| Okara is a by-product in the processing of traditional soybean products in our country.Its production is very high.In addition to being rich in protein,fat,vitamins and trace elements,the dietary fiber content is 50%of its dry matter.It is a high-quality and inexpensive dietary fiber resource with better physiological effects and wide application prospects.However,wet okara has high moisture content,which is unbeneficial for processing and highly perishable.Most of them are used as fodder or directly discarded,resulting in waste of resources and environmental pollution.Based on the study of wet okara vacuum microwave drying（VMD）dynamics and dielectric properties,this article studied the effects of different vacuum microwave drying parameters on the drying effect of okara,and compared with hot air drying（HD）,microwave drying（MD）and vacuum freeze drying（VFD）,explored the influence of the addition amount of red jujube,xanthan gum,and magnesium stearate on the okara chewable tablets sensory score and hardness.The conclusions of the full text are as follows:（1）With the increase of microwave power,drying temperature and loading capacity,the variation of DR of okara showed great difference,and the drying stage mainly had rising speed and falling rate.The water effective diffusion coefficient（Deff）of VMD increased with the rise of microwave power and drying temperature,but decreased with the rise of loading capacity.The Weibull function could simulate the change of MR in VMD process of okara better.The scale parameter a value decreased with the rise of microwave power and drying temperature,and increased with the rise of loading capacity.The shape parameter βvalue was greater than 1 under different drying conditions.（2）Under the different wet basis moisture content or temperature,the dielectric constant（ε′）and dielectric loss factor（ε″）of okara decreased with the rise of the frequency.In the range of 1 MHz～1 GHz,when the frequency was constant,the ε′ andε′of okara increased with the rise of wet basis moisture content or temperature.In the range of 1 GHZ～3 GHZ,when the frequency was constant,theε″ of okara increased with the rise of wet basis moisture content.When the frequency was 2.45GHz,the ε″of okara decreased with the rise of temperature,increased with the rise of wet basis moisture content,and the ε″ increased with the rise of wet basis moisture content.The okara thickness of VMD should not exceed 1.89cm.There was no significant difference between the predicted and measured values of ε′and ε" models,which can predict the dielectric properties of okara well.（3）Regression models of drying rate,chromatic aberration ΔE with the stepwise variable-temperature VMD process parameters were established,which were significant（P<0.05）and the lack of fit were non-significant（P>0.05）,indicating the models could be used to analyze and predict the drying process parameters on the influence of the drying rate and chromatic aberration Δ E.The optimal VMD process parameters of okara were as follows:drying temperature of the first phase was 50℃,drying time of the first phase was 25min,and drying temperature of the second phase was 75℃.Under this condition,the drying rate of okara was 7.16g/（g.h）,chromatic aberration ΔE was 6.12.（4）The staged variable-temperature VMD had the highest drying rate.The obtained okara had the highest rehydration rate,SDF content,TAA content,flavorful AA content,water holding capacity,swelling capacity and its surface morphology were the best.VFD had the lowest drying rate and the highest energy consumption per unit,its okara had the best color and the highest protein and fat content.The particle size of the staged variable-temperature VMD and VFD okara were smaller and the particle size distribution was more uniform.The okara obtained by the variable-temperature VMD has better drying quality and could be used in the development of subsequent functional products.（5）The regression models of the sensory score and hardness of okara chewable tablets with the ingredients were established,and the models were significant（P<0.05）,there was no significant in the lack of fit（P>0.05）,which could be used to predict the sensory score and hardness of okara chewable tablets.The best formula of okara chewable tablets was as follows:red jujube was 42%,xanthan gum was 10%and magnesium stearate was 0.5%.In these conditions,the sensory score of okara chewable tablets was 75 and the hardness was 60N.To solve the problem of low utilization rate of wet okara,this study established the okara vacuum microwave drying Weibull function model and the dielectric property model of okara,built the regression models of the staged variable-temperature VMD drying rate and chromatic aberration ΔE,and optimized the process parameters,established the regression models of the sensory score and hardness of okara chewable tablets with the red jujube,xanthan gum,magnesium stearate addition amount,obtained the best okara chewable tablets formulation.This study is of great significance to the comprehensive utilization of okara. |
