Molecular fractionation of starch by density-gradient ultracentrifugation

Jae Wook Yoon, Seung Taik Lim

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Amylose and amylopectin in corn and potato starches were fractionated by centrifugation at 124,000g for 3-72 h at 40°C in a gradient media, Nycodenz, based on their sedimentation rate differences. The fractions were collected from a centrifuge tube, and then analyzed by the phenol-sulfuric acid method and iodine-binding test. Amylopectin, a large and highly branched starch molecule, migrated faster than amylose and quickly reached its isopycnic point with a buoyant density of about 1.25 g/mL, exhibiting a sharp and stable carbohydrate peak. Amylose, which is a relatively small and linear molecule, however, migrated slowly in a broad density range and continued moving to higher density regions, eventually overlapping with amylopectin peak as the centrifugation continued. This could indicate that the buoyant density of amylose is similar to that of amylopectin. Under centrifugal conditions of 3 h and 124,000g, amylose and amylopectin molecules were clearly separated, and the presence of intermediate starch molecules (11.5 and 7.7% for corn and potato starch, respectively) was also observed between amylose and amylopectin fractions. The amylose content of corn and potato starches was 22.6 and 21.1%, respectively, based on the total carbohydrate analysis after the ultracentrifugation for 3 h. In alkaline gradients (pH 11 or 12.5), the sedimentation rate of starch molecules and the buoyant density of amylopectin were reduced, possibly due to the structural changes induced by alkali.

Original languageEnglish
Pages (from-to)611-617
Number of pages7
JournalCarbohydrate Research
Volume338
Issue number7
DOIs
Publication statusPublished - 2003 Mar 28

Fingerprint

Amylopectin
Amylose
Ultracentrifugation
Fractionation
Starch
Solanum tuberosum
Molecules
Zea mays
Centrifugation
Sedimentation
Carbohydrates
Iohexol
Proton-Motive Force
Centrifuges
Alkalies
Phenol
Iodine

Keywords

  • Density-gradient
  • Nycodenz
  • Starch
  • Ultracentrifugation

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Organic Chemistry

Cite this

Molecular fractionation of starch by density-gradient ultracentrifugation. / Yoon, Jae Wook; Lim, Seung Taik.

In: Carbohydrate Research, Vol. 338, No. 7, 28.03.2003, p. 611-617.

Research output: Contribution to journalArticle

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