Relations Between Amylose Content and Physicochemical Properties of Starches from White and Red Sorghum Varieties

This research aims to determine the relationship between amylose content and physicochemical properties in white and red sorghum starches. Five varieties of red sorghum and four varieties of white sorghum were evaluated. The chemical properties, the amylose content, the resistant starch content, scanning electron microscopy, the absorption and solubility index in water, the viscosity profile, the thermal properties, and the correlation between the amylose content were determined. Sorghum starches had an amylose content between 24.51% and 34.34%, but did not show any relationship with color. Regarding the microstructure, the starches that appear larger granules (20–30 µm) have lower amylose content. Sorghum red varieties shown higher values in gelatinization enthalpy, pasting temperature and water absortion index, this effect was attributed to the formation of complexes with phenolic compounds. Starches with a higher proportion of amylose shown lower viscosity profiles and a high thermal stability. Correlation matrix analysis reveals that amylose content had a negative correlation with water absorption index, water solubility index, maximum viscosity, minimum viscosity, and positive correlation with the resistant starch content. The amylose content can define the potential application of the sorghum starches. The present study investigated the relationship between the amylose content and the physicochemical properties of native starches of red and white sorghum. It was found that color sorghum starch had a relationship with thermal properties, viscosity, and water absorption index, but the amylose content determined the majority of the physicochemical properties of sorghum starches.