Consequences of dynamic high-pressure homogenization pretreatment on the physicochemical and functional characteristics of citric acid-treated whey protein isolate

This study investigated the physicochemical and functional characteristics of citric acid (CA)-treated whey protein isolate (WPI) by dynamic high-pressure homogenization (DHPH) at different pressure levels (0, 25, 50, 75, and 100 MPa, 3 cycles). The number of macromolecular polymers increased in CA-treated WPI with DHPH at 0-100 MPa by the analysis of molecular size distributions. DHPH can reduce the particle size of WPI and CA treated WPI. Additionally, the content of free sulfhydryl groups and surface hydrophobicity of WPI and CA treated WPI increased after DHPH treatment (p < 0.05). Also, DHPH promoted gel formation in the CA treated WPI, with the gel hardness increased by 43.66% after DPHP pretreatment at 100 MPa (p < 0.05). Meanwhile, after DPHP pretreatment at 100 MPa, emulsifying activity index (EAI) of CA-treated WPI and WPI increased by 13.15% and 27.36%, respectively (p < 0.05). Thus, DHPH pretreatment could enhance the degree of crosslinking of the CA-treated WPI and improve its gel and emulsifying properties, broaden the application of WPI in food processing.