Staged structural changes of fermented chicken breast myofibrillar protein: Conformational unfolding and aggregation

Fermented chicken breast is promoted as a healthier alternative to traditional high-fat fermented meat products, yet its quality depends critically on the structural state of myofibrillar protein (MP). To clarify how MP deteriorates during extended natural fermentation, this study established a 150-day fermentation model and systematically monitored MP degradation, oxidation, conformational change, and aggregation behavior. Partial least squares regression (PLSR) and hierarchical cluster analysis (HCA) were combined to relate structural transitions and aggregation. SDS-PAGE showed pronounced degradation of myosin heavy chain and actin from day 20 onward. By day 150, total sulfhydryl content dropped by 45.5%, surface hydrophobicity rose markedly, α-helix content fell from 39.89% to 30.51%, and β-sheet content increased from 21.51% to 33.56%. Concurrently, solubility decreased by approximately 70% and particle size increased seven-fold relative to the initial state. PLSR identified surface hydrophobicity (VIP = 1.054) and the α → β secondary-structure transition (VIP = 1.050) as the principal determinants of aggregation, and HCA pinpointed day 20 and day 60 as critical turning points in the deterioration trajectory. Protein oxidation and conformational unfolding drove irreversible aggregation through hydrophobic interactions and disulfide cross-linking. Together with degradation of the myofibrillar structural proteins, these processes led MP toward a state of extensive hydrolysis, oxidation, and insolubility. This study provides a quantitative basis for understanding the structural evolution and aggregation behavior of MP during extended fermentation, with implications for controlling the quality of fermented chicken breast.