Sorghum starch properties as affected by growing season, hybrid, and kernel maturity

The objective of this study was to evaluate the physical and chemical changes that occur in sorghum starch during grain maturity. Two sorghum hybrids were grown in irrigated plots in 2008 and 2009; upon reaching the mid-bloom stage in maturity approximately 200 heads were tagged in each plot. Samples were collected beginning ten days after anthesis (DAA) until harvest. The samples were then decorticated and the starch isolated. The starch granule size distribution was greatly affected by the collection date as well as the growing season and hybrid. The samples ranged from 16.3% amylose in 10 DAA to 23.3% amylose in 35 DAA. The crystallinity of the starch decreased as the DAA approached physiological maturity (35 DAA). Starch thermal properties were also altered due to DAA, most notably the ΔH was 16.1 J/g at 14 DAA, 11.95 J/g at 35 DAA, and 9.45 J/g at 56 DAA. The unique chemical and thermal properties of the starches could allow for utilization of the starch in differing applications.