Pickering emulsion hydrogel as a promising food delivery system: Synergistic effects of chitosan Pickering emulsifier and alginate matrix on hydrogel stability and emulsion delivery

Application of Pickering emulsions in food systems is often limited by their compatibility and their effectiveness in delivering food actives. In this work, we developed a model Pickering emulsion hydrogel system using chitosan as the Pickering emulsifier and Ca-alginate hydrogel beads as the carrier. The synergistic effects between the two materials on the physicochemical stability of the hydrogel formed and the delivery of the immobilized emulsions were investigated. The Ca-alginate hydrogel was found to efficiently immobilize the chitosan-stabilized Pickering emulsions with an immobilization efficiency exceeding 99%, even at a high oil loading of 70% v/v and a chitosan concentration as low as 0.1% w/v. Both the adsorbed chitosan particles on the oil-water interfaces and excess non-adsorbed chitosan particles interacted electrostatically with the alginate matrices to enhance the hydrogel network strength. In comparison to the hydrogel beads containing Tween-80-stabilized emulsions and non-stabilized emulsion, the hydrogels containing Pickering emulsion were significantly more stable under high osmotic pressure and in the presence of low concentrations of destabilizing ions. In the in vitro studies, the Ca-alginate matrices prevented the release of the emulsions at pH 1.2. The emulsions were fully released at pH 7.4 and the release rate was found to be influenced by the concentration of chitosan particles. Interestingly, the chitosan particles remained adsorbed on the oil droplets upon release. This work demonstrates that the alginate-based chitosan-stabilized Pickering emulsion hydrogel system could be an effective immobilization and delivery system for food applications.