Effect Of Different Sterilization Methods On Physicochemical Properties And Antioxidant Capacity Of Fresh Pear Jujube Juice

Pear jujube (Zizyphus jujube Mill.cv. Lizao) which is also called Dalingzao or Cuizao, isa rare excellent fresh jujube, which is one of country recommended fresh and late-maturingvarieties in recent years. Pear jujube is well-known for its appearance, crunchy texture, highsugar content and especially rich in nutrition. Pear jujube is deeply favored by consumers athome and abroad. Our study research utilize optimal enzyme solution to extract fresh jujubejuice, use high pressure sterilization and microwave sterilization technology for jujube juicesterilization, study different sterilization methods on physicochemical properties andantioxidant capacity of fresh pear jujube juice in order to open up new ways to improve theutilization of fresh jujube. Main results obtained were as follows:(1) The optimum made for fresh jujube juice is an pectinex enzyme dosage of80mL/t,an amylase enzyme dosage of120mL/t and an pectinase enzyme dosage of120mL/t,hydrolysis temperature55℃, hydrolysis time60min. The fresh jujube juice under the bestconditions of enzymatic hydrolysis soluble solids is21.0%, titratable acid0.65%, T62599.2%,fumaric acid content3.2mg/L, HMF16mg/L and light transmittance can reach98.5%. Thefresh jujube juice can keep fresh jujube nutritional ingredients and is a natural, nutrient-richdrinking. Fresh jujube juice drinks will have broad prospect of development value and themarket, and expand new ways of development and utilization of the fresh jujube.(2) Different sterilization methods on fresh jujube juice sterilization and physicochemicalproperties exist a certain differences. Using ultra-high pressure sterilization technology forfresh jujube juice can better keep original flavor of fresh jujube juice. Fresh jujube juice islower titratable acid content, higher light transmittance and non enzymatic browning degreeby ultra high pressure sterilization technology. There is especially significant difference ontitratable acidity, light rate of non-enzymatic browning, and Vc content of different sterilizedjujube juices. Fresh jujube juice color differences analysis are found that ultra-high pressuresterilization can be well kept original color and flavor of fresh jujube juice.(3) Different sterilization methods on fresh jujube juice phenolics and antioxidantactivity exist a certain differences. Fresh jujube juice by ultra-high pressure sterilization inlow temperature or room temperature can keep better antioxidant substance and phenolicacids. Pasteurized can obviously reduce the VC, total phenol, flavonoids and other functional ingredients of fresh jujube juice. The total phenols and flavonoids retention rates of fresh juiceafter ultra-high pressure sterilization are86.08%,99.67%respectively and proanthocyandinscontent49.48~85.84%mg GSPE eq.\100g FW. Different sterilization methods of fresh jujubejuice in antioxidant capacity indicators have significantly different difference.(4) Catechin, epicatechin, rutin, gallic acid, catechin, ferulic acid and clove acid weremain detected phenolic compounds. There is highly significant relationship between the Vccontent and antioxidant capacity coefficient, R value can reach0.994. Ferulic acid of freshjujube juice and its ABTS+reducing ability have a significant relationship, R value can reach0.993. Different sterilization methods have significant effect on soluble sugar and organic acidcontent in fresh jujube juice. The sucrose content of fresh jujube juice is not detected afterheat sterilization process. Total soluble sugar content is in the range of5.187~7.610g/100gFW and total organic acid content in the range of750.55~1053.41mg/100g FW. Ultra highpressure sterilization technology can keep fresh jujube juice better antioxidant functioningredient, and is more suitable for fresh jujube juice production and processing requirements.(5) Different sterilization methods on fresh jujube juice sterilization and physicochemicalproperties exist a certain differences during storage. Using ultra-high pressure sterilizationtechnology for fresh jujube juice processing in low temperature storage can not only maintainthe better quality of jujube juice but also maximize the retention Vc content of jujube juice.When fresh juice is storaged after different sterilization methods process, the titratable acidity,browning and total color difference value is gradually increased, the transmittance do notchange significantly，pH, total sugar and Vc content decrease. Ultra-high pressure sterilizationis the best sterilization ways for jujube juice during storage at low temperature.