Xiao Qian, Lim Loong-Tak, Zhou Yujia, Zhao Zhengtao
School of Food Science and Technology, Hunan Agricultural University, Hunan 410128, China; Department of Food Science, University of Guelph, N1G 2W1 Ontario, Canada.
Department of Food Science, University of Guelph, N1G 2W1 Ontario, Canada.
Food Chem. 2017 Sep 1;230:611-617. doi: 10.1016/j.foodchem.2017.03.097. Epub 2017 Mar 18.
The dynamics of water in pullulan film-forming solutions during drying were investigated by low-field nuclear magnetic resonance. At the begin of drying, two transverse relaxation times (T) at around 32.77 and 2149ms were attributed to bound and free waters in pullulan samples, respectively. An additional T value, ascribed to the tightly bound water in entanglement zones of pullulan chains, appeared at around 3.51ms as the drying process continued (beyond 1080min of drying time). The observed three relaxation times revealed the multi-exponential relaxation behavior of water in pullulan. Moreover, the polymer exhibited spatial heterogeneity with increasing drying time from 1200 to 1920min. On the basis of diffusive and chemical exchange model, the dimension range of pullulan network decreased from 7.69-32.66 to 4.73-18.14µm as the pullulan films solidified. Furthermore, the rate of chemical exchange between water and pullulan significantly increased at the later stage of drying process.
采用低场核磁共振技术研究了普鲁兰多糖成膜溶液干燥过程中的水分动力学。在干燥开始时，普鲁兰多糖样品中约32.77和2149ms的两个横向弛豫时间（T）分别归因于结合水和自由水。随着干燥过程的持续（干燥时间超过1080分钟），在约3.51ms处出现了另一个T值，该值归因于普鲁兰多糖链缠结区的紧密结合水。观察到的三个弛豫时间揭示了普鲁兰多糖中水分的多指数弛豫行为。此外，随着干燥时间从1200分钟增加到1920分钟，聚合物呈现出空间异质性。基于扩散和化学交换模型，随着普鲁兰多糖膜固化，其网络尺寸范围从7.69 - 32.66减小到4.73 - 18.14µm。此外，在干燥过程的后期，水与普鲁兰多糖之间的化学交换速率显著增加。
