Antioxidant properties of lipote (Syzygium polycephaloides (C.B. Rob.) Merr.) flesh and seeds as affected by maturity and processing method

Abstract

Lipote (Syzygium polycephaloides (C. B. Rob.) Merr.) is a Philippine endemic tree whose berries have a potential for functional food development. This study aimed to investigate the effect of the maturity stage (unripe, half-ripe or fully ripe) and processing (blanching at 90±5°C for 2 mins and steaming at 105±5°C for 5 mins) on the antioxidant content (total phenolic content (TPC), total flavonoid content (TFC), and total anthocyanin content (TAC)) and antioxidant activity by DPPH, ABTS, and FRAP assays, of lipote flesh and skin (referred herein as flesh) and seeds. Results showed that maturity and processing significantly affect the antioxidant contents and activities of fresh lipote flesh and seeds. Blanched lipote flesh generally had higher TPC, TFC, and antioxidant activities than their unprocessed and steamed counterparts. Blanched unripe flesh had the highest TPC (33.57±0.27 mg gallic acid equivalents [GAE]/g) and antioxidant activity measured by ABTS, FRAP, and DPPH assay (92.31±1.28 mg Trolox equivalents [TE]/g, 123.83±0.86 mg TE/g, and 74.02±0.33 mg TE/g, respectively) while blanched fully ripe flesh had the highest TFC (27.98±0.08 mg quercetin equivalents [QE]/g) and TAC (18.11±0.11 mg cyanidin-3-glucoside equivalents [C3GE]/g). Lipote seeds, especially unripe ones, have appreciable antioxidant contents and antioxidant activity, even greater than that of lipote flesh. Unprocessed unripe seeds had the greatest TPC, TFC and antioxidant activity by DPPH assay (123.56±0.94 mg GAE/g, 111.90±0.14 mg QE/g and 465.89±1.86 mg TE/g, respectively). It is recommended that blanching be used as a processing step to increase the antioxidant content of lipote flesh while lipote seeds should be investigated further for nutraceutical applications due to their high antioxidant properties.