Cinnamaldehyde nanoemulsions; physical stability, antibacterial properties/mechanisms, and biosafety

Cinnamaldehyde has a strong biological activity, with an obvious effect in killing foodborne pathogens. In this study, an optimal formula of cinnamaldehyde nanoemulsion (CN) was selected and characterized by mean droplet size analysis, confocal laser scanning microscopy (CLSM) and Turbiscan analysis. The results showed that the optimal formula was composed of 6% w/w cinnamaldehyde, 10% w/w surfactant EL-90 (castor oil polyoxyethylene ether), and 84% w/w deionized water. The droplet size of CN was very small, reaching 48 nm, and the droplet distribution was uniform. Also, the fluctuation of the multi light scattering spectrum of CN was very stable. It was found that CN had a strong antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to its lipophilic nature and induction of oxidative stresses. For E. coli, the minimum bactericidal concentration (MBC) was 0.5 mg mu L-1. Compared with E. coli, CN had a weak inhibitory effect on S. aureus. It was also revealed that CN had a high cyto-compatibility on L02 cells; the survival rate of the control group was 96.7%, and the total apoptosis rate was 3.25%. The survival rate of the L02 cells in the treated group with CN (0.05, 0.15, and 0.25 mu g mu L-1) was 95.6%, 95.1% and 86.3%, respectively, which reveals their high safety. The findings of this study provides an effective reference for the development of food-grade preservatives in the future.

Automated summary

Cinnamaldehyde nanoemulsion (CN) showed strong antibacterial activity against foodborne pathogens, with an optimal formula containing small droplet size and uniform distribution. It exhibited effective killing effects on Escherichia coli and Staphylococcus aureus, while maintaining high cytocompatibility with L02 cells, indicating potential as a safe food-grade preservative in the future.