Study On The Impact Drying Technology Of Bitter Melon Flake Gas Jet

Bitter melon is a kind of plant resource used as medicine and food,which contains bitter melon polysaccharides,saponins,steroids,triterpenes,alkaloids,protein,organic acids,vitamins,trace elements and other nutrients.Besides,it has exhibited many kinds of functions,such as anti-virus,anti-oxidation,anti-tumor,lower blood sugar,improve human immunity and so on.Fresh bitter melon can not be easy stored for a long time as its high water content,so dehydration dried is an effective method to extend its storage period.Drying the bitter melon can not only shorten the storage space,enrich the product structure,balance the needs of season,but also can make full use of the health care value of bitter melon,reduce the waste of resources.At present,the main methods of the bitter melon slice for preparing are traditional natural drying and hot-air drying,but its quality is difficult to control,the drying period is too long and the energy consumption is too high.However,the technology of air-impingement jet drying has many advantages including well quality products,fast quick transfer and low energy consumption,and it also has been successfully applied in the study of a variety food materials.In this paper,the effects of the air-impingement drying condition were studied on the drying characteristics of the bitter melon slice and the drying kinetics model was established to predict the moisture change in the drying process.Then the regression equations between inspection indexes(rehydration ration,the Vc content,color difference and unit energy consumption)and dry conditions(air temperature,air velocity and slice thickness)were established by response surface,and the comprehensive objective function was established combined with genetic algorithm,and the comprehensive optimization of parameters were determined.Finally,the changes of chlorophyll,polysaccharides and saponins and its influence of temperature on drying process of bitter melon slice were studied.All of studies provide a theoretical basis for the practical production of bitter melon slice.After the experimental study,the main conclusions were as follows:1.The air-impingement jet of bitter melon slice was mainly the falling rate drying.All the factors including the air temperature,air velocities and slice thickness had influence on the air-impingement jet drying characteristics of bitter melon slice,and their influences were in an order of the air temperature>air velocities>slice thickness.Among them,the influence of air temperature and slice thickness is more obvious than air velocity.But in the actual situation,because the air temperature is too high,can lead to the appearance of bitter melon yellowing and a large number of nutrients losing,so the drying temperature should not be more than 60℃ in process of the production.2.The water effective diffusion coefficient(Deff)in the air-impingement drying of bitter melon slice was increased with the increase of air temperature,air velocity and slice thickness.The maximum water effective diffusion coefficient was 2.9668×10-9 m2·s-1,and the activation energy was 29.89 kJ mol-1.3.Fitting the selected five models with the measured data under the condition that the air temperatures between 40 and 80℃,air velocities between 9 and 13 m·s-1 and slice thickness between 2 and 6 mm.Two term exponential model had the best fit,which was the optimum model of the bitter melon slice in air-impingement jet drying.4.The optimum processing parameters of the bitter melon slice in air-impingement drying were obtained by genetic algorithm were:air temperature was 58.5℃,air velocity was 11 m/s,slice thick was 3 mm.5.With the drying process,the content of chlorophyll and saponins of bitter melon were significantly reduced,and the content of bitter melon polysaccharide was slightly less.6.The temperature had a certain degree of influence on the chlorophyll,saponins and polysaccharide of bitter melon,and its influence degree were:bitter melon chlorophyll>bitter melon saponins>bitter melon polysaccharide.In order to preserve more bitter melon nutrition,we should not use too high temperature during the drying process of bitter melon slice.