Abstract:This study explored the collapse phenomenon and the properties of thermal history of the lactose solution by freeze -dried microscope system and differential scanning calorimetry. The two results of measurement were combined to determine the glass transition temperature Tg′ in the freeze-concentrated state and the change rule of the collapse temperature Tc. The influence of different cooling rates on the Tg′ and Tc of the lactose solution was analyzed，and the defects in the drying layer during the drying process were observed.The influence of the freezing characteristics of the solution on the sublimation process was analyzed，and the change rule of the collapse temperature Tc was determined. The results showed that there were two step transitions of low temperature and high temperature in the heat flow-temperature curve during the heating process of lactose solution，and the Tc measured by the freeze-dried microscope system was between the two transitions.Tg′was determined as the low temperature transition，and the cooling rate had little effect on the Tg′.The smaller the degree of under cooling，the lower the ice nucleation rate，but it was conducive to the growth of ice crystals.The effect was better when drying，which effectively promoted water sublimation. This study found that in the freeze-dried process，the drying effect was superior when the cooling rate was 20 ℃/min and 30 ℃/min，with only cracking phenomenon occurred，whereas collapse occurred at other cooling rates.