Oxidation-induced structural modifications and their impact on water retention in Yak meat proteins across pH and NaCl gradients

This study explores how oxidation affects yak meat proteins and water retention under varying pH (5.0 and 8.0) and NaCl gradients (0.1 and 0.6 mol/L). Elevated H 2 O 2 levels increased protein carbonyl and dityrosine content while reducing sulfhydryl groups, tryptophan fluorescence, and water-holding capacity (WHC). However, high salinity and pH 8.0 exhibited better water retention as evidenced by lower centrifugal loss (22.07%) and cooking loss (45.01%) than pH 5.0 (26.14%, 47.66%) after 60 mmol/L H 2 O 2 treated. Low-field Nuclear Magnetic Resonance analysis showed oxidation converted immobilized water to free water, while salt and high pH increased immobilized water (95.32%) compared with pH 5.0 (92.94%) at 60 mmol/L H 2 O 2 treatment. Microscopy revealed oxidation-induced muscle fiber disruption, with less damage at pH 8.0. Oxidation also weakened gel properties, including WHC, whiteness, and rheological behavior, though pH 8.0 gels performed better. These findings clarify how oxidation, pH, and salt interact to influence protein structure and water retention, offering a theoretical basis for improving yak meat processing and storage, particularly in high-altitude regions where yak meat is a dietary staple.