Study On Drying Characteristics And Quality Changes Of Aromatic Chinese Herbal Pieces During Processing

Objective:In this paper,the aromatic Chinese herbal medicines Aurantii Fructus and Menthae Haplocalycis Herba from Jiangxi are taken as a breakthrough,and according to the processing and drying characteristics of the producing areas and the actual requirements of"drying efficiency-quality of decoction pieces",the scientific basis for selecting the best hot air temperature,wind speed,pressure（vacuum degree）and other technological parameters for drying with drying time is expounded.Furthermore,the drying process of Aurantii Fructus and Menthae Haplocalycis Herba was predicted and quantified,and the effects of different drying methods on their quality were clarified from the perspective of volatile components and flavor characteristics,so as to realize scientific optimization of drying technology of Aurantii Fructus and Menthae Haplocalycis Herba,and establish a foundation for quality control and evaluation mode of aromatic traditional Chinese medicine.Methods:1 Study on drying kinetics of Aurantii Fructus and Menthae Haplocalycis HerbaHot air drying and vacuum drying of Aurantii Fructus（50,60,70℃）and Menthae Haplocalycis Herba（35,45,55℃）and hot air drying with different wind speeds（1,3,5 m/s）were studied according to different parts and textures.The dry base moisture content of Aurantii Fructus and Menthae Haplocalycis Herba were measured,and the relationship between dry base moisture content and dehydration rate under different drying conditions was analyzed.2 Study on drying mathematical model and physical parameters of Aurantii Fructus and Menthae Haplocalycis HerbaThe relationship between water content and time of Aurantii Fructus and Menthae Haplocalycis Herba under different conditions of hot air drying and vacuum drying was simulated by seven classical drying mathematical models such as Midilli,Lewis and Page,and the best drying model was established to determine the effective water diffusion coefficient(D_eff)and activation energy（E_a）of Aurantii Fructus and Menthae Haplocalycis Herba.3 Effects of different drying methods on volatile components of Aurantii Fructus and Menthae Haplocalycis HerbaHS-GC-MS was used to compare the difference of volatile components of Aurantii Fructus and Menthae Haplocalycis Herba after drying under different conditions,and the change law of volatile components of Aurantii Fructus and Menthae Haplocalycis Herba under different drying conditions was preliminarily analyzed and studied.4 Analysis of flavor characteristics of different dried Aurantii Fructus and Menthae Haplocalycis Herba based on electronic noseThe odor and composition information of different dried products of Aurantii Fructus and Menthae Haplocalycis Herba were obtained by electronic nose technology,and the sensory properties of Aurantii Fructus and Menthae Haplocalycis Herba after drying under different conditions were evaluated by principal component analysis.Results:1 Study on drying kinetics of Aurantii Fructus and Menthae Haplocalycis HerbaThe initial dry basis moisture content of fresh Aurantii Fructus was 3.66±0.64g/g.The drying results showed that the drying time of Aurantii Fructus by hot air at 50-70℃was 54 h,38 h and 24 h respectively,and the drying time of Aurantii Fructus by hot air at 1 m/s,3 m/s and 5 m/s was 52 h,51 h and 48 h respectively.The drying time of Aurantii Fructus by hot air at 50℃was 2.25 times that of 70℃,and the drying time of Aurantii Fructus by hot air at 1 m/s was 1.08 times that of 5 m/s.The drying time of Aurantii Fructus in vacuum at 50-70℃was 79 h,55 h and 35 h respectively,and the drying time at 50℃was 2.26 times that at 70℃.The initial dry base moisture content of fresh Menthae Haplocalycis Herba was 5.35±0.01 g/g.The results showed that the drying time of Menthae Haplocalycis Herba by hot air at 35-55℃was 10 h,7 h,5 h,1m/s,3 m/s,10 h,9.5 h and 9 h respectively.The drying time of Menthae Haplocalycis Herba by hot air at 35℃was twice as long as that at 55℃,and the drying time of Menthae Haplocalycis Herba by hot air at 1 m/s was 1 h different from that at 5 m/s.The vacuum drying time of Menthae Haplocalycis Herba at 35-55℃was 36 h,22 h and 15 h,respectively,and the vacuum drying time at 35℃was 2.4 times that at 55℃.In different drying methods,the drying rate of Aurantii Fructus and Menthae Haplocalycis Herba by hot air is higher than that by vacuum drying.2 Study on drying mathematical model and physical parameters of Aurantii Fructus and Menthae Haplocalycis HerbaThe fitting results of drying mathematical model showed that the average statistical parameters of Midilli model of Aurantii Fructus dried by hot air at 50-70℃were R²=0.9996,χ²=5.97×10^-5,RMSE=3.35×10^-9,respectively;The average values of statistical parameters of Midilli model of hot air drying with 1 m/s,3 m/s and5 m/s wind speed are R²=0.9995,χ²=6.97×10^-5 and RMSE=5.81×10^-9,respectively.The average values of statistical parameters of Midilli model of hot air drying with 1 m/s,3 m/s and 5 m/s wind speed are 0.9995,6.97×10^-5 and 5.81×10^-9.The mean values of Midilli model parameters of Aurantii Fructus dried