Study On The Characterization Of Citrus Fruits Quality, Flavonoids And The Determination Of The Adulteration Of Orange Juice

Citrus is the biggest fruit in the world. In China, the planting area of Citrus in 2006 has come to 1814.5 thousand hectare and the production was more than 1789 million metric tons, which was the first and second, next to Brazil in the world respectively. The biochemical materials in citrus fruits such as flavonoids, carotenoids and limonoides not only have active effects of anti-oxidantion, anti-cancer, prevention of circulatory disorders, anti-inflammatory, anti-allergic, anti-bacterial and so on but also can be used as the marks of screening species initially and adulteration detection of orange juice. The physical & chemical characters and contents of flavanoids of 83 citrus samples cultivated in three gorges districts and 68 varieties collected from Chinese citrus germplasm resource garden were analyzed. The variation of the every index was analyzed by statistical software, and based on results, the classification function of the main cultivated varieties, the relative relation among different varieties revealed by the character of juice, the model of adulteration for orange juice were discussed.. The main results of this paper are as follows.1) A RP-HPLC method was developed for simultaneous determination of 7 flavanones (narirutin, naringin, hesperidin, neohesperidin, didymin, naringenin, hesperetin) and 3 polymethoxylated flavones (sinensetin, nobiletin, and tangeretin) in citrus within 35 minutes. A waters Symmetry C18 column was used with 0.2% acetic acid solvent and acetonitrile as mobile phase at a flow rate of 1.0 mL /min. The column temperature was 25℃and the UV detection wavelengths were 287 nm and 330 nm. The flavonoids were qualified by external standard, and the linear ranges of 10 flavonoids were 0.01～20mg/L (r≥0.9988) , and the detection limits were 0.005～0.01lmg / L. The average recoveries of flavonoids in juice and dry peel power were 94.20%～106.58% and 95.15%～101.19% respectively; RSD were 1.15%～5.41% and 1.47%～3.78% respectively. The results indicate that the method is fast, sensitive, reproducible and practical for the routine analysis of flavonoids in citrus.2) The physical & chemical character and contents of flavanoids of 83 citrus samples cultivated in three gorges districts were analyzed. The results showed that the soluble solids, sugar and acid varied greatly and the coefficient of variability of the index of fruit shape, rate of juice and rate of edible material were smaller than other characters in orange, madarin, pumelo and lemon. The main flavonoids in juice of common sweet orange, navel orange, Ponkan and Satsuma mandarins were hesperidin, narirutin, didymin, sinensetin , nobiletin and tangeretin. The amount of hesperidin was heighest, then was narirutin and didymin. The amount of polymethoxylated flavones of sinensetin , nobiletin and tangeretin was richest in Ponkan juice, which amount to 8.50 mg/L, but they were lower in common orange, navel orange and Satsuma mandarins. The main flavonoids in juice of pumelo and lemon were narirutin, naringin and hesperidin, and the highest in pumelo was naringin and the highest in lemon was narirutin. The results showed the amount of flavonoids varied greatly but the ratio of flavonoids varied little.3)The variables of physical & chemical character and contents of flavanoids were simplified by Mahalanobis distance method and selected 10 variables from 22 variables. The classification functions of common orange, navel orange, Ponkan and Satsuma mandarins were established based on the 10 variables. Y1=9.990 X_RS +1.239 X_Vc+2.564 X_SSM/TA+0.187 X_HES -0.470 X_DIDY+34.579 X_NBL+38.827 X_TNG+68.732 X_NAR/HES-20.022 X_APMFs+245.751 X_SNT/PMFs -141.315; Y2=12.018 X_RS+ 1.287 X_Vc+3.172 X_SSM/TA+0.225 X_HES-0.453 X_DIDY+32.262 X_NBL+40.844 X_TNG+102.431 X_NAR/HES-19.396 X_PMFs+242.498X_SNT/PMFs-79.077; Y3=6.785 X_RS+0.561 X_Vc+4.710 X_SSM/TA+0.347 X_HES-2.016X_DIDY +136.977 X_NBL+102.087 X_TNG+139.780 X_NAR/HES-71.182 X_PMFs+296.171 X+_SNT/PMFs-304.856;Y4 =10.506 X_RS+0.551 X_Vc+3.041 X_ASSM/TA+0.284 X_HES-1.289 X_DIDY+40.770 X_NBL+38.71 1 X_TNG+ 184.325 X_NAR/HES-24.687 X_PMFs+140.168 X_SNT/PMFs-126.867. The orginal counts were used to test the classification functions, and the 96.15% were classified correctly. The data of 18 orange samples from Chinese Citrus Germplasm Resource Garden were used to test the classification functions, and two common oranges were classified as Navel orange. The reason may be the samples were complicated and the index such as SSM/TA of acidless orange was similar to Navel's.4) The physical & chemical character and contents of flavanoids of 68 citrus biotypes from Chinese citrus germplasm resource garden were analyzed. The results showed the physical & chemical