HARVEST MATURITY RELATED CHANGES AND THEIR INFLUENCE ON ANTIOXIDANT POTENTIAL IN ´GOLDEN SMOOTHEE´ APPLES

Abstract

Changes in non-enzymatic antioxidant potential (DPPH, ascorbate content) and in enzymatic antioxidant potential (SOD, CAT and POX activity) were assessed in 'Golden Smoothee' apples in relation to harvest date. Fruits were harvested six times on a weekly basis (from 18 th august to 22 nd September) from two different orchards in the Lleida area (Spain). Changes in antioxidants were related to changes in maturity indexes for each orchard. The main purposes of the study were to investigate whether a delay in harvest date caused an increase in the level of active oxygen scavenging activity and to establish the optimal harvest date in order to maximise antioxidant potential and thereby improve fruit quality during postharvest storage. Total antioxidant potential increased significantly with increasing maturity for each orchard. In contrast, ascorbate levels remained stable during the first four weeks and then decrease during the last two weeks. This opposite behaviour of ascorbate and total antioxidant potential showed that ascorbate alone was not the most important antioxidant compound for determining the total antioxidant potential of the fruit. Others compounds such as phenols are involved and it is likely that changes in the solubility of these compounds during on-tree ripening which determine the apple total antioxidant potential. Changes in enzymatic antioxidant potential paralleled those of ascorbate, a result that showed the direct relationship between non-enzymatic and enzymatic antioxidant potential.