| Fruit radish has a high health care value,as it can be eaten fresh like fruit,cooked and used medicinally,and is rich in vitamin C and other nutrients.However,fruit radish is easy to rot and deteriorate in fresh storage.To ensure its quality,it is important to find the best storage technology and study the super ice temperature preservation storage technology.In this paper,we conducted a lot of theoretical and experimental research on fruit radish storage by using pre-cooling and super ice temperature technology,firstly,by adding freezing point regulator and combining with pre-cooling technology,we measured the corresponding super ice temperature values under different treatment conditions(17 sets of experiments);then we set the storage temperature according to the super ice temperature values and conducted super ice temperature preservation storage experiments(17 sets of experiments),and measured the weight loss rate,soluble solids,respiration Then the super ice temperature freshness storage was pre-cooled to 3℃,and the fruit radish treated with freezing point regulator was put into the storage,and the empty storage pre-cooling experiment and the fruit radish storage experiment were carried out and the corresponding temperature field simulation was performed;finally,the numerical simulation of the effect of chiller air speed and position on the temperature field of the super ice temperature freshness storage was carried out to obtain the optimum chiller to make the temperature field Finally,the numerical simulation of the effect of chiller air speed and position on the temperature field of super ice temperature fresh storage was carried out to obtain the best air speed and position of chiller for more uniform distribution of temperature field,which is more favorable to the fresh storage of fruit and radish.The main research contents are as follows:(1)Combined with freezing point adjustment and pre-cooling techniques,experiments were conducted to measure the freezing temperature value and super freezing temperature value of fruit radish.Four concentrations of sorbitol,lactose,calcium chloride and vitamin C,0.5%,1.0%,1.5%and 2.0%,respectively,were used to prepare 16 groups of freezing point conditioners.The 16 groups of freezing point regulators were then pre-tempered to 0℃,and the fruit radish was soaked until its central temperature dropped to 3℃,and the fruit radish was treated with freezing point regulators and pre-cooled at the same time,at which time the superfreezing temperature value of the fruit radish was measured.Sixteen groups of superfreezing temperature values were obtained under different freezing point regulators and different concentrations,and the superfreezing temperature values of fruit radish were significantly adjusted by using freezing point regulator treatment compared with those of fruit radish without freezing point regulator treatment.(2)Experimental studies on the effect of pre-cooling+super ice temperature storage on the quality of fruit radish were conducted.The quality changes of fruit radish during super ice temperature storage were analyzed by comparing the treatment group with the control group without freezing treatment after super ice temperature storage by freezing point adjustment of four concentrations(0.5%,1.0%,1.5%and 2.0%)and four freezing point regulators(sorbitol,lactose,calcium chloride and vitamin C)in combination with pre-cooling.The experimental results showed that the combination of pre-cooling and freezing point regulator soaking also pre-cooled the fruit radish while regulating the freezing point;the super ice temperature freshness storage could effectively inhibit the increase of weight loss of fruit radish,inhibit the decrease of soluble solids content,reduce the respiration rate of fruit radish internal cells.ensure the better quality of fruit radish and prolong its freshness storage time.The combination of pre-cooling with sorbitol solution at a concentration of 2.0%and super ice temperature storage was more effective in ensuring the quality of fruit radish.(3)Empty storage pre-cooling and fruit radish storage experiments and their numerical simulations.The first stage of the experiment:the super ice temperature freshness storage was pre-cooled from the initial temperature of 20℃ to 3℃ for the super ice temperature freshness storage pre-cooling experiment.Monitoring points were set up at different locations in the super ice temperature freshness storage to monitor the temperature change in the storage.The second stage of the experiment:after the fruit radish was put into the storage,the fresh storage was continued to cool down from 3℃ to-1.5℃.Accordingly,physical and mathematical models were established to conduct numerical simulations of the temperature field inside the freshness store.The first stage of simulation:the cold air blown by the chiller cools down the air inside the store to 3℃ and the temperature distribution is more uniform.The second stage of simulation:the temperature inside the warehouse continues to drop,the highest temperature at the stack,the corners and the gap between the two fans are the next highest,and the temperature inside the super ice temperature preservation warehouse gradually reaches uniformity with time change.The numerical simulation results are compared with the experimental data to verify the correctness of the simulation and to provide a basis for the later numerical simulation of the super ice temperature preservation library.(4)Numerical simulation of the temperature field of the super ice temperature freshness storage.In order to ensure the uniform distribution of temperature field to make the fruit radish better during super ice temperature preservation storage,numerical simulation of the effect of chiller air speed and position on the temperature field of super ice temperature preservation warehouse was carried out on the basis of the previous simulation to determine the reasonable chiller air speed and its position.A physical model of fruit radish placed in 8 stacks in the super ice and temperature store was established to simulate the effect of chiller air speed and position on the temperature field in the store.The simulation results show that the chiller installation position and air speed have an effect on the uniformity of the temperature field in the storage;the larger the air speed of the chiller,the smaller the change of the temperature field in the fresh storage,and the more uniform the distribution.The air temperature in the center of the refrigerator is lower than the air temperature on the side of the refrigerator when the fan is installed on one side;when the fan is installed on both sides,the air temperature at both ends of the refrigerator decreases more rapidly than when the fan is installed on one side,but in the case of larger air speed,the airflow has the problem of mutual interference,which affects the uniformity of the temperature field. |
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