Microstructure and inter-molecular forces involved in gelation-like protein hydrolysate from neutrase-treated male gonad of scallop (Patinopecten yessoensis)

Neutrase-hydrolyzed male gonad of scallop (Patinopecten yessoensis) displayed a gelation-like profile, whereas the underlying mechanism was unknown. In this study, the microstructure and inter-molecular forces involved in the gel network of scallop (P. yessoensis) male gonad hydrolysates (SMGHs) were investigated, by monitoring changes of its gel strength in presence of different chemicals. The results showed that SMGHs chiefly consisted of peptides both below 1000 Da (46.86%) and above 10,000 Da (30.30%), and exhibited a porous, three-dimensional network, with firmness of 40.49 ± 1.96 g, cohesiveness of 479.02 ± 37.04 g·s and adhesive force of 23.69 ± 1.92 g, which were similar with that of 1.0–1.5% guar gum, 1.5% carrageenan, 1.0–2.0% xanthan gum and 0.5–1.5% gelatin. Addition of urea, and propylene glycol (PG) decreased the gel strength of SMGHs with the increase of concentration, and only a very weak gel was observed when the concentration of urea reached 8 M. The overall gel properties of SMGHs were improved in the presence of 0.3 M NaCl, KCl, CH3COONa and NaSCN (p < 0.05). However, elevated salt concentration led to decreased gel properties of SMGHs, especially the inhibiting effect of NaSCN at 3 M. In addition, inclusion of dithiothreitol (DTT), 2-mercaptoethanol (2-ME), and N-ethylmaleimide (NEM) also diminished the gel properties at high concentration (p < 0.05), but not severely, and their addition did not change the gelation-like profiles of SMGHs. These results suggest that the gel network of SMGHs was primarily maintained by hydrophobic, electrostatic interactions and hydrogen bonds.