Formation of electrostatic complexes using sodium caseinate with high‐methoxyl pectin and carboxymethyl cellulose and their application in stabilisation of curcumin

Despite many reported bioactivities of curcumin, its application is limited due to its low bioavailability, solubility and stability. Proteins have been reported to stabilise curcumin in aqueous media, and stabilisation of curcumin could be enhanced when proteins form an electrostatic complex with polysaccharides. In this study, electrostatic complexes of sodium caseinate (NaCas) were prepared using high‐methoxyl pectin (HMP and NaCas‐HMP) and carboxymethyl cellulose (CMC and NaCas‐CMC). NaCas to polysaccharide ratio of 1:2 resulted in the lowest turbidity and sedimentation. The electrostatic complexes were more stable than native NaCas against pH change and ionic strength. Binding of curcumin to NaCas and the electrostatic complexes were confirmed by UV‐vis and fluorescence spectra and Fourier transform infrared spectroscopy (FT‐IR). The electrostatic complexes showed a higher binding constant and protected curcumin better than the native NaCas. This study suggests that the electrostatic complexes may be a superior carrier to NaCas at an acidic environment.