| Fresh aquatic products are popular among consumers,but there are some problems in the process of sale and storage,such as short shelf life and decline of edible quality caused by microbial pollution.Therefore,the sterilization,preservation and safety quality control of aquatic products such as fresh grass and fish are the bottleneck of industrial development.The traditional thermal sterilization method will destroy the quality of fresh aquatic products and is not suitable for fresh products.Chemical preservation has some problems such as chemical residue and food safety.Due to high equipment cost and high technical requirements,ultrahigh voltage cannot be applied in large scale industry.Therefore,a new cold sterilization method is needed to treat fresh aquatic products.Low temperature plasma cold sterilization technology in the process of treatment does not have obvious temperature rise,suitable for temperature sensitive fresh aquatic products;At the same time,it can kill a variety of microorganisms,for the microorganisms in the food has a good inhibition effect,has the advantages of extending the shelf life of food,less impact on the quality of food,no residual substances after action,in the fresh aquatic products sterilization and storage of fresh has a great prospect of application.The purpose of this study was to study the effects of low temperature plasma on the quantity of microorganisms and the safety and quality indexes of raw straw fish during storage,and to study the physical and chemical properties and gel properties of myofibrillary proteins in fish,so as to provide a theoretical basis for the industrial application of low temperature plasma cold sterilization technology in fresh aquatic products.The main research results of this paper are as follows:1.Effect of cold plasma treatment on germicidal efficiency and storage quality of fresh grass and fishUsing dielectric barrier low temperature plasma equipment(DBD)in different voltage(40,50,60 and 70 k V)under the opposite grass fish processing 3 min,microbial populations in the samples(total number of colonies,the total number of E.coli,and total number of Pseudomonas)and the quality index(color,p H,glucosinolates barbituric acid value,sensory evaluation and histamine content)changes during storage,The correlation between histamine content and quality index was analyzed.The results showed that the bactericidal effect of plasma cold sterilization on fresh grass fish was significantly increased with the increase of voltage(p < 0.05),the total number of colonies,Pseudomonas and Escherichia coli in the 70 k V treatment group decreased by 1.0,1.2 and 1.1 log CFU/g,respectively.The total number of colonies in the control group exceeded the limit of 6 log CFU/g at the 4th day of storage,and exceeded the limit of 70 k V at the 8th day.Compared with the control group,thiobarbituric acid reactive substance(TBA)value was increased after plasma treatment.Therefore,the shelf life of fresh grass and fish treated with low temperature plasma was extended by 4 days compared with the control group.In addition,low temperature plasma treatment can reduce the histamine content during storage,and has no significant effect on other quality indexes.In conclusion,low temperature plasma cold sterilization technology can effectively prolong the shelf life of fish to the 8th day,and help to reduce the accumulation of histamine and maintain the quality of fish.2.Effects of plasma actived latin acid on microbial decontamination and quality of grass crapThe effects of different preparation times(2,3 and 4 min)of plasma activated latin acid(PALA)on the meat quality of fresh grass carps during storage were investigated.The number of microorganisms(total number of colonies,total number of Escherichia coli and total number of Pseudomonas)and the physicochemical quality(color,p H,thiobarbituric acid value,water retention and lipoxygenase activity)in the samples were detected during storage.The results showed that the inhibitory effect of PALA on the number of microorganisms in fresh grass fish was significantly increased with the increase of preparation time(p < 0.05),the total number of colonies,Pseudomonas and Escherichia coli in PALA-4 group decreased by 1.50,1.39 and 1.40 log CFU/g,respectively.From the perspective of total number of colonies,the shelf life of fresh grass and fish in PALA-4 group was extended to the 8th day,which was 4 days longer than that in the control group.After PALA treatment,the activity of lipoxygenase in the samples was decreased,and the lipid oxidation degree of the fresh grass fish during storage was inhibited.In addition,PALA treatment had no significant effect on the quality indices of fresh grass and fish(p > 0.05).The above results indicated that PALA treatment of fresh grass fish could effectively reduce the number of microorganisms,prolong the shelf life of fish,and had no significant effect on the quality of fish.3.Effect of cold plasma treatment on physicochemical and gel properties of myofibrillar proteinsIn order to investigate the effects of low temperature plasma on the physicochemical and functional properties of myofibrillar proteins(MP),a dielectic barrier discharge(DBD)was performed to evaluate the fibrillar proteins.DBD and plasma activation-tied Latin acid(PALA)were used as treatment methods,and myofibrillar protein in grass fish was used as research object.The solubility,surface hydrophobicity,total sulfhydryl content,SDS-PAGE,circular dichromatography and the whiteness,water retention and gel strength of MP gel were determined.The results showed that the solubility of MP in water and the content of total sulfhydryl group decreased with the increase of treatment voltage and time(p < 0.05),and the surface hydrophobicity of myofibrin increased(p < 0.05).The MP bands were not degraded,the secondary structure of the protein was changed,the α-helix was decreased,theβ-corner and irregular coiling were increased.After plasma treatment,the physicochemical properties of myofibrillar proteins were changed,and the whiteness,water holding capacity and gel hardness of the protein gels were improved. |
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