Physicochemical studies of starch from foxtail millet ( Setaria italica Beauv.)

Abstract

Properties of starch granules prepared from 53 varieties of foxtail millet were examined by scanning electron microscopy, amperometric iodine titrimetry and differential scanning calorimetry. The granular size of the starches ranged from 6.8 to 11.8 μm in diameter on average. The wavelength at maximum absorption ( λ max) for iodine-starch complexes ranged from 579 to 600 nm and blue values (absorbance at 680 nm, BV) ranged from 0.350 to 0.495 except for two waxy varieties. Amylose contents of non-waxy varieties obtained by amperometric titrimetry ranged from 11.4 to 27.1%. DSC analysis for starch gelatinization indicated that peak temperatures ( T p) of all the samples ranged from 62.5 to 75.1 °C, their enthalpy ( ΛH) varied from 8.2 to 13.5 J/g, respectively, and that there was a positive relationship between T p and ΛH. From a correlation matrix of physicochemical parameters of the millet starch, we observed the following: correlations between particle size and four parameters (enzymic degradation of starch granules, amylose content, λ max and BV), between amylose content and two parameters ( λ max and BV), and between ΛH and three parameters (amylose content, BV and T p).