Contribution of protein conformation and intermolecular bonds to fish and pork gelation properties

Changes in protein conformation and intermolecular interactions during gelling were measured to explore the basis for the different gel properties of fish and pork pastes after heat treatment. Raman spectral analysis revealed that, in the unheated pork sample, more tyrosine residues were buried or involved as hydrogen bond donors than in the fish counterpart. Hydrophobic interaction increased and then decreased with increasing temperature, reaching a maximum value at 60 and 70 °C for fish and pork samples, respectively. Formation of disulfide bonds mainly occurred at 70–80 °C for fish, and 50–60 °C for pork samples. Incubation at 4–40 °C induced abundant non-disulfide covalent cross-linking in fish, but not in pork samples. The differences in protein conformation and intermolecular bonds possibly contributed to diverse gelation properties between fish and pork samples. At 40 and 50 °C, the breaking force of fish samples was significantly higher than that of pork. However, higher breaking force was observed in pork samples above 60 °C. Pre-incubation at 40 °C significantly increased the breaking force of the cooked fish sample, but had little effect on the breaking force of the cooked pork sample. In addition, incubating pork paste at 40 °C could decrease the cooking loss of the cooked pork sample.