Multiscale analysis on the fibrillation of whey protein isolate induced by cold plasma treatment: regulation mechanism of aggregation morphology and its emulsifying properties

Cold plasma (CP) treatment can alter the structure of proteins and modify the physicochemical property. However, the mechanism of CP-assisted acidic-thermal protein fibrillation during different fibrillation degrees is essential to explore. This study aimed to investigate the effect of CP-assisted acidic-thermal fibrillation on the structural, physicochemical, and emulsifying characteristics of whey protein isolate (WPI) and its ability to stabilize high internal phase emulsions (HIPEs). Results indicated CP exhibited significant potential for promoting the formation of WPI fibrils (WFs), as evidenced by a 1.84-fold increase in Thioflavin T fluorescence intensity and enhanced β-sheet content from 13.72% to 43.77%. FTIR and SEM analyses confirmed that CP induced unfolding of the WPI structure and the formation of highly ordered, filamentous aggregates. The fibrils induced by CP exhibited superior emulsifying activity index (32.66 m 2 /g) and emulsion stability index (89.24 min), representing 2.1- and 1.8-fold increases over the native WPI, respectively. Moreover, the CP-induced WF stabilized HIPEs with the smaller droplet sizes, higher apparent viscosity, and enhanced storage stability. The driving force of CP-assisted self-assembly fibrillation mainly involved hydrogen bonds and electrostatic interactions. The HIPEs stabilized by PWFs exhibited the superior thermal and ultraviolet stability of encapsulated lycopene. The highest retention rate (56.10%) was obtained in the HIPEs. This work revealed that CP-assisted fibrillation provided an efficient, green, and controllable strategy to tailor the structure and interfacial functionality of proteins, revealing the important role of CP in regulating the protein fibrillation process.