Pectic Polysaccharides of Fruits: Characterization, Fractional Changes and Industrial Application - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 227

in this line is to provide fundamental knowledge on the chemical composition and
qualitative parameters of the fruit pectin which are useful for industrial purposes. A
comparative characterization of the pectin isolated from the peels of lime, sour orange,
sweet orange, and grapefruits showed that the yield of pectin (dry weight basis), jelly
grade, setting time, esterification value, equivalent weight, methoxyl content, acetyl
content, molecular weight, and intrinsic viscosity in the Citrus species had ranged
as 14.5-17.2%, 180-225, 1.0-5.0 min, 56.1-63.2%, 859-1452, 7.40-8.62%, 0.32-
0.46%, 67,000-92,600 and 3.2-4.4, respectively (Alexander and Sulebele, 1980).
The albedo of Spanish lemons represents 61.3, 12.4, and 10.4% galacturonic acid for
three different fractions respectively that is chelating-soluble, alkali-soluble and the
residues (Ros et al., 1996). The de-esterification pectin of Citrus unishiu was further
degraded by endo -polygalacturonase and the degradation products yields high and
low molecular fractions of 39.5 and 1.8% respectively as esterification values (Mat-
suura, 1987). The labeling study on the chemistry of pectic substances in grapefruit
provided evidence that (Baig et al., 1980) galacturonic acid was the only uronic acid
with about 76% by weight of pectic polysaccharides. The remaining 24% was ac-
counted for by neutral sugars viz. rhamnose, arabinose, xylose, mannose, galactose
and glucose, mannose and glucose, which were in equal properties constituted 5% of
the total neutral sugars and rhamnose, arabinose, xylose and galactose, and glucose
constituted 16.3, 33.3, 13.4, and 31.5% respectively of the total neutral sugars com-
ponents of the labeled polysaccharides. The water extract of cell wall polysaccharides
of Limonia acidissima contains pectic polymers substituted with side chains compris-
ing mainly of 1,5 - 1,3,5- linked arabinose together with 1,4→, 1,6→, 1,3,6→ linked
galactose and lesser amounts of 1,2,4→ and 1,3→ linked galactose residues (Mondal
et al., 2002). The citrus peel consists of homogalacturonans (HGs) stretches of similar
length and similar number of galacturonic acids (Yapo et al., 2007). Low-pressure an-
ion exchange and size-exclusion chromatography fractionations of xylose-rich pectin
of yellow passion fruit ( Passiflora edulis var flavicarpa Degener) reveals that HGs
are the predominant polymer though rhamnogalacturonans accounts about 17% of the
pectin (Yapo and Koffi, 2008).
The molecular weight, esterified carboxyl group contents, anhydrouronic acid con-
tent and the intrinsic viscosity of the pectin, extracted from mango are varied between
the varities cultivated. The weight average molecular weights of pectin from Alphan-
so, Kitchener and Abu Samaka varieties of mango were found as 1.6 × 10 4 , 2.1 × 16 4 ,
2.7 × 10 4 , and the intrinsic viscosity are 0.60, 0.89, and 1.22 respectively (Saeed et al.,
1975). However, the fruit peel of mango contains an appreciable amount of pectin and
also it varied among the varieties of mango fruit. For example, the pectin yield, me-
thoxyl content, anhydrouronic acid content, value of esterification, molecular weight,
jelly-grade of three mango varieties viz. Dasheri, Langra, and Alphanso had ranged
from 13 to 19, 8.07 to 8.99, 58.40 to 61.12, 83.38 to 85.93, 1,05,000 to 1,61,700, and
155 to 200%, respectively (Srirangarajan and Shrikhande 1977). Neukom et al. (1980)
and O'beirne et al. (1982) reported that all pectic substances of apple fruits are not
rhamnogalacturonan and the galacturonic acid rich polymer of chelator-soluble pectin
are of lower in amount of arabinose, galactose and rhamnose residues. The analysis on
the cellulosic residue pectin of apple fruits reveals that it has a highly ramified RG I