Comparative proteomic and metabolomic profiling of transparent versus opaque pigeon egg albumen.

BACKGROUND: Pigeon albumen exhibits superior gel properties and a characteristic translucent appearance, yet substantial variation in albumen transparency exists among individual eggs. The molecular basis underlying this quality difference remains poorly understood, particularly regarding protein and metabolite compositional profiles. RESULTS: We employed label-free quantitative proteomics and untargeted metabolomics to compare transparent and opaque pigeon egg albumen. A total of 55 differentially expressed proteins and 34 differential metabolites were identified. Transparent albumen showed marked upregulation of endoplasmic reticulum-resident chaperones (BiP, calreticulin) and protein disulfide isomerases, whereas vesicle-trafficking proteins (RAB7A, ACTR2) were downregulated. Metabolically, lysophospholipids were the most substantially increased compounds (LysoPA, fold change [FC] = 2.22; LysoPI, FC = 2.14), while l-carnitine (FC = 0.48) and 2-methyl-5-vinylpyrazine (FC = 0.46) were the most decreased. Integrated correlation network analysis revealed 99 significant protein-metabolite associations, predominantly involving polyphenolic compounds. CONCLUSION: These compositional profiles suggest that enhanced endoplasmic reticulum protein folding capacity, altered lipid composition, and redox-related modifications collectively distinguish transparent from opaque albumen. Our findings provide quantitative molecular evidence for albumen quality variation in pigeon eggs and inform composition-based strategies for quality grading, feed optimization, and processing innovation in the poultry industry. © 2026 Society of Chemical Industry.