Longfeng Fruit Vacuum Ice-temperature And Super-Cooling Preservation Experiment And Heat And Mass Transfer Theory

With the advancement of technology,fruit and vegetable preservation technology is also being upgraded.More and more compound preservation technology has been applied in practice.In this paper,vacuum preservation,ice temperature preservation,and ultra-ice temperature preservation are combined respectively,and the advantages of combining them are better for fruit and vegetable storage.Vacuum preservation can quickly cool down,and can quickly diffuse harmful gases such as ethylene,carbon dioxide and ethanol produced by fruits and vegetables.The ice temperature preservation can preserve the flavor of fruits and vegetables to a greater extent,so that the storage of fruits and vegetables maintains higher quality.The fruit and vegetable storage is carried out in the unfrozen area below the freezing point,and the temperature area where the fruits and vegetables remain active can be expanded,and some fruits and vegetables can be stored instead of the freezing technology to reduce the energy consumption.Compared with the ice temperature preservation,the temperature is lower,so the ultra-ice temperature preservation It can extend the storage period and shelf life of fruits and vegetables to a greater extent.Before the experiment,the test bench was modified,and the vacuum cryogenic tank was insulated to check its sealing performance and improve.Add a temperature probe(PT100)and calibrate it before the experiment begins.Taking the Longfeng fruit of Harbin specialty as the experimental object,the ice temperature and ultra-ice temperature of Longfepg fruit were measured under five different pressures of normal pressure,0.08MPa,0.06MPa,0.04MPa and 0.02MPa.Five kinds of pressure ice temperature measurement experiments were carried out on Longfeng fruit which was not treated with freezing point regulator,and the sorbitol solution with concentration of"0.5%","1%" and "2%" was prepared and the concentration was "0.5%".,"1%","2%" lactose solution,and soaking Longfeng fruit,measuring the ice temperature value of Longfeng fruit treated under five different pressures,comparing and analyzing the ice temperature and ultra-ice of Longfeng fruit Wen,found that with the change of pressure,the ice temperature and ultra-ice temperature values have been affected to a certain extent,and the Longfeng fruit super-ice temperature treated by the lactose solution is higher than the sorbitol solution as a whole.Under the pressure of normal pressure,0.08MPa,0.06MPa,0.04MPa,0.02MPa,sorbose treated with no freezing point regulator and with concentration of "0.5%","l%" and "2%"respectively Longfeng fruit treated with alcohol solution and lactose solution with concentration of "0.5%","1%" and "2%" was stored in ice temperature and ultra-ice temperature storage,five kinds of pressure,7 kinds of treatment methods,a total of 35 groups experiment.The experimental results showed that the Longfeng fruit treated with the concentration of "0.5%" lactose solution under the pressure of 0.04MPa had the best storage effect.The physicochemical theory of fruits and vegetables was studied.On this basis,the hypothesis of Longfeng fruit ice temperature storage was simplified.The physical and mathematical model of heat and mass transfer of Longfeng fruit was established,and the mathematical model was programmed and simulated.Finally,The results obtained by the solution are not completely consistent with the experimental results.After analysis,the main reason for this result is that many assumptions were made when the model was built,which led to the model solution not fully consistent with the experimental results.