Study On The Fruit Quality Changes Of Navel Orange On Tree Storage And The Late-ripeing Navel Orange

Study was carried out on the quality changes during Cara Cara [Citrus sinensis Osbeck cv.], Skagg's Bonanza(C. sinensis Osbeck cv.) and Newhall(C. sinensis Osbeck cv.) navel orange of on-tree storage in different amount fruits on tree, with the aim of finding the optimal harvest limit and cultivars for on-tree storage. Meanwhile, it was determined that the concentrations of sugar and acid in the fruits as well as pigment of peel of Fengjie 72-1 and its late mature mutant i.e. Fengjie 95-1 navel orange. The main results were as follows:1. On the tree storage of navel orange, the quality was not much affected by different amount fruits on tree (hundred percent fruits on tree, three-quarter fruites on tree and a half fruites on tree), the period of on-tree storage connected with cultivar. As a whole, the ratio of sugar to acid increased while total acids decreased constantly, the content of Sucrose presented significant decline in the end of February, in the middle ten days of February and in the end of January respectively, so the best harvest limit on the tree storage of Cara Cara navel orange was the end of January and the last harvest date was the end of February. We considered fruits of Skagg's Bonanza navel orange should be collected before the middle ten days of February and Newhall navel orange which having the shortest term on tree storage was in the end of January.2. Fruits on the tree storage not only became coloury for the chlorophyll content nearly tended to zero and the carotinoid contents increased constantly, but also increased quality of Cara Cara navel orange for the total sugar content and the ratio of sugar to acid had significant increase whereas the contents of total acid significantly decreased during fruits on the tree storage. Fruits can maintain original quality on the tree storage period of Skagg's Bonanza and Newhall navel orange for the total sugar content, the total acid content and the ratio of sugar to acid had no significant change entirely.3. Among the three varieties, fruits of Cara Cara navel orange which was adaptive to on-tree storage had the longest period on the tree storage for the absolute value of taste exponential and the Glucose content increased, this made thick sweet taste and better flavor, the next was Skagg's Bonanza navel orange, then was Newhall navel orange.4. The changes tendency of depletion chlorophyll content and increment of carotinoid content in the peel between Fengjie 72-1 and Fengjie 95-1 navel orange showed identity, and the two pigments had negatively correlation in content during fruit ripening. The chlorophyll content between Fengjie 72-1 and Fengjie 95-1 navel orange had significant difference in the early stage(Oct.~Nov.) while no significant difference inthe later stage(Dec.~Jan.), and the former were lower than the latter throughout the ripeness, meanwhile the carotinoid content between the two varieties in the two stages were reversal in significance, and the carotinoid content of Fengjie 95-1 navel orange was lower than that of Fengjie 72-1 navel orange in the later stage of ripeness.5. Organic acids, mainly constituted by citric acid, presented a decline tendency in the peel and pulp during the Fengjie 72-1 and Fengjie 95-1 navel orange fruit ripening, and the malic acid, citric acid and total acids in the peel between the two varieties had more or less difference in different stages. Total acids of pulp were higher than that of peel in significant level, and the content of citric acid and malic acid in the pulp of Fengjie 95-1 navel orange were higher than that of Fengjie 72-1 navel orange, and the total acids between the two varieties had more significant difference from the last ten days of August to the middle ten days of November, namely early stage of ripeness, while no significant difference from December to February of next year, namely late stage of ripeness.6. The contents of Fructose, Glucose, Sucrose, and total sugars presented increasing trend in the whole during fruit ripening, and the content of reducing sugars were higher than that of non-reducing sugar, namely Sucrose. Different sugars accumulated in different tissue of navel orange, hexose was the major ingredient in the sugars accumulation in the peel of navel orange, while, Sucrose in the pulp. Various sugars contents in the pulp of Fengjie 72-1 navel orange were higher than that of Fengjie 95-1 navel orange, but no significant difference between the two varieties in the ripening date. In addition, the hexoses contents in the pulp of Fengjie 72-1 navel orange remarkably increased all the time from September to February of next year, but the period of significant increase in the pulp of Fengjie 95-1 navel orange arised from the middle ten days of December to the middle ten days of February of next year, furthermore, the Sucrose content in the pulp of Fenjie 72-1 navel orange had obvious drop from the middle ten days of January to the middle ten days of February, but that of Fengjie 95-lnavel orange still significantly increased then and there, and besides, quality and flavor also heightened constantly.