Sanitization Strategies Against Listeria monocytogenes: Mechanistic Elucidation and Practical Validation in Prepared Salad

L. monocytogenes is a persistent pathogen in prepared salads that often survives through the viable but non-culturable (VBNC) state. To address this, a study evaluated a multi-hurdle sanitization strategy combining ultrasound (US), slightly acidic electrolyzed water (SAEW), and phenyllactic acid (PLA). This triple combined treatment exhibited a significant synergistic bactericidal effect, reducing L. monocytogenes counts below the detection limit and completely inhibiting the formation of VBNC cells. Mechanistic analysis revealed that the treatment triggered irreversible cell membrane damage, characterized by increased membrane permeability, intracellular protein leakage, and disrupted zeta potential. When applied to prepared salads, the combined method successfully extended their refrigerated shelf life (at 4 °C) to 9 days. Furthermore, this treatment effectively maintained the texture, color, and odor profile of the samples while preserving the activities of antioxidant enzymes. Overall, the US + SAEW + PLA strategy provides a highly efficient, non-thermal approach to ensuring both the microbial safety and sensory quality of prepared salads, offering a promising alternative technology for the food processing industry.