Fluctuation of Limonin Concentrations in Different Fruit Compartments during the Developing Period of Three Orange Cultivars

In this paper, the changes of limonin concentrations in different fruit compartments during the developing period were investigated in three representative orange cultivars. They were 'Xuegan', 'Zhongyu #7', and 'Fengji'; the latter two are seedless oranges. The results of this study confirm that limonin was presented in entire oranges throughout the mature period. The concentration of limonin was two times in peel than in juice sacs. With the maturity, limonin concentration in peel and sacs tended to decrease. In turn, it was increased in seeds of the seeded cultivar at the latter mature period which is much higher than in the juice sacs and peel, demonstrating that limonin is transferring into seeds. This is especially ture in 'Xuegan' that limonin in seeds was 6 and 12 times higher than respectively in peel and juice sacs in Dec. Generally, the limonin concentration in 'Xuegan' was higher than other two cultivars in Aug. to Sept., while it was rather in reverse in Oct. to Nov. At the late mature stage, the ranking of limonin in fresh juice sacs is as follows: 'Fengji' (0.025 mg.g(-1)) > 'Zhongyu #7' (0.015 mg.g(-1)) > 'Xuegan' (0.011 mg.g(-1)) which are higher than the threshold value of human-being accepted bitterness value of 0.006 mg.g(-1), requesting an attention in making juice product because of bitterness.