Variation of bioactive compounds and antioxidant activity of carambola (Averrhoa carambola L.) fruit at different ripening stages

The variations in bioactive compounds and antioxidant activity of carambola (cv. B17) fruit at different ripening stages were investigated. The carambola fruit was harvested from week 9 until week 13. Ascorbic acid (AA), total phenolic content (TPC), total flavonoids content (TFC), total carotenoids content (TCC), beta-carotene, tocopherol homologues (alpha, beta, gamma and delta) and sugar composition (sucrose, glucose and fructose) were analyzed for each sampling week. Antioxidant activity was measured with 2,2-diphenyl-1-picrylhydrazil(DPPH) and beta-carotene/linoleic acid model(BCLAM) assays. The results showed that AA, TCC and sugar composition were significantly (P < 0.05) increased while TPC, TFC and beta-carotene showed reversed trends as ripening process was in progressed. Interestingly, the tocopherol compounds varied differently with contribution of alpha- and beta-tocopherols highest on week 12 and then decreased on week 13 but gamma- and delta-tocopherols were constantly decreased during ripening. Meanwhile, antioxidant activities for both assays were significantly (P < 0.05) decreased. Multivariate analysis revealed a notable variation of tested attributes among the ripening stages. Bioactive compounds such as TPC, TFC, beta-carotene, gamma- and delta-tocopherol were found to be dominant in unripe fruit while those of sugar (sucrose, glucose and fructose), TCC, alpha- and beta-tocopherol were prominent in the ripe fruit. The findings of this study advocate harvesting of carambola fruit at an appropriate stage to get maximum nutritional benefits. (C) 2014 Elsevier B.V. All rights reserved.