Promoting the formation of β-lactoglobulin amyloid fibrils induced by cold plasma treatment: self-assembly mechanism, emulsifying properties, and stability

The structural conversion of β-lactoglobulin (β-LG) into amyloid fibrils offers an effective strategy for developing functional biomaterials with enhanced physicochemical properties and functionalities. This study investigated the effect of cold plasma (CP) and ultrasound pretreatments on β-LG fibril (β-LGF) under acid-heat conditions (pH 2.0, 90 °C, 10 h) and explored the relationship between fibril structure and functional performance. Compared with the control, CP pretreatment significantly increased ThT fluorescence intensity by 1.9-fold, indicating enhanced fibril formation. Dynamic light scattering revealed that CP-treated fibrils (P-β-LGF) exhibited a reduced average particle size (183.6 ± 4.7 nm) and narrower distribution (PDI = 0.21) compared with ultrasound-treated (243.1 ± 6.5 nm) and control samples (278.4 ± 7.8 nm). FTIR and CD spectra confirmed the structural transition from α-helix to β-sheet, while SEM micrographs showed elongated, uniformly dispersed fibrils after CP pretreatment. Functionally, P-β-LGF exhibited the highest emulsifying activity index (51.2 m 2 /g), emulsion stability index (87.3%), and antioxidant activities, the emulsions stabilized by P-β-LGF-Dextran complex exhibited the superior thermal and ultraviolet stability of encapsulated lycopene. The highest retention rate (91.6%) was obtained in the emulsion. These findings demonstrated that CP treatment is an effective, green, and tunable strategy to regulate protein conformation and fibrillation kinetics, thereby enhancing the structural and functional properties of β-LG, providing new insights into the design of protein-based delivery systems for bioactive compounds.