SHEAR THINNING PROPERTIES OF SORGHUM AND CORN STARCHES

The paste viscosities of sorghum and corn starches were studied with a Brabender viscograph. Sorghum starches and the laboratory-prepared corn starch gave higher paste consistencies than did the two commercial corn starches. Considerable variation existed in shear thinning of starches. In general, sorghum starches shear-thinned more than corn starches, although certain sorghum starches gave low shear thinning. When the hot pastes were sheared at high speed, sorghum starches thinned more than corn starches. The gelatinization characteristics did not appear to be related to shear thinning of sorghum starches. Swelling power at 95-degrees-C was lower for corn starch than it was for sorghum starch. Solubility of both corn and sorghum starches at 95-degrees-C varied among the cultivars. The reasons for high shear thinning of certain sorghums requires further investigation.