Characterization of storage starches from quinoa, barley and adzuki seeds

The structures and physicochemical properties of storage starches from quinoa, barley and adzuki seeds were investigated and compared in this study. The median size of the starches were 1.0 μm for quinoa, 17.5 μm for barley and 33.0 μm for adzuki, respectively. The amylose content was 7.1% in quinoa starch, 29.2% in barley starch, 21.2% in adzuki starch. The number-average degrees of polymerization (DPn) of amylose was 900 for quinoa, 1700 for barley and 1800 for adzuki. Quinoa amylose had maximum number of branches (average number of chains per molecule (NC) 11.6) among the three starches, while adzuki amylose had almost no branches (NC 0.4). The DPn of amylopectin was 6700 for quinoa, 8000 for barley and 4500 for adzuki. Quinoa amylopectin contained extremely numerous LC (Longest Chain) (13.0%) and short chains, a few long chains, and had a unique chain length distribution as a waxy amylopectin. Adzuki amylopectin contained the fewest and the longest short chains but the highest number of long chains among the three starches. The relative crystallinity of the starch granules was 35.0% for quinoa, 19.7% for barley and 25.5% for adzuki. But, adzuki starch granules had the highest ΔH1 and transition temperature, the lowest susceptibility to enzyme, and water absorption power. Starch granules were present in three complete different ultrastructures.