Studies On Contents And Composition Of Sugar And Acid In Citrus From Different Species And Production Areas

With the development of market economy and improvement of people's living condition, fruit quality is gradually concerned by people. In order to detect the difference of fruit quality between different production areas and cultivars, Ponkan mandarin (Citrus reticulata Blanco), Okitsu wase ( Citrus reticulata Blanco), Newhall navel orange (Citrus sinensis L.) and 37 citrus cultivars were used as materials. In order to provide the theoretical way for citrus cultivars introduction and regionalization, study was carried out on the difference of fruit sugar and acid contents and their accumulation character in 37 citrus cultivars in the present paper. The major results are as follows:1. A capillary gas chromatography (GC)method for the simultaneous determination of organic acids, sugars and sugar alcohols extracted from citrus fruit flesh was described. Citrus fruit flesh was extracts in 80% methanol together with imidazole buffer 0.1 M, pH=7. The use of two internal standards, an accurate derivatization and a proper calibration of the GLC conditions allowed an accurate quantitative analysis of the compounds detected in the unknown samples. Organic acids, sugars and sugar alcohols in purified extracts were converted to their trimethylsilyl (TMS)/ TMS-oxime derivatives prior to separation and detection by capillary GC with flame ionization detection (FID). The compounds of interest were converted to their trimethylsilyl (TMS)/TMS-oxime derivatives using hydroxylamine hydrochloride, hexamethyldisilazane and trimethylchlo -rosilane. The FID reponse to derivatized compounds was generally linear in the concentration range 5-800μg/ml.2. Sugar and acid contents were investigated in 37 citrus cultivars. Sucrose accounted for about 58% of the total sugar, and citric acid for about 85% of the total acid contents in fruit. And the fructose contents in citrus fruit were little higher than that of glucose, with significant positive correlation. No significant difference was between the sucrose content of the fruit of each cultivar, while the ratio of sucrose in total sugar in Citrus grandis Osbeck was the highest, which was prominently higher than that of in Citrus reticulate Blanco, Citrus sinensis Osbeck and Citrus sp×Citrus sp cultivars. However, the fructose and glucose contents of the fruit of Citrus grandis Osbeck were evidently lower than that of other citrus fruit. And malic acid content in Citrus sp×Citrus sp was remarkably higher than that in Citrus reticulate Blanco, Citrus sinensis Osbeck and Citrus sp×Citrus sp.3. The sugar and acid contents of Newhall navel orange (Citrus sinensis L.), Ponkan (Citrus reticulata Blanco) and Okitsu wase (Citrus reticulata Blanco) from different production areas were different. The soluble solid content of Newhall navel orange fruitfrom Gannan in Jiangxi Province (GN-JX), the West of Fujian Province (W-FJ), the area between the South of Hunan Province and the North of Guangxi Zhuang Autonomous Region (A-SN) and Three Gorge Area (3-GA) was not different but remarkably higher than that of Danjiang Reservoir Area of Hubei Province (DJ-R of HB). And the total sugar content ranking from high to low was GN-JX, W-FJ, 3-GA, A-SN and DJ-R of HB, while no significantly difference exist in between GN-JX and W-FJ and between 3-GA and A-SN. Furthermore, the sucrose, fructose and glucose contents in that fruit flesh in different production fields ranking were similar with total sugar. As to titratable acidity, no difference was investigated in GN-JX, W-FJ, 3-GA, A-SN, DJ-R of HB. No difference was shown in sucrose, fructose, glucose and the titratable acid contents of Ponkan from different production areas of Fujian province and Hubei province, while the soluble solid of Ponkan from areas of Fujian province was higher than those from areas of Hubei province. Sucrose, fructose, glucose and soluble solid contents of Okitsu wase from different production areas of Zhejiang province were higher than those of Hubei province, but the titratable acid content was reverse. Sugar and acid contents of Okitsu wase from Shimen of Hunan province is similar with those from Zhejiang province.4. During the process of room temperature storage, the sucrose, fructose, glucose and citric acid contents of HB pummelo in Wuhan and Danjiangkou increased and then decreased, with no significant fluctuation in malic acid content. And the sucrose, fructose, glucose, citric acid and malic acid contents of HB pummelo in Wuhan are higher than those of HB pummelo in Danjiangkou in the corresponding period. The sucrose, fructose, glucose and citric acid content reached peak on the 40th day (Feb. 16th). The fructose and glucose contents of Newhall navel orange in Xingshan and Anyuan showed up tendence. While the sucrose content of Newhall navel orange in Xingshan showed up and then down tendence, however, it showed down tendence in Newhall navel orange in Anyuan. The malic acid content of Newhall navel orange in Xingshanis was higher than that of Newhall navel orange in Anyuan with a quick drop tendence. And the citric acid content of Newhall navel orange in Xingshan and Anyuan showed slow a drop tendence.