Characteristic Fishy Compounds Of Silver Carp Mince And Interaction With Proteins

Freshwater resources were rish in china,and the production increased with years.Silver carp,as one of the major freshwater fish in our country,are widely used in surimi and its products processing.However,the strongly inherent fishy smell of silver carp affected the acceptance of consumers seriously.Rinsing,as the main method to remove the smell substances in surimi processing,could just remove part of smell substances,and there are still residues.The main reason analyzed was that the complexity of the fishy smell composition,and most fishy smell compounds combined with large molecules such as proteins in mince matix.Thus,clarifying the mechanism of interaction of fishy compounds removing differently with proteins was particularly important to optimize the deodorization process,and improve the quality of freshwater fish surimi.In this paper,to provide theoretical support to the achieving the effective deodorization on the freshwater fish surimi,the effects of different traditional rinsing process for silver carp surimi fishy aroma were stidied.The interactions of characteristic fishy compounds with fish protein and the corresponding influencing factors were dicussed,and the mechanism of interactions with myosin were further analyzed.The main research results are as follows:?1?The volatile compounds in the silver carp fish meat were extracted by two thchnologies,solid phase micro extraction?SPME?and solid adsorption material extraction?MMSE?,and further analyzed by GC-MS?GC-MS?.Respectively,36 and 57volatile compounds were detected in the silver carp.Combined with the odor activity value?OAV?analysis,13 volatile compounds were selected and identified as aroma active compounds?AACs?.?2?Using electronic nose?E-nose?and traditional sensory evaluation method distinguishes the overall flavor of silver carp fish ment before and after rinsing.The change of AACs of silver carp fish ment before and after rinsing were analyzed by MMSE-GC-MS.Four AACs?heptanal,octanal,nonanal,1-octen-3-ol?were selected as the silver carp surimi's characristic fishy compounds?CFCs?which were considered removal difficultly and providing a greater impact on surimi quality,according to the residual and the OAVs of AACs.?3?The binding abilities of main surimi proteins?myofibrillar proteins,myosin,actin?to CFCs?heptanal,octanal,nonanal,1-octen-3-ol?were evaluated by the measurement of headspace concentration?[HS]?.Results indicated that myosin,as the major constitute of myofibrillar proteins,was the primary binding receptor to the volatiles.Under trial conditions,the binding capacities of myosin to different CFCs were influenced by the pH,ionic type and ionic strength in different degrees.In the condition of neutral pH of high ionic strength,myosin showed stronger binding abilities to KFCs.The abilities of myosin bond to heptanal and octanal weakened in the the presence of Mg²⁺compared to K⁺and Na⁺,while bond to nonanal and 1-octen-3-ol strengthened.The effect of K⁺and Na⁺on binding of myosin to heptanal,octanal and nonanal were insignificant?P>0.05?,but that to 1-octene-3-ol were significant?P<0.05?.?4?The interaction of myosin with CFCs?haptanal,octanal,nonanal and1-octen-3-ol?were studied by CFCs'headspace analysis.Based on the studies of thermodynamic models?Scatchard-Hildebrand equation and Klotz plot?,the Gibb's free energy??G?of myosin to the four CFCs studied were all below 1,indicating that the interactions were spontaneous.Compared with other liner-chain aldehydes?haptanal,octanal and nonanal?,1-octen-3-ol had more binding sites and higher binding constant to myosin protein.Moreover,the binding affinity of myosin to linear-chain aldehydes deceased with the chain length of the aldehydes.?5?The interaction mechanism of myosin with CFCs?haptanal,octanal,nonanal and 1-octen-3-ol?were studied by myosin's multi-spectral analysis.UV spectra indicated that interaction with CFCs changed myosin peptide chain conformation.Fluorescence spectroscopy showed CFCs could cause myosin fluorescence quenching occured,which were identified as static quenching.According to the Stern-Volmer equation,the binding constants and binding sites were obtained to determine the quenching mechanism,which were consistent with the results of the headspace analysis.Further thermodynamic parameters suggested that hydrogen is the main force between myosin and CFCs.Circular dichroism revealed that interaction of myosin with CFCs caused the?-helix content of secondary structure significantly increased,which further confirmed the presence of hydrogen bonding.These results could provide theoretical basis for improving the existing rinsing method aiming to achieve effective deodorization of surimi.