Effects Of Ozone Water Treatment On Oxidation And Gel Properties Of Grass Carp Myofibrillar Protein

Freshwater surimi production often uses ozone deodorization and bleaching to produce high-quality surimi.Ozone as an oxidant can generate a variety of free radicals in water,which can oxidize and modify the myofibrillar protein of fish.Thereby the surimi gel properties are affected.There are few related studies on the mechanism of ozone-mediated myofibrillar protein oxidation.In this experiment,myofibrillar protein(MP)was extracted before ozone treatment.Taking pure grass carp myofibrillar protein as the research object,the effects of ozone water treatment on the structure,gel properties and thermal aggregation behavior of grass carp myofibrillar protein were systematically studied.Proteomics technology is used to determine oxidation differential proteins.The purpose of the study is to provide a theoretical basis for further elucidating the mechanism of ozone water-mediated protein oxidation,the application of ozone in the aquatic product processing industry,and the improvement of the quality of surimi products.Conclusions of this study were as following:1.The ozone water of 0,1,2,3,5,7 and 10 mg/L was used for treatment grass carp myofibrillar proteins,respectively and the grass carp MP structure was found to be oxidized to a certain degree.The results showed that as the ozone water concentration increasing,the carbonyl and surface hydrophobicity increased significantly(P<0.05).Compared with the control group,when the ozone water concentration was 10 mg/L,the carbonyl content and surface hydrophobicity increased by 121.09%and 31.27%.The total sulfhydryl content and endogenous fluorescence intensity decreased significantly(P<0.05),indicating that the oxidized protein generated disulfide bonds and tryptophan residues undergone oxidative modification.The results of Raman spectroscopy showed that the?-helix was gradually transformed into?-turn,and the structure stability of the protein decreased.Ca²⁺-ATPase activity increased first and then decreased.The treatment group of 5 mg/L ozone water reached a maximum of 0.318±0.035?mol Pi/mg pro/h.The sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern showed that the protein molecules were cross-linked after treatment with ozone water,and aggregates were mainly formed through disulfide bonds,and the protein did not degrade significantly during this process.2.The grass carp MP gel was prepared by two-stage heating of oxidized protein,and the effect of ozone water treatment on the properties of grass carp MP gel was analyzed.The results showed that:ozone oxidation could cause changes in grass carp myofibrillar protein gel properties.Hardness and chewability increased first and then decrease,and there was no significant change in elasticity and cohesiveness(P>0.05).After treatment with low concentration ozone water,the gel strength,WHC and the content of immobilized water increased significantly.At the same time,the gel had a more dense and ordered network structure.While after treatment with high concentration ozone water,the gel strength and WHC decreased significantly,the gel structure became looser,the pores became larger,and the part immobilized water in the gel was converted to free water.This indicated that high-concentration ozone water oxidation hinderd the formation of stable gel structure.As the degree of the oxidation increases,the content of ionic and hydrogen bonds decreased significantly,while the content of hydrophobic interactions and disulfide bonds increased first and then decreased.In summary,the results showed that treatment with ozone at a suitable concentration can improve the quality of myofibrillar gel.3.Before heating,the turbidity,particle size and surface hydrophobicity of the protein increased with the increase of ozone water concentration,while the endogenous fluorescence,active sulfhydryl groups and solubility showed a downward trend.It could be seen from AFM that as the degree of oxidation increases,the number of protein aggregate increases.As a whole,no strong protein aggregation occurred in each treatment group.After heating,the maximum fluorescence intensity of all experimental groups decreased,indicating that the heating caused the protein structure to change.And the fluorescence quenching phenomenon was more obvious after two-stage heating,in which the 10 mg/L treatment group has the most significant decrease(P<0.05).After heating,the turbidity,particle size and surface hydrophobicity of all experimental groups increased significantly,and the solubility decreased significantly;while the free sulfhydryl showed a trend of increasing first and then decreasing.According to AFM,each group of proteins aggregates to form a large number of aggregates.The uniformity and regularity of aggregate distribution under one-stage heating were poor(except for the 7 and 10mg/L treatment groups),while under two-stage heating aggregates of proteins(except 10 mg/L treatment group)were in order and uniform in size.4.A total of 1019.0 proteins were identified in 0,5,10 mg/L ozone water treating protein samples,of which 650.0 were quantifiable.Compared with the treatment group of 5 mg/L and0 mg/L,10 differential proteins were screened out,of which 9 expressions increased and 1expression decreased.Compared with the treatment group of 10 mg/L and 0 mg/L,10differential proteins were screened out,7 of which increased in expression and 3 decreased in expression.Compared with the treatment group of 10 mg/L and 5 mg/L,21 differential proteins were screened out,of which 20 expressions increased and 1 expression decreased.Differential proteins related to ozone oxidation have the following functions:protein binding,ion binding,macromolecular complex binding,muscle composition,hydrolase activity,oxidoreductase activity,etc.Ozone water treatment causes the difference in the content of these proteins,which may also affect the myofibrillar protein gel and thermal aggregation performance.