Biological Systems Engineering, Department of


Date of this Version

May 1996

Document Type



Published in Journal of Food Process Engineering 19:2 (1996), pp. 153–170; doi 10.1111/j.1745-4530.1996.tb00387.x Copyright © 1996 Food & Nutrition Press, Inc., Trumbull, Connecticut; published by Blackwell Publishing. Used by permission.


The influence of screw configuration and screw speed on the residence time distribution and product expansion was determined for rice meal processed in a corotating twin screw extruder. Screw speed had strong effect on the E(t)- and F(t)-diagrams, with the mean residence time varying inversely with screw speed from 206 s to 256 s. the F-diagram was modeled by the combination of perfect mixing and plug flow. the P estimates, which express the fraction of material in plug flow, varied inversely with screw speed from 0.41 to 0.55 for the operating conditions in this study. Both screw configuration and screw speed were statistically significant to the expansion ratios of rice extrudate, with the expansion in the height ranging from 2.98 to 4.13.