Copigment-polyelectrolyte complexes (PECs) composite systems for anthocyanin stabilization

Abstract

This study aimed to explore copigment-polyelectrolyte complexes (PECs) composite systems for simultaneous color intensification and stabilization of anthocyanins. The polysaccharide-based PECs consisting of chitosan and chondroitin sulfate were fabricated at different pHs (3.3, 4.0, and 5.0) and incorporated various copigments, including catechol (CAT), gallic acid (GA), gallic acid ethyl ester (GAEE), and (-)-epigallocatechin gallate (EGCG). We found that copigments could modulate anthocyanin loading into PECs and color quality of formulations, depending on the formulated pH and types of copigments. At pH 3.3 and 4.0, the incorporation of copigments simultaneously improved the red color and encapsulation efficiency of PECs, whereas these effects were not pronounced at pH 5.0. Stability assay demonstrated the synergistic effect of copigmentation and PECs encapsulation at pH 3.3 on protection of anthocyanin against nucleophilic attack of ascorbic acid. This phenomenon was attributed to the additional dense network created by hydrogen bonding between copigments and polysaccharides as well as the formation of hydrophobic environments inside PECs. The strongest copigmentation effect was observed for GAEE, followed by CAT, GA, and EGCG. However, the stabilizing effect of copigments was negligible or even opposite at pH 4.0 and 5.0. Our findings on pH- and copigment-dependent modulating effects should guide the design of copigment-PECs composite systems as carriers for natural colorants, such as anthocyanin, in nutraceuticals and functional foods.