Nutritional quality evaluation of four icebox cultivars of watermelon fruit during their development and ripening

Watermelon is a satiating fruit supplemented with health promoting components like sugars, antioxidants mainly lycopene, minerals etc. The biochemical composition, including antioxidants, and the specific activities of enzymes of watermelon fruit of four icebox cultivars were compared at their sequential stages of development and ripening and also an attempt has been made to determine their nutritional quality. The accumulation of sugars was found to be concomitant with the fruit development and ripening of all the presently studied icebox cultivars, but maximum accumulation of sugars occurred in ‘Beauty’ cultivar compared to that of other three cultivars. This phenomenon of sugar accumulation coincided with the increased activity of sucrose phosphate synthase in pre-ripened stage and decreased activities of invertases (acid, neutral) in the course of ripening of ‘Beauty’, but with their maximum activities in young fruit of ‘Karina King’. Antioxidants such as lycopene, ascorbic acid, phenols, polyphenols, anthocyanin and flavanols were found in more quantity in the fruit of ‘Beauty’ followed by ‘Suman 235’ at their ripened stage than that of other cultivars of watermelon. Antioxidant enzymes, POD and SOD, displayed their significant activities during early stages of ripening in all the icebox cultivars. However, a strong positive correlation was observed between total polyphenols and lycopene with total antioxidant activity. The rate of mineral accumulation was higher in the early stages of fruit development in all the cultivars. Based on the patterns of accumulation of sugars, lycopene and other antioxidants and increased activities of enzymes in the fruit of Beauty’, it may be concluded that the fruit of ‘Beauty’ has better nutritional quality when compared to all the other three cultivars of watermelon fruit.