Study On The Drying Process Control Strategy Of "Quality Assurance And Synergy" Of Chinese Herbal Extract

BackgroundDry extract is an important intermediate material for the manufacture of Chinese medicine solid preparations,and it can directly affects the quality of the clinical efficacy of the preparations.Drying is one of the essential process in the preparation of dry extract,with the purpose to remove most of the water mass,in order to facilitate comminution and preparation processing afterwards.At present,the common methods of drying Chinese medicine extract are vacuum drying and spray drying,in addition,microwave vacuum drying is of great application value because of its fast drying speed and low energy consumption.Due to the large viscosity and high moisture content of Chinese medicine extract,drying is often difficult,with long drying time and high energy consumption.Moreover,the long heating time is not conducive to the quality of dried extract.There are also some problems in production and research,such as drying end point mainly rely on experience to judge,it is easy to cause the moisture content and viscosity differences among batches,finally influence the stability of molding process;drying technology is extensive,"One more"is a common phenomenon exists in the same enterprise and adversely affect the quality of dried extract.At the same time,the related research reports are insufficient,the understanding of the drying process is not enough,and lacking the relevant theoretical guidance.In this paper,in order to ensure the extract quality and improve the efficiency of drying process,drying characteristics andthe heat and mass transfer theory and the influence of process parameters onextract quality were studied,and eventually,the drying process control strategy of"quality assurance and synergy"was clarified.Furthermore,a neural network model of drying process was established to control the drying process and provide a guarantee for the quality of dried extract.Object1.Studying extract drying characteristics to deepen the understanding of the drying process and lay the foundation for elucidate the drying process control strategy of"quality assurance and synergy"of Chinese herbal extract.2.Using the theory of migration activation energy theory to explain the characteristics of heat and mass transfer during the drying process of Chinese medicine extract,and to provide theoretical basis for the regulation strategy of"synergy"drying process.3.The chemical components that are sensitive to drying technology were screened and used as the process evaluation index to define the influence rule of drying process parameters on dried extract quality,and to provide theoretical basis for the regulation strategy of"quality assurance"drying process.4.Summing up the above research results and studying the regulation strategy of the drying process characterized as"quality assurance and synergy".5.A predictive control model for drying process is established based on neural network model,in order to improve the control level of drying process and improve the quality of Chinese medicine extract.Methods1.The main drying methods including vacuum drying,microwave vacuum drying and spray drying were studied.2.Salvia miltiorrhiza phenolic extract which containing heat-sensitive ingredients and water extract of Rhizoma Polygonati which characterized as polysaccharide-rich and highly viscous as well as licorice extract containing saponin components were adopted as model drugs.Salvia miltiorrhiza phenolic extract and licorice extract are collected by the Pharmacopoeia.3.The drying rate curve under different process parameters and the temperature curve of the actual heating of the material are used to analyze the drying characteristics of Chinese herbal extracts,grasp the influence rules of process parameters,and define the"quality assurance and synergy"drying control strategy.4.Based on the law of conservation of energy,combining the drying rate and the internal vapor pressure of the material,the mathematical equation of migration activation energy theory was established to explain the heat and mass transfer characteristics during drying process of Chinese medicine extract and provide a theoretical basis for improving drying efficiency.5.Based on the similarity evaluation of fingerprints,principal component analysis and partial least-squares analysis were used to analyze the influence of process parameters on the quality of dried extract.Then,the main difference components that contributed greatly to the similarity of fingerprints were screened as process evaluation indicators.At the same time,three evaluation indexes including color,browning index and 5-hydroxymethylfurfural related to browning reaction were assessed.Eventually,the influence of drying process parameters on dry paste quality was clearly defined.6.According to the research results of drying characteristics,migration activation energy and quality evaluation,drying process control strategy of"quality assurance and synergy"of Chinese herbal extract was put forward.7.Multilayer perceptron and radial basis function are used to establish neural network model.Through comparative analysis,a better fitting model is chosen to control the drying process of Chinese herbal extract and improve process control level.Results1.According to the drying rate changes in drying process of microwave vacuum drying and vacuum drying,the drying process is divided into three stages including accelerating drying period,constant speed drying period and deceleration drying period.The temperature of the extract varies with the change of the drying rate.A rapid temperature rise in accelerating the drying period,the slow rise of temperature in the constant speed drying period and the rapid rise of temperature in the reduced speed drying period were observed.As the material temperature in the reduced speed drying periodincreases rapidly to a elevated temperature,this stage is determined as the quality control period.The strategy to increase the drying rate and reduce the heating temperature of the material was put forward:For microwave vacuum drying,increasing the microwave power density,reducing the thickness of the material layer,lowering the pressure in the accelerating drying period and the constant speed drying stage,and appropriately raising the pressure in the reduced speed drying period can increase the drying rate;decreasing the thickness of the material layer and reducing the pressure can help to reduce