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1. 1. Measurement of the flow properties of starch pastes with the precision and accuracy required for industrial purposes is feasible. The methods described utilize the Corn Industries viscometer and a modified Stormer viscometer. The former provides a continuous record of the change in flow properties during pasting at a controlled cooking temperature; the latter supplements the data obtained during pasting with a rate of shear-shearing stress curve from which the apparent viscosity, expressed in poises, can be computed at any given rate of shear. 2. 2. Rheological data on a variety of commercial starches were obtained. The effect of rate of shear, concentration of the starch, and other factors are discussed. In all cases a curve typical of pseudoplastic flow was obtained. 3. 3. Continuous decrease in apparent viscosity occurs during the pasting process with the greatest change in the first hour; for many starches a fairly level viscosity is obtained after one hour cooking at 90–92°C. Vigorous agitation, in contrast to that obtained with low-speed sweep agitators, produces a more rapid decrease in viscosity, but differences in agitation apparently do not alter the nature of the pasting process. 4. 4. The effect of rate of shear on the computed values for apparent viscosity is great. Satisfactory measurements can be made only when the rate of shear is constant or when the magnitude can be determined and specified. The measuring methods described are reproducible and characterize the starches with respect both to rate of pasting and the flow properties of a given paste at different rates of shear. Industrial measurements can be made more precise by these means, and discrepancies in standardization and grading can be largely eliminated.

1. 1. By means of an embedded-disk gelometer the properties of starch gels can be determined with adequate precision to distinguish between consecutive commercial grades of acid-modified corn starches, and between gels of the same starch which differ by 0.5% in starch concentration. 2. 2. Gels of acid-modified as well as unmodified corn starch are elastic to the yield point. 3. 3. The percentage increase in rigidity and breaking strength of gels during aging from 4 to 24 hr. depends on the modification of the starch. The increase is greater for starches of higher modification. 4. 4. The effect of temperature of cooking starches on the properties of their gels varies with the degree of modification of the starch. 5. 5. With increasing modification of the starch, the consistency of the hot pastes of acid-modified corn starches decreases to a greater extent than do the rigidity and breaking strength of their gels.