A NEW METHOD FOR MEASURING THE GLASS TRANSITION TEMPERATURE OF AQUEOUS SOLUTION AND FOOD BY DSC
Glass transition temperature is a very important parameter in freeze-drying and cryopreservation. The glass-transition temperature of the maximally freeze-concentrated solution (Tg’) can not be obtained directly , although there are many methods to measure it. Otherwise the glass-transition temperature of the partially freeze-concentrated solution (Tgf) can always be obtained directly. In this paper, the new concept of Tgf is brought forward and a new method is gave for measuring Tgf of aqueous solution and food using differential scanning calorimetry（DSC）, which is based on annealing samples for long periods of time at different temperatures. The influence of annealing temperature on Tgf is studied. 20％ and 45％ glucose,10％ and 25％ PVP and concentrated strawberry juice solution are chosen as samples.For glucose, it is found that the Tgf increases initially with annealing temperature up to -50℃, and decrease as the temperature continues to increase and exhibition linear relation (P＜0.01) obviously. It takes on the same disciplinarian for glucose of different concentrations. It is concluded that the Tg’ can be determined by intersection of the two curves reflecting the Tgf change with annealing temperature. The optimal annealing temperature(-50℃ ) and accurate glass transition temperature (Tg’, -55.3℃,Onset）of glucose are obtained. It takes on the same disciplinarian for PVP and strawberry juice solutions (linear relation (P＜0.05)). The optimal annealing temperature(-14℃, -49.5 ) and accurate glass transition temperature (Tg’, -18.1℃, -52.8℃,Onset）of PVP and strawberry juice solutions are respectively obtained.
Glass transition temperature Differential scanning calorimetry Annealing Aqueous solution Food.
Guoyan ZHOU Xiudong YE Tsechao HUA
Institute of Cryomedicine and Food Refrigeration, Shanghai University of Science and Technology Shanghai, 200093, China
国际会议
The 22nd International Congress of Refrigeration(第22届国际制冷大会)
北京
英文
2007-08-21（万方平台首次上网日期，不代表论文的发表时间）