Study On Winter Jujube Vacuum Ultra-ice Temperature Preservation And Storage Experiment And Heat And Mass Transfer

Winter jujube is a common fruit in northern my country.Due to its delicate texture and rich water content,Winter jujube is very easy to lose water,soften,rot and lose its commercial value during storage.In this paper,fresh Winter jujube is taken as the experimental object,and the storage technology suitable for Winter jujube preservation is determined through the vacuum ultra-ice temperature preservation experiment.The ice temperature and ultra-ice temperature of Winter jujube were measured under six pressures of atmospheric pressure,80kPa,60kPa,50kPa,40kPa,and 20kPa.In this paper,the direct measurement method is used to measure the ice temperature of the winter jujube without freezing point adjustment in a vacuum cryogenic tank;the ultra-ice temperature measurement experiment was carried out on Winter jujube treated with 0.5%,1%,2%lactose solution and 0.5%,1%,2%sorbitol solution,respectively.With the change of the pressure,the type and concentration of freezing point regulators,the ice temperature and ultra-ice temperature of Winter jujube have been affected to a certain extent;among them,the ultra-ice temperature drops the most under 80kPa,after 2%lactose The solution-treated Winter jujube has an ultra-ice temperature of-5.9℃.The vacuum ice temperature and ultra-ice temperature storage experiments of winter jujube were carried out under six pressures of atmospheric pressure,80kPa,60kPa,50kPa,40kPa,and 20kPa.The storage temperature is set according to the measured ice temperature and ultra-ice temperature of winter jujube under six different pressures.Put the winter jujubes that have not been treated with freezing point regulators,with a concentration of 0.5%,1%,2%lactose solution and with 0.5%,1%,2%sorbitol solution into the fresh-keeping bag,and placed in a vacuum Storage in low-temperature tanks.The storage quality of winter jujube under different pressure,different freezing point regulator types and concentrations was studied.The soluble solid content,weight loss rate and hardness of Winter jujube under different storage conditions were measured,which were used as indexes to judge the storage effect of Winter jujube.It can be concluded that the quality after treatment with 1%sorbitol solution under 40kPa is better,and it is more suitable for the preservation and storage of winter jujube.The heat and mass transfer analysis and numerical simulation of the winter jujube cooling process are carried out.From a theoretical point of view,the reasons for temperature change and mass transfer of Winter jujube in the cooling process are analyzed,and the cooling process of Winter jujube is simplified and assumed.On this basis,a two-dimensional finite element heat and mass transfer physics of Winter jujube is established.Models and mathematical models simulate the temperature cloud map at various time points during the storage and cooling process of winter jujube.The simulation results of Winter jujube’s temperature are basically consistent with the actual experimental results,and the temperature error does not exceed 3℃.Analyze the cause of the error,which may be caused by some assumptions made when building the model.