Research Of Acidic Electrolyzed Water And Slurry Ice Technology During Preservation Of Large Yellow Croaker(Pesedosciaena Crocea)

Aquatic products are a kind of main animal food.Pseudosciaena crocea is known as"national fish"and is one of the four traditional Marine economic fish species in China.Compared with livestock products,the body of aquatic products is soft and rich in water,protein and unsaturated fatty acids.After death,they begin to deteriorate under the action of microorganisms and endogenous enzymes.At present,large yellow croak is mostly stored,transported and sold in large quantities in the way of frozen whole fish.However,the complete cold chain covering the whole process of fishing（acquisition）,processing,storage,transportation and distribution of large yellow croaker in China has not been improved in the circulation process.Therefore,it is very important to study an economic and effective way to maintain the quality of products after catching to extend the shelf life and improve the value of products.Acidic electrolyzed water（AEW）is a green and safe new bactericide with wide spectrum antibacterial properties.AEW is another active form of Acidic electrolyzed water ice.Slurry ice（SI）is a two-phase homozygous mixture composed of small,smooth ice particles and liquid carrier.It has strong loading cooling capacity,low and controllable final temperature,and little mechanical damage to products.It is a new green refrigerant with great potential in the processing and preservation of aquatic products.The research of acidic electrolyzed water combined slurry ice on large yellow croaker during preservation storage is few,so this study through the design of experiment,the slurry ice combined acidic electrolyzed water coupling technology applied in the same link or different fresh-keeping storage link,play the synergy between barrier factors,in the actual application level for large yellow croaker cold-chain logistics operational mode of shipping.The second chapter explores the acidic electrolyzed water pretreatment effect and quality of large yellow croaker reduce bacteria,acidic electrolyzed water application needs to take into account the available chlorine concentration,soaking time,charging liquid ratio for the single factor investigation,the three factors of different levels of large yellow croaker p H value,color,quality and structure,the influence of the total number of colonies,sensory characteristics,according to the results of single factor experiment with orthogonal experiment.A set of pretreatment parameters of acidic electrolyzed water which can effectively reduce bacteria without significantly affecting the quality of large yellow croaker are obtained,which is the basis of subsequent preservation,storage and transportation of large yellow croaker.Conclusions:（1）In terms of available chlorine concentration,no significant difference in p H,ventral B value,firmness,or elasticity of large croakers between nil and fresh samples with available chlorine concentration in the range of 0-40mg/L（P>0.05）,total number of colonies significantly decreased with nil nil（P<0.05）.（2）From the soaking time:acid electrolytic water sterilization needs a certain time,when the soaking time reaches15min,the sterilization rate is 83%,and there is no significant difference between sensory characteristics score and fresh sample（P>0.05）.（3）In terms of ratio of feed to liquid:The change of ratio of feed to liquid has no significant effect on texture of great croakers（P>0.05）,but mainly affects B nil value and total number of colonies in color of great croakers.When ratio of feed to liquid exceeds 1:4,B nil value on the belly is significantly reduced（P<0.05）,and gold color decreases significantly.（4）Orthogonal experiment results showed that the effective chlorine concentration was 40mg/L,the soaking time was 15min,and the ratio of material to liquid was 1:4.Compared with the fresh samples,the color,texture and sensory characteristics of large yellow crocea were not significantly different when soaked in acidic electrolyzed water under the characterization parameters.In chapter 3,the effects of acidic electrolyzed water pretreatment combined with different ice storage methods on the quality of large yellow croaker during storage were studied,and the changes of physical and chemical indexes,microbial indexes,microstructure and sensory characteristics of large yellow croaker during storage were measured.The results showed as follows:（1）comparing the effects of acidic electrolyzed water pretreatment on the preservation effect of large yellow croaker under the same ice storage mode,it was found that the pretreatment could significantly reduce the initial total number of bacteria,slow down the color change of the body surface of large yellow croaker at the initial storage stage,and delay the time to reach the freshness level 1;（2）the longitudinal comparison pretreatment composite differences in different ways iced fresh,found that the acidic electrolyzed water ice and slurry ice can inhibit microbial growth,slow muscle fiber organization structure deterioration and extend the shelf life of products,but because of its fast cooling and uniform slurry ice,the characteristics of low temperature and constant has obvious advantages in middle and later periods of the storage.The shelf life of AEW+SI group,SI group,AEW+AEWI group,AEWI group,AEW+CI group and CI group was 19 d,19 d,15 d,13 d,11 d and 9 d,respectively.（3）Combined with QIM evaluation and analysis,slurry ice storage has little mechanical damage to the body,and has no adverse effects on the body surface color and eyeball morphology of large yellow crocea at the initial stage of storage.Based on the analysis of all evaluation indexes,AEW+SI group could play a synergistic effect between acidic electrolyzed water and slurry ice barrier factor,and maintain the product freshness level 1 within 7 days and reach the end of shelf life 19days while maintaining good sensory quality.The fresh-keeping effect was the best.The fourth chapter on the basis of the first two chapters,in combination with the actual situation of large yellow croaker cold-chain logistics transportation,coupling in pre-treatment by acidic electrolyzed water combined slurry ice,in suitable link simulation without transport（24 h）composite slurry ice transport process,with total sulphur content,Ca²⁺-ATPase activity and carbonyl content as the main indicators,To observe the changes of protein characteristics of large yellow croaker（Croaker）during the simulated circulation under different conditions.At the same time,the K value was used as the freshness observation index,the total number of colonies was used as the microbial observation index,and the comprehensive quality of the products was evaluated by combining QIM.The results show that:（1）From the perspective of ice-free transportation,the contents of total sulfhydryl group,carbonyl group and odor score were significantly different from those of fresh samples after 24 h ice-free transportation.However,due to the combination of slurry ice precooling and acid electrolytic water bacteria reduction pretreatment before ice-free transportation,all indicators were still better than the group without precooling+CI+CI.（2）From the perspective of later storage process,the difference of ice is the main factor leading to the different shelf life of samples,and the fundamental reason is the environmental temperature provided by different kinds of ice for product storage.Slurry ice can provide low and stable final temperature,effectively inhibit the total sulfhydryl content,decrease of Ca²⁺-ATPase activity and delay the increase of carbonyl content.Taking pretreatment+NI+SI group as an example,compared with acidic point hydrolysate ice and broken ice storage group,the shelf life of pretreatment+NI+SI group can be prolonged by 2 d and 8 d,respectively.（3）From the overall simulated circulation process,there were no significant differences in the total number of colonies,total thiol content,Ca²⁺-ATPase activity and carbonyl content between the pretreatment+SI+SI group and the pre-+NI+SI group during 3 d-15 d storage（P>0.05）,and the indexes had similar trends,and the shelf life was 2 d different.Combined with QIM evaluation,QI variation trend of the two groups was similar during the whole storage process.It was indicated that after a short period of ice-free transportation,slurry ice was added in time for subsequent storage,and the indexes of the product would not change rapidly in a short time.