Arabinose and ferulic acid rich pectic polysaccharides extracted from sugar beet pulp

Abstract

Arabinose and ferulic acid rich polysaccharides were extracted from sugar beet pulp using two extraction methods: a sequential extraction with H 2O (2 times). NaOH/EDTA (2 times), and 4 M NaOH (2 times; method A) and a sequential extraction in which the NaOH/EDTA extraction was replaced by an autoclave extraction (2 times; method B). Both extraction method A and B yielded approximately 45% of the sugar beet pulp polysaccharides. For both method A and B. three extracts with increasing neutral sugar content were obtained: two NaOH/EDTA extracts and a 4 M NaOH extract for method A next to two autoclave extracts and a 4 M NaOH extract for method B. The sugar linkage composition indicated the presence of arabinose rich rhamnogalacturonan (‘hairy regions’) and homogalacturonan (‘smooth regions’) in all extracts. The sugar compositions of the NaOH/EDTA extracts were very similar to the autoclave extracts. A remarkable difference was the higher amount of ester groups in the autoclave extracts: next to methyl esters and acetyl groups, they also contained relatively high amounts of feruloyl groups. Size-exclusion chromatography using RI- and UV-detection showed that all extracts were heterogeneous with respect to molecular weight distribution. Ferulic acid was particularly located in the high molecular weight populations of the autoclave extracts.