A pH-sensitive W/O/W emulsion-bound carboxymethyl chitosan-alginate hydrogel bead system through the Maillard reaction for probiotics intestine-targeted delivery

Although various types of water-oil-water (W/O/W) double emulsions were explored and applied for intestine-targeted delivery, further research was needed to protect probiotics from the gastrointestinal barrier. Thus, this study aimed to encapsulate probiotics through a gel bead-bound emulsion system to improve the ability to resist the external environment, and sustained release of probiotics. In this study, sodium caseinate (NaCas)-κCarrageenan (κCar) by Maillard reaction was prepared as the external emulsifier. Then emulsions combined with sodium alginate (SA)-carboxymethyl chitosan (CMCS) hydrogel shells to encapsulate the internal aqueous phase of L. rhamnosus 76 (LR76) for intestinal targeted delivery. The gel shell assembled with SA and CMCS in a citric acid solution was demonstrated by the combination of hydrogen bonding (protonated carboxyl –COOH and –OH) and electrostatic interactions (-COO- and –NH3+) through IR spectroscopy. The system also showed excellent pH responsiveness and good thermal stability. The in vitro gastrointestinal simulated experiment showed the release of probiotics was managed through their swelling behavior with survival rate reaching 90.69 ± 0.04%. The slow-release properties of gel beads were also verified in vivo, which could be applicable in animals for further healthy effects. The 16S rRNA analysis revealed a high relative abundance of Lactobacillus from the Firmicutes, highest up to 88.08%. The above results suggested that the hydrogel bead system could be used as carriers for encapsulating probiotics, which provided a theoretical basis for the future application of probiotics in the food and pharmaceutical industries.