These enzymes can hydrolyze protopectins and pectins to smaller chains like galacturonic acid
(Sun et al., 2006), leading to a reduction of water holding capacity.
was used as standard, and controls of boiled extract were run.
Usually, pectin contains 65% galacturonic acid
and may show three kinds of forms: the linear homopolygalacturonan and the ramified, rhamnogalacturonan I and II (WILLATS et al., 2006).
Sugar composition of fractions C and D was analyzed by the methylation method (McGarvie and Parolis, 1981), confirming the presence of arabinose, xylose, galactose, rhamnose and galacturonic acid
. The total amount of monosaccharides contained in fractions C and D was determined by a "two-step" process consisting in an initial hydrolysis of polysaccharidic structures and in the quantification of monosaccharide content (expressed as rhamnose) in the hydrolysed fractions by the phenol-sulphuric acid test (Dubois et al., 1956; Mankarios et al., 1979).
Total uronic acids were estimated colorimetrically by means of galacturonic acid
as the calibration standard (Ahmed and Labavitch, 1977).
Citrus peel waste can be utilized for the production of galacturonic acid
as it considered being a pectin-rich agro waste (10).
Phytochemical reports on Ziziphus species has revealed the presence of polysaccharides (Yamada et al., 1985; Zhao et al., 2006a), a pectin composed of D- galacturonic acid
, L-rhamnose, D-galacturonic acid as methyl ester and O-acetyl groups (Shimizu and Tomoda, 1983), cyclopeptides (Barboni et al., 1994; Gournelis et al., 1998; Singh et al., 2002), peptide alkaloids (Tschesche et al., 1974), flavonoides (Nawar et al., 1984; Cheng et al., 2000), dodecaacetylprodelphinidin B3 (Weinges and Schick, 1995), Ziziphine N, O, P and Q (Suksamrarn et al, 2005), saponins and fatty acids (Zhao et al., 2006b).
The analyses were calibrated against galacturonic acid
and the absorbance measured at 400 and 450 mm to determine the difference in absorbance due to uronic acids.
Polygalacturonase is a de-polymerizing enzyme which catalyze [alpha]-1,4 glycosidic linkage in pectin chain to yield galacturonic acid
units (Kim et al., 2017).
The calibration curve was conducted with D- galacturonic acid
, and the PG activity was expressed as mmoL of galacturonic acid
per gram of dry weight per minute (mmoL [g.sup.-1] [min..sup.-1]).
The standard monosaccharides mannose (Man), rhamnose (Rha), glucuronic acid (GlcA), galacturonic acid
(GalA), glucose (Glc), galactose (Gal), xylose (Xyl), arabinose (Ara) and fucose (Fuc) were all purchased from Sigma.
(1956) and expressed as g of glucose 100 [g.sup.-1]; d) soluble and total pectins: extracted according with McCready and McComb (1952) and quantified through the Bitter and Muir (1962) technique, the results being expressed as % galacturonic acid