Structure of dicarboxyl malto-oligomers isolated from hypochlorite-oxidised potato starch studied by 1H and 13C NMR spectroscopy

Anita Teleman*, Kristiina Kruus, Erja Ämmälahti, Johanna Buchert, Kari Nurmi

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

35 Citations (Scopus)

Abstract

The main oxidised component in hypochlorite-oxidised potato starch was isolated by anion-exchange chromatography after enzymatic hydrolysis. The primary structure of the isolated oligosaccharides was determined by 1H and 13C NMR spectroscopy, using homonuclear and heteronuclear two-dimensional techniques. The isolated pentamer and hexamer contained one glucose unit oxidised to a dicarboxyl residue. As the hypochlorite oxidation has occurred at positions C-2 and C-3 of a glucose unit, the introduced carboxyl groups caused ring cleavage between the carbons C-2 and C-3. The ring-cleaved dicarboxyl residue had glycosidic linkages on both sides, implying that this oxidation pathway does not result in depolymerisation. The vicinal coupling constant between H-4 and H-5 in the ring-cleaved dicarboxyl residue was 3.2 Hz, showing that the gauche orientations are preferred. As a result, a different bending of the starch chain is observed and is probably, therefore, one of the reasons why hypochlorite oxidation reduces the tendency to retrogradation. The pK(a) values (3.0) were determined from the pH-dependent chemical shifts of H-1, H-4 and H-5 of the dicarboxylic residue. Copyright (C) 1999 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)286-292
Number of pages7
JournalCarbohydrate Research
Volume315
Issue number3-4
DOIs
Publication statusPublished - 28 Feb 1999
MoE publication typeA1 Journal article-refereed

Keywords

  • Alpha amylase
  • Glucoamylase
  • HPAED-PAD
  • Oxidised starch, structure
  • Ring-cleavage

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