Spectral analysis of the impact of various polysaccharides on the entrapment of curcumin by whey protein isolate

This study employed spectroscopic methods to investigate the interactions between whey protein isolate/polysaccharide (WPI/PS) complexes and curcumin. The UV–visible absorption spectra and fluorescence spectra indicated effective binding of curcumin to WPI and its complexes with chitosan (CS), carrageenan (CAR) and carboxymethylcellulose (CMC). This binding significantly increased the UV–visible absorption intensity of curcumin, with its maximum fluorescence emission peak shifting from 552 nm to 510 nm. Fluorescence kinetics analysis suggested that the binding constant between curcumin and WPI/CS complexes reached a maximum of 4.0794 × 10 5  L/mol. Circular dichroism and infrared spectroscopy indicated that the higher binding constant was attributed to the binding of CS, which reduced the α-helix structure and exposed hydrophobic groups of WPI. Curcumin entrapped by WPI/CS complexes showed the highest DPPH radical scavenging activities, UV and thermal stability. In summary, the WPI/CS complexes effectively protect curcumin against various environmental stresses and maintain its antioxidant properties.