Study On Drying Characteristics And Quality Changes Of Gastrodia Elata Blume Under Infrared Drying

Gastrodia is the tubers of the perennial herb Gastrodia elata Bl.,which is a valuable Chinese herbal medicine and a common health food raw material.Modern pharmacological and clinical studies have shown that it has a good beneficial therapeutic effect on insomnia,migraine,hypertension,cardiovascular and cerebrovascular diseases,diabetes and neuropathy.The water content of fresh G.elata is as high as 80%.The drying processing is the key link to ensure the quality of the medicinal materials.In order to facilicate the drying process and obtain high-quality pieces,G.elata usually first be steamed and then dried.However,steaming will change the structure and composition of gastrodia.Therefore,the dehydrated process of G.elata after steaming is different from the fresh G.elata.The drying characteristics are still unclear.As a modern drying technology,infrared drying has been widely applied in the drying process of materials due to fast drying efficiency,good appearance quality of dry products and simple equipment.It has a great significance to study the drying process of G.elata in order to ensure the quality of G.elata.In this study,the infrared drying technology was used to study the drying characteristics of G.elata.The drying kinetic was established through nonlinear fitting.A nondestructive low-field nuclear magnetic resonance(LF-NMR)and magnetic resonance resonance(MRI)was introduced to monitor the water variation of G.elata.The high performance liquid chromatography(HPLC)was used to analyzed the content of multi-index chemical components,discussed the difference of different drying method.These results provided theoretical basis and technical support for the comprehensive development and utilization of G.elata resources.1.Research the drying characteristics of G.elata under infrared blast drying after steaming and establish the drying kineticIn the infrared drying process of G.elata,the drying rate was faster while the temperature rose and the radius decreased.The effect of temperature on the drying rate was greater than that of the radius.The drying process mainly occurred in falling rate periods.According to statistical parameters on 6 drying kinetics,the Page model described and predicted the drying process of G.elata more accurately than others.R2,?2 and RMSE were 0.9991,7.633×10-5 and 0.0011.The Fick's second law of diffusion was employed to calculate the value ofmoisture effective diffusivity(Deff),which ranged from 1.9251×10-8~4.0528×10-8 m2/s,the activation energy was 17.1374 kJ/mol.This research results could provide technical foundation for the post-harvest processing and comprehensive utilization of G.elata.2.Research the water variation in G.elata by LF-NMR and MRIThree water states(bound,immobilized,and free)in G.elata samples were investigated through multiexponential fitting and inversion of the NMR data.The water states and water content of G.elata were changed after steaming.During the drying process at different temperatures,both peak area and relaxation time were changed,and the higher the temperature,the faster the change.Significant correlations were found among MC,L*,b*,and NMR parameters.The correlation coefficient between the calibration and the verification of the PLSR model is higher than 0.9,which can predict the moisture content in G.elata.3.Effect of different drying methods on the quality changes in G.elataThe L* value(brightness)at 40,60 and 80 ? gradually decreased,the L* value was the highest in the freeze-drying method;the a* value(redness)was the highest at 80 ?;the b*value(yellowness)in drying and 80 ? were higher than other methods.The rehydration rate of drying method is much lower than other methods.As for chemical components,the freezedrying method has the highest content of gastrodin and Ballyson,while the lowest content in the method of drying.With the increase of temperature,the content of gastrodin and Barryntoside A increased gradually,and the content of p-hydroxybenzyl alcohol and phydroxybenzaldehyde decreased gradually.The content of adenosine in the drying method was much higher than other methods.By comparing the appearance and the change of the index component content,60 ? drying is the better way.