Effects On The Quality Of Sea Bass By Different Thawing Treatments Based On Physicochemical Characteristics,Spatial Effects And Molecular Dynamics Simulation

The general characteristics of fish products are high water content and easy to deteriorate.In the process of storage,processing,transportation and sales,fish products are prone to decay under the action of their own enzymolysis and the action of microorganisms,resulting in a decline in the quality of fish products.With the increase in the production of sea bass,the sale of live fish has been unable to meet market demand.In order to extend the shelf life and avoid shortages due to distance and seasons,sea bass are sold frozen.Thawing is a process in which ice crystals melt,and it is difficult for the melted food to return to its original fresh state.Therefore,people are committed to researching new thawing methods to better solve the quality changes of frozen foods during the thawing process.This paper studies the effect of magnetic nano combined with radio frequency thawing(RT-Mag)or microwave thawing(MT-Mag)on the quality characteristics of sea bass after thawing.Using molecular dynamics simulation technology to study the changes in the conformation of the sea bass myosin heavy chain by its thawing method,which can replace the traditional analysis technology to further understand the physical motion behavior of protein molecules under the action of electric and magnetic fields.Provide theoretical guidance and technical support for the development of thawing technology.The main conclusions are as follows:1.Studies four kinds of thawing methods:magnetic nano combined with radio frequency thawing(RT-Mag)or microwave thawing(MT-Mag),microwave thawing(MT)and Radio frequency thawing(RT)on sea bass freshness,moisture migration and thermal stability of protein.The influence of the conductivity is used to study the freshness of the fish,scanning electron microscopy(SEM),the Low field nuclear magnetic used to evaluate the organizational structure and moisture state,fish XRD to explore the effects of fish protein crystal structure,analysis of DSC,dynamic rheology thawed fish protein conformation changes.The results showed that RT-Mag and radio frequency thawing(RT)reduced the mobility and loss of immobilized and non-mobile water,had the most compact and ordered network structure.Decreases in the T_max and enthalpies were observed in the thawing treatments expect for RT-Mag during the thawing process.the treatment groups of RT-Mag and MT-Mag could improve the freshness of fish,reduce the damage to the myofibrillars of the samples,and improve the water retention of the samples after thawing.This proves the potential of RT-Mag treatment in thawing.2.This work was aimed to explore the effects on the properties of sea bass myofibrillar protein(MP)and structure under different thawing treatments.Changes in secondary structures,tertiary structure,rheological behavior,protein profiles and protein aggregation were investigated.Results revealed that magnetic nanometer combined with radio frequency thawing(RT-Mag)and magnetic nanometer combined with microwave thawing(MT-Mag)increased the?-helical content and decreased?-sheet content,while RT-Mag had minimal effect on the secondary protein structure.The appearance of polymerized protein band of SDS-PAGE indicated that RT-Mag and MT-Mag occurred a mild oxidation.In addition,the changes of zeta potential and particle size indicated that MP pretreated by RT-Mag and MT-Mag had less aggregation and degradation.The UV second derivative showed that the effect of RT-Mag treatment was closer to that of FS,and the improvement effect of protein aggregation and oxidation was better.The degree of oxidation and aggregation of histones in RT-Mag treatment is weak,and the degree of protein degradation is low,which can be used as an alternative method to improve MP performance and meat quality.3.Four different thawing methods were used:magnetic nanometer combined with microwave thawing(MT-Mag),magnetic nanometer combined with radio frequency thawing(RT-Mag),radio frequency thawing(RT)and microwave thawing(MT)to change the conformation of myosin heavy chain(MHC).The results showed that Compared with the FS,the hydrogen bond number and radius of gyration of the RT-Mag and RT groups were less decreased.STRIDE analysis showed that the content of?helix was relatively high in RT-Mag and MT-Mag groups.The dipole moment,root mean square fluctuations and hydrophilicity were affected by the applied electric field and magnetic field.These conclusions provide a theoretical realization of understanding the protein conformational transition during the thawing process and the realization of quantification,and provide guidance to choose better thawing conditions without loss of nutritional properties.