Effect of enzymatically produced tuna oil acylglycerol on the characteristics of gelatin O/W emulsion during microencapsulation using complex coacervation

Complex coacervation is an effective process to deliver ingredients for functional food applications. A stable oil-in-water (O/W) emulsion with desired characteristics significantly affects the complex coacervation and the quality of final microcapsules. In this study, tuna oil was partially hydrolyzed using TL100 and ADL lipases to produce acylglycerols TL100-AC and ADL-AC, respectively. These lipids were subsequently stabilized by gelatin in the O/W emulsion, followed by the complex coacervation with sodium hexametaphosphate. The effect of lipids on emulsion properties, such as interfacial properties, rheological properties, protein conformation and microcapsule formation during complex coacervation, was investigated. Compared with tuna oil-based emulsion, acylglycerol-based ones exhibited reduced droplet size (<600 nm), zeta-potential, interfacial tension (<8 mN/m) and interfacial protein concentration (about 80%). The gelatin in the acylglycerol-based emulsions had reduced beta-sheet and slightly increased random coil contents. Compared with the one containing tuna oil, the ones containing acylglycerol possessed higher complex coacervation yields (>75%). These changes were beneficial to the formation of coagulant and flocculant so that gelatin-stabilized acylglycerol-based O/W emulsion resulted in improved complex coacervation between gelatin and sodium hexametaphosphate. This study provides a scientific basis for designing specific gelatin O/W emulsions and microencapsulation for the stabilization and delivery of omega-3 fatty acids.