Structural changes of ovalbumin under alkaline-thermal induction and its gelation mechanism

Ovalbumin (OVA), the major protein in egg white, has attracted attention for its gel-forming properties. pH and temperature are the key parameters regulating protein conformational changes and gel formation. At present, there have been many studies on the structure and gelation mechanism of OVA under thermal and acidic conditions, but there is still a lack of systematic elaboration on how the combination of alkaline-thermal treatment affects the structural changes and gelation process of OVA. To address this issue, spectroscopy, molecular dynamics (MD) simulation, small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) were used to elucidate the mechanism of alkaline-thermal-induced OVA gelation at multiple scales. The results showed that OVA transitioned from the native state to a molten globule (MG) state under alkaline-thermal induction. In the secondary structures, the α-helix decreases with the enhancement of residue deprotonation and electrostatic repulsion, the β-sheet becomes a relatively stable structural skeleton, and the tertiary structure is partially unfolded. The MG state of OVA resembles a "Janus-like" particle, with ordered regions providing electrostatic repulsion and steric hindrance, while disordered regions mediate attraction. Under the balance between electrostatic repulsion and attraction, proteins were driven to self-assemble into "beaded" oligomeric fibers to form transparent gels. The above findings can provide theoretical guidance for the development of new gel foods and the industrial production of traditional gel foods.