Publication no. C-2004-0202-03R |  VIEW ARTICLE

Physicochemical Properties and Molecular Structures of Starches from Millet (Pennisetum typhoides) and Sorghum (Sorghum bicolor L. Moench) Cultivars in Nigeria.

Terna Gaffa (1), Yasushi Yoshimoto (1), Isao Hanashiro (1), Osamu Honda (2), Sadamichi Kawasaki (2), and Yasuhito Takeda (1,3). (1) Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima University, Kagoshima 890-0065, Japan. (2) Kumamoto Flour Milling Co., Ltd. Hanazono-1, Kumamoto 860-8625, Japan. (3) Corresponding author. Phone and Fax: (81)992858641. E-mail: <takeda@chem.agri.kagoshima-u.ac.jp> Cereal Chem. 81(2):255-260. Accepted November 3, 2003. Copyright 2004 American Association of Cereal Chemists, Inc.

Some physicochemical properties and molecular structures of starches from millet (Pennisetum typhoides, Doro and Gero) and sorghum (Sorghum bicolor, red and white) in Nigeria were examined. Starch granules of millet and sorghum were 3-14 µm and 4-26 µm in diameter, respectively. Millet cultivars had similar peak viscosities (204-205 RVU) on pasting, while sorghum showed similar minimum viscosities (155-156 RVU). The actual amylose content (%) calculated from iodine affinity (IA, g/100 g) was 20.1 and 21.4 for sorghum and 21.3 for millet. The IA of amylopectin was high (1.27-1.42) and its average chain lengths were 20-21 with beta-amylolysis limit of 56%. Amylopectins showed a polymodal molecular weight distribution on a molar basis. The distributions differed among the samples with a higher amount of larger molecules in Doro and red sorghum. Weight- and molar-based distributions of debranched amylopectins on HPSEC were polymodal with weight-based distribution showing presence of long chains. Peak DP values for A+B(1) and B(2)+B(3) chain fractions were 13-16 and 42-43, respectively. The (A+B(1))/(B(2)+B(3)) ratio on molar basis (9.0-11.5) was similar to maize and rice amylopectins. Peak DP on molar-based distribution for white sorghum and millet amyloses were similar (490-540) and the DP(n) range was narrow (1,060-1,300), but weight-based distribution profiles differed. The average chain lengths were 260-270 with 3.9-4.8 chains per molecule.