Effect of Heat Treatment on the Binding of Fish Myosin with Fishy Odor Compounds
Freshwater fish has strong fishy odor, which has always been one of the bottlenecks restricting the surimi processing in China. Myosin, as the predominant components of surimi, not only affect the gelation properties of surimi products, but also affect the release of fishy odor substances. However, there is little information on the interaction between proteins and fishy odor compounds. The present study investigated the mechanism of the interactions between fishy odor compounds and proteins. The myosin-fishy odor compounds model systems were established to investigate the binding of fish proteins to fishy odor, using headspace-gas chromatography/mass spectrometry (HS-GC-MS), molecular simulation and spectroscopy. The change of protein conformation, aggregation behavior and fishy odor binding ability under different heat-induced conditions were investigated by spectroscopy, SDS-PAGE, zeta potential analysis and HS-GC-MS. The results showed that the binding capacity between the fish proteins and selected fishy odor compounds increased significantly with the increase of carbon chain length and unsaturation, and the adsorption capacity of alcohols was significantly lower than that of aldehydes. The bonds between fish myosin to the selected fishy odor compounds were mainly hydrophobic interaction, hydrogen bonding and covalent bonding. The binding of fishy odor compounds to proteins was strongly influenced by changes in the structure and surface of proteins during the heating process. During the initial heating, the flavor-binding ability increased, which was likely attributable to the increased surface hydrophobicity and total sulfhydryl content and the unfolding of secondary structures of proteins by exposure of reactive amino acids, sulfhydryl groups, and hydrophobic bonding sites. Nevertheless, lengthy heating caused protein refolding and accelerated protein aggregation, thus reducing hydrophobic binding sites and weakening the resultant binding capacity of proteins to flavor compounds.