ABSTRACT:Sugar beet pulb (SBP) pectins were isolated from the proteolysis hydrolysates or extracted by HCI (pH 1.5, 85°C for l-6h and pH 1.5, 4h at 40--90°C), ethylenediamine tetraacetate (EDTA, 0.2%, pH 3.3, 85°C, 1, 4h), ammonium oxalate (AO, 0.2%, pH 3.3, 4h), and sodium hexametaphosphate (SHP, 0.2%, pH 3.3, 4h). An optimal HCI extraction (pH 1.5, 85°C, 4h) yielded 16.94% pectin from the dewaxed and protein-free SBP. The HCI extracted pectin contained 84.61% galacturonic acid and low ash, 2.69%. The degree of methylation was over 60% in all the pectin samples, indicating that the sugar beet pectin is a high methoxy pectin. The degree of acetylation ranged between 10.80% and 14.78%, resulting in poor gelling capacity of the pectins. The pectins also contained 7.21 % to 10.73% neutral sugars, which were mainly arabinose and galactose. The molecular-average weights ranged between around 60000 and 90000 Da. It was found that lignin in SBP cell walls is tightly associated with pectin. Besides the esterified ferulic acid, seven other phenolic monomers, principally vanillin and p-hydroxybenzoic acid, were initially identified in the alkaline nitrobenzene oxidation of bound lignin in the isolated pectin samples.KEY WORDS Sugar Beet Pulp / Pectin / Galacturonic Acid / Sugars / Molecular Weight / Extraction / Ferulic Acid / Phenolics / Lignin / Sugar beet pulp (SBP) is a by-product of the sugar refining industry, and it is used as animal feed at relatively low price. It consists mainly of polysaccharides (approximately 70% of the dry matter), of which pectin (25%), arabinan (21 %), and cellulose (24%) prevail. It is therefore a potentially rich source. 1 • 2 The pectins of sugar beet are complex heteropolysaccharides containing galacturonic acid, rhamnose, arabinose, and galactose as the major sugar constituents. They are characterized by a backbone of ix-(l -4)-linked galacturonic acid residues, forming long smooth regions which may be interrupted by hairy regions, consisting of a 1 : 1 ratio of galacturonic acid and (l-2)-linked rhamnose residues in the backbone, and a high degree of substitution of the rhamnogalacturonan. Some rhamnose residues carry side chains, consisting mainly of (l-5)-linked a-arabinans with branches attached to position 3, (l-4)-linked /J-galactans of low polymerization degree, and highly branched (l-3,6)-linked galactans. 3 • 4 Beet pectins, however, differ from pectins isolated from apple or citrus by their high rhamnose content, 5 by the presence of acetyl groups linked to the a-o-galacturonic acid and by the presence of ferulic acid; which is associated almost exclusively with the pectic side chains and is found ester-linked to either the C-2 of arabinofurance or to the C-6 of galactopyranose residue. 6 • 7 Further studies suggest that the ferulic acid is distributed about equally between the arabinan and galactan moieties of SBP. 4 • 8 Due to the low molecular weight and the presence of acetyl groups, the pectins of SBP have poor gelling properties and low viscosity which limit its use a...