Insight into comparison of binding interactions and biological activities of whey protein isolate exposed prior to two structurally different sterols

Although sterols have multiple physiological functions, low solubility and weak emulsifying properties of sterols affect their application in the food industry. However, binding interaction between protein and sterol potentially enhances its biological activities and emulsifying properties. In this work, effects of two structurally different sterols, namely ergosterol (ES) and γ-oryzanol (γS) on binding interactions, emulsifying properties, and biological activities of whey protein isolate (WPI)-sterol complexes were investigated and compared. Fluorescence spectroscopies and molecular docking presented that binding affinity of WPI treated with γS was stronger than that with ES. Importantly, WPI-γS exhibited stronger absolute value of ζ-potential, surface hydrophobicity, emulsifying characteristics and biological activities than WPI-ES. Principal component analysis (PCA) showed that emulsifying characteristics and biological activities of all the samples were positively correlated. This study provided a theoretical basis for the development and practical application of protein-sterol complexes as functional ingredients in food industry.