Formation of concentrated particles composed of oppositely charged biopolymers for food applications – impact of processing conditions

Abstract

Abstract Associative complexation approaches are promising tools to generate mixed biopolymer particles with tailor-made physicochemical properties. However, association of oppositely charged biopolymers typically occurs under acidic conditions and low biopolymer concentrations. The present study aims to investigate intrinsic and extrinsic parameters to generate concentrated biopolymer dispersions which could be utilized as structuring agents in food matrices. We therefore utilized a multistep procedure. Firstly, solutions of whey protein isolate (WPI) and pectins with different degrees of esterification (DE) were mixed under neutral conditions at various ratios (WPI:Pectin 1:2, 1:1, 2:1, 5:1, 8:1). Secondly, the pH was adjusted to 3 to promote complex coacervation. Thirdly, complex dispersions were subsequently heat-treated to tailor their overall water content, whereas temperatures below (ϑ = 50–55 °C) and above (ϑ = 90–95 °C) the proteins denaturation were applied. Phase separation behavior, microstructural, rheological and electrical properties of the complexes were investigated by surface charge, turbidity, particle size, rheometry and light microscopy measurements. Results revealed that complexes composed of WPI and pectin with a low DE formed rather small and dense particles, whereas large aggregates were observed when the pectinś DE was increased. Concentrated complex dispersions with water contents ≥80% could be manufactured regardless of heating temperatures, whereas complexes maintained their particulate structures upon re-dispersion. Results are of importance for future studies where we intend to incorporate concentrated biopolymer particles as fat replacer in meat and dairy matrices.