Preparation and characterization of an antimicrobial bilayer nanoemulsion encapsulated with eugenol/citral and its application in strawberry preservation

In this study, we aimed to prepare an eugenol/citral emulsion with desirable physicochemical properties and antimicrobial activity for use in strawberries preservation. A bilayer emulsion containing citral and eugenol was prepared based on the interactions between whey protein isolate and chitosan. Various parameters were optimized to obtain an antimicrobial emulsion with optimal physical and chemical properties. The bilayer emulsion consisted of 1.0% v/v oil mixture of eugenol and citral, 0.7% v/v whey protein, and 0.3% v/v chitosan. The appearance, structure, physicochemical properties, and antimicrobial activity of the emulsion were determined. Compared to the single-layer emulsion, the pale-yellow bilayer emulsion exhibited a shear-thinning fluid with good stability. The bilayer emulsion displayed good antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Aspergillus niger, with minimal inhibitory concentrations of 25.6, 12.8, and 40 μL/mL, respectively. The emulsion also exhibited good strawberries preservation performance. Overall, this study provides a valuable candidate for fruit-preservation applications.