Synergistic effects of monocaprin and carvacrol against Escherichia coli O157:H7 and Salmonella Typhimurium in chicken meat preservation

Escherichia coli O157:H7 and Salmonella Typhimurium are both foodborne pathogens commonly found in contaminated chicken meat. In this study, the combined effects of monocaprin and thymol, carvacrol, citral, and cinnamaldehyde against both pathogens were investigated to evaluate their effects in chicken meat preservation. Among the combinations, only the combination of monocaprin and carvacrol exhibited distinct synergistic effects on both pathogens in vitro. This combination showed a stronger synergistic biofilm inhibition and bactericidal effect than monocaprin or carvacrol alone. SEM and TEM microscopy showed that the combined treatment synergistically damaged the morphology of E. coli O157:H7 and S. Typhimurium. DAPI/SYTOX Green double-staining, outer and inner membrane permeability, membrane potential, and reactive oxygen species (ROS) generation experiments were performed to further assess the synergistic action. Results indicated that carvacrol rapidly increased the outer membrane permeability, allowing monocaprin to enter the cell of both pathogens, and damage the plasma membrane, and monocaprin increased the ROS accumulation effect of carvacrol, resulting in cell death. Monocaprin and carvacrol also showed synergistic effect on retarding the growth of E. coli O157:H7 and S. Typhimurium in chicken breast meat during storage at 4 °C. Besides, the results of sensory evaluation, including appearance, odor, firmness and overall acceptance, showed that the combined treatment reduced deterioration of the sensory properties of chicken breast meat. These findings suggest that this combination may be used as a novel approach to the preservation of chicken meat.