Study on the characteristics of W1/O/W2 emulsion delivery system stabilized by soybean protein isolate/(−)-epigallocatechin gallate/exopolysaccharides complex

In this study, a ternary complex was prepared using soybean protein isolate (SPI), (−)-epigallocatechin gallate (EGCG), and exopolysaccharides (EPS) produced by Lacticplantibacillus plantarum A114. It systematically evaluated the stabilization on W 1 /O/W 2 emulsions and protective effects on the encapsulated L. plantarum A114 upon long-term storage, pasteurization, and in vitro simulated gastrointestinal digestion. The physical stability and microstructure of the emulsions were analyzed by particle size, ζ-potential, creaming index, and rheological behaviors. The survival rate of the strain was determined by flow cytometry during 28-day of storage (4 °C), after pasteurization and in vitro simulated gastrointestinal digestion to assess their protective efficacy. The results showed that compared with the emulsions stabilized by native SPI, (EGCG-SPI)-EPS stabilized emulsion was with the smallest particle size and the lowest degree of emulsion separation during 28-day storage period, and the survival rate of L. plantarum A114 increased by 1.23 times during storage, 0.88 times after pasteurization, and 1.45 times after in vitro simulated gastrointestinal digestion. These results suggested that the emulsions stabilized by (EGCG-SPI)-EPS complex exhibited superior physical stability and protective effects on encapsulated strains. In addition, this study further observed the microstructure of the strains encapsulated in the emulsion stabilized by different complex using confocal laser scanning microscopy (CLSM). The results indicated that the introduction of EGCG and EPS could construct a composite interface layer with stronger physical barriers and antioxidant protection through the synergistic effect with SPI, thereby significantly improving the stability of W 1 /O/W 2 emulsion system and the protective effect on L. plantarum A114. To sum up, the (EGCG-SPI)-EPS ternary complex presented the best protective synergistic effect and was an extremely promising targeted delivery system for probiotics. This study has important guiding significance for the development of probiotic functional foods with high survival rates.