Effects Of Different Needle Spacing And Pretreatment Methods On Drying Characteristics Of Goji Berry In High Voltage Electric Field

In order to systematically and comprehensively investigate drying characteristics and mechanisms in high voltage electric field,drying experiments of goji berry were conducted by blocking ionic wind,changing needle spacing,different pretreatment methods,and electrohydrodynamic partially combined with oven drying.Drying characteristics,quality parameters of goji berry fruits were measured.The microstructure of goji berry is detected by the method of infrared spectroscopy and scanning electron microscopy.The main results are as follows:In the experiments of blocking ion wind and different needle spacings,the effect of ion wind on drying speed is great,and the effect of non-uniform electric field on the retention of effective components is great.The drying rate of goji berry decreases with the increase of needle spacing.Needle spacing has a great influence on the speed of ionic wind,rehydration rate,and polysaccharide contents.The effective moisture diffusion coefficient and the electrical conductivity disintegration index decreases with an increase in needle spacing.The microstructure of goji berry fruits dried in a high voltage electric field drying system significantly changed.The difference of the internal structure of goji berry under different needle spacings was analyzed by the two index sequence method of common peak rate and variation peak rate in infrared fingerprint.Using the non-linear fitting method,7 models were used to fit the dry data.It was found that these models can be used to describe the regular variation of electrohydrodynamics drying curve under different needle spacing.In the different pretreatments combined with electrohydrodynamic?EHD?drying experiments,the drying rate of goji berry after pretreatment was significantly higher than those of non-pretreated,and the different pretreatment methods had different effects on the drying characteristics of goji berry in a high voltage electric field drying system.The effects of different pretreatment methods on effective moisture diffusion coefficient were listed in descending order as follows:KOH>Na OH>Na₂CO₃>ultrasonic>sucrose ester.The pretreatment has a great influence on the rehydration rate,specific energy consumption and microstructure of goji berry dried by EHD.It was established that two index sequence analysis of infrared spectroscopy during goji berries drying process and analyzed the difference of goji berry internal structure among five pretreatment methods.In the different ultrasonic pretreatment method combined with electrohydrodynamic?EHD?drying experiments,the drying speed of goji berry after ultrasonic pretreatment was significantly higher than that of the control.Ultrasonic pretreatment has a great influence on the drying rate,effective moisture diffusion coefficient and rehydration rate,and has little effect on the shrinkage rate.By means of scanning electron microscope and infrared spectrum,it was found that the microstructure of goji berry was significantly changed by ultrasonic pretreatment.During the electrohydrodynamic?EHD?drying partially combined with oven drying,the drying rate of goji berry was significantly higher than that of oven drying and the control.Under the two-stage drying processing of electrohydrodynamic?EHD?drying and oven drying,at the early stages the electrohydrodynamic?EHD?drying has a greater effect on the drying of goji berry,and in the later stage the oven drying has a greater effect.The electrohydrodynamic?EHD?partially combined with oven drying have great influence on drying rate,rehydration rate,the effective moisture diffusion coefficient and polysaccharide content,and have little effect on shrinkage and flavonoid content.The electrohydrodynamic?EHD?drying partially combined with oven drying caused a significant change in the microstructure of goji berry according to scanning electron microscopy and infrared spectroscopy.The drying experiments of goji berry were conducted by changing different experimental conditions in high voltage electric field,the variation law of drying characteristics,quality parameters,and the microstructure was found.It provides a theoretical basis and practical guidance for understanding characteristic parameters and mechanisms of electrohydrodynamic?EHD?drying technology,improving the disadvantages and drying efficiency of electrohydrodynamic?EHD?drying technology.