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Unit and Internal Chain Profile of Millet Amylopectin

¹Department of Food Science, University of Guelph, Guelph, ON N1G2W1, Canada. ²Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108-1038, U.S.A. ³Corresponding author. Phone: (612) 624-1764. Fax: (612) 625-5272. E-mail: kseethar@umn.edu

The unit chain compositions of debranched foxtail, proso, pearl, and finger millet amylopectins and their φ,β-limit dextrins were analyzed by high-performance anion-exchange chromatography. The φ,β-limit dextrins reflected amylopectin internal chain profiles. The amylopectins had average chain lengths ranging from 17.94 to 18.12. The ranges of external chain length, internal chain length, and total internal chain length of the millet amylopectins were 11.85–12.33, 4.75–5.09, and 11.64–12.28, respectively. The relative molar concentration of B-chains in the amylopectins was close to 50% in all samples. Significant differences were, however, observed in the proportions of very short “fingerprint” B-chains (B_fp, degree of polymerization 3–7) and the major group of short B-chains (BS_major): foxtail and proso millets possessed high amounts of B_fp-chains, whereas finger and pearl millets had higher amounts of BS_major-chains, suggesting possible differences in the fine structure of the clusters and building blocks of the amylopectins. Millet amylopectin can be classified structurally as type 2.