Encapsulation of Citral in Edible Films and Coatings: Nanoemulsions vs. Coarse Emulsions

Nanoemulsions are increasingly used for encapsulation of active compounds in the food industry, especially in liquid food products. Employing nanoemulsions in edible coatings for the delivery of active agents to solid food is less explored. In this paper, nanoemulsified edible coatings were employed for the delivery of citral, a natural aroma compound that also possesses antimicrobial properties. Two polysaccharides, chitosan and carboxymethyl cellulose (CMC) were used as the carrying matrices for citral. Optimal conditions for a formation of active edible films and coatings were found. The stability, physical and mechanical properties, morphology and biological activity of the nanoemulsified edible films and coatings were studied and compared with the films and coatings that contain coarse emulsions of citral. The nanoemulsified films showed lower water vapor permeability (WVP), better elasticity and higher Young`s modulus values compared to that of films with coarse emulsions. In addition, E-SEM images of the nanoemulsified films showed a more organized and dense morphology compared to that of coarse-emulsified films. When applied to fresh-cut melons, among all the treatments, the nanoemulsified coatings offered superior antimicrobial protection and provided the coated fruit with excellent appearance.

According to microbiological studies, coatings that contained 1.6% and 2.4% v/v citral nanoemulsions, significantly reduced bacterial, yeast and molds counts, up to 5 log ratio, in comparison with untreated fruit.

The potential of nanoemulsification approach for encapsulation and delivery of citral in edible films and coatings was demonstrated. This approach could be utilized for delivery of additional natural agents and formation of other types of active edible films and coatings.