Study On Quality And Bactericidal Kinetics Of Jujube Juice Treated With UHP-UW

Jujube is warm and sweet which has rich nutritional value.However,due to the short storage time and perishability of fresh jujube,a natural jujube juice product was developed by adding natural ingredients in order to improve the economic value and utilization of jujube.UHP technology can maintain the original color,flavor and nutrients of food.However,the high pressure required for sterilization makes the equipment wear out and cost high.While UHP-UW technology can not only improve the bactericidal and inhibitory effect,but also greatly reduce the consumption cost.Firstly,this topic studied the quality of four varieties of red dates.Secondly,the varieties of ingredients are selected and the amount of additives is determined.On this basis,the single factor experiment was carried out and the response surface method was applied to optimize the sterilization process.The effect of UHP-UW on the quality of turbid jujube juice was studied.Finally,the bactericidal effect of UHP,UW and UHP-UW treatment was studied and the model fitting and dynamic analysis were carried out.The results are as follows:(1)Through the four varieties of red jujube sensory,color,nutritional components,antioxidant properties,texture and other indicators.The results showed that the a*values of the four kinds of jujube were negative,b*values were positive,and the color was yellowish-green.The brightness of Dali jujube was the greatest.The total sugar,reducing sugar,reducing sugar in the total sugar content and total acid content of Lingwu jujube were the highest.The reducing sugar content in the total sugar content of Dali jujube was the smallest,and the moisture content was the highest,which was more suitable for beating.DPPH clearance rate,reducing power and ·O2-clearance from big to small in turn was respectively:Dali jujube>LingWu jujube>Chaoyang jujube>Maya jujube,Dali jujube>LingWu jujube>Maya jujube>Chaoyang jujube.The hardness range was 545.21?858.62 g,masticability range was 122.23?130.87 g,elasticity range was 0.71-0.91,cohesion range was 0.20?0.24 g,brittleness range was 473.41?751.36 g.Among them,the brittleness of Dali jujube was the biggest.Liquid-mass technology was used to detect the possible substances in Dali jujube.The separation conditions applied had good separation detection results.The compounds screened from the original data were divided into three categories:acid,ester and others.Among them,ester compounds accounted for 68.28%was most.(2)The quality characteristics of the four kinds of kiwifruit as natural ingredients were studied.Hayward kiwifruit was more suitable to be added as ingredients.And ester compounds accounted for the largest proportion in the liquid-mass test results was 66.95%.The optimal additive amount of kiwi pulp was 20%.The single factor experimental results of the best quality of jujube juice were UHP pressure 200 MPa,pressure maintaining temperature 30?,pressure maintaining time 10 min,UW power 165W,and ultrasonic time 20 min.The response surface method was used to optimize the sterilization process conditions,and the response value was taken as the comprehensive score.The highest comprehensive score and the best sterilization process conditions were 200 MPa ultra-high pressure,30 min pressure holding time and 19 min ultrasonic time.The comprehensive score was 8.52,and the error with the predicted value of the model was 0.70%.(3)The effect of UHP-UW on the quality of turbid jujube juice was studied.The results were as follows:with the increase of storage time,the brightness of jujube juice decreased,the green value weakened,the yellow value deepened,and the color difference gradually increased.Both pH and SSC contents showed a decreasing trend,but the variation range was not large.The content of total phenol and Vc decreased with the prolonging of storage period.The total number of colonies and the number of molds and yeasts gradually increased.And the Browning degree also showed an increasing trend,with a fast growth rate in the early stage and a slow growth rate in the late stage.The absorption value of suspension stability decreases gradually.The absorption value at low temperature was higher than that at room temperature.In conclusion,low temperature was more suitable for storage of jujube juice.The ratio of ester compounds in turbid jujube juice samples was 67.52%.(4)The effects of UHP,UW and UHP-UW treatment on the total bacterial colonies,mold and yeast in the turbid jujube juice were investigated.The results showed that the synergistic treatment of turbid jujube juice was significantly better.The longer the pressure and time,the more inactivation.The sterilization effect was UHP-UW>UHP>UW.The dynamic analysis results of the model fitting parameters obtained by weibull model fitting were as follows:the R2 of the weibull model was all? 0.900,which had high fitting accuracy and could accurately represent the inactivation law of microorganisms in the turbid jujube juice.With the increase of the scale parameter b,the rate of inactivation of microorganisms increased.The shape parameter n increased to different degrees,but all of them were less than 1.The closer the value of n was to 1,the more stable the inactivation rate was,and the more linear the inactivation curve was.