|Fractionation and Characterization of Pectin Polysaccharides from the Peel of Taiwan Liu-cheng Orange
Chan-Chiung Liu*, Hui-Ping Huang
Department of Food Science, National Pingtung University of Science and Technology;
1, Shuefu Road, Neipu, Pingtung 912, Taiwan
Liu-Cheng orange (Citrus sinensis Osbeck) belongs to Rutaceae family and Citric genus, is one of the dominant economic fruits in Taiwan. Annual production is approximately two hundred and thirty thousand tons. Many researches indicted that citrus pulps contain various functional ingredients, such as flavonoids, phenolic acids, ascorbic acid, carotenoids, pectins, etc, yet few explorations on characterization of pectin polysaccharides were found. The objective of this research is to explore the polysaccharide composition of orange peel, and further characterize it through fractionation and purification; antioxidant activities of these major polysaccharide components were also evaluated. Pectin polysaccharides are obtained from acid extraction and ethanol precipitation of orange peel. Fractionation is executed by gel chromatography. The results showed citric acid extraction yielded higher pectin than that by hydrochloric acid extraction, reached 20.04% and 15.63%, respectively; while total carbohydrate and galacturonic acid contents, amounted to 48.91-56.85%, 9.20-39.77%, respectively. Monosaccharides are mainly composed by glucose, arabinose, galactose, rhamnose, xylose and glucosamine (trace). The structure of pectin polysaccharides was comprised of α and β-glycosidic bonds, also trace 1,3-β- glycosidic linkage by FTIR. Weight average molecular weight (M.W.) of pectin extracted by hydrochloric acid (HCl) are 371 kDa (HCP), 252 kDa (H-F1), 189 kDa (H-F2), 95 kDa (H-F3), respectively. While M.W. of pectin extracted by Citric acid are 334 kDa (CCP), 231 kDa (C-F1), 152 (C-F2), 95 kDa (C-F3), respectively. Among the different fractions, H-F3 and C-F3 exhibited the strongest scavenging activity against DPPH radical, hydroxyl radicals, also highest chelating ability, reducing power ability and TEAC. The fractions were further analyzed by high-performance liquid chromatography for the polyphenolic compounds in pectin polysaccharides. The antioxidant capacity is tentatively presumed not only related with extraction mediums, molecular weight, and monosaccharide compositions; but also related with types of polyphenolic compounds.
Keywords: Liu-cheng orange, pectin polysaccharide, antioxidant capacity, galacturonic acid
*Corresponding author: 1, Shuefu Road, Neipu, Pingtung 912, Taiwan; Tel: 886-8-7740403; Fax: 886-8-7740378; E-mail: firstname.lastname@example.org