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A procedure similar to the one commonly used with mixers has been utilized to develop a model for estimating the shear rate in co-rotating twin screw extruders. Newtonian and non-Newtonian fluids were used to estimate the average shear rate for three screw configurations of a Baker Perkins (MPF-SOD) twin screw extruder. As would be expected, the shear rate was highly correlated to the screw speed. At a given screw speed, 30 forwarding paddles generate the highest rate of shear, followed by feed screws and single lead screws, No data was found in the published literature to provide comparison with the results of this work. However, the model has performed well in heat transfer analysis of twin screw processes.The procedure is sensitive to screw conjguration. accounts for the shearing effects in the different regions within the extruder barrel, and covers a range of screw speeds (100-400 RPM) typical of what is encountered in industrial pilot plants. Even though much more work remains to be done before the shear rate can be confidently characterized for composite screw configurations, this technique provides a sound foundation.

The effect of date syrup on pasting, rheological, and retrogradation properties of cornstarch gels was investigated using an HR‐2 Discovery Rheometer equipped with a pasting cell and parallel plate geometry. Pasting and rheological measurements were made on 6% (dry basis) corn starch with different levels of date syrup (starch:syrup; 1:0, 1:1, 1:2, or 1:3). The pasting measurements showed that addition of the date syrup increased the pasting temperature with increasing date syrup levels versus controls. Rheological measurements showed that peak viscosity and elastic modulus (G’) increased with increases in date syrup (1:2–1:3) but this decreased at 1:1 versus control. Changes in elastic modulus as a result of cold storage for 1 wk decreases with increases in date syrup concentration. This suggested that the date syrup could be an effective sweetener in reducing starch gel retrogradation during cold storage.

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