Nanoemulsions of thymol and eugenol co-emulsified by lauric arginate and lecithin

• Nanoemulsions of eugenol or thymol were prepared with lauric arginate (LAE) and lecithin.
• Emulsions prepared with LAE and lecithin were less turbid than those with one surfactant.
• Nanoemulsions with LAE and lecithin showed negligible coalescence and Ostwald ripening.
• Nanoemulsions showed similar antibacterial activities as free LAE in tryptic soy broth.
• Nanoemulsions had similar anti-listerial but lower anti-E. coli O157:H7 activities than LAE in milk.

Lauric arginate (LAE) is a cationic surfactant with excellent antimicrobial activities. To incorporate essential oil components (EOCs) in aqueous systems, properties of EOC nanoemulsions prepared with a LAE and lecithin mixture were studied. The LAE–lecithin mixture resulted in stable translucent nanoemulsions of thymol and eugenol with spherical droplets smaller than 100 nm, contrasting with the turbid emulsions prepared with individual emulsifiers. Zeta-potential data suggested the formation of LAE–lecithin complexes probably through hydrophobic interaction. Negligible difference was observed for antimicrobial activities of nanoemulsions and LAE in tryptic soy broth. In 2% reduced fat milk, nanoemulsions showed similar antilisterial activities compared to free LAE in inhibiting Listeria monocytogenes, but was less effective against Escherichia coli O157:H7 than free LAE, which was correlated with the availability of LAE as observed in release kinetics. Therefore, mixing LAE with lecithin improved the physical properties of EOC nanoemulsions but did not improve antimicrobial activities, especially against Gram-negative bacteria.