EXTRACTION AND PHYSICOCHEMICAL CHARACTERIZATION OF PECTINS FROM SUGAR-BEET PULP

Sugar beet pulb (SBP) pectins were isolated from the proteolysis hydro lysates or extracted by HCl (pH 1.5, 85 degrees C for 1-6h and pH 1.5, 4h at 40-90 degrees C), ethylenediamine tetraacetate (EDTA, 0.2%, pH 3.3, 85 degrees C, 1, 4h), ammonium oxalate (AO, 0.2%, pH 3.3, 4h), an d sodium hexametaphosphate (SHP, 0.2%, pH 3.3, 4h). An optimal HCl ext raction (pH 1.5, 85 degrees C, 4h) yielded 16.94% pectin from the dewa xed and protein-free SEP. The HCl extracted pectin contained 84.61% ga lacturonic 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 mai nly arabinose and galactose. The molecular-average weights ranged betw een around 60000 and 90000 Da. It was found that lignin in SEP cell wa lls is tightly associated with pectin. Besides the esterified ferulic acid, seven other phenolic monomers, principally vanillin and p-hydrox ybenzoic acid, were initially identified in the alkaline nitrobenzene oxidation of bound lignin in the isolated pectin samples.