The Effects of Ultrasonic Pretreatment and Enzymatic Modification on the Structure, Functional Properties, and In Vitro Digestion of Whey Protein Isolate

In this study, the structure and functional and in vitro digestion properties of whey protein isolate (WPI) modified by ultrasonic pretreatment combined with a double oxidase system containing horseradish peroxidase (HRP), glucose oxidase and D-glucose were assessed. SDS-PAGE results confirmed the occurrence of crosslinking reactions. Ultrasonic treatment significantly increased HRP-mediated WPI crosslinking, as demonstrated by reductions in free amino and sulfhydryl groups. CD and FTIR spectroscopies indicated that the structure of the crosslinked WPI was more stable. The particle size of the modified WPI was significantly reduced, resulting in better colloidal stability. Compared with the untreated WPI, the crosslinked WPI possessed enhanced surface hydrophobicity, gelation properties, emulsion stability, and thermal stability but reduced digestibility. These findings provide new insights into ultrasonication combined with a double oxidase system to further improve the structure and functional properties of proteins and broaden their application range in the food industry.