Study On Keep-alive And Preservation Technology Of Macrobrachium Rosenbergii

This article takes Macrobrachium rosenbergii as the experimental object,starting from the aspects of keeping alive methods,factors affecting keeping alive,water quality control during keeping alive,and compound fresh-keeping technology,etc.The effects of lowering temperature,CO₂anesthesia and the control of the ammonia nitrogen content on the survival rate,survival time,water quality indexes,and physiological and biochemical indexes of Macrobrachium rosenbergii were investigated to optimize the technological conditions with the best keep-alive transportation;at the same time,a preliminary study was carried out on the preservation effect of the compound preservative,and an efficient,low-cost,and safe compound preservation agent formula was optimized through the response surface method.The results are as follows:?1?The mechanism of affecting keep-alive by lowering temperature was studied and the changes of water quality index and the physical and physicochemical indexes of muscle,blood and liver and other shrimp body tissues during the keep-alive process were examined.The results show that the best keeping-alive condition of Macrobrachium rosenbergii is:after 24 hours of cultivation,the shrimp water mass ratio is 1:12,and the survival rate can reach 100%within 24 hours of keeping at 20?.Under this condition,the water quality dissolved oxygen and p H all changed within a suitable survival range,and the content of ammonia nitrogen and total bacteria increased;muscle glycogen,muscle p H and muscle ATP decreased,and sarcolactic acid rose;blood ALT and AST were significant increased;liver glycogen,liver T-SOD activity and MDA content all changed significantly.It shows that the changes of water quality index will affect the normal physiological metabolism of shrimp body muscle,blood and liver tissues,thus affecting its survival time and survival rate.?2?To explore the effect of CO₂ anesthesia on the preservation process of Macrobrachium rosenbergii.The research shows that after treatment with 150 mg/L CO₂ anaesthesia concentration,Macrobrachium rosenbergii was preserved at a temperature of 18?and a shrimp water mass ratio of 1:10,the survival rate after 48h was more than 90%.Under this condition,the total ammonia nitrogen,the dissolved oxygen and p H of water changed within the suitable survival range,muscle ATP,muscle glycogen and liver glycogen were significantly reduced to varying degrees, producing a large amount of lactic acid,causing muscle p H to drop;The activity of AST and ALT increased significantly.The activity of T-SOD and MDA in liver were negatively correlated and significantly changed.It shows that CO₂ anesthesia can alleviate the stress of shrimp body to extend the survival time and survival rate.?3?The optimum condition of zeolite modification process was determined by orthogonal experiment,and the effects of ammonia nitrogen concentration and p H,zeolite dosage and adsorption time on the adsorption performance of modified zeolite were tested.The changes of survival rate and water quality index during the keep-alive process were studied,and the characterization of modified zeolite were analyzed.The results showed that zeolites with particle size of 1?2mm were modified with microwave?230W,10min?and then ultrasound?560W,28k Hz,50min?to enhance Na Cl solution?0.8mol/L?modification.The removal rate of 30g/L modified zeolite into the water with a p H of 7.00 is 98.86%for 1 hour,and the removal rate of ammonia nitrogen is 98.86%,which is 20.88%higher than that of unmodified zeolite;The characterization showed that the modified zeolites increased the specific surface area without damaging the crystal lattice,and significantly increased the exchange rate of Na⁺and the ratio of Si to Al,which could well maintain the charge balance.The survival rate of Macrobrachium rosenbergii was significantly improved and its water quality index was effectively controlled.Therefore,the zeolite prepared by the combination of ultrasonic wave and microwave to enhance Na Cl modification can effectively remove ammonia nitrogen to prolong the survival time and improve the survival rate of Macrobrachium rosenbergii.?4?To explore the optimal formula of fresh-keeping Macrobrachium rosenbergii with compound preservative and its effect on preservation.Based on the single-factor experiment,?-poly-L-lysine??-PL?,tea polyphenols?TP?and chitosan?CS?were selected as composite preservatives by Box-Behnken central portfolio experimental design and response surface methodology?RSM?.The optimal formula of composite preservation technology was determined,and the preservation law of Macrobrachium rosenbergii was revealed by the determination of volatile base nitrogen?TVB-N?,thiobarbituric acid?TBA?value,total colony count and sensory evaluation.The best formula of compound preservative is:0.32%?-PL,0.33%TP,2.3%CS.It has been proved that the response surface model fits well with the actual situation.Under this condition,the colony growth of Macrobrachium rosenbergii can be inhibited to a certain extent,the fat oxidation can be slowed down,and the shelf life of Macrobrachium rosenbergii can be extended from 4d to 9d under refrigeration?4±1??.It indicates that the cold storage auxiliary compound preservatives can effectively prevent the spoilage of Macrobrachium rosenbergii to extend its shelf life.