Study On The Changes Of Sugars, Acids And Anthocyanin Biosynthes Is In The Different Apples During Coloration

Fruits quality and commercial value depends on their color quality and content of sugarand acids, so many scientists pay attention to study of this field, especially the regulationmechanism of coloration, already being as one point of the most popular plant secondarymetabolism research. This research project was conducted at the Apple Experimental Farm ofNorthwest A&F University. Taking dark red cultivar ‘Starkrimon’, red cultivar ‘Pink Lady’,green cultivar ‘Granny Smith’ and yellow cultivar ‘Golden Delicious’ as sample. The aim ofthis study is to provide theory basis for parent selection of fruit quality breeding andcontrol-mechanism of biosynthesis anthocyanins. This first stage is using paper bags to avoidlight for apple fruits, the second stage is removing the paper bags, then find the changing lawof types and content of soluble sugar, organic acids, also study the fruits appearance colordegree, types of anthocyanin, activity of the related anthocyanin enzymes (phenylalanineammonia-lyase, PAL; chalcone isomerase, CHI; dihydroflavonol4-reductase, DFR andUDP-Glucose: flavonoid-3-O-galactosyl transferase, UFGT). The main result as follow:(1) Soluble sugars were extracted from apple fruits by ultrasonic-assisted waterextraction. A Sugar PakTMI6.5mm×300mm (Waters) column was used to separate solublesugars. The mobile phase was redistilled water with a flow rate of0.5mL/min. The columntemperature were set as80℃. Under chosen experimental conditions, five soluble sugarscould be successfully separated. All the calibration curves for these soluble sugars displayed agood linear relationship with correlation coefficients above0.9998and repeatability RSDs of0.27%-2.34%(n=5). The recovery rates of five soluble sugars were in the range of90.1%-106.20%. Conclusion: The method is convenient, rapid, accurate and applicable to determinesoluble sugars in apple fruits.(2) After bag removal, the L*, b*and h0values decreased, a*values increased and C*values dropped at first and rose later. The main manifestations on color of apple peel included:surface color (red color) development rapidly, which tends to mask the ground color (yellowand green color); brightness of fruit surface decreased and color saturation increased。(3) There were different anthocyanins in different apple cultivars. Three anthocyanins, cyanidin3-galactoside, cyaniding3-glucoside chloride and cyaniding3-arabinoside wereidentified in ‘Pink lady’ and ‘Starkrimon’, and two anthocyanins, cyanidin3-galactoside andcyaniding3-arabinoside, were found in ‘Granny Smith’ and ‘Golden Delicious’; there weresignificant differences in contents of different anthocyanins, cyanidin3-galactoside was themost abundant anthocyanin. The anthocyanin content progressively changed after bagremoval especially in the first six days, the results also showed that the first six days after bagremoval is a very important stage for the bagged apple coloring. Significant negativecorrelation were observed between the cy3-gal accumulation of4cultivars and L*, b*. Andsignificant positive correlation were observed between cy3-gal and a*. So cy3-gal was themore important factor in the surface color of apple.(4) There weren’t differences in organic sugars of4apple cultivars. Malic acid, oxalicacid, citric acid, and succinic acid were identified, however the contents of various organicacids were different, the highest amount of organic acids was malic acid. Concentrations oforganic acids quickly increased during0~2DABR, suggesting that synthesis of these showsthat fruit bagging inhibited the organic acid synthesis.(5) It was found that the soluble sugars were similar in ‘Starkrimon’‘Pink Lady’,‘GrannySmith’ and ‘Golden Delicious’, the only difference was its relative contents. Five solublesugars were identified in all cultivars, and the highest was fructose, followed by glucose andsucrose, galactose and sorbitol contents were the lowest. Analysis shows, that during applecoloring, significant positive correlation was observed between the changes of anthocyanins,especially cy3-gal contents and sucrose contents during coloration in apple, which indicatedthat sucrose might be responsible for the regulation of cy3-gal biosynthesis in apple skin.(6) The debagging4cultivars showed lower PAL、CHI、DFR and UFGT activities thanthose of exposed peel, and the activities of4cultivars rapidly increased at first, and thenslowly increased until15DABR, this show that the activities of PAL、CHI、DFR and UFGTwere induced by light. There were differences in PAL, CHI, DFR and UFGT activities of4apple cultivars. PAL, CHI and DFR activities were higher in red cultivars than those ofnon-red cultivars apple peel, and UFGT activities were higher in late-maturing varieties thanthose of medium varieties. The cy3-gal accumulation of non-red cultivars tested was notsignificantly correlated with PAL, CHI and DFR activity, but was significantly correlatedwith UFGT activity. During the reddening of non-red apples, UFGT may be the moreimportant factor in the anthocyanin biosynthesis.