The Effects Of Simulated Storage And Transportation Temperature And Different Thawing Methods On The Quality Of Red Sea Bream(Pagrus Major)

Red sea bream?Pagrus major?has tender meat and high nutritional value.It is distributed in all four sea areas of China.Like other fish,red sea bream is easily putrefied and difficult to store.Frozen storage and low temperature transportation is one of the most important means to maintain its freshness and quality for a long time.But the storage and transportation process is easily affected by the temperature fluctuation.Frozen products is usually thawed before processed or eaten.The quality and nutritional value of the product are closely related to the thawing conditions.Therefore,it is of great significance to adopt more effective,convenient,economic and safe thawing methods before processing and eating.In this paper,the effects of temperature fluctuation on the quality characteristics of red sea bream were studied,and the effects of different thawing methods on the physical and chemical properties,spatial conformation and microstructure of myofibrillar protein of red sea bream were further studied,the effects of different thawing methods on the microbial diversity of red sea bream were investigated to provide theoretical guidance for the development and application of thawing techniques.The main conclusions are as follows:1.Three conveying chains?control group,L1 and L2?were designed to simulate the process of circulation and transportation.The results showed that the quality of red sea bream varied slightly with the temperature fluctuation,and the quality deterioration of L2 was the most serious in the most significant fluctuation group,after 168 h,pH value reached 6.38,TVB-N value reached16.1 mg/100g,TBA value reached 0.07 mg/100g,hardness and chewiness increased to 510.65 g and 135.20 mJ,elasticity value decreased to 0.4 mm,and colony count reached 3.11 lg CFU/g,respectively,significantly higher than the control group.Therefore,the higher the temperature fluctuation,the faster the quality deterioration of red sea bream.2.The effects of four thawing methods on the quality characteristics,protein conformation and water status of red sea bream were studied.In this experiment,the thawing loss,texture,thermal stability,microstructure and water distribution of the dorsal muscles of red sea bream were determined,and the myofibrillar protein was extracted,the particle size,UV absorption spectra,intrinsic fluorescence and rheological properties were determined.The results showed that CS@Fe₃O₄?Chitosan nanoparticles?had the lowest thawing loss,good water-holding capacity,and could effectively maintain the hardness,elasticity and cohesiveness of fish meat.Compared with far-infrared thawing?FT?and microwave thawing?MT?groups,CS@Fe₃O₄ far-infrared thawing?CFT?and CS@Fe₃O₄ microwave thawing?CMT?could slow down the protein oxidation,and the protein tertiary conformation was stable,the system is stable and its structure is compact and orderly.CS@Fe₃O₄ may make up the shortcomings of single microwave and far infrared thawing technology,and has a certain application potential.3.Based on the combination of high-throughput sequencing and traditional microbial counting methods,the impact of different thawing treatments on the microbial diversity of red sea bream was studied objectively and comprehensively.CFT and CMT can effectively slow down TVB-N and pH increase,but also can slow down the growth of microorganisms.In the four groups of thawing treatment,the proportion of pseudomonadaceae was significantly decreased.After 24 hours of thawing,vibrionaceae decreased rapidly,while pseudomonadaceae,bacillaceae and thermoaceae increased significantly,becoming the dominant species.FT and MT were far apart at principal component level,CFT was close to CMT sample.The results showed that the microbial species and composition of FS,FT and MT samples were different from other samples.