the heating temperature of the material;The microwave power density has little effect on the drying rate in the reduced speed drying period,but decreasing the microwave power density at this period will help reduce energy consumption.For vacuum drying,increasing the drying temperature,lowering the pressure,and reducing the thickness of the material layer can help to increase the drying rate;Lowering the drying temperature,decreasing the thickness of the material layer,and reducing the pressure can reduce the heating temperature of the material.For the material moisture content,reducing the moisture content can shorten the drying time,but increase the concentration time.Therefore,it is necessary to comprehensively consider the concentration section and the drying section to determine the initial moisture content of the material.The reasons for the occurrence of the surface crusting and blasting in the drying process were also analyzed.:surface crust phenomenon is due to surface water loss rate is greater than the internal moisture migration rate and the sooner the drying rate is,the earlier the surface crusts appear.Blasting is due to the excessive pressure of vaporization on the surface of the material after surface crusting,it also has a certain relation with the nature of the material,when the material with high water content or containing saponin components are more susceptible to happen.2.The migration activation energy can quantitatively describe the change of difficulty degree duringthe process of of water reduction.As the drying continues,the migration activation energy increased gradually,indicating that the difficulty of drying was increasing.The drying temperature,the microwave power density and the thickness of the material layer are the main factors affecting the migration activation energy during the drying process.The higher the drying temperature or the microwave power density is,the lower the activation energy of the whole drying process is.The thickness of the material layer has a great influence on the migration activation energy in the later stage of drying(water content reduced to about 20%).The thicker the layer,the greater the migration of activation energy,which makes it more difficult to dry.3.HPLC fingerprint evaluation results show that the high similarity of the drying process of dry extract and the concentrated solution was above 0.94,it can be seen that drying process has little effect on common components.The results of the PCA and PLS-DA analysis show that there are differences in the quality of dry extracts obtained from various process parameters,and the different peaks are screened out.It was confirmed that salvianolic acid B was the differential component in the Salvia total phenolic acids,and the neoglycolic acid and glycyrrhizic acid were the different components in the licorice extract.Then,the above ingredients and the polysaccharide content in the Huangjing extract were assessed as the evaluation indicators.It was found that each process parameter can affect the content of the index components in the dried extract.Excessive drying temperature and long drying time are not conducive to the quality of the dried extract.4.Based on the above findings,the"quality assurance and synergy"control strategy for the drying process of Chinese medicine extracts was proposed and studied.The research results show that the appropriate temperature,pressure and microwave power change during drying process can reduce the heating temperature of the material,increase the drying rate,reduce the energy consumption,and ensure the quality of the dry extract.For constant speed period and accelerated drying period,low pressure and high vacuum drying temperature and microwave drying power can be used.For the falling rate drying period,lower drying temperature or microwave power and higher pressure can be used.In order to solve the problems of microwave vacuum drying in large-scale production,a vacuum-microwave vacuum combined drying method was proposed which can overcome the problem of low drying rate caused by the time consuming of vacuum drying and the low effective utilization rate of microwave energy due to the difficulty of drainage in drying oven at the early stage of microwave vacuum drying.5.A prediction model for the surface temperature and drying rate of materials in the microwave vacuum drying process of Salvia miltiorrhiza phenolic acid extract was established,according to the fitting results,the R~2 values of the multilayer perceptron and radial basis function models are 0.961 and 0.914,respectively,and the multi-layer perceptron neural network prediction model shows better prediction performance.Conclusions1.Drying characteristics of vacuum drying and microwave vacuum drying of Chinese herbal extracts were clarified.The results suggesting that suitable dynamic drying process parameters can improve drying rate and reduce material heating temperature and providing a data support for the implementation of the"quality assurance and synergy"drying of the Chinese herbal extract.2.The heat and mass transfer characteristics of Chinese herbal extracts during the drying process were analyzed from the perspective of the internal vapor pressure of the materials based onmigration activation energy theory.The effect of process parameters on the migration activation energy of material during the drying process was explored,and the drying strategy of"quality assurance and synergy"was defined.3.HPLC fingerprint combined with pattern recognition technology is helpful to confirm the sensitive chemical composition of the process and this method is simple and feasible.The chemical component sensitive to the process is used as the evaluation index of the process,and results indicated that low temperature and rapid drying process is of great significance for protecting the chemical composition of the extract and ensuring the quality of the Chinese herbal extract.In addition,the quality control research ideas about using of process-sensitive chemical composition as process control indicators was put forward.4.Appropriate variable temperature,variable pressure,variable microwave power drying processes and vacuum-microwave vacuum drying combined drying methods help to better achieve the process control of"quality assurance and synergy"drying.5.The neural network prediction model has good prediction performance and intelligence characteristics,it provides a research method for the process control of Chinese herbal extracts drying.