Effect of Sterilization and Storage Temperature on the Composition, Content and Antioxidant Activity of Polyphenol Compounds in Lychee Juice

With Junhong lychee juice as the research object the effects of different sterilization methods (70 ℃ and 121 ℃) and different storage temperatures (4 ℃ and 45 ℃) on the release of phenolic substances in lychee juice were explored. The changes of phenolic contents, antioxidant activity and composition of phenolic were mainly determined. The results showed that after high temperature sterilization of lychee juice at 121 ℃, its phenolic content and antioxidant activity of the lychee juice increased significantly compared with untreated lychee juice and 70 ℃ pasteurized lychee juice (P<0.05). At the storage time of 0 h, the amount of oxidative Absorbance Capacity (ORAC) of high temperature sterilized lychee juice increased by 40.24% and 39.00%, respectively, compared with the untreated lychee juice and pasteurized lychee juice. The gallic acid content in high temperature sterilized lychee juice was increased (P<0.05) and (−)-gallocatechin was generated. (−)-Gallocatechin accounted for 91.74% of the total phenolic compounds in 121 ℃ high-temperature sterilized lychee juice. 4 ℃ and 45 ℃ storage temperature had significantly influence on the phenolic compound content in lychee juice. Untreated lychee juice and pasteurized lychee juice increased significantly in phenolic substances at 45 ℃ (P<0.05), while high-temperature sterilized lychee juice decreased significantly (P<0.05). In summary, heat treatment have a significant effect on the change of phenolic compound content in lychee juice, which can promote the release of phenolic substances and improve lychee juice antioxidant activity.