Changes in phenolics and antioxidant activity at each step of processing from pomegranate into nectar

Abstract

Effect of all processing steps on polyphenols and antioxidant activity was investigated during an industrial scale pasteurized pomegranate nectar production, from which sampling was done at 12 steps of the process. Total phenolic (TPC), flavonoid (TFC), anthocyanin (TAC), tannin contents (TTC), antioxidant activity (TAA) (2,2'-azinobis-3-ethylbenzo-thiazoline-6-sulphonic acid diammonium salt (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing ability of plasma (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays), phenolic and anthocyanin profiles were analyzed in those samples. TPC, TFC, TTC and TAA were highest in whole pomegranate. For all analyses, peeling and processing into nectar resulted in significant losses, except for TAC data obtained for peeling. Losses at mashing (for TFC 24%), pressing (for TAC 13%, TTC 48%, TAA 21-63%), pasteurization (for TFC 76%, TAA 42-77%) and ultrafiltration (for TPC 18%, TFC 28%, AA 17-19%) were also significant. Pomegranate nectar, when compared with fresh edible fruit, retained 19% of TPC and 14% of TAC at the end of processing, however, as initial values were very high for pomegranate, pasteurized nectar is still a promising source of polyphenols.