Study On The Quality Change Law And Occurrence Mechanism Of Three Kinds Of Squid Frozen Storage

Squid is delicious and nutritious.It is a high-protein and low-fat aquatic product.It is rich in a variety of essential amino acids for the human body,and the essential amino acid composition is close to total protein,so it is liked by consumers.Illex argentinus,Ommastrephes bartrami and Dosidicus gigas are the three most common squids in our country.Squid is usually stored and transported in the form of frozen storage,and the quality of squid will inevitably be affected during storage and transportation.Therefore,the research on the quality characteristics of different types of squid is of deep significance for the later study of the shelf life of different types of squid and production and processing applications.However,the research on the characteristics of different kinds of squid is still scarce.In this paper,the quality changes and mechanisms of three kinds of squid during freezing storage are studied.The main research contents are as follows:1?The quality changes of three kinds of squids frozen at-18?for 120 days were studied.It was found that the quality of the three types of squid continued to decline as the freezing time increased.The p H value of Dosidicus gigas is always lower than the other two squids during the whole freezing period,and the volatile base nitrogen(TVB-N)content is significantly higher than the other two squids on the 90th day(p<0.05),and after120 d The whiteness and hardness are significantly higher than the other two squids,while the elasticity is significantly lower than the other two squids(p<0.05);the water content and water activity,myofibril protein content,Ca²⁺-ATPase activity,and total sulfhydryl content of the Illex argentinus The rate of decrease in solubility of protein and protein was significantly higher than that of the other two squids(p<0.05),while the rate of thawing loss and the increase rate of turbidity level were higher than those of the other two squids.During the freezing process,Illex argentinus thiobarbituric acid(TBA)content and malondialdehyde(MDA)content increased significantly lower than the other two kinds of squid(p<0.05);the Ommastrephes bartrami emulsion characteristics(EAI)and emulsion stability(ESI)decreased the fastest,and its muscle The foamability and foam stability of fibrillin were significantly lower than the other two squids after being frozen for 120 days,and the increase rate of carbonyl content was significantly higher than that of the other two squids(p<0.05).In addition,the microscopic electron microscope scanning and HE staining observation results showed that the microstructure of the three kinds of squids was destroyed after being frozen for 120 days,and the Ommastrephes bartrami was the most serious.This shows that the quality of the three kinds of squids decreases with the increase of frozen storage time,but the squid species are different,and the changes of different quality characteristics during the frozen storage process are also different.2?The quality changes of three kinds of squids during 8 d cold storage at 0?were studied.The quality changes of the three kinds of squid during the cold storage and freezing process show basically similar laws,and only a few quality characteristics are different.Among them,TVB-N content increased with the increase of refrigeration time,and the increase rate of Illex argentinus was the fastest;SDS-PAGE electrophoresis results showed that the protein degradation of Ommastrephes bartrami after 8 days of refrigeration was severe;ATP staining revealed the content of type II muscle fiber in Illex argentinus Compared with the other two kinds of squid,the content of type?muscle fiber in the three squids decreased after 8 days of refrigeration,and the content of type?muscle fiber increased;Van Gieson staining showed that the three kinds of squid collagen fibers had a small amount of proliferation,and the Ommastrephes bartrami muscle fiber rupture was the most serious.Through the detection of the flavor analyzer,it was found that 33,50and 36 volatile substances were identified in Illex argentinus,Ommastrephes bartrami and Dosidicus gigas,respectively.During the entire storage period,the content of3-furanmethanol in Dosidicus gigas was significantly higher than that of the other two squids(p<0.05),trimethylamine is only found in Illex argentinus,while the ketones and aldehydes in the Ommastrephes bartrami are higher than the other two squids.3?The differentially expressed proteins of three squids were studied.The proteomic analysis of the three species of squid was carried out by mass spectrometry analysis,differential protein expression analysis,subcellular structure localization,gene theory(GO)function annotation analysis and homologous protein cluster(COG)analysis.The results showed that compared with Dosidicus gigas,Illex argentinus has 28 up-regulated proteins and 21 down-regulated proteins,while Ommastrephes bartrami has 33 up-regulated proteins and 24 down-regulated proteins;only 5 are identified in Ommastrephes bartrami and Illex argentinus.Two different proteins,showing a high degree of similarity.GO function annotations indicate that these differential proteins(DAPs)are mainly involved in binding,catalytic activity,cellular processes and metabolic processes,and these processes are related to the structural integrity of the protein In addition,COG analysis shows that DAPs are mainly concentrated in translation,ribosomal structure and biogenesis,cytoskeleton,energy production and conversion,carbohydrate transportation and metabolism,and signal transduction mechanisms.Freezing induction greatly affected the functional properties of DAPs in the cytoskeleton,and caused varying degrees of damage to the flavor,color,texture and protein properties of the three kinds of squid muscles.Based on the study of the quality changes of three kinds of squid during freezing and cold storage as the starting point,through the analysis of differentially expressed proteins,it is concluded that the quality changes of the three squids during freezing and cold storage are the same,but DAPs dominate the storage process.Status,and therefore the rate of quality change.This study provides a theoretical basis for the subsequent control of the quality deterioration of different kinds of squid frozen storage.