We compared the quality parameters of the large red-fleshed watermelon cultivar 'Matsuribayashi 777'; sugar content and composition, Brix, sweetness, carotenoid content, and amino acid content. Immature and mature fruits were harvested 30 days after pollination (accumulative temperature about 750℃) and 42 days after pollination (accumulative temperature about 1,150℃), respectively. Immature fruits were allowed to ripen in a cool, dark place for 17 days, with the same accumulative temperature of mature fruits (after-ripening fruits). Brix, sucrose content, and total sugar content of the after-ripening fruits were significantly lower than those of the mature fruits, but fructose content was significantly higher, and there was no difference in sweetness. β-carotene content of the after-ripening fruits were not higher than the mature fruits, but total lycopene content had same levels. In general, citrulline (Cit), glutamine (Gln), and arginine (Arg) content accounted for about 70% of the total amino acid content. Gln content was the highest in the mature fruits and tended to decrease in after-ripening fruits. Cit and Arg contents were not significantly different among any of the fruits. These results suggest that ripening technology could be applied to watermelons if the harvest time and ripening conditions for immature fruits are optimized. The establishment of this technology is expected to reduce the occurrence of overripe fruits. In addition, it would shorten the cultivation period and lead to a reduction in field management efforts.
