Imine-bond reinforced double interface in water-in-oil-in-water emulsions and application on Lactobacillus plantarum encapsulation

Water-in-oil-in-water (W/O/W) emulsions are kind of promising vehicles for delivering hydrophilic and hydrophobic components. In this study, the double interfaces of W/O/W emulsion was modified to improve their properties. Specifically, in situ dynamic imine chemistry was used to crosslink the interfaces in W/O/W emulsions. W/O/W emulsions were prepared that contained whey proteins in the inner and outer aqueous phases and polyglyceryl polyricinoleate (PGPR), a hydrophobic emulsifier, in the oil phase. Aldehyde oils were added to the oil phase of the emulsions to chemically react with the proteins in both the inner and outer water phases. The stability, interfacial property and permeability of W/OW emulsions were characterized using microscopy observation, tensiometer and diffusion extent determination. Then, the gastrointestinal protection and delivery of probiotics in W/O/W emulsion was determined. The results showed that the modified W/O/W emulsions possessed high storage stability. The diffusion of Rhodamine B and hydrogen ions between the internal and external aqueous phases was retarded after cinnamaldehyde interfacial modification. Atomic force microscopy images, interfacial rheology analysis and chemical composition analysis confirmed the interaction occurrence between the lipophilic aldehyde and whey protein. After the optimization of aldehyde oils, probiotics encapsulated in W/O/W emulsion exhibited enhanced cell viability during long-term storage and after going through gastric digestion site. Overall, our results provide useful information that may facilitate the design of W/O/W emulsions that can protect probiotics from harsh environments.