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Empirical Modeling of Mean Residence Time in a Co-Rotating Twin-Screw Extruder with Rice Flour

¹Dept. Agricultural and Biosystems Engineering, South Dakota State University, 1400 North Campus Drive, Brookings, SD 57007. ²Dept. Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave., St. Paul, MN 55108. ³Dept. Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108. ⁴Dept. Food Science, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2, Phone: 204-474-9065. Fax: 204-474-7630. Gary_Fulcher@UManitoba.CA ⁵Yangtz Scholar Distinguished Guest Professor, Nanchang University. ⁶Corresponding author. Phone: 612-625-1710. Fax: 612-624-3005. E-mail address: ruanx001@umn.edu ⁷General Mills, 9000 Plymouth Ave. N., Golden Valley, MN 55427.

Mean residence time of rice flour in a twin-screw extruder was determined using a blue tracer. Variables studied included moisture content, screw speed, barrel temperature, and screw configuration. Mean residence time increased with the increase of the barrel temperature and with the addition of reverse and kneading elements. Mean residence time was significantly related to screw speed, moisture content, die pressure, and screw configuration (P < 0.05). An empirical model was developed to predict mean residence time with the ability to reflect the changes of the barrel temperature and screw configuration. The effects of different extrusion operating conditions including screw speed, moisture content, barrel temperature, and screw geometry on the mean residence time were considered in the model. The validity of the developed model was extensively evaluated and verified using different screw geometries and other processing variables. The mean residence times predicted by the developed model are in good agreement with the experimental data.