EFFECT OF DEGREE OF RIPENING ON THE CHEMICAL CHARACTERISTICS AND ANTIOXIDANT PROPERTIES OF JUICE FROM LIME (Citrus aurantifolia), LEMON (Citrus limon) AND GRAPE FRUIT (Citrus paradisi)

Abstract

The influence of degree of ripening on the chemical characteristics and antioxidant properties of juice from lime, lemon and grapefruit was investigated. The unripe lemon gave the highest juice yield (22 ml/100g) at that ripening level while the ripe lime gave the highest yield (43 ml/100g) at that ripening stage. The pH values of the juice ranged between 2.77 - 3.27 (unripe), 2.22 - 3.57 (half-ripe) and 2.77 - 3.75 (ripe) while the ascorbic acid content at different ripening stages also ranged between 68.92 - 81.25 g/100ml (unripe), 15.17 - 62.3 g/100ml (half-ripe) and 14.53 - 49.22 g/100ml (ripe). The total phenolic content of the fruit juice was also affected by stages of ripening giving 2.07 - 7.2 μg GAE/mL (unripe), 1.41 - 5.31 μg GAE/mL (half-ripe) and 0.99 – 4.14 μg GAE/mL (ripe); indicating a decreasing order as the ripening progressed. The antioxidant capacity of the juice from the fruit showed the highest value for the unripe fruit. The Ferric-reducing antioxidant power (FRAP) values were 3.72 – 9.53 μmol/L Fe(II)/g (unripe), 2.84 – 7.2 μmol/L Fe(II)/g (half-ripe) and 2.51- 4.58 μmol/L Fe(II)/g (ripe). Similar trend was also obtained for the antioxidant capacities of the fruit juices using 2, 2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and total antioxidant capacity (TAC) methods, respectively. The conclusion derivable from this study is that the stages of ripening actually affected both the chemical characteristics and antioxidant properties of fruit juice obtained from lemon, lime and grapefruit.