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Physicochemical properties of six cultivars of Cheju citrus fruits were investigated according to the harvest date. The fruit index of Citrus. unshiu Marc. var. miyagawa, C. natsudaidai H_(AYATA) and C. sudachi ranged from 1.14 to 1.38 with oval form. The fruit index of C. grandis OSEECK, C. aurantiun LINN and C. platymamma. Hort. SWINGLE ranged from 0.89 to 1.03 with a round form. The fruit weight showed the heaviest in C. grandis, followed by C. natsudaidai, C. aurantiun, C. unshiu, C. platymamma and C. sudachi. The rate of flesh showed the highest in C. unshiu, followed by C. platymamma, C. natsudaidai, C. sudachi. C. grandis and C. aurantiun. The ratio of juice showed the highest in C. unshiu, followed by C. sudachi, C. platymamma., C. natsudaidai., C. grandis, C. aurantiun. C. unshiu and C. platymamma, which showed a possibility to be used as raw materials for juices. The soluble solid and the Brix/acid ratio of all the varieties increased as the fruits ripen. Especially those of C. unshiu and C. platymamma were high(10.39, 7.67) in full ripe compared to other varieties. Acid content of C. natsudaidai, C. aurantiun, C. grandis and C. sudachi was sustained higher than 3∼5% from the middle of September to the middle of January, and there was the possibility of manufacturing aromatic products like citrus vinegar. The C. sudachi contained the highest content of vitamin C. 77.48 ㎎/100 g. The correlation between vitamin C. extraction and season was insignificant. Rind and color value of all varieties were investigated, and the value of the L, a and b increased as the fruits were ripen. The value of a of rind of C. natsudaidai H_(AYATA) and C. grandis until the end of November was negative. This means that their color was not presented by November since the chlorophyll was in the rind, unlike the colors of the rind of C. unshiu, C. sudachi and C. platymamma which were completed by that time.
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