Incorporation of antimicrobial nanoemulsions into complex foods: a case study in an apple juice-based beverage

Despite the proven antioxidant and antimicrobial efficiency of nanoemulsions as carriers of essential oils, there is scarce research on their behavior once incorporated into complex food matrices. In the current work, lemongrass or mandarin essential oil (LEO or MEO) nanoemulsions were formulated using three different continuous phases (water, an apple juice model and an apple juice-based beverage). Droplet size, ζ-potential, colloidal stability as well as the antioxidant and antimicrobial activity were studied. The increase in the complexity of the continuous phase promoted the formation of nanoemulsions with smaller sizes. Consequently, creaming phenomena was prevented in complex systems. Moreover, nanoemulsions formulated using the apple juice-based beverage presented a high antioxidant activity, with values of up to 400 mg Eq. Trolox/mL, probably due to the presence of polyphenols. Nevertheless, nanoemulsions presented slower and lower inactivation kinetics at increasing complexity of the continuous phase, which may be related to the ability of sugars to protect cell damage. This work evidenced that antimicrobial nanoemulsions within complex food matrices leads to higher colloidal stability and antioxidant activity, but lower bactericidal activity than nanoemulsions alone. Hence, it provides valuable information for the design of complex foods with nanoemulsions as delivery systems of functional ingredients.

This study was supported by the Ministerio de Economía y Competitividad throughout the project AGL2018-65975-R (Fondo Europeo de Desarrollo Regional (FEDER) and Ministerio de Economía y Competitividad). Anna Molet-Rodríguez and Ana Turmo-Ibarz thank the University of Lleida for their pre-doctoral fellow-ship. Laura Salvia-Trujillo thanks the ‘Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya’ for the Beatriu de Pinós post-doctoral grant (BdP2016 00336).