Study On Drying Characteristics And Quality Of Far-infrared Vacuum Dried Winter Jujube Slices

Jujube,a plant of the genus jujube in the family rhizoaceae,is favored by people because of its rich nutrition and high health value.However,fresh jujube is not easy to be stored due to its large water content after picking,so it has become the main processing method of Chinese jujube processing industry to make the jujube slices and keep them dry.Steps of far infrared vacuum drying technology is applied in this article to xinjiang dried piece,first of all,the overall structure of the far red vacuum drying equipment,heating system,vacuum system,control system,man-machine interface,the optimization design,and illustrates its general structure,working principle,optimization of parts,such as the radiation temperature,relative pressure,slice thickness on the drying characteristics of winter date sheet and water effective diffusion coefficient,the influence of dongzao piece of far infrared vacuum drying kinetics model is set up,explore the color difference of different factors on the steps of dried slices,after water ratio,Vc content,the influence of the sensory quality of change,Finally,the far-infrared vacuum drying process of winter jujube slices was optimized and verified to determine the optimal drying process parameters,so as to provide a reliable basis for the processing of winter jujube slices.(1)After optimized design,zkt-50 eb far-infrared vacuum drying equipment can quickly reach and maintain operating temperature and vacuum degree.Meanwhile,it can set heating duration,vacuum intensity and temperature parameters of each heating plate,and can achieve real-time monitoring,control and recording.In the process of drying test,the equipment is stable in performance,safe and reliable,and does not produce harmful gas such as pollution to materials.It can be used for drying most fruits and vegetables,and can effectively improve the drying rate and quality requirements of dry products.(2)The drying process of winter jujube slices is mainly divided into two stages: the ascending drying stage and the descending drying stage,but most of the drying time is in the descending drying stage.In the far-infrared vacuum drying process of winter jujube slices,each drying parameter has a significant influence on the drying rate of the jujube slices.The drying rate of winter jujube slices was in direct proportion to radiation temperature and relative pressure,and in inverse proportion to slice thickness.The effective diffusion coefficient of water in winter jujube slices was 0.9757~5.1795×10-8m2·s-1,which increased with the increase of relative pressure and slice thickness,and first increased and then decreased with the increase of radiation temperature.The change of the thickness of winter jujube slices had the most obvious effect on the internal water diffusion.Through the three common fruits and vegetables drying dynamics model fitting comparison,build on dongzao far infrared vacuum drying,the optimal fitting effectPage dynamic model,determine the equation of constant K and n,Page model equation,to fitting the model validation,the results show that the predicted values and experimental values of the model fitting effect is good,can accurately predict effectively dongzao far infrared vacuum drying process.(3)In the single-factor experiment,the influence of various drying parameters on the quality of dried winter jujube slices was analyzed.The results showed that: with the increase of relative pressure,the Vc content,rehydration ratio and sensory quality of winter jujube slices increased,and the color difference value decreased.With the increase of radiation temperature,the Vc content,rehydration ratio and sensory quality of winter jujube slices first increased and then decreased,and the color difference increased.With the increase of slice thickness,the Vc content,color difference and sensory quality of winter jujube slices first increased and then decreased,and the rehydration ratio decreased.(4)According to the combined test design principle of box-benhnken center,with drying temperature,relative pressure and slice thickness as independent variables,and color difference,rehydration ratio and Vc content as detection indexes,the technology of far-infrared vacuum drying of winter jujube slices was analyzed on the corresponding response surface,and the regression equation of each index was obtained.The results showed that: Each index model,significantly better fitting degree,have a certain reliability,can use this model to forecast the result of the experiment analysis,steps of far infrared vacuum drying slices the best process conditions for the radiation temperature of 54.62 ?,the relative pressure is 60 kpa,slice thickness is 3 mm,dongzao reach a safe moisture content,the optimal value of 5.43,color difference after water than the optimal value of 3.52,Vc content,the optimal value of 28.92 mg / 100 g.