| Mackerel is one of the most important economic fish in China.Mackerel is rich in nutrients,among which EPA eicosapentaenoic acid and DHA 22 carbon hexaenoic acid are the highest.Mackerel will undergo corruption during freezing storage,and fat and protein will be oxidized to varying degrees.Due to the proliferation of bacteria,histidine deammoniation results in the formation of toxic histamine.The protein surface hydropHobicity,carbonyl,sulfhydryl and SDS,fatty acid value,peroxide value,malondialdehyde(MDA)and fatty acid composition were measured in frozen mackerel block.At the same time,the composition of surface microflora during freezing storage was studied,and the microbe Ann in mackerel was considered.The effects of sodium isoascorbate and carrageenan oligosaccharide on the quality of frozen mackerel were discussed.The main research contents and conclusions of this paper are as follows:1 Study on the law of protein oxidation in mackerel muscle during cryopreservation: With the increase of cryopreservation time,the content of myofibrillar protein of mackerel decreased continuously,and the quality of mackerel meat showed different degree of protein oxidation.During the later period of frozen storage,the protein content of mackerel muscle began to change significantly,and its surface hydrophobicity and carbonyl began to rise rapidly.The carbonyl content increased by 0.27 nmol/mg and 0.42 nmol/mg from the40 th day to the 60 th day and the 80 th day of frozen storage.The surface hydrophobicity was 130.6 UG on the 100 th day of freezing storage,which was three times as high as that on the 10 th day.The sulfhydryl content of protein decreased by 1.6 mmol/g in the later period of frozen storage.Muscle elasticity,glue stickiness,elasticity and hardness decreased continuously.In addition,the odor and color of mackerel changed greatly during frozen storage.From the above,the quality deterioration of mackerel was weak in the early stage of frozen storage,and the protein quality of mackerel muscle decreased greatly with the increase of frozen storage time in the later stage.2 Study on lipid oxidation of mackerel during cryopreservation: with the increase of storage time,the oxidation of fat in mackerel appeared in different degrees.During freezing storage,the pH value of the muscle of mackerel(mackerel)decreased first and then the upper body,while the peroxide value increased first and then decreased.The acid value and the content of malondialdehyde(MDA)increased with the increase of time.After freezing for 40 days,mackerel began to produce a certain bad smell,the color gradually lost its luster,and became dim in the late frozen storage.During freezing storage,the flavor,color and fatty acid composition of mackerel(mackerel)changed greatly.3 The change of microbial community in frozen mackerel was analyzed based on high throughput sequencing.The main dominant bacteria in fresh mackerel were Sphingosine and Acinetobacter.After freezing for a period of time,Bacillus belongs to(Paenibacillus),Aeromonas,and so on,which gradually becomes the dominant bacteria in frozen storage of mackerel.On the 100 th day of freezing storage,the main species of mackerel was Enterobacter,Aeromonasand Vibrio and so on.4 The effect of carrageenan oligosaccharides on the quality of frozen mackerel:carrageenan oligosaccharides can effectively improve the quality of frozen mackerel,slow down the oxidation of protein,slow down the surface hydrophobicity and carbonyl formation,and make the protein spatial structure stable.The acid value of mackerel,the content of malondialdehyde(MDA)and fatty acids increased rapidly,but the peroxide value had no regularity in this experiment,which needed to be analyzed in combination with other data.In general,carrageenan oligosaccharides have significant antioxidant effects on protein and fat of frozen mackerel,which can prolong the shelf life of frozen mackerel. |
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