Study On Drying Process Of Liuwei Dihuang Pills Based On Pulsed Vacuum Drying Technology

Objective:Drying is an indispensable process in the production process of Chinese medicine pills,which directly affects the quality of the pills formation and clinical efficacy.In this paper,Liuwei Dihuang Pills?LDP?as an model drug were studied,and the drying characteristics under different drying process parameters of hot air drying and vacuum pulsation drying were studied.Then mathematical model of drying was established.The existence and variation of moisture in each drying process parameters were studied and analyzed.Finally,the quality of the pills under various process parameters was compared and the vacuum pulsation drying process of Liuwei Dihuang concentrated pills was optimized.It provides a reference for the study of the drying mechanism of Chinese medicine pills and the optimization of drying process.Methods:The drying curves and drying rate curves of LDP under hot air drying and vacuum pulsating drying were established,and the effective diffusion coefficient of water and drying activation energy were calculated.The Weibull distribution function was used to simulate the drying process of LDP,and the physical meaning and influencing factors of various parameters in the function were analyzed.LF-NMR technique was used to study the variation of water state of LDP during hot air drying and vacuum pulsating drying.The quality of LDP was compared by measuring hardness,content and dissolution time.The vacuum pulsating drying process of Liuwei Dihuang concentrated pills was optimized by response surface methodology.Quality comparison of different drying processes of pills was made by measuring hardness,content and dissolution time.Response surface methodology was used to optimize the vacuum pulsating drying process of Liuwei Dihuang concentrated pills.Results:In the drying process,the drying process of water pellets and concentrated pellets could be divided into two stages:acceleration stage and deceleration stage.The drying characteristics of Liuwei Dihuang water pills and concentrated pills were significantly affected by drying methods and drying parameters,temperature has a significant effect,and vacuum holding time and atmospheric pressure time have no significant effect.The effective water diffusivity of Liuwei Dihuang water pills ranged from 1.05×10^-105.24×10^-1010 m²·s^-1,and that of concentrated pills ranged from2.77×10^-115.07×10^-1010 m²·s^-1.Under the conditions of hot air drying and vacuum pulsating drying,the activation energies of water pellets were 36.83 and 21.34kJ·mol^-1,and those of concentrated pellets were 59.76 and 54.39 kJ·mol^-1,respectively.Weibull distribution function could be well fitted and applied to the drying process of LDP.Liuwei Dihuang water pills contained water in two states:bound water and semi-bound water,while Liuwei Dihuang concentrated pills only contained water in one state of bound water.With the prolongation of drying time,the absorption peaks migrated to the left and the signal amplitude decreased obviously,which indicated that the dryer to the later stage,the less the degree of water freedom,the more difficult it was to be dried.Weibull distribution function could be well fitted and applied to the drying process of LDP.Liuwei Dihuang water pills contained water in two states:bound water and semi-bound water,while Liuwei Dihuang concentrated pills only contained water in one state of bound water.With the prolongation of drying time,the absorption peaks migrated to the left and the signal amplitude decreased obviously,which indicated that the dryer to the later stage,the less the degree of water freedom,the more difficult it was to be dried.The total peak area of low-field NMR of LDP has a significant linear relationship with the dry-base moisture content.Vacuum pulsatile drying can reduce the loss of components and the dissolution time of pills more effectively than hot air drying.The optimum parameters of vacuum pulsating drying for Liuwei Dihuang concentrated pills were vacuum holding time 5 min,atmospheric holding time 7 min and drying temperature 62?.Conclusion:The drying characteristics of Liuwei Dihuangshui Pills and concentrated pills were significantly affected by drying methods and drying parameters,and the temperature effects were more significant.The effects of vacuum holding time and atmospheric pressure time were less obvious.Under the hot air drying conditions,the power of moisture migration during the drying of the pills was mainly the temperature difference.The water state of the pills was related to the type of the pills.Changing the drying mode and drying parameters was not change the water state.Using the same drying method,the energy consumed by drying the concentrated pills was much greater than that of the dried water pellets.Compared with hot air drying,vacuum pulsation drying consumed less energy,reduced active ingredient loss,and reduced the dissolution time of the pills.It showed that the vacuum pulsation drying method can be used as a new drying method for drying Chinese medicine pills.In general,this study provided a theoretical basis and data support for the study of the drying mechanism of Chinese medicine pills and the choice of drying methods.