[Analyze moisture transformation and transport rules during processing of Paeoniae Radix Alba by using low-field NMR].

Moisture status and content during the processing of Paeoniae Radix Alba were studied by nuclear magnetic resonance (NMR) and nuclear magnetic resonance imaging (MRI) to investigate the changes of transverse relaxation time (T ₂) and MRI images during boiling and drying processes of Paeoniae Radix Alba. The results showed that water in Paeoniae Radix Alba fresh products was major of free water, and in the boiling process, the content of free water increased whereas the content of bound water declined. At the end of boiling, content of free water reached over 90%. During the drying process, T ₂ moved to the left, and moisture mobility was reduced. The MRI image directly showed that moisture transfer was outside-in process for both increase and decrease. At the end of drying, remaining moisture was mainly present in inner layer of Paeoniae Radix Alba. Quality and appearance were affected by the change of moisture during processing process of medicinal herbs. NMR and MRI could provide direct reference evidence for its moisture changes, and the results of this study could provide direct references and technical support for optimization of processing process of root medicinal materials and evaluation of Chinese herbal pieces.