Encapsulation of probiotics (Lactobacillus plantarum) in soyasaponin–soybean protein isolate water-in-oil-in-water (W/O/W) emulsion for improved probiotic survival in the gastrointestinal tract

In this study, soyasaponin (Ssa), corn oil, and soybean protein isolate (SPI) were used to prepare a water-in-oil-in-water (W/O/W) double emulsion system that can protect Lactobacillus plantarum (L.P) in the upper gastrointestinal tract for delivery to the small intestine and colon. Incorporating different amounts of L.P (0.1–0.6% (w/v)) in the W/O/W double emulsion caused the viscoelastic modulus and droplet size of the L.P-embedded emulsion system to change, and the emulsion system transformed from a non-Newtonian fluid to a "solid-like" gel. These results revealed that L.P encapsulation led to significantly improved stability of the W/O/W emulsion. In addition, different concentrations of L.P had different effects on the survival rate of L.P in simulated digestive fluids, and after in vitro digestion, L.P was naturally delivered from the stomach into the intestines. The optimal concentration of L.P for obtaining a stable emulsion was found to be 0.3%, and the survival rate of the encapsulated L.P in the small intestine was as high as 78.96% after 1 h. Thus, choosing an appropriate amount of L.P was crucial. The W/O/W emulsion system effectively maintained the viability of L.P and successfully delivered it to the small intestine and colon.