The Changes In Contents Of Sugar & Acid Along With The Fruit Ripening Of Bingtangcheng And Dahong Sweet Orange

The content of sugar and acid in citrus fruits and their ratio are essential in deciding the fruits quality. Consequently, the flavor of citrus fruits (sweet or acid) depends heavily on the constitution, content, and proportion of sugar and acid. However, for many of the citrus-growing regions, it is a serious problem that the citrus is too high in acid and too low in sugar. Therefore, it is of significance both theoretically and practically to make researches into the metabolism of organic acid in cirus fruits, and explore the accumulation mechanism of organic acid in citrus fruits at both physical and molecular level and make regulations. This experiment adopted the method of HPLC to determine the content of sugar and acid during the maturing process of Bingtangcheng(Citrus sinensis) and 'Dahong' sweet orange(Citrus sinensis Osbeck) with the contrast of average sweet oranges. This experiment is carried out with the intention to find out the content changing pattern of sugar and acid during fruits'ripening process, the influence of different types, content, and proportion of sugar and organic acid on the flavor the citrus fruits. The followings are the measurements:1. Adopting the HPLC method to determine the content of sugar and organic acid in Bingtangcheng(Citrus sinensis),'Dahong'sweet orange(Citrus sinensis Osbeck) and 'Putong'sweet orange fruits, filtrate the liquid through a gauze after squeezing 5 citrus fruits. Using centrigal force to separate the filtrate at the rate of 5000r/min under 12℃. With HRC-NH2℃(M) sugar analysis column as stationary phase, and acetonitrile as mobile phase,determine the content of glucose, frucose and sucrose in citrus fruit juice under the column temperature of 40℃and with the flow rate of lml/min, which lead to a recovery of 106.6%-116.6%; With ODS-SP (C18) analytical column (4.6mm x150mm,5μm) as stationary phase, and 3% methanol and 0.01mol/LK2HPO4 as mobile phase, determine the content of different sugar in citrus fruits juice under the column temperature of 40℃and with the flow rate of 0.6ml/min and a wavelength of 210nm. The recovery is 93.3%-103.4%.2. The content of glucose, fructose and sucrose are increased in S form during the maturing process of Bingtangcheng(Citrus sinensis),'Dahong'sweet orange(Citrus sinensis Osbeck) and 'Putong'sweet orange. At maturity, the largest proportion is sucrose,40%, 45.7% and 50.6%,Second is glucose,31.2%,28.4% and 25.6%,the smallest is fructose,28.8%,26% and 23.7%.There is little differences in sugar content between three fruit varieties,'Dahong'sweet orange(Citrus sinensis Osbeck) is slightly higher than Bingtangcheng(Citrus sinensis), and Bingtangcheng(Citrus sinensis) is a little more than 'Putong'sweet orange.3. There is little difference among the three three fruit varieties in the malic acid content and it keeps small-scope fluctuation during maturing process.However, the content of citric acid are significantly different. August 20,'Dahong'sweet orange is the highest,'Putong'sweet orange is the second smallest, and BingTangCheng(Citrus sinensis)is minimum,respectively is 44.62mg/ml,34.58mg/ml and 26.64mg/ml. The content of citric acid in BingTangCheng(Citrus sinensis)is 40.3% less than 'Dahong'sweet orange's. During the maturing process of fruit,citric acid is decreased and the fastest is BingTangCheng(Citrus sinensis),then 'Dahong'sweet orange and 'Putong'sweet orange.November 30,BingTangCheng(Citrus sinensis)citric acid content is 8.07 mg/ml, 69.7% is reduced.'Dahong'sweet orange is 18.84 mg/ml,57.8% is reduced."Putong'sweet orange is 19.51 mg/ml,43.6% is reduced.The content of citric acid in BingTangCheng(Citrus sinensis) is 57.2% less than 'Dahong'sweet orange's.4. Results show that there is no distinct difference between Bingtangcheng(Citrus sinensis) and Dahong'sweet orange(Citrus sinensis Osbeck) in the total sugar content at maturity. The content of total acid in Bingtangcheng(Citrus sinensis) is always less than 'Dahong'sweet orange's. Citric acid content and drop speed are significant different between two fruit varieties. So the change in citric acid is the major influencing factors for flavor.