Effect of frozen time on Ctenopharyngodon idella surimi: With emphasis on protein denaturation by Tri-step spectroscopy

Abstract As frozen surimi, the key raw material of surimi products, is commonly stored at low temperature, surimi quality especially its protein constantly deteriorates through long periods of storage, thus integrated evaluation of protein denaturation would be essential for quality control of surimi industry. The objective of this study is to investigate the effect of frozen time on surimi by exploring the denaturation mechanism of surimi protein during low temperature storage by Tri-step infrared spectroscopy. During frozen storage, FT-IR peaks of 1219 cm−1, 1238 cm−1 (amide III) and 1396 cm−1 (-CH3) gradually attenuate from strong to weak and finally disappear, while 1534 cm−1 (amide II), 1611 cm−1 and 1638 cm−1 (amide I) also have obvious changes in surimi. Spectral curve-fitting results disclose that the contents of α-helix and β-sheet are continuously decreased and transformed to random coil and β-turn. 2DCOS-IR results further reveal that the denaturation process of protein can be generally divided into three periods: stable period, slow change period and deterioration period.