الفهرس 
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Abstract
In the present work. the pectic substances of the
prickly pear stems and orange peel have been investigated
and more information about the structural features of
these polysaccharides were obtained. Besides valuable
knowledge. about technological and chemical characterization
were acquired to evaluate these pectins commercially.
The yields of pectic substances from orange peel and
Egyptian prickly pear pectin were 26.02% (orange peel pectin).
14.27% (prickly pear pectin. fraction A), 13.9% (prickly pear
pectin. fraCtion ”B”) and 17.41% (prickly pear pectin, mixed
sample), on dry basis. The preliminary investigation of the
properties of extracted pectins were carried out. The
results obtained were compared with those from citrus and
other pectins. •
I.R spectrum of these polysaccharides showed that the
major glycosidic linkages in t~e different types of pectins
under the study are of the cr~ype in Cl pyranose conformations.
also positive specific optical rotation can SUpport this
assumption.
Molecular weight is one of the most important factors
affecting pectin quality and has a marked influence on gelly
grade. The mOleCUlar weights for different types of pectins
were determined and the results showed that average moleCUlar
weights ranged from 50,000 to 78,000. Molecular sieve
chromatography were applied using 5300 and 5
500
. The
results indicated that all samples under study had a wide
range of molecular weights with relatively small differences
in distribution of neutral sugar between eluted fraction.
These pectins are highly physically heterogeneous but
chemically homogeneous in terms of Mw fractions.
Pectin depolymerization was carried out using acid
hydrolysis and enzymatic degradation. The examination of
the hydrolysate by paper chromatography indicated that the
bUilding units tOf pectins were galacturonic acid as major
components. Galactose, rhamnose and arabinose were found
as minor components in the case of citrus pectin and orange
peel pectin. In the case of prickly pear pectin fractions”A”
and ”S” galacttronic acid, arabinose galactose, rhamnose
and xylose were identified as bUilding units. No glucose
was detectable in any of the different types of pectin under
study, this support that pectins were free from dextrens.
The results of the hydrolysis of pectins by acid and enzymatiC
hydrolysis indicated that the molar ratio of the bUilding
sugars by the two methods were slightly different for each
pectin except prickly pear pectin fraction ”A” which
con tains a high proportion. of neu tral sugar. The eaterase
of the pentosanase 36L has different effects on each type
of pectin. This is due to the difference in the chemical
structure of pectin and to the shape of the molecules.
Also, polygalacturonase and lyase combined together had
a different effect on each type of pectin under the study.
Hydrolysis of pectin in 0.25 M trif1uoroacetic acid at
100·C for one hour produced a white precipitate. The
infra-red spectra for tQe white precipitate from different
types of,pectin was compared with that of po1ygalacturonic
acid (obtained from Sigma Company). It was found that a
large degree of simi1arty existed between the spectrum of
the po1ygalacturonic and those from the precipitate
obtained.
Fractionation of pectins was achieved by ion exchange
chromatography, using DEAE-cellu1ose. A preliminary
fractionation of pectins on DEAE-cellu1ose was carried out
to select the sUitable conditions for fractionation. The
recovery of samples was quite satisfactory of DEAE-cellu10se l
and a linear gradient (5-500 mM) Na phosphate at pH 6.5 was
accomplished. Five fractions were obtained from the
elution pattern of citrus pectin. on the other hand, four
f~actions were obtained from the other type of pectins.
The properties of the fractions were studied, the molar
ratios for pentoses, anhydroga1acturonic acid and neutral
hexoses were calculated. Acid hydrolysis and enzymatic
pectin breakdown were carried out. the results were in good
agreement with those of other pectins. Molecular weights
of the fractions for different types of pectins were
determined from the relation between the molecular weight
and intrinsic viscosity. l.R. spectra of the eluted
fractions for the pectins was achieved. The results
indicated that l.R spectra of eluted fractions for the
different pectins were similar to those of the original
pectins. These results, can roughly support that there
is a homogenity in type of linkage and groups in the
different pectin fract1ons.
The methylation of pectins was accomplished using
dimethyl sulfoxide as a solvent and dimethylsulphonyl
anion (base) and iodomethane as methylating reagent.
Separation and examination of the fission products of the
methylated pectin using paper chromatography technique
microanalytical and phys1cal measurements. The results
showed the presence of 2-0-methyl-D-gala~turonic, 2,3-di-
O-methyl-O-galacturonic ac~d. 2,3,4-tri-O-methyl-D-galact_
uronic acid, 2,3,6-tri-O-methyl-O-galactopyranose, 3,4-di-
O-methyl-L-rhamnopyranose. 2.3-di-O-methyl-L-arabino_
furanose and 2,3,5-tri-O-methyl-L-arabinofuranose in the
case of orange peel pectin and citrus pectin while in the
case of prickly pear pectin (fraction A) and (fraction B)
the presence of2,3-di-O-methyl-O-xylopyranose and 2,3,4-
tri-O-methyl-D-xylopyranose were found, in addition to the
above methylated monomers.
These resulLs proved that the presence of main backbone
chain consists of 1,4 linked galacturonic acid. The presence
of 2-0-methyl-D-galacturonic acid may be most probably to
the presence of branching in the main chain by (1-+3) glycosidic
bonds. The isolation of 3,4 di-O-methyl-L-rhamnopyranose
permitted the assumption that rhamnose may be
included in the main chain polysaccharides chain by (1-+2)
bonds or it may take part of side chain.
The resulLs of methylation indicated that the neutral
sugars may be presented as branchings and linked to the
main chain of pectic acid. The galactone units are linked
by (1-i>4) glycosidic -linkage while the arabinose units are
linked by (1~5) glycosidic linkages. In addition to that
the presence of 2,3,5 tri-O-methyl-L-arabinofuranose
represents the terminal units of these branchings.
Finally, (the presence of 2,3 di-O-methyl-D-xylopyranose
and 2,3,4 tri-O-methyl-D-xylopyranose from methylated
prickly pear pectins (UAU, ”8”) indicated that these neutral
monomers are branchings and linked by (1~4) glycosidic
linkages.
The quality of pectins in the present work was determined
on the basis of the SAG tests. According to the results
obtained, orange peel pectin, prickly pear pectin fraction
(fraction B) and prickly pear pectin (mixed sample) are
suitable to form firm high gel strength in comparison
with investigated pectin. as reported in literature.
Prickly pear pectin (fraction A) can be used in the
purposes which require low content of AUA and low
methoxyl content such as medical purposes.