Amylose determination of native high-amylose corn starches by differential scanning calorimetry

Differential scanning calorimetry (DSC) was investigated as an alternative method to more conventional iodine-binding methods for determining starch amylose in a maize breeding program, because it requires fewer steps. In addition, many current DSC instruments are now equipped with sampling robots for performing automated analysis. The iodine-binding method and a recently described DSC method for amylose determination were compared using five commercial starch samples. In addition, two sets (Set 1 and Set 2) of germplasm samples obtained from a high-amylose breeding program were examined using each method. Correlation coefficients (r ²) between the two methods for the commercial starch samples, Set 1 and Set 2 were found to be 0.99, 0.89 and 0.82, respectively, suggesting a good correlation but with greater discrepancy between them with increasingly higher amylose values. The DSC method appeared to have an improved repeatability, because its associated CV value was lower (4.1 %) compared to the iodine-binding method (5.8%). It was concluded that the DSC method should be effective in discriminating high-amylose genotypes in a breeding program specifically designed to identify maize starches with amylose values at or above 70%.