Effect of Cooling Rate on Freeze-drying Characteristics of Pear Melon Cells

In order to explore the effect of cooling rate on the freeze-drying process of pear melon cells, the pear melon cells were subjected to different cooling rates (5, 15, 25, 35, 50 °C/min) based on cryomicroscopy imaging technology and vacuum freeze-drying technology. The freeze-drying visualization experiment was carried out, and the changes of cell morphological parameters (equivalent diameter, area, circumference, volume) and internal pressure during the freeze-drying process were analyzed. The characteristic parameters of porous materials (porosity) of dry tissue were studied. The results showed that: The freezing temperature generally decreased with the increase of the cooling rate. During the freeze-drying process, when the cooling rate was 25 °C/min, the changes of cell morphological parameters and internal pressure were the smallest. With the increase of cooling rate, the change rate of cell morphological parameters and internal pressure first decreased and then slowly increased. The cell morphology and internal pressure of pear melons changed greatly under too high and too low cooling rates, which was not conducive to the freeze-drying of pear melons. When the cooling rate was greater than 5 ℃/min, the porosity was larger and less affected by the cooling rate, and only small fluctuations occured within a certain range. The optimal cooling rate of pear melon was 25 ℃/min, and the cell morphology and solute damage were the least at this cooling rate.