Theoretical And Experimental Study On Storage Technics And Qulity Disintegration Of The Fruits And Vegetable

Cold chains is the very systematic engineering of freshness of fruits and vegetables,which is directly related with the loss of of fruits and vegetables after their post-harvest. Pre-cooling and cold storage of the cold chains were discussed. Phenomenon of heat and mass transfer, disintegration of quality and technics of cold story were studied in detail. The main contents and conclusions of this paper are as follows:1 Testing and analysis on the cold storage with constant temperature and constant humidityFull-frequency drop in temperature and conversion drop in temperature were compared. The latter has some merits of smooth drop and small amplitude of temperature in despite of shortage of longer time.Several modes of providing wind were studied. Flow equalization with pore plate is better than the traditional modes such as one fan, two fan and jacket. Heat impact on the circumstance in the cold storage was analyzed because of the door open and some precautionary measures were advanced.2 Experimental study on the forced-air pre-cooling of fruits and vegetablesExperiments on the forced-air pre-cooling of apples and cucumbers were carried out to analyze influence of temperature of cold air, humidity of it, velocity of it and void ratio of apples and cucumbers on pre-cooling process. Velocity of 1.5m/s is the best operation velocity. Good results are obtained with low temperature(no chilling injury) and high humidity air(80%RH above). void ratio of apples and cucumbers has little influence on the pre-cooling time when the air velocity is higher than 1.5m/s, while it has great influence on the pre-cooling time when the air velocity is lower than 0.75m/s. So more fruits and vegetables are advised to be pre-cooled at high air velocity, while which reduce the efficiency of pre-cooling at low air velocity.3 Theoretical study on the coupling of heat transfer and mass transfer.Nondimensional mathematical model was established of torispherical fruits and vegetables and qusi-cylindrical fruits and vegetables. Influences of some key parameters(for example,Re) on the pre-cooling process were investigated theoretically. The theoretical analysis was validated by experimental results. 7931 of Re and 2787of Re are the best operation ones respectively for torispherical fruits and vegetables and qusi-cylindrical fruits and vegetables. 4 Study on quality disintegration model of fruits and vegetables and optimization of cold storage craftPhenomena of mass transfer of Dutch cucumber in cold storage were analyzed in detail on the basis of principle of mass transfer. Linear dynamics model and exponential dynamics model based on biochemical process were applied to fit analysis on experiment datum of the key quality of Dutch cucumber such as water loss, soluble solid content and firmness of Dutch cucumber. Disintegration models of the three kinds of quality were obtained in several conditions of storage. Mechanism of keeping fresh of several storage methods is investigated. It is concluded that cold storage with preservative film after pre-cooling(pre-cooling to 4℃with cold air of 2℃,95%RH and velocity of 1.5m/s) or preheating (storage with 39℃,95%RH and velocity of 1.5m/s for 2~4hours)is the best technics. The results are much helpful for storage of other fruits and vegetables because of their comparabilities.