Elaboration and characterization of O/W cinnamon (Cinnamomum zeylanicum) and black pepper (Piper nigrum) emulsions

Essential oils of black pepper (Piper nigrum) and cinnamon (Cinnamomum zeylanicum) have shown an antimicrobial effect against disease-related pathogens and food spoilage bacteria. However, the hydrophobic nature of oils limits their use as natural preservatives within a food matrix. Therefore, the main objective of the present work was to prepare and characterise oil/water (O/W) micro- and nanoemulsions of black pepper and cinnamon essential oils elaborated by ultrasound and high-pressure homogenisation (HPH). For both methods, optically transparent systems with a particle size <100 nm and ζ-potential < −30 mV were obtained. During storage, cinnamon essential oil and blended cinnamon-pepper essential oil nanoemulsions exhibited greater physical stability compared to micro-emulsions. Furthermore, the ultrasound processed cinnamon essential oil nanoemulsion presented greater physicochemical stability and antimicrobial properties against Listeria monocytogenes and Escherichia coli than the pepper essential oil nanoemulsion. The results of this study could be useful for designing antimicrobial delivery systems for food safety and preservation.