Formation and microstructural characterization of whey protein isolate/beet pectin coacervations by laccase catalyzed cross-linking

The purpose of this study was to characterize the properties of stable and reinforced protein–polysaccharides complex coacervations firstly formed by electrostatic interaction between WPI and beet pectin, and followed by laccase cross-linking through ferulic acid present in beet pectin. The interaction of whey protein isolate (WPI, 6 g/100 ml) with beet pectin (0–0.16 g/100 ml) in aqueous solutions was studied at different pH (3–7). ζ-potential and light-scattering techniques were used to provide information about the electrical charge and aggregation of individual biopolymers and complex coacervations. Stable WPI/beet pectin complex coacervations were formed when system consisted of 6 g/100 ml WPI and 1 g/100 ml beet pectin at pH 3.5. The microstructure and viscoelastic properties of WPI and beet pectin complex coacervations in the presence of laccase (0, 100, 300 U) was also studied using FT-IR, rheology, and confocal laser scanning microscopy (CLSM) techniques. The results obtained clearly showed that laccase catalyzed cross-linking of ferulic acid present in beet pectin had a remarkable influence on the physical properties of WPI–beet pectin complex coacervations microstructure. The reinforced complex coacervations formed fine networking structures which may provide convenient means for food industry to incorporate bioactive components into food products.