Zhang H, Dudley EG, Harte F
Applied Environmental Microbiology, 2017
In this study, the effect of individual lecithin phospholipids on the antimicrobial properties of eugenol against E. coli C600 was investigated. We tested five major phospholipids common in soy or egg lecithin (DPPC, DSPC, DPPE, DPPA and DPPS) and one synthetic cationic phospholipid (EPC 18:0). Among six phospholipids, DPPC, DSPC, DPPE, DPPA, and the cationic 18:0 EPC showed critical synergistic concentrations that significantly improve the inactivation effect of eugenol against E. coli after 30 min of exposure. At the critical synergistic concentration, an additional ca. 0.4-1.9 log reduction (ca 0.66-2.17 log CFU/mL reduction) in microbial population was observed when compared to eugenol-only (control) treatments (ca 0.25 log reduction). In all cases, increasing the phospholipid amount above the critical synergistic concentration (different for each phospholipid) resulted in antimicrobial properties similar to eugenol-only (control) treatments. DPPS did not affect the antimicrobial properties of eugenol at the tested concentrations. The critical synergistic concentration of phospholipids was correlated to their critical micelle concentrations (CMC).
Essential oils (EOs) are naturally occurring antimicrobials, with limited use in food due to their hydrophobicity and strong aroma. Lecithin is used as a natural emulsifier to stabilize EOs in aqueous systems. We previously demonstrated that within a narrow critical concentration window, lecithin can synergistically enhance the antimicrobial properties of eugenol. Since lecithin is a mixture of different phospholipids, we aimed to identify which phospholipids are crucial for the observed synergistic effect. This research studies the bioactivity of lecithin phospholipids, contributing to a rational design when using lecithin to effectively control foodborne pathogens in foods.
Zhang H, Dudley EG, Harte F. Critical synergistic concentration of lecithin phospholipids improve the antimicrobial activity of eugenol against Escherichia coli. Appl Environ Microbiol. 2017 Aug 25. pii: AEM.01583-17. doi: 10.1128/AEM.01583-17.