Gel properties of rice proteins-pectin composite and the delivery potential for curcumin: Based on different concentrations and the degree of esterification of pectin

Abstract

The effects of pectin concentrations and esterification degree (DE) on the gelling properties of Rice proteins (RPs)-pectin composite gels were investigated. And the encapsulation characteristics and in vitro curcumin release ability of composite gels were assessed. The concentration gradient was 0.5%, 1.0%, 1.5% and 2.0%, the DE gradient was 35%, 60% and 75%. It was found that pectin increased sol system net charge and induced the disaggregation of large protein aggregates. The intermolecular electrostatic repulsion plays a critical role in it. Pectin interacted with RPs via mainly hydrogen-bonding and attached itself to the surface of RPs. Increasing the viscoelastic and stability of RPs-pectin composite sols. The inclusion of DE-35% pectin at a concentration of 1.5% reduced the content of α-helix and increased β-sheet and β-turn, resulted in superior gel microstructure and water holding capacity. Further studies revealed that the composite gels, formulated with 1.5% concentration of DE-35% pectin, displayed excellent curcumin encapsulation efficiency, loading capacity, and cumulative release rate. Its curcumin releasing behavior in simulated colonic fluid followed non-Fickian diffusion mechanism and could effectively deliver it to colon.