Study On Water Migration Characteristics And Quality Control Of Liuwei Dihuang Pills During Drying

Object:Drying is an important step in chinese medicine pill production,which has important influence on pill quality assurance.In this paper,the representative pills of Liuwei Dihuang water pills and the representative pills of Liuwei Dihuang pills concentrated pills with traditional Chinese medicine extract as the main components were studied,the water migration rule,temperature change,the index component of the pill and the regional hardness change of the pill affected by water content were studied during the two drying methods of hot air drying characterized by heat conduction and external heating and microwave drying characterized by heat radiation and internal heating.The heat and mass transfer mechanism and characteristic quality changes during pill drying were described,which provided a new idea for the selection of pill drying scheme.Methods:The temperature changes of central layer（10 mm）,middle layer（5 mm）and surface layer（0 mm）of Liuwei Dihuang pills,water pills and concentrated pills were studied under two drying methods of hot air（50,60,70,80,90℃）and microwave（160,200,240,280,320 W）.The drying curves of water pill and concentrated pill were established under five drying conditions of hot air and five drying conditions of microwave power.Low field nuclear magnetic resonance（LF-NMR）technique was used to study the changes of water state in pellets under two drying methods and at different drying levels.Magnetic resonance imaging technology was used to study the water migration rule and the change of water interface layer of pill under two drying methods.The content changes of index components in the pill during drying were studied by HPLC.The overall and regional hardness changes of water pills and concentrated pills under two drying methods were measured by physical property tester.Results:The outer temperature of Liuwei Dihuang water pills and concentrated pills was higher than the inner temperature under hot air drying,and the inner temperature was higher than the outer temperature under microwave drying.Under the two drying methods,the heating rate of concentrated pills was higher than that of water pills.Microwave（200,240,280,320 W）drying pellets had higher temperature than hot air drying pills.With the increase of drying temperature and microwave power,the drying rate of water pill and concentrated pill increased.At the same time,under the same drying condition,the drying rate of water pellets is greater than that of concentrated pills.In the process of microwave drying,the drying rate of water pills is greater than that of water pills.Visualized images of magnetic resonance imaging showed that the interface layer of water pills and concentrated pills gradually migrated from the outer layer to the inner layer with the increase of drying time by hot air drying and concentrated pills,while the interface layer of water pills and concentrated pills gradually migrated from the inner layer to the outer layer with the increase of drying time by microwave drying.Under the drying methods of hot air and microwave,only T₂₁and T₂₂peaks existed in the T₂inversion spectrum of water pills and concentrated pills,that is,only bound water and semi-bound water existed in pills,and no free water was detected.In addition,with the increase of drying time,the inversion spectrum peak migrated to the left and the transverse relaxation time decreased under the two drying modes.The content of paeonol decreased gradually with the increase of drying time,temperature and microwave power under hot air and microwave drying.The content of monoside and maganin changed little.The hardness test results of physical property tester showed that hot air drying water pills,concentrated pills,temperature increased the overall hardness of pills,pill outer hardening area increased.With the increase of microwave power,the overall hardness of water pills and concentrated pills increased,and"hard core"appeared inside the pills,and the core area gradually increased with the increase of drying time.Conclusions:The drying results of Liuwei Dihuang water pills and concentrated pills under hot air and microwave showed that hot air drying was the heat conduction method to heat pills,starting from the outer layer of pills.With the increase of drying time,heat is gradually transferred from the outer layer to the inner layer,and the moisture interface layer gradually migrates from the outer layer to the inner layer of the pill.The outer layer first"hardens",and the"hardens"area gradually extends to the inner layer of the pill.Microwave drying is a heat radiation heat transfer mode.Under the microwave drying mode,the pill is heated from the inside and gradually transfers heat to the outer layer.The moisture interface layer also gradually migrates to the outer layer.Compared with hot-air drying pills,microwave drying time is shorter,and the content of internal components is higher.