IMO/D-甘露醇水溶液玻璃化转变温度的确定及冻干过程塌陷现象分析

采用冻干显微镜和差示扫描量热法(DSC)研究了溶液的塌陷温度Tc和热历史特性,将两种测量结果相结合确定冷冻浓缩状态下的玻璃化转化温度Tg',分析不同升降温速率对低聚异麦芽糖(IMO)溶液Tg'及Tc的影响,根据D-甘露醇反玻璃化和强化冰晶结构的特性,研究其对IMO溶液Tg'和Tc的影响.结果 表明:溶液的热历史存在低温...

Determination of Glass Transition Temperature of IMO/D-Mannitol Aqueous Solution and Analysis of Collapse Phenomenon during Freeze-drying Process of Solution

The T_c(collapse temperature)and thermal history of the solution were studied using freeze-drying microscopy and differential scanning calorimetry(DSC),the T_g′(glass transition temperature of the maximally freeze-concentrated state)was determined according to the two results obtained.The effects of different heating and freezing rated on T_g′and T_c of isomaltose(IMO)solution were analyzed.The effect of D-Mannitol solution,according to its characteristics reverse glass transition and enhancement of ice crystal structure,on T_g′and T_c of IMO solution was investigated.It could be concluded that the low and high temperature transitions presented in the thermal history of sample solutions.The measured T_c existed between the end of low temperature transition and the beginning of high temperature transition,and the low temperature transition was identified to be glass transition according to the freeze-concentrated state of solutions.The freezing rates had no significant effect on T_c and T_g′,and T_c was 3~4℃higher than T_g′.However,the higher the freezing rate,the more obvious the collapse phenomenon,with the increasing of heating rate,T_c and T_g′increased and collapse phenomenon aggravates,T_c increased more obviously,the drying effect was better at 1℃/min.With the reduction of IMO/D-Mannitol ratio,T_g′decreased and the devitrification phenomenon became more obvious,the most was 5:5,the drying effect of 9:1 and 5:5 was better than that of IMO solution,the collapse was worst at 8:2,T_c was 6~7℃higher than T_g′.When a small amount of D-Mannitol was added,the dried structure was better preserved,T_c was higher than that of IMO solution at 9:1,and the drying layer maintained better.