Study On Key Problems And Shelf Life Modeling Of Live Shellfish For Waterless Transportation

In order to solve the problem of high quality waterless transportation of live bivalves,the key problems of transportation,such as depuration and temporary keeping,transportation conditions,sealed packaging,and shelf life prediction,were studied based on biological nature for live bivalve’s samples of Patinopecten yessoensis,Argopecten irradias and Ruditapes philippinarum.The recirculated water system of depuration and temporary keeping was appiled to realize the integration of live bivalves depuration and gradient cooling for connecting the transportation of live shellfish waterless transport at low temperature.Based on the principle of material balance,the ammonia excretion rate and oxygen consumption rate of biological metabolism were combined to calculate the total ammonia nitrogen and oxygenic demand of the recycled water system,which applied in calculating the circulating water volume of the system.Then the design,construction and debugging of the system were completed,and a new integrated mode of shellfish depuration and gradient cooling temporary cooling was established.The growth demands of Patinopecten yesoensis could be adequately satisfied by the range of water temperature and dissolved oxygen.No deaths were found while live samples were being depurated and temporarily kept with the CI ranged from 4.82 to 5.06.The total bacteria remarkably decreased with the time.The samples were divided into three groups based on three different pre-process in order to study the quality of transport based on the different pre-process.As a result,in group 1(depuration for 48h),the first death occurred after 56 h,and in group 2(depurationfor 24h and temporary keeping for 24 h),the first death occured shown after 104 h.In group 3(directly transport),all shellfishes died in 64 h and the bacteria number in group 3 was significantly different from that in group 1 and 2.The consumption of glycogen in group 2 was delayed by the gradual cooling procedure.With this experiment,the 24 h depuration followed by 24 h gradient cooling procedures is proved to be efficient for the waterless-low-temp transportation.The survival rates and nutrient component were studied in live Patinopecten yessoensis(PY)after purification and temporary rearing with different unitized transport tubs(group 1:polyethylene boxes without ice;group2:polyethylene boxes with ice,group3:semiconductor thermal insulation box,group4:semiconductor thermal insulation box).The results showed that the temperature and the cooling way of the tubs affect the survival rate of PY in closed container.The findings indicated that the cooling way of compressor and semiconductor slowly reduced the rate of consumption of glycogen,crude protein and crude fat,and also prolong the survival time,so the stress mechanism of different refrigeration methods on shellfish was clarified.The live Scallop(Argopecten irradias)and clam(Ruditapes philippinarum)were treated by sealed package in the forms of vacuum,oxygen and air at 0℃、5℃、10℃ and 15°.The results showed that the survival time and the value of sensory quality of scallops treated at 0℃ and 5℃ were prolonged and enhanced than those at 10℃ and 15℃.Specifically,at the temperature of 0℃ and 5℃,the growth of rate of bacterial count,chrominance and weight lost were slower than that at 10 0C and 15℃,and the 0℃ was more conductive to prolonging the survival time and rearing the quality of live scallop,therefore the reaction rate of those quality indexes were accelerated with the increase of storage temperature.The results show that sealed packaging with oxygen was more conductive to rearing the quality of live bivalve,and also provides theoretical basis for shelf life prediction and evaluation of sealed package Argopecten irradias and Ruditapes philippinarum.The research aims to establish shelf life model of Argopecten irradias and Ruditapes philippinarum with different package using Arrhenius equation.The zero-order kinetics model could describe chrominance and glycogen with high accuracy of the sealed package Argopecten irradias with oxygen,air,vacuum packaging.At the same time,the changes of the total bacteria density and pH value were all well fitted with the first order reaction kinetics.For the live Ruditapes philippinarum,the first-order kinetics model could describe the glycogen of vacuum packaging,the total bacteria density of oxygen and air packaging with high accuracy.At the same time,the changes of weight loss,pH value and chrominance with oxygen packaging,the total bacteria of density vacuum packaging,glycogen and chrominance of air packaging,glycogen of oxygen packaging were all well fitted with the zero order reaction kinetics.The shelf life prediction model applied Arrhenius of live bivalves was established based on verified experiment,and the dynamic models of key quality index such as glycogen established in this study were effective in predicting the shelf life of seal package Argopecten irradias and Ruditapes philippinarum.The results provide satisfactory references for the sealed packaging and predicting shelf life of live shellfish.