Synergistic effect of naringenin and mild heat for inactivation of E. coli O157:H7, S. Typhimurium, L. monocytogenes, and S. aureus in peptone water and cold brew coffee

Abstract

This study aimed to investigate the bactericidal effect of naringenin (NG), a plant-derived flavonoid, and its synergistic effect with mild heat (MH) treatment at 50 °C in peptone water (PW) and ready-to-drink cold brew coffee (RDC). Among various NG concentrations (1–20 mM), 10 mM NG resulted in the greatest inactivation for Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus. In RDC, NG + MH treatment resulted in a 5–8-log reduction in all pathogens after 10 min, except for S. aureus. In contrast, NG or MH treatment alone exhibited only marginal bactericidal effects. From inactivating mechanism analysis, lipid membrane destruction and intracellular enzyme inactivation were the key factors for pathogen inactivation. Cell membrane and enzyme dysfunctions were identified in propidium iodide (PI) uptake test, membrane potential assay, and membrane protein analysis. Furthermore, NG + MH exerted minimal influence on the quality attributes of RDC in pH, color, and total phenolic content. These results indicated that the NG + MH treatment system effectively ensured microbial safety in cold brew coffee while enhancing its nutritional value and preserving quality attributes.N