Drying process of pullulan edible films forming solutions studied by low-field NMR

卷:230

Xiao, Qian ; Lim, Loong-Tak ; Zhou, Yujia ; Zhao, Zhengtao

Hunan Agr Univ

关键词: Pullulan;    Edible films;    LF NMR;    T-2 relaxation time;    Diffusive and chemical exchange model;   

DOI  :  10.1016/j.foodchem.2017.03.097

学科分类：食品科学和技术

【 摘 要 】

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-2) at around 32.77 and 2149 ms were attributed to bound and free waters in pullulan samples, respectively. An additional T-2 value, ascribed to the tightly bound water in entanglement zones of pullulan chains, appeared at around 3.51 ms as the drying process continued (beyond 1080 min 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 1920 min. On the basis of diffusive and chemical exchange model, the dimension range of pullulan network decreased from 7.69-32.66 to 4.73-18.14 mu m as the pullulan films solidified. Furthermore, the rate of chemical exchange between water and pullulan significantly increased at the later stage of drying process. (C) 2017 Elsevier Ltd. All rights reserved.