Molecular structure and some physicochemical properties of high-amylose barley starches

The molecular structure and some physicochemical properties of starches fro m 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, Norm al Glacier (NG). The hue amylose contents of HAG-A, HAG-N, and NG were 41.0 , 33.4, and 23.0%, respectively. Iodine affinities before and after defatti ng of starch, and thermograms of differential scanning calorimetry, indicat ed that MAG-A and HAG-N starches had a higher proportion of amylose-lipid c omplex than did NG starch. The amylopectins from MAG-A and HAG-N were simil ar to NG amylopectin in average chain length (18-19), beta-amylolysis limit (beta-AL 56-57%), number-average degrees of polymerization (DPn 6,000-7,50 0) and chain length distribution. Very long chains (1-2%) were found in amy lopectins from all cultivars. HAG-A amylopectin had a larger amount of phos phorus (214 ppm) than the others. The amyloses from MAG-A and HAG-N resembl ed NG amylose in DPn (950-1,080) and beta-AL (70-74%). However, HAG-A and H AG-N had a larger number of chains per molecule (NC 2.4-2.7) than NG amylos e (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.