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Molecular Structure and Some Physicochemical Properties of High-Amylose Barley Starches

¹United Graduated School of Agricultural Sciences, Kagoshima University, 1-21-4, Korimoto, Kagoshima 890-0065, Japan. ²Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima, University 1-21-4, Korimoto, Kagoshima 890-0065, Japan. ³Takenouchi Barley Processing Inc., 4-12-4, Nanei, Kagoshima 891-0122, Japan. ⁴Corresponding author. E-mail: takeda@chem.agri.kagoshima-u.ac.jp. Phone/Fax: +81-99-285-8641.

The molecular structure and some physicochemical properties of starches from two high-amylose cultivars of barley, high-amylose Glacier A (HAG-A) and N (HAG-N), were examined and compared with those of a normal cultivar, Normal Glacier (NG). The true amylose contents of HAG-A, HAG-N, and NG were 41.0, 33.4, and 23.0%, respectively. Iodine affinities before and after defatting of starch, and thermograms of differential scanning calorimetry, indicated that HAG-A and HAG-N starches had a higher proportion of amylose-lipid complex than did NG starch. The amylopectins from HAG-A and HAG-N were similar to NG amylopectin in average chain length (18–19), β-amylolysis limit (β-AL 56–57%), number-average degrees of polymerization (DP_n 6,000–7,500) and chain length distribution. Very long chains (1–2%) were found in amylopectins from all cultivars. HAG-A amylopectin had a larger amount of phosphorus (214 ppm) than the others. The amyloses from HAG-A and HAG-N resembled NG amylose in DP_n (950–1,080) and β-AL (70–74%). However, HAG-A and HAG-N had a larger number of chains per molecule (NC 2.4–2.7) than NG amylose (1.8) and contained the branched amylose with a higher NC (9.5–10.6) than that of NG amylose (5.8), although molar fractions of the branched amylose (15–20%) were similar.