Interaction Between Soy Protein Isolate (SPI) and Water-Soluble Persian Gum to Form Stable Colloidal Complexes

This study aimed to investigate the electrostatic interaction between soy protein isolate (SPI) and water-soluble part of Persian gum (PG) as function of pH (2–7), protein to polysaccharide mixing ratio (MR 8:1–1:10), and total concentration of biopolymer (TC 0.1, 0.3 and 0.6% W/W). The results showed that the formation of soluble complexes was initiated near the isoelectric point (pI) of SPI. Decreasing the MR reduced the values of two critical pH (pH φ and pH opt ) with a more considerable effect at TC of 0.1% W/W for pH opt . The effect of ionic strength was also studied using two salts (NaCl and CaCl 2 ) at different concentrations (0–200 mM). Increasing ionic strength prevented the interaction due to the charge screening effect. Particle size and zeta potential of physically stable complexes ranged from 466 to 701 nm and − 70 to − 82 mV, respectively. The relative viscosity of SPI/WPG mixture was decreased from 2.20 to 1.24 during pH reduction from 6.0 to 3.8 confirming the compaction phenomenon. The stable colloidal systems might have applications in designing delivery systems for utilization in food products and beverages.