Development Of Clear Pomegranate Juice

The processing of clarifying pomegranate juice was studied, including processes for clearing pomegranate juice and maintaining the attractive color ; and non-thermal technology——Pulsed electric fields was applied to sterilize the juice.Firstly, the processes for clearing pomegranate juice and maintaining the attractive color were investigated. The results showed that gelatin- tannin was more suitable than pectinase and chitosan to clear the juice. 0.05% gelatin and 0.04% tannin were added to get the clear juice, without cooked flavor and secondary sedimentation. Then 0.25 ~ 0.03% citric acid was added to adjusting the pH of the juice to 3.0. And 0.02% ascorbic acid was added to resistant oxidation. With the combined effect of citric acid and ascorbic acid, the degradation of the anthocyanin in juice was slow down.The traditional thermal pasteurization processes are effective on sterilization of the pomegranate juice. However, they bring about many adverse effects. For example, they may change the color of the pomegranate juice, cause the undesirable cooking flavor, and destroy sensitive components, etc. The loss of sensory qualities (color, flavor and taste) during heat processing, especially the sterilization, has retarded the development of pomegranate juice. Pulsed electric fields (PEF) was applied to the pasteurization of pomegranate juice, and the changes in the physicochemical properties of the juice were researched. The result showed that electric field intensity and process time were determining factors. About 3.62 and 3.59 lgs reduction of E. coli and L.innocua were achieved at 35 kV/cm for 200 microseconds (2μs pulse width, 100Hz). Under the same condition, 2.34 and 0.74 lgs reduction of yeast and A. niger were found.No significant changes in the color, clarity, content of polyphenosl and anthocyanin were observed after PEF treatment. The result of GC-MS showed that the main flavor substance in pomegranate juice was metahanal, and after thermal treatment the content of it reduced 17%. Compared with conditional thermal sterilization , the treatment of PEF brought less influence on juice flavor. The results of storage experiment showed that PEF brought the juice a stability in storage more than 5 months in 4 oC, the total count of bacteria colonies were not detected, and the total count of yeast and mold were less than 10 cfu/mL.