Theoretical Analysis And Experimental Research On Vacuum Infrared Green Energy Saving Composite Drying Process

As an important component of the rapid development of modern agriculture,fruit and vegetable food processing technology is the core.How to overcome the problems of low efficiency,poor quality and large energy consumption exposed in the traditional drying processing technology is one of the main trends of the development at this stage.In this paper,a combined drying technology of infrared radiation and vacuum drying is proposed,which can evaporate water at a lower temperature in a vacuum environment and reduce energy consumption to the greatest extent.The technology has been proved to be effective in drying some types of fruits and vegetables,greatly improving the comprehensive quality of agricultural products,increasing the added value of agricultural products,increasing agricultural efficiency,increasing farmers' income,and promoting the development of food industry.In this paper,the theoretical analysis and experimental research of vacuum infrared green energy-saving composite drying are carried out.The material quality evaluation,mass heat transfer and gas molecular dynamics model are established.The effects of temperature,vacuum degree and material thickness on drying characteristics and quality are obtained.Then,according to the model parameters,the vacuum infrared drying equipment is designed and a three-dimensional model is established.Through calculation and post-processing analysis,the flow field distribution law is obtained to verify the rationality of the drying furnace design.At the same time,the influence of temperature,vacuum degree and material thickness on drying characteristic index and color difference index,such as shrinkage,moisture content and rehydration ratio,is analyzed based on single factor experiment,which is used to verify the model.Through the orthogonal test of the drying process,the best process parameters of vacuum infrared drying were studied with chlorophyll content,VC retention rate,total saponin content,apparent observation and sensory evaluation of Momordica charantia tablet as evaluation indexes.The specific conclusions are as follows:(1)under different drying temperature,the lightness value of balsam pear tablet decreases gradually with the increase of temperature,and the effect of vacuum on the apparent change of balsam pear tablet drying is not significant,while the thicker balsam pear tablet is,the smaller the effect on the drying quality is.(2)With the decrease of the absolute pressure in the drying furnace,the evaporation of water increases gradually,and the vacuum degree has a significant effect on the low-temperature drying kinetics of materials.However,with the increase of the temperature difference between the dried materials and the surrounding environment,the water reduction rate increases with the increase of the drying temperature.(3)The vacuum infrared drying had no significant effect on the green content and Vc content of balsam pear leaves(P<0.05).The comprehensive quality of balsam pear met the production requirements.The optimal technology combination of balsam pear slice drying was determined as the material thickness of 4 mm,the drying temperature of 55?,and the vacuum degree of 10 kPa.The drying equipment design was more reasonable and could better predict the change of material moisture content.