A Model for Mechanical Degradation of Wheat