Synergistic effects of ultrasound and Na+ on soy protein isolate-hemp protein isolate-carboxymethyl cellulose composite emulsion gels: Evaluating the potential for low-salt gel foods.

Abstract

This study aimed to address the structural deficiency of plant protein gels by investigating the impact of ultrasound power levels and Na+ concentrations on the characteristics of soy protein isolate (SPI)-hemp protein isolate (HPI)-carboxymethyl cellulose (CMC) composite emulsion gels (S/H/C gels). The results revealed that low-concentration Na+ (100-300 mM) can effectively shield the charges on protein surfaces, facilitate efficient aggregation of protein molecules, and encourage the conversion of some α-helix into β-sheet, thereby promoting the creation of a gel network structure. Ultrasonic treatment (400 W) further induced protein denaturation, promoting the exposure of hydrophobic groups and the creation of disulfide bonds, resulting in a well-developed three-dimensional network structure. At an appropriate Na+ concentration (300 mM), gel hardness increased from 97.16 N to 104.64 N, the storage modulus G' reached its maximum value, and the proportion of β-sheet structure increased significantly. This demonstrated excellent water-holding capacity (increased by 15.56%) and digestive characteristics. Nevertheless, excessive ultrasonic power (600 W) or high Na+ concentration (600 mM) led to excessive protein aggregation and loosening of the network structure, disrupting the continuity of the oil droplet-protein interface and thereby degrading the performance of the emulsion gel. This study elucidates the synergistic mechanism between ultrasound and Na+ in controlling the multidimensional qualities of plant protein emulsion gels, providing a theoretical basis for developing low-salt gel foods.