Effects of Chitosan Addition on In Vitro Digestibility of Protein-Coated Lipid Droplets

In this study, we characterized the protein-coated lipid droplets with/without cationic polysaccharide under in vitro oral, gastric, and small intestinal conditions. The effects of chitosan (CHI) addition on the mean particle diameter, zeta-potential, micro-structure, rheological properties, microstructure and lipid digestion of emulsions containing whey protein isolate (WPI) at pH 6.5 or 3.0 were investigated. At pH 6.5, the protein charge was negative, strong electrostatic attraction between the oppositely charged CHI and WPI led to the increase in emulsion viscosity and size, while at pH 3.0, both CHI and WPI were positively charged, CHI molecules could not be attracted onto the surface of positively charged protein-coated droplets, and it has weaker effect on the interfacial properties of emulsions. The results showed that WPI–CHI electrostatic interactions played an important role on the physical property, microstructure and lipid digestion of protein-coated lipid droplets. In the simulated gastrointestinal model, the structures were more stable and the lipid digestion rates decreased significantly in WPI–CHI stabilized emulsions compared to WPI-stabilized emulsions. These results suggest that mixed emulsions can be used to design delivery systems for controlling the physicochemical properties of bioactive lipophilic compounds in the food and pharmaceutical industries.