Study On Key Technology Of Processing And Storage Quality Of Prunus Mume Juice

Prunus mume Sieb.et Zucc.,also known as green plum,has unique flavor and high nutritional and health value.However,with its extremely sour flavor,fresh Prunus mume is not popular with the public,so it is often processed into deep processing products such as fruit juice and wine.However,during these processing,there are problems such as low juice yield and eundesirable enzymatic browning.In this study,Prunus mume was used as raw material to explore the optimal enzymatic extraction process of Prunus mume juice,analyze the primary and secondary factors causing browning of Prunus mume juice,and find the optimal combination of anti-browning agents.The effects of different sterilization methods on the bactericidal effect,physicochemical index and volatile flavor components of Prunus mume juice were compared,and the quality of sterilized Prunus mume juice during storage was analyzed.The main research contents and results are as follows:(1)With the juice yield of Prunus mume juice as the response value,the optimum extraction process of Prunus mume juice was determined by response surface optimization design test.The results showed that the optimum extraction conditions were as follows:pectinase addition was 0.06%,enzymolysis temperature was 34.6?,enzymolysis time was1.4 h(about 84 min),the juice yield of Prunus mume juice increased from 53.41%to 79.58±0.97%,and the squeezing performance of Prunus mume juice was significantly improved.(2)Pearson correlation analysis was used to investigate the correlation coefficient R² between BD and?E,total phenol,ascorbic acid,reducing sugar,5-HMF,amino acid nitrogen,TSS and pH value of Prunus mume juice.The BD of Prunus mume juice at different storage temperatures was significantly positively correlated with 5-HMF,and negatively correlated with ascorbic acid.Using stepwise linear regression equation,a mathematical model was established to predict the browning degree of Prunus mume juice:Y=0.880 X₆-12.301 X₅+8.269(X₆ is 5-HMF,X₅ is ascorbic acid).It is concluded that the browning of Prunus mume juice during storage may be mainly caused by Maillard reaction and ascorbic acid oxidative decomposition in non-enzymatic browning.Then three anti-browning agents,citric acid,ascorbic acid and calcium chloride,were used to optimize the response surface experiment.The optimal compound addition amounts were 0.26%,0.26%and 0.20%,respectively,which could effectively reduce the BD of Prunus mume juice.The verification experiment results showed that the BD of Prunus mume juice was 6.43 at 15 d storage,which was basically equal to 6.70at 6 d storage without anti-browning agent.(3)Control check(CK)was used as the control group to compare the effects of Pasteurization(P),ozone(O₃),ultrasonic(US)and high hydrostatic pressure(HHP)sterilization methods on the physicochemical properties,microbial indexes and volatile flavor components of Prunus mume juice,so as to find a suitable sterilization method for Prunus mume juice.Through the comparative study,it was found that O₃ and US treatments had significant effects on BD,?E,total phenols,reducing sugar,TSS,pH value and volatile flavor components in Prunus mume juice(P<0.05),and the sterilization effect was general,and the sterilization rate was not more than 80%.P and HHP treatment decreased the BD of Prunus mume juice,and retained good volatile flavor components,and had significant effects on?E,TSS and pH value(P<0.05).However,there was no significant difference in reducing sugar,5-HMF and amino acid nitrogen content(P>0.05).The volatile flavor components were retained well,and the sterilization effect was significant,and the sterilization rate was more than 90%.The experimental results showed that both P and HHP technologies were suitable for sterilization treatment of Prunus mume juice,and had relatively small effect on the overall quality of Prunus mume juice,which could better retain its color,flavor and physical and chemical components.(4)Prunus mume juice after pasteurization and high hydrostatic pressure sterilization was stored at 4?,25? and 37? to monitor the storage characteristics and quality changes.The microbial indexes during the storage period of Prunus mume juice were determined,including physicochemical indexes(BD,?E,total phenol,reducing sugar,5-HMF,amino acid nitrogen,TSS and pH value),molds and yeasts(M&Y)and aerobic plate count(APC),and the differences in volatile flavor components before and after storage.The results showed that the quality of Prunus mume juice treated with HHP was better maintained at 4? shortly.