| Taking Antarctic krill as the research object,this paper first measured the changes of basic nutrients,color difference,amino acid composition and content of Antarctic krill in different months in a fishing cycle in area 48.1 of the same Antarctic sea area;Secondly,the effects of different biological preservatives and treatment methods on the quality of Antarctic krill during frozen storage were studied;Then,based on the pre drying heat treatment of Antarctic krill,through different steaming time,taking sensory score,cooking loss,water content,texture,polyphenol oxidase activity and protease activity as evaluation indexes,the more appropriate heat treatment conditions are selected,so as to provide theoretical reference for the subsequent production of high-quality Antarctic krill dry products;Finally,the sensory score,color difference,texture,water content and free amino acid content of Antarctic krill under different drying conditions were analyzed to provide theoretical support for the subsequent industrialized processing of instant Antarctic krill on board.(1)Using Antarctic krill as raw material,the changes of protein content,fat content,water content,ash content,color difference and amino acid composition of Antarctic krill with time in different fishing months were analyzed.The results showed that due to the influence of Antarctic sea season,the protein content and fat content were relatively high in April and may;From April to may,L * value was higher,a * value reached the lowest in April,and b * had no significant change in the whole fishing cycle;In addition,Antarctic krill is rich in 18 kinds of free amino acids,all essential amino acids required by human beings,and meets the definition of high-quality protein by the United Nations agricultural and food organization / World Health Organization(FAO / who),and the E /T is as high as 43.46% and 43.36% in April and may,and the E / N is as high as 74.67%and 74.46% in April and may.Therefore,from the comprehensive results,Large scale fishing can be carried out in April and may in area 48.1,and higher quality Antarctic krill can be obtained.(2)In order to explore the effects of different preservatives and treatment methods on the quality of Antarctic krill during frozen storage,and further improve the quality of Antarctic krill processed on board.In this paper,the effects of three different preservatives(chitosan 1%,tea polyphenol 0.5%,ascorbic acid 8g / L)and treatment methods(freezing in the preservative solution,soaking in the preservative solution for 10 min,fishing out the leachate and freezing)on the quality of Antarctic krill under the condition of frozen storage at-20 ℃ were studied.The results showed that with the extension of frozen storage time,TVBN,TBARS,K value,total number of colonies and p H of all treatment groups showed a significant upward trend,and the preservation effect of immersion group was significantly lower than that of other groups(P < 0.05);The juice leaching volume of soaking group was significantly lower than that of other groups(P < 0.05);When frozen for 10 months,the senses of all groups were unacceptable.The quality of Antarctic krill treated by immersion freezing is better than that by immersion freezing;The treatment with preservative was better than that without preservative.The quality of Antarctic krill was better preserved after immersion in the frozen place of chitosan.(3)This chapter studies the effects of different steaming time on the quality of Antarctic krill.The raw materials are Antarctic krill that have just been caught on board for 2 hours and treated by steaming.Taking sensory score,cooking loss,water content,texture,polyphenol oxidase activity and protease activity as evaluation indexes,the results showed that the hardness and chewability of Antarctic krill increased rapidly during steaming,while with the extension of steaming time,the hardness and chewability remained relatively stable at first,and then showed a downward trend.In addition,with the extension of cooking time,the cohesion of Antarctic krill increased gradually,while the elasticity decreased gradually.It was found that the polyphenol oxidase,protease and other active substances in Antarctic krill could effectively inhibit their activity at higher temperature;Although the enzyme activity decreased 3 minutes before steaming,it did not inactivate,and there were varying degrees of browning.When steaming for 5-6minutes,the polyphenol oxidase in Antarctic krill was inactivated,but the shrimp body was damaged.Therefore,the best steaming condition should be steaming for 4 min when polyphenol oxidase and protease are inactivated.(4)According to the experimental results in the previous chapter,the best heat treatment condition before drying is steaming for 4min.The sensory score,moisture content,texture,color difference and free amino acid content during drying are studied and analyzed.The results showed that the sensory score of the direct drying group reached the maximum of 88.6 points at 6 hours and 92.3 points at 4 hours after heat treatment;The moisture content decreased continuously.The direct drying group reached 20.54%after 6 hours of drying,and the drying group reached 20.42% after 4 hours of drying after heat treatment.With the increase of drying time,the hardness and chewability of Antarctic krill continued to increase,and the elasticity and cohesion decreased.The hardness of Antarctic krill dry products without heat treatment decreased after 8 hours of drying,The elasticity decreased gently in the first 6 hours,and the cohesion decreased continuously,which was similar to the change trend of elasticity,and its chewability and hardness had the same change trend;After heat treatment,the elasticity,cohesion and chewability of the group were the same as those of the group without heat treatment;After heat treatment,the fresh amino acids in the drying group reached the maximum value of 666.52mg/100 g at 6 hours,which was higher than the maximum value of 573.6 mg / 100 g at 8 hours in the direct drying group,the sweet free amino acids in the drying group reached the maximum value of 1048.81 mg / 100 g at 6 hours and 1345.54 mg / 100 g at 8 hours in the direct drying group,The content of bitter amino acids in the direct drying group increased continuously during the whole drying process,while the content of bitter amino acids in the drying group decreased after 4 hours of drying after heat treatment.In conclusion,the quality of dried products of Antarctic krill can be improved to the greatest extent by drying it for 4-6 hours after steaming for 4 minutes. |
