Effects of Screw Restrictions on the Performance of an Autogenous Extruder

The Brady Crop Cooker is a low‐cost autogenous extruder capable of manufacturing products suitable for human consumption in less developed countries (LDC). Versatility is achieved by the design of the extruder which directly affects its operation. One such design aspect is the inclusion of internal screw channel restrictions. The effects of location and number of restrictions on operation and product quality were studied. Results indicated that restrictions affected the location of the mechanical energy input and therefore temperature profiles along the screw. Increasing the number of restrictions also promoted cleavage of starch molecules due to the resulting higher shear in the screw channel.