Effects And Mechanism Of Lipase On Gel Properties Of Surimi Gels From Catfish

In recent years,there are more and more researches on the processing of surimi products with fatty fish.Protein in fatty fish has a certain gel ability,but the presence of a large amount of fat in fatty fish will hinder the gel process of surimi protein,resulting in poor gel quality of surimi products.As a natural biocatalyst,lipase has been applied maturely in fat-rich meat products to improve the quality of products.However,the effect of lipase on surimi protein gel are lacking in research.In this study,we take the catfish,a kind of fatty fish,as the research object.The changes of fat and the gel properties of surimi gel were investigated,and the mechanism was discussed under lipase treatment.The main contents of this paper are as follows:1)Effect of lipase on gel properties of catfish surimiThe lipase was added during the rinsing and chopping process.The effects of lipase on the gel properties of the surimi were studied by measuring the fat content of the surimi,the gel strength,the water holding capacity and the whiteness of the gel.The effects of different addition methods of lipase were compared.The results showed that after the addition of lipase,the fat content decreased,the gel strength and whiteness of the surimi gel increased significantly(P<0.05),but the water holding capacity did not change significantly.In addition,the increment of gel strength with lipase in chopping process(up to 129.2%)was higher than that in rinsing process(up to 71.78%).Therefore,the further research on the mechanism of adding fat was carried in samples with lipase added in chopping process.2)Mechanism of the effect of lipase on the gel properties of catfish surimiThe chemical forces,surface hydrophobicity of the protein,fat oxidation and protein oxidation were measured.The degree of protein aggregation and network structure of the surimi gel were evaluated by SDS-PAGE electrophoresis and scanning electron microscopy to explore the influencing mechanism.The results showed that after adding lipase,the content of ionic bond and hydrogen bond decreased,while the hydrophobic interaction and the surface hydrophobicity of the protein increased,indicated that the fat changes after adding lipase promoted protein unfolding.The decrease in sulfhydryl groups and the increase in disulfide bonds are contributed to maintain the gel structure.According to the increase of the TBARS value and carbonyl content,it was found that the fat oxidation and the degree of oxidation of the protein were increased after lipase treatment.Combined with the changes of the myosin heavy chain band of SDS-PAGE gel electrophoresis,and the denser and tighter microstructure of gel in scanning electron microscopy directly described the effect of lipase on the improvement of the gel characteristics of surimi.3)Effect of fat hydrolysate on surimi gelIn order to explain the mechanism of fatty hydrolysates in surimi gel,the crude fish oil of catfish and lipase were reacted to simulate the fat hydrolysis process in the surimi processing.Added it to the fat-free surimi gel to verify the effect of fat change on the strength of the protein gel.The results showed that the degree of fat hydrolysis first increased and then tended to stable.The gel strength and whiteness increased after adding the fatty hydrolysates such as monoglycerides and diglycerides to surimi gel,but the water holding capacity showedno significant changes,which further verified the effect of fatty hydrolysates on the improvement of surimi gel propertiesIn summary,lipase can intervene the protein gel process of surimi gel by control the fat,and to achieve the improvement of gel properties of surimi in fatty fish.It can be used in the processing and production of surimi fish with fatty fish.