Deciphering photooxidation-induced phase-separation aggregation of liquid egg white via amino acid residue responses

The mechanism of photo-oxidative phase-separation aggregation in liquid egg white protein (EWP) under light storage (0-12,000 LUX) was elucidated. The results indicated that light-induced reactive oxygen species (ROS) directly oxidised aromatic amino acid residues. This led to a significant increase in dityrosine content and a marked conformational transition. Meanwhile, the photo-triggered unfolding of EWP molecular chains enhanced the flexibility, exposing polar and hydrophobic groups. Consequently, the proteins underwent phase separation and aggregation driven by hydrophobic interactions and weak hydrogen bonds. This aggregation increased the viscosity of the high light-exposed EWP. However, due to the lack of a rigid, supportive network, the resulting aggregates exhibited decreased storage and loss modulus upon subsequent thermal gelation. Dilution disrupted these hydrophobic interactions and hydrogen bonds, causing the aggregates to dissociate into smaller fragments with smaller particle size. These findings provide critical insight for controlling the photo-oxidative deterioration of liquid egg white.