Key Processing Technology And Shelf Life Prediction Of Blueberry Juice

Blueberry fruit contains rich nutrient element and active ingredients,resulting in high antioxidant activity that provides health benefits.Traditional blueberry drinks generally contains blueberry juice content and add all kinds of food additives.The blueberry juice without any food additives was studied in this paper,and the juice would have prominent healthy function.The studies were primarily carried out about the key processing technologies of blueberry juice,such as blanching,enzymatic treatment and sterilization.In addition,the shelf life of the blueberry juice was predicted.The contents and results were as follows:?1?Effect of blanching conditions on the quality of blueberry juiceThe studies were carried out about the effects of different blanching conditions on the nutrition ingredient and antioxidant activity of blueberry juice to obtain the optimum blanching temperature and time.The results showed that the blanching could obviously decrease peroxidase activity in blueberries,and the peroxidase activity was inactive at 80? for 6?15 s,85? for 3-15 s,90? for 3?15 s.The moderate blanching could improve the color of blueberry juice and the dissolution of soluble solids,so the soluble solids contents,total sugar contents and juice yields increased too.However it has reduced the total acidity,vitamin C contents,anthocyanin contents,total phenolic contents,total flavonoids contents,SOD activity and antioxidant activity of blueberry juice.Based on these results,the lower blanching temperature and the shorter blanching time should be chose under the premise of ensuring the inactivation of peroxidase.The optimal blanching condition was 80? for 6 s.?2?Enzymatic process conditions optimization of blueberry juice extractionIn order to explore the blueberry juice extraction effect with complex enzyme,response surface method was used to optimize the enzymolysis conditions based on the single factor experiments.The results showed that the two multiple regression equation models of anthocyanin contents and juice yield for the enzyme treatment conditions were extremely significant,and they could be used to analyze and predict the anthocyanin content and juice yield of blueberry juice.Through the response surface analysis,the optimum enzymolysis conditions were enzyme addition 0.0084%,enzymolysis temperature 45.4?,enzymolysis time 2.26 h.At this time,the anthocyanin contents of blueberry juice were 38.4877 mg/100mL,and the juice yields were 79.8344%.Compared with the control group,the juice yields,total acidity,anthocyanin contents,soluble solids contents,total phenolic contents and total flavonoids contents of blueberry juice prepared under the optimum conditions increased significantly.There was no significant difference in color,total sugar contents,SOD activity.Vitamin C contents decreased significantly,DPPH radical scavenging capacity increased by 8.84%,and ·OH radical scavenging capacity increased by 4.3%.?3?Effect of sterilizing process on the quality of blueberry juiceThe studies were carried out about the effects of different pasteurization and high-pressure steam sterilizing conditions on the microbial indicators,nutrition ingredient and antioxidant activity of blueberry juice.The results showed that heat sterilization at 80? for 4?16 min or at 105? for 30?120 s could effectively kill microorganisms.The sterilization was not conducive to preserve the color of blueberry juice.After sterilization,the total acidity had no significant difference,and the soluble solids contents,total sugar contents,vitamin C contents,anthocyanin contents,total phenolic contents,total flavonoids contents and superoxide dismutase?SOD?activity decreased significantly.The DPPH and OH radical scavenging ability decreased significantly.However,the total soluble solids,total sugar,anthocyanin,total phenolics and total flavonoids remained above 85%.So the result of optimum sterilizing condition was 80? for 8 min or 105? for 60s.?4?Storage quality changes and the shelf life prediction of blueberry juiceThe changes of storage quality were studied about two kinds of products sterilized at 80?for 8 min and at 105? for 60 s.The shelf life of the products was predicted by the Q₁₀ model of ALST method.The results showed that total number of bacterial colony and coliform groups in the two kinds of products at 4?,27? and 37? were not detected at the end of the shelf life test.The soluble solids contents and total acidity of blueberry juice were relatively stable during storage,the anthocyanin contents decreased faster.The storage quality at 4? was better.The shelf life of the sample sterilized at 80? for 8 min was 91 days under the storage condition of 20?,and its shelf life was 165 days under the storage condition of 4?.The shelf life of the sample sterilized at 105? for 60 s was 102 days under the storage condition of 20?,and its shelf life was 194 days under the storage condition of 4?.