character of C. reticulata Blanco varied largely because the source of the were complicated. The edible qualities of C. kinokuni and Pentitsao were good, while wild Mangshan tangerine,Bian Ju were not suitable for edit while they were good resources of bioactive constitutents. The physical & chemical character of orange and pomelo were better. The content of titratable acid of grapefruit juice was high, which reaching 1.32～1.79g/100mL, while the ration of soluble solid material and titratable acid was only 4.4～5.1. The sour orange was not suitable for edible too while it was a good product for pharmaceutical use and its flower, leave and fruit can be used as material to extract essential oil. The edible quality of C. ichangensis was bad and can only be used as rootstock.The contents of flavanone glycosides were higher than aglycones in all biotypes. In these flavanone glycosides, hesperidin and narirutin were distributed wildly and they were detested in every biotype, then didymin, neohesperidin and naringin.The aglycones, Sinensetin, nobiletin and tangeretin were also distributed wildly, but naringenin and hesperetin were only detected in little varieties. The types and contents of flavonoids in different biotypes varied largely. The main flavonoids in C. reticulata Blanco and hybrids were hesperidin, narirutin, didymin, sinensetin, nobiletin and tangeretin, and the highest was hesperidin,which got to 188.98 mg/L, then was narirutin, didymin in turn.Neohesperidin, naringin, naringenin and hesperetin only were detected in little varieties. The main flavonoids in C. sinensis Osbeck were hesperidin, narirutin, didymin, sinensetin, nobiletin and tangeretin, and the highest was hesperidin too. The main flavonoids in pumelo were naringin, hesperidin and narirutin, and the highest was naringin, which amount to 77.88 mg/L. The main flavonoids in grapefruit were naringin, hesperidin, narirutin, neo hesperidin, hesperetin and didymin, and the content of naringin (651.88 mg/L) was highest. The main flavonoids in lemon were hesperidin, naringin and narirutin, and the highest was hesperidin, with the average contents of 55.87 mg/L. The main flavonoids in sour orange were naringin, narirutin, and didymin, and the highest was naringin, with the average contents of 173.87 mg/L. The main flavonoids in C. ichangensis were included naringin, hesperidin, narirutin, neohesperidin, naringenin, hesperetin and sinensetin, and the richest was naringin(177.60 mg/L).5)Nine principal component were got from 27 indexes about physical & chemical character and contents of flavanoids by analysis of variance, and the score of PCA were calculated. The PCA scores of sample were used to. The results of K-cluster analysis showed that pomelo and lemon could be separated from other species respectively, and the C. reticulata Blanco and C. sinensis Osbeck couldn't be separated. The graph of hierarchical cluster, which indicated the distances between the species, showed that Mangshan wild orange had the longest distance from the other species, then was Bian Ju, pumelo, Jianshan orange, Zhu Ju, Man Ju and so on. The Euclidean distance between samples of C. sinensis Osbeck were very closed, Tian Cao tanglo also had the short Euclidean distance to C. sinensis Osbeck. The Euclidean distances of samples of grapefruits were short, and Euclidean distances among grapefruits, sour orange, C. ichangensis were short too.6) Five varieties were selected from 25 by Z-statistics, which were X_DIDY,X_NAR/HES,X_PMFs,X_SNT/PMFs and X_NBL/PMF(actually they were six initial index). An alteration model for orange juice was established by logit model using these selected varieties. The alteration model isy=1-e^-x/1+e^-xIn which x=0.603X_DIDY-142.058X_NAR/HES+2.430X_PMFs+54.384X_SNT/PMFs-143.634X_NBL/PMFs+5 1.671As the fitted results of all manderine, hybrid juice were below 30%, and the fitted results of most common orange juice were above 70%, so threshold value was decided as 30%. When the fitted figure less than 30%, the sample was considered alteration by the model, when the fitted results figure more than 30%, the sample was considered pure orange, but when the figure below 70% and above, the sample cannot be discriminated by the model.This dissertation possesses the following innovations: (1)The physical & chemical character and contents of flavanoids of main cultivated citrus samples and citrus biotypes were analyzed systematically. The database for types and contents of flavonoids of citrus juice in China were established initially, which could be basic information for identification of juice adulteration, product standards development, screening biotypes and choosing right processing materials.(2) Flavonoids were first used as evaluation index to establish the model for evaluation the authentic of orange juice suitable for China.