Effect of thermal and nonthermal processing methods on the structural and functional properties of whey protein from donkey milk

This study evaluated the effect of thermal, ultrasonication, and UV treatment on the structural and functional properties of whey proteins from donkey milk. Whey proteins exhibited notable stability in nonheat-treated environments, but their structural and functional characteristics were notably affected by excessive heat treatment. The application of high-temperature long-time thermal treatment resulted in a decrease in fluorescence intensity and foaming and emulsification stability, as well as considerable damage to the active components of the proteins. Specifically, the preservation of lysozyme activity was only 23%, and lactoferrin and IgG exhibited significant losses of 70% and 77%, respectively. Nonthermal treatment methods showed superior efficacy in preserving the active components in whey proteins compared with heat treatment. Ultrasonic treatment has demonstrated a notable capability in diminishing protein particle size and turbidity, and UV treatment has been observed to have the ability to oxidize internal disulfide bonds within proteins, consequently augmenting the presence of free sulfhydryl groups, which are beneficial to foaming and emulsification stability. This study not only offers a scientific basis for the processing and application of donkey milk whey proteins but also serves as a guide to produce dairy products, aiding in the development of dairy products tailored to specific health functions.