Effect of emulsifier and droplet size on the antibacterial properties of emulsions and emulsion‐based films containing essential oil compounds

Abstract

In this study, the physical properties and antibacterial activity of emulsions prepared through four different combinations of essential oils (EOs) (trans-cinnamaldehyde [TC] and citral) and emulsifiers (sodium caseinate and lecithin) were investigated. The results showed that the four different nanoemulsions had nanometric sizes ranging from 142.3 to 273.1 nm, exhibiting high negative zeta potential (−25.3 to −42.7 mV) at pH 7. Nanoemulsions containing TC exhibited higher antimicrobial activities against Escherichia coli and Listeria innocua than nanoemulsions containing citral irrespective of the emulsifier used. These nanoemulsions were then incorporated into low methoxyl pectin films and the obtained results showed that films containing TC stabilized by sodium caseinate had a larger inhibition zone than the one stabilized by lecithin irrespective of the EO used. Finally, the obtained results showed that nanosized emulsions were more stable than microsized ones, but no significant differences were observed concerning their antibacterial activity. Practical applications This work should be an interesting basis for developing innovative antimicrobial packaging containing nanoemulsions. The interfacial membrane that surrounds the droplets of the emulsified antimicrobial provides an additional barrier that the active agent should cross before leaving the polymer matrix of the packaging film. Thus, the release kinetics will be modified and the efficiency could be improved.