Characterization of Amaranth and Quinoa Starches

Abstract

Starch granules were prepared from mature grains of 9 samples of Amayanthus and 4 samples of Chenopodium quinoa. By the ordinary gel permeation chromatograph (GPC) of Pseudomonas isoamylase-debranched starch materials, the amylose content of amaranth starches was in a range of 0-28%. Thus, we confirmed that there were normal, low amylose, and waxy types of amaranth starches. The amylose content of quinoa starches was 25-27%. The ratio of short chains to long chains of amylopectin of these starches was in a range of 2.2-3.3 and somewhat lower than or similar to that of normal maize starch. Isoamylase-debranched materials were separated by HPLC with a differential refractometer (RI) and low-angle laser light-scattering photometer (LALLS) as detectors as one means, and by high-performance anion exchange chromatography with a pulsed amperometric detector (HPAEC-PAD) as the other. We found that amylopectins of Amayanthus and Chenopodium quinoa had increased amounts of long B chains and decreased amounts of short chains as compared to the waxy maize amylopectin, however, they had increased amounts of short chains with DP (degree of polymerization) from 8 to 12. Amaranth starches had slightly higher temperatures of gelatinization (T0, Tp and Tc) and smaller heats of gelatinization (d H) by differential scanning calorimetry (DSC) as compared to normal maize starch. Quinoa starches showed lower T0, T p and T and smaller ΔH. Amaranth and quinoa starch granules were digested by amylases faster than those of normal maize.