Stability of citral in emulsions coated with cationic biopolymer layers.

Multilayer emulsions containing citral were prepared by the layer-by-layer deposition technique based on the electrostatic interaction between negatively charged emulsion droplets and two positively charged biopolymer coatings, chitosan (CS) and ε-polylysine (EPL). The optimum concentrations of both CS and EPL were determined through the ζ-potential and particle size measurements and were found to be 1.5 mg/mL for CS and 6 mg/mL for EPL. Quartz crystal microbalance with dissipation monitoring (QCM-D) was conducted to monitor the binding between emulsion droplets and cationic polymers, and our results proved the existence of strong interactions between emulsions and the cationic polymer coatings. The stability of citral and the production of the off-flavor compounds were analyzed by solid-phase microextraction gas chromatography (SPME-GC). The results suggested that the addition of the cationic CS interfacial layer was effective in improving the stability of citral during storage.