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

Lipote (Syzygium polycephaloides (C. B. Rob.) Merr.) is a Philippine endemic tree whoseberries have a potential for functional food development. This study aimed to investigatethe effect of the maturity stage (unripe, half-ripe or fully ripe) and processing (blanchingat 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 anthocyanincontent (TAC)) and antioxidant activity by DPPH, ABTS, and FRAP assays, of lipoteflesh and skin (referred herein as flesh) and seeds. Results showed that maturity andprocessing significantly affect the antioxidant contents and activities of fresh lipote fleshand seeds. Blanched lipote flesh generally had higher TPC, TFC, and antioxidant activitiesthan their unprocessed and steamed counterparts. Blanched unripe flesh had the highestTPC (33.57±0.27 mg gallic acid equivalents [GAE]/g) and antioxidant activity measuredby 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 ripeflesh 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, especiallyunripe ones, have appreciable antioxidant contents and antioxidant activity, even greaterthan that of lipote flesh. Unprocessed unripe seeds had the greatest TPC, TFC andantioxidant activity by DPPH assay (123.56±0.94 mg GAE/g, 111.90±0.14 mg QE/g and465.89±1.86 mg TE/g, respectively). It is recommended that blanching be used as aprocessing step to increase the antioxidant content of lipote flesh while lipote seeds shouldbe investigated further for nutraceutical applications due to their high antioxidantproperties.