Soy Protein Isolate-Chitosan Maillard Graft-Stabilized Curcumin-Loaded Emulsions for Encapsulation and Sustained Release

Abstract

Hydrophobic bioactive compounds are difficult to deliver because of poor water solubility, limited stability, and uncontrolled release. In this study, chitosan-soy protein isolate (CS-SPI) conjugates were prepared by dry-heat Maillard reaction and used as natural polymeric emulsifiers for curcumin-loaded emulsions. The highest grafting degree of 15.3% was obtained at 70 °C, 74.50% relative humidity, 96 h, and a CS:SPI mass ratio of 1:3. Compared with chitosan and CS-SPI non-covalent complex-stabilized emulsions, the CS-SPI conjugate-stabilized emulsion showed the smallest droplets (7.23 μιη) and a more uniform distribution. It maintained high encapsulation efficiency after 6 days of storage (94.28%) and suppressed burst release during simulated gastric digestion, extending curcumin release to about 72 h. These results suggest that CS-SPI conjugates improve emulsion stability and sustained-release performance.