Characterisation and food application of curcumin bound to sodium caseinate–polysaccharide electrostatic complexes

Abstract

Summary Electrostatic complexes between sodium caseinate (NaCas) and high‐methoxyl pectin ( HMP ) or carboxymethyl cellulose ( CMC ) were used to stabilise curcumin in this study. Effect of pH on the characteristics of the complex was evaluated, finding pH 4 was optimum. Zeta potential of NaCas‐ CMC (−33.59) was larger than that of NaCas‐ HMP (−22.19) at pH 4, implying higher colloidal stability. The complexes protected curcumin from heat treatment, and antioxidant activity of curcumin bound to the complexes was similar to that of native curcumin. Incorporation of sucrose partially prevented freeze drying‐induced aggregation of the complex, especially for NaCas‐ HMP . In a model beverage, curcumin bound to the complexes showed higher colour stability. In vitro bioaccessibility of curcumin bound to NaCas‐ HMP (53.0%) and NaCas‐ CMC (51.6%) was higher than the native curcumin (21.4%). This study suggests that curcumin bound to the complexes, especially NaCas‐ HMP ‐bound curcumin may be used as a potential food colourant where transparency is needed.