Pea protein isolate–high methoxyl pectin soluble complexes for improving pea protein functionality: Effect of pH, biopolymer ratio and concentrations

Abstract

Recently, there is a strong interest in the incorporation of pea protein as a preferred alternative animal protein into protein fortified beverage because of its cheaper price, more sustainable and gluten free that can be claimed in label. However, poor functionality of pea protein such as acidic solubility and thermal stability has limited their applications in dispersed food systems such as beverage. The aim of this study was to enhance the functionality of pea protein isolate (PPI) by forming soluble complexes with high methoxyl pectin (HMP). The effect of PPI–HMP mixing ratio (1:1–20:1) and PPI concentrations (0.05 and 1.00 wt %) on critical pH transition point (pHs), a key parameter differentiating between soluble and insoluble complexes formation, was investigated using turbidimetric analysis, phase diagram, and ζ–potential. Critical pHs decreased to pH 3.5 as PPI–HMP mixing ratio decreased from 20:1 to 1:1. The ζ–potential results showed a shift in net charge neutrality from pH 4.8 in homogenous PPI solutions to pH 3 for PPI-HPM mixtures with 1:1 ratio. However, HMP induced phase separation of PPI–HMP mixtures at both higher biopolymer concentration (>1.50 wt %) and neutral pH values was observed presumably via a thermal incompatibility mechanism. The pH- percentage solubility of PPI–HMP mixtures at fixed PPI concentration (1.00 wt %) was mixing ratio dependent. When increasing HMP concentration, the pH of minimum protein solubility for biopolymer mixture was shifted towards more acidic condition as compared to PPI alone. Apparent viscosity and thermal denaturation temperature of soluble complexes at fixed PPI concentration (1.00 wt %) slightly increased due to the formation of new net structure in the PPI–HMP systems. The findings derived from this research could provide useful information in the design of pea protein fortified beverage with enhanced pea protein stability.