Nowadays, it is grown all over the world wherever there is sufficient rainfall and irrigation to sustain the trees. 7 Citrus is cultivated in native to tropical and subtropical regions. Pectins are widely used as food additives (E440) with gelling and stabilizing properties in jams, jellies, marmalades, milks and confectionery products. 6 Commercial pectins are extracted at low pH and high temperature. 4 The main raw materials used to produce commercial pectin are apple pomace and citrus peel, 5 sugar beet and sunflower heads. Intracellular pectins provide the channels for passage of nutrients and water. 3 In the cell walls they serve as one of the main agents cementing the cellulose fibrils and may be linked covalently to other polymers. The primary structural feature of pectin is a linear 1, 4 α linked D-Galacturonic acid chain with varying degrees of methylation, where they are responsible for different physiological processes. 1, 2 Pectins are structural polysaccharides present within all dicotyledonous plant cell walls. The term “pectin” was introduced by Henri Braconnot because of the gelling properties of these substances. Pectic substances in fruits were discovered by the French chemist Louis Nicolas Vauquelin in tamarind fruit. Keywords : grapefruit peel pectin, commercial citrus pectin, neutral sugars composition, degree of esterification, methoxyl content, acetlyation, gel-forming property Introduction Gel-forming property of grapefruit peel pectin was of good quality similar to commercial pectin. The grapefruit peel pectin contained L-arabinose, D-galactose, L-rhamnose and D-xylose. The acetyl content for the white grapefruit peel pectin was 1.634% and for the red was 0.55%, lower in comparison with the corresponding citrus pectin of 0.624.
Both grapefruit peel pectin were higher in their methoxyl content 8.875% for the red and 7.542% for the white, while corresponding citrus pectin was 6.798%.
The grapefruit peel pectin for the red and white differed in their degree of esterification (DM 51.24-55.01%) and 50.848% for corresponding citrus pectin. The yield of grapefruit peel pectin was 25% (dwb) It was found that pectin of the two types of grapefruit peels were similar in anhydrouronic acid content (AUА 60.95%). Chemical and physicochemical characterization of all pectin was accomplished. Comparative investigations were carried out with purified commercial citrus pectin. Grapefruit peels were treated with 95% alcohol and the obtained alcohol-insoluble solids (AIS) were subjected to a sequential extraction with hot distilled water and hot 0.5% HCl. The present study was focused on the potential of red and white grapefruit peel as a source of pectin.
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