Formation and physicochemical properties of insoluble complexes resulted from high methoxyl pectin-protein interactions

The present work studied the complex coacervation of high methoxyl pectin (HMP) with three proteins [Whey protein isolate (WPI), Sodium caseinate (SC) or pea protein isolate (PPI)] during acidification. Each protein and HMP were mixed at various ratios (1:1 to 10:1) with the sum of their concentrations ranging from 0.2 to 1.1%. Complex coacervate formation, as investigated by phase diagrams and zeta potential measurements, depended on the protein and the strength of the electrostatic protein-HMP interactions. Omicron ptimum coacervation was achieved at 6:1 mixing ratio and at pH 4 for SC and WPI or pH 3 for PPI. The complexes formed at these conditions were isolated and studied further in terms of their colour, moisture content, solubility, pH, conductivity, kinematic viscosity, density, porosity, flowability and cohesiveness. Their behaviour differed from the behaviour of their constituents. Overall, the mixtures with PPI differed from the remaining mixtures not only in their phase behaviour but also on the properties of their complexes. This deviation was attributed to weaker attractive forces between HMP and PPI. The results of the present study can be useful for the modulation of HMP based biopolymer complexes and their exploitation as structuring or encapsulating agents in food matrices.