Abstract: The purpose of this study is to assess the effect of cold storage on textural properties of cooked Monopterus albus and to explore the underlying mechanism. Monopterus albus were stored cold for different periods before being cooked at 100 ℃ for 5 min. Cooking loss, textural properties and chemical forces were determined, and sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) and Raman spectroscopic measurement were conducted. The results showed that as storage time increased, moisture loss during cooking increased, while hardness and springiness were not significantly changed (P > 0.05); cohesiveness and gumminess were significantly increased on the second and third day (P < 0.05), respectively; chewiness and resilience increased first and then decreased (P < 0.05). Hydrophobic interaction and disulfide bonds were the most important forces between various proteins in cooked Monopterus albus. Hydrophobic interactions tended to decrease gradually whereas the disulfide bonds increased initially and then decreased with increasing cold storage time. For each storage period, disulfide bond content was positively correlated with springiness, chewiness and resilience (P < 0.05). SDS-PAGE showed that protein components with molecular mass less than 30 kDa and equal to approximately 30, 37 and 60 kDa may be involved in the formation of disulfide bonds, thereby possibly affecting textural properties in cooked Monopterus albus. Raman spectroscopy analysis indicated that the hydrophobicity of tryptophan and tyrosine residues decreased, which was consistent with the change of hydrophobic interactions. The secondary structure analysis indicated the transformation of α-helix and random coil structures into β-turn and β-sheet occurred mainly during the first three days of cold storage while α-helix and β-sheet conformations were transformed into β-turn and random coil during the late storage stage, leading to a more disordered structure. Taken together, we concluded that disulfide bonds and hydrophobic interactions are the main forces between various proteins in cooked Monopterus albus, and changes in these forces can cause protein conformation to disordered, thereby leading to changes in textural properties of Monopterus albus after cooking.

Key words: Monopterus albus, cold storage, cooking, texture, protein