Inhibition mechanism of membrane-separated silver carp hydrolysates on ice crystal growth obtained through experiments and molecular dynamics simulation

The membrane-separated silver carp hydrolysates (>10 kD, 3-10 kD and < 3 kD) displayed abilities to mitigate oxidation and denaturation of myofibrillar protein and cryoprotective activities for frozen surimi. However, the mechanism of the membrane-separated fractions on ice crystal growth in the system is still unknown. Therefore, the cryoprotective activities (recrystallization inhibition, RI and thermal hysteresis activity, THA) of the fractions were investigated and the mechanism was explored by molecular dynamics (MD) simulation to predict the probable binding sites and model the possible interactions between the peptides and water/ice. The fractions < 3 kD displayed remarkable RI activity, with significantly higher THA (0.60 ± 0.13 °C) and lower amount of ice nuclei (4.74 ± 0.53%) than that of fractions > 10 kD and 3-10 kD. The results of MD simulation certified that the main peptides in the fractions < 3 kD interacted firmly with water molecules and inhibited growth of ice crystals with mechanism compatible with Kelvin effect. Hydrophilic and hydrophobic amino acid residues in the membrane-separated fractions offered synergistic effects on the inhibition of ice crystals.