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A water-in-oil-in-water (W/O/W) emulsion for the encapsulation of salidroside (Sal) was constructed. This study aimed to detect the impact of whey protein isolate (WPI) on the microstructure and stability of Sal W/O/W emulsion, which was prepared by two-step emulsification. First, Sal and sodium alginate (SA) were added to the inner water phase, and polyglycerol polyricinoleate (PGPR) was added to the oil phase to prepare a water-in-oil (W/O) emulsion. Second, different concentrations of WPI were added to the outer water phase containing SA to prepare a Sal W/O/W emulsion. The microstructure, stability, moisture distribution, rheological properties, and encapsulation efficiency of Sal were detected. The results showed that the particle size and the size distribution range became smaller and narrower with increasing WPI concentration. When the concentration of WPI was greater than 2%, the double-layer structure remained stable over 28 days of storage at 4 °C. Moreover, when the WPI concentration reached 4%, the entrapment efficiency of Sal was the highest. These results indicated that the optimum concentration of WPI was 4%.
Zhang et al. (Wed,) studied this question.