Shear thinning properties of sorghum starch
1995
Subrahmanyam, S.N. | Hoseney, R.C.
This study was made to determine the causes of variations in shear thinning properties of sorghum starches. Shear thinning was measured as loss of viscosity with stirring at 95 degrees C for 1 hr in the Brabender visco-amylograph. Certain cultivars of sorghum gave starches that shear thinned less than other sorghum starches. Removal of starch lipids by exhaustive extraction with methanol did not affect shear thinning. However, propanol-water defatting of sorghum starches at 100 degrees C gave starch pastes that either did not shear thin or shear thinned less. This appeared to be the result of a change in the starch, because adding the extracted lipid back did not result in a system with its original properties. Other factors examined in an effect to explain shear thinning were swelling, solubilization, gelatinization characteristics, iodine binding capacity, and phosphorus content. Relatively high correlations were found between shear thinning and swelling after 1 hr of stirring at 95 degrees C (r = 0.91) and solubility after 1 hr of stirring at 95 degrees C (r = 0.96).
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