Formation mechanism of complex coacervation of chayote (Sechium edule) pectin-sodium caseinate in aqueous solution

Chayote (Sechium edule) is a kind of vegetable with high economic value, and its pectin has potential application in processed food. In this study, the phase behavior, turbidity, Zeta-potential, rheological behavior, FTIR, microstructure, and thermal properties were used to investigate the complex coacervation of the chayote pectin (CP) and sodium caseinate (CAS) in aqueous solution, with apple pectin as the control. The results showed that the impact of pHs and CAS-CP mixing ratios on phase behavior was comparable to apple pectin. When the pH value was above CAS's isoelectric point (Ip4.6), there were mainly hydrogen bonding and hydrophobic inter-action between CAS and CP, forming a soluble complex. In contrast, the formation of insoluble complexes was driven by electrostatic attraction when the pH was below Ip4.6. The formation of complexes shifted towards lower pH as CP addition increased. The CAS-CP mixture fluid had shear thinning property. There was the greatest electrostatic attraction between CAS and CP at pH 3.5. At the same time, the secondary structure of CAS may have changed during the formation of the complexes. The complexes formed by CAS and CP had good thermal properties. The results of this study provided a theoretical basis for applying CP as a novel raw material in food processing.