Antimicrobial activity and chemical stability of cinnamon oil in oil-in-water nanoemulsions fabricated using the phase inversion temperature method

The water-dispersibility and antimicrobial activity of cinnamon oil is enhanced by encapsulating it within oil-inwater nanoemulsions. This study investigated the impact of oil phase composition on the minimum inhibitory concentration (MIC) of cinnamon oil nanoemulsions against Escherichia coli, Salmonella enterica serovar Typhimurium (S. Typhimurium), Staphylococcus aureus and Vibrio parahaemolyticus. The nanoemulsions were fabricated using the phase inversion temperature (PIT) method, which simply involves heating a mixture of surfactant, oil, and water about the PIT and then quench cooling with stirring. The antimicrobial activity of cinnamon oil is largely due to cinnamaldehyde, which is highly susceptible to chemical degradation. For this reason, the decrease in cinnamaldehyde content and increase in a major reaction product (benzaldehyde) were measured in the cinnamon oil nanoemulsions during storage. The antimicrobial activity of cinnamon oil nanoemulsions increased (lower MICs) as the droplet size decreased. Cinnamaldehyde was degraded during emulsification and after storage for 31 days. These results have important implications for the improvement of the antimicrobial activity and stability of encapsulated cinnamon oil using nanoemulsion-based delivery systems.