Chemical changes and antioxidant activity in pomegranate arils during fruit development

Abstract

The present research work describes the major chemical changes and antioxidant activity and their significance during development of pomegranates. Pomegranate arils showed a significant ( P ⩽ 0.05) increase in total soluble solids, total sugar and reducing sugar contents up to 100 days of fruit development, followed by a steady-state in their rate of accumulation. The highest anthocyanin pigment content (138 mg/100 g) was observed in 100 day-old fruit. Significant ( P ⩽ 0.05) decreases, of 76.2% and 71.1% in the concentration of ascorbic acid and total phenolics, respectively, were recorded from 20 to 100 days of fruit development. The equilibrium concentration of these chemicals on the 100th day marked the attainment of optimum maturity and onset of ripening of pomegranate fruit. After an initial rapid decrease (by 66.9%) in total protein content, pomegranate arils showed a significant ( P ⩽ 0.05) increase (by 58.7%) during the late-developmental stages (80–120 days). The high antioxidant activity (71.2%) of arils recorded in 20 day-old fruit decreased significantly (by 13%) up to 60 days, concomitant with a decrease in ascorbic acid and total phenolics by 68.4% and 63.9%, respectively. An increase in antioxidant activity by 10.6% in the late-developmental stage was due to a build up of anthocyanins. The trend in accumulation and depletion of the above mentioned chemicals marked the different stages of fruit development, maturity and onset of ripening. A decrease in anthocyanin pigment concentration (9.3%) from 100 days onwards, as well as a significant decrease in acidity was found to be the major chemical factor for increased incidence of internal browning in over-ripe fruits.