in vacuum at50-70℃were R²=0.9994,χ²=0.0001 and RMSE=0.0087,respectively.The average statistical parameters of Midilli model of Menthae Haplocalycis Herba dried by hot air at 35-55℃were R²=0.9992,χ²=1.12×10^-4,RMSE=9.15×10^-9,respectively.The average statistical parameters of Midilli model for hot air drying of Menthae Haplocalycis Herba with 1 m/s,3 m/s and 5 m/s wind speed were R²=0.9993,χ²=8.67×10^-4 and RMSE=4.80×10^-9,respectively.The average statistical parameters of Midilli model for hot air drying of Menthae Haplocalycis Herba with 1 m/s,3 m/s and5 m/s wind speed were 0.9993,8.67×10^-4,respectively.The mean values of statistical parameters in Midilli model of vacuum drying Menthae Haplocalycis Herba at 35-55℃were R²=0.9992,χ²=0.0001 and RMSE=0.0091,respectively.The results of physical parameters show that the effective diffusion coefficient of Aurantii Fructus dried by hot air at 50-70℃is 2.63×10^-6～6.61×10^-6 m²/s,and the activation energy（Ea）is 42.36 k J/mol;The effective diffusion coefficients of Aurantii Fructus were 2.63×10^-6～2.82×10^-6 m²/s with the wind speed of 1 m/s,3 m/s and 5m/s;The effective diffusion coefficient and activation energy（Ea）of Aurantii Fructus dried in vacuum at 50-70℃were 2.16×10^-6～4.37×10^-6 m²/s and 33.92 k J/mol,respectively.The effective diffusion coefficients were 3.86×10^-6～7.77×10^-6 m²/s and the activation energy was 38.43 k J/mol;The effective diffusion coefficients of hot air drying Menthae Haplocalycis Herba were 3.86×10^-6～4.95×10^-6 m²/s at 1 m/s,3m/s and 5 m/s wind speeds;The effective diffusion coefficients and activation energy were 9.40×10^-7～2.08×10^-6 m²/s and 33.19 k J/mol respectively.3 Effects of different drying methods on volatile components of Aurantii Fructus and Menthae Haplocalycis HerbaThe results of HS-GC-MS showed that 56 compounds were identified from different dried products of Aurantii Fructus,among which 10 common components（Terpinene,（+）-Limonene,γ-Terpinene,Terpinolene,D（+）-Camphor,D-Carvone,（-）-α-Pinene,β-Elemene,β-Copaene,Germacrene D）were found.29,33,27,28,31 and27 compounds were identified from Aurantii Fructus dried by hot air at 50-70℃and different wind speeds respectively,which accounted for more than 94.60%of the volatile components.22,26 and 26 compounds were identified by vacuum drying at50-70℃,which accounted for more than 93.36%of the volatile components.Among them,the content of（+）-Limonene and Germacrene D was high,the content of（+）-Limonene ranged from 63.65%to 74.28%,and the content of Germacrene D ranged from 3.57%to 10.07%.The results of HS-GC-MS showed that 47 compounds were identified from different dried Menthae Haplocalycis Herba,including 6 common constituents（（+）-Limonene,3-Carene,D-Carvone,β-Bourbonene,（-）-α-Gurunene,Germacrene D）.17,24,23,17,17,22 compounds were identified from Menthae Haplocalycis Herba dried by hot air at 35-55℃and different wind speeds respectively,accounting for more than 70.94%of the volatile components;15,18 and 18 compounds were identified by vacuum drying at 35-55℃,accounting for more than 65.02%of the volatile components.Among them,the contents of D-carvone,（+）-Limonene and Germacrene D were high.The contents of D-Carvone ranged from 19.99%to 63.11%,（+）-limonene ranged from 10.58%to 20.75%,and Germacrene D ranged from 4.70%to 9.18%.4 Analysis of flavor characteristics of different dried Aurantii Fructus and Menthae Haplocalycis Herba based on electronic noseThe results of electronic nose radar analysis and principal component analysis showed that the aroma components of Aurantii Fructus and Menthae Haplocalycis Herba were mainly aromatic compounds and amines.The total volatile components of Aurantii Fructus and Menthae Haplocalycis Herba under different drying methods and conditions are roughly the same,but their response intensity to electronic nose metal sensor is obviously different;Under different hot air drying conditions,the characteristic response value of Aurantii Fructus dried at 50℃is obviously stronger than that at 60℃and 70℃,and the first wind speed（1 m/s）is stronger than that at the second wind speed（3 m/s）and the third wind speed（5 m/s）;The response value of different dried peppermint is 35℃>45℃>55℃;The second wind speed（3 m/s）>the first wind speed（1 m/s）>the third wind speed（5 m/s）.Conclusions:Midilli model is the best model to accurately describe and quantify the drying process of Aurantii Fructus and Menthae Haplocalycis Herba under different conditions of hot air drying and vacuum drying.With the increase of temperature and wind speed,the dehydration rate is faster,the effective water diffusion coefficient is gradually increased,and the drying time of medicinal materials is shorter.Under various drying conditions,the volatile components of Aurantii Fructus were retained more completely after hot air drying at 50-60℃and the first wind speed（1 m/s）,while those of Menthae Haplocalycis Herba were retained more completely when hot air drying at 35-45℃and the second wind speed（3 m/s）,which could greatly reduce the drying cost and provide scientific basis for the optimization of processing and drying technology of Aurantii Fructus and Menthae Haplocalycis Herba in producing areas.