Study On The Functional Components And Antioxidant Capacities Of Siji Pummelo (Citrus Grandis Osbeck) Fruit

Siji pummelo (Citrus grandis Osbeck) is considered to be a characteristic Fruit inCang Nan which lies in Zhe Jiang province. Nowadays it is mainly for eating and itsfunctional components has not been explored, so we studied on the main functionalcomponents of different tissues in different periods. In addition, the optimum ultrasonicextracting conditions of naringin from Siji pummelo peel were studied. The main resultswere as follows:1. Different pummelo tissues in different periods were in different porportion. Theedible rate increased at storing for 9 week and then declined, while the change ofpeel was opposite. Nutrition indexes of pummelo juices in immature period werelower than in mature period, on the contrary, titrable acidity was higher. The solublesolid, soluble total suger and reducing suger reached the summit after storing 5weeks, and declined with storage time increasing. The suger acid ratio and solid acidratio were the highest after storing 13 weeks. Protein changed little during thestoring, only reached the summit at 13th week. Water content of pummelo juiceswere signifiant negative correlation (p＜0.05) with soluble solid content, total sugerand reduced suger. Juice yield had signifiant negative correlation (p＜0.05) with thesuger acid ratio and solid acid ratio.2. After analysing the functional components in pummelo juice for different periods, wefound that total phenols content reached 45.71mg/100mL after storing 5 weeks, andlowest in the matured pummelo juice. Neohesperidin of 3.94 mg/L was only foundin immature pummelo juice. Naringin content was 25.03 mg/L in matured pummelojuice, declined as the storing time going and can't be detected after storing 13 weeks.Naringenin hadn't been found in pummelo juice. Naringin reached the summit28.46mg/L in immature pummelo juice. Nomilin reached the summit 40.30mg/L inimmature pummelo juice. While limonin reached 109.74mg/L after storing 13weeks.3. After analysing the main flavonoids in different tissues of Siji pummelo peel in different periods, we found naringin existed in each tissues, the distributing contentwere mesocarp＞pericarp＞epicarp, it reached the summit 40.68 mg/g in immaturepericarp. Naringenin only existed in immatured peel and as high as 137.1μg/g inepicarp, but both hesperidin and neohesperidin weren't detected. Limonin andnomilin had a high content in pericarp, next is epicarp and mesocarp. The content ofLimonin and nomilin reached 515.9 mg/100g and 346.1mg/100g respectively inimmature fruit's pericarp. The content of total phenols reached the summit inmesocarp and the lowest in pericarp but both's naringin content increased afterstoring 9 weeks. For naringin in pericarp, its increasing happened after storing 13weeks.4. To evaluate the antioxidant activities of different extracts, we used DPPH, FRAP andABTS assays. The antioxidant results of DPPH and FRAP showed that, mesocarp＞epicarp＞pericarp. And the results of ABTS showed that, epicarp＞mesocarp＞pericarp. The different extracts of tissues from pummelo peels showed differentantioxidant activities under three systems, the antioxidant capability of FRAP andDPPH were consistent, whereas the antioxidant effect of ABTS had a significantcorrelation with the content of naringin (p＜0.05).5. We also discuss Vc and the total phenols' contribution to the antioxidant activities ofpummelo juice extract, we found Vc's contribution rate to antioxidant capability wasdifferent in different assay. In DPPH assay, Vc's contribution rate reached 50.38%.The antioxidant effect of pummelo juice reached the summit after storing 5 weeks.In ABTS assay, total phenols had a significant correlation with antioxidantcapability (p＜0.05). After the content of Vc deducted from pummelo juice,antioxidant capability declined to the minimum of the mature juice. Total phenolshad a significant correlation with antioxidant capability determined by ABTS andFRAP assays.6. The effects of ultrasonic temperature, time, power, solid-liquid ratio and ethanolconcentration factors on the naringin extraction rate had been investigated bysingle-factor experiments. Based on above works, the orthogonal layout method was used in the optimization of technological parameters. The result showed that whenextraction time was 1 hour, the optimum conditions of ultrasound extraction onnaringin were as follows: ultrasonic temperature was 50℃, solid-liquid ratio was1:30, ethanol concentration was 50% and ultrasonic power was 25w. By the aboveconditions, the extraction rate of naringin was 5.437g in 100g dry pummelo peels.