Rheology and granule size distributions of corn starch dispersions from two genotypes and grown in four regions

Starch was extracted from corn of two genotypes (Clint and P3730) grown during the 1997 season in four regions in New Zealand and Australia. The granule size distributions in unheated and heated (80°C, 2–120 min) 2.6% starch dispersions (STDs) were different. Most of the heated STDs exhibited shear-thinning behavior, but dispersions of a Clint starch exhibited shear-thickening behavior at shear rates >300 s−1. The power law consistency coefficient of the STDs increased, but their flow behavior index decreased with heating time. Values of the consistency coefficient of all the STDs were found to be related to the cube of the mean granule diameter. Frequency versus storage modulus (G′) data of a 5% Clint STD heated at 80°C, 30 min, showed increase in G′ with ω in a convex down manner, while the other STDs showed typical increase in a convex up manner.