Effects of theaflavins on protein structure and gel properties in frozen unwashed surimi

The industrial production and storage of unwashed surimi continue to face significant challenges in gel quality control. This study investigated the protective effects of theaflavins extract (TFs) on oxidative denaturation of myofibrillar protein (MP) and sarcoplasmic protein (SP), as well as on the gel properties of unwashed surimi during freeze-thaw cycles. The results showed that MP underwent more significant oxidative denaturation than SP after freeze-thaw treatment. Notably, the addition of 1 g/kg TFs provided greater protection against protein denaturation and surimi gel damage compared to 2 g/kg TFs. Supplementation with 1 g/kg TFs significantly mitigated freeze-induced changes in MP solubility, Ca 2+ -ATPase activity, carbonyl content, and conformation ( P < 0.05). These changes resulted in improved surimi gel microstructure and functional properties, including gel strength, water distribution, and water-holding capacity. These findings provided valuable insights and practical guidance for applying TFs to enhance protein oxidative stability and improve the quality of unwashed frozen surimi. • TFs of 1 g/kg delayed protein oxidative denaturation in frozen unwashed surimi. • TFs improved the gel structure and strength of freeze-thawed surimi. • TFs mitigated water migration and uneven distribution in frozen surimi gel. • TFs enhanced surimi gel by reducing MP oxidation and structure deterioration.