Process Optimization And Quality Characteristic Analysis Of Vacuum Freeze-Dried Jujube Slices

Vacuum freeze-drying is the material under vacuum conditions,water sublimation to achieve the drying effect,the maximum retention of nutrients,but the energy consumption is high.In this paper,we analyzed the effect of the lyophilization model,analyzed the effect of the heating on the vacuum lyophilization time,and the effect of the pretreatment combined with the heating on the nutritional composition of jujube slices.(1)The optimal condition of ultrasound infiltration pretreatment was investigated.The permeant(sucrose,fructose,corn syrup and maltodextrin)were processed by ultrasound,and the drying curve significantly shortened the vacuum lyophilization time,and the effects of the quality fraction of pretreatment factors,ultrasonic penetration time,temperature and power on the lyophilization time were analyzed.Based on the results of one-factor test and orthogonal test,the mass fraction was 50% corn syrup,the ultrasonic penetration time was 40 min,the penetration temperature was 60℃,and the power was 300 W.(2)A model of ultrasonic infiltration preconditioning was studied.Based on Fick’s second law,the drying model of the lyophilization curve was obtained by vacuum freeze drying.The results show that the highest fit of Page model is 0.9892,which can be used to describe the lyophilization process of ultrasonic osmosis-pretreatment date slices.The relationship between quality score M,penetration time T,ultrasonic power W,and ultrasonic temperature C and moisture ratio(MR)were obtained by Origin software.(3)The effect of procedural warming on the lyophilization time of jujube slices was studied.Analyze the effect of heating conditions on the vacuum freeze drying rate and calculate the energy consumption of heating drying.The high eutecting point of jujube slices pretreated with corn syrup can reduce the energy consumption of prefreezing.Procedure warming includes rapid warming,medium speed warming,and slow warming.The results show that the rapid heating can shorten the vacuum freeze-drying time and improve the drying efficiency.The energy consumption for different program heating conditions is calculated,and the minimum energy consumption is 15.617 k J/g.(4)The nutritional quality characteristics of the freeze-dried jujube slices were studied.The microstructure of date slices was analyzed by electron scanning microscopy.The content changes of Vc,phenolic substances and total flavonoids in jujube tablets were determined,the brightness value change of jujube tablets was determined,and the sensory color of jujube tablets was evaluated.To determine the rehydration rate of jujube slices,the freeze-dried jujube slices have more structural pores,faster drying rate,and higher rehydration rate,and the taste is better after rehydration.The results showed that it had a bad effect on nutrients,and the ultrasound treatment process was accelerated.