Molecular structure and some physicochemical properties of waxy and low-amylose barley starches

The molecular structures and physicochemical properties of starches from an actual waxy (HB 340) and two low-amylose (CDC Candle and Sumiremochi) cultivars of barley were examined and compared with those of a normal cultivar (CDC Dawn). HB 340 starch had no detectable amylose. The amylose content was 2.2 and 11.4% in CDC Candle and Sumiremochi starches, respectively, being much lower than that in CDC Dawn starch (25.4%). The starches of HB 340, CDC Candle and Sumiremochi showed a higher viscosity and breakdown on the viscogram than CDC Dawn starch, and HB 340 starch showed the highest ΔH of peak 1 and no peak 2 on the DSC thermogram. The amylopectins resembled each other in average chain-length (19–20), β-amylolysis limit (β-AL 53–54%) and chain-length distribution. The amyloses of CDC Candle and Sumiremochi were larger (DPn 1680 and 1560, respectively) and contained the branched amylose with a lower number of chains (NC 6.1–10.4) than CDC Dawn amylose (DPn 1220, NC 13.8) CDC Candle amylose had a higher molar fraction (45%) of the branched molecule than the others (21–26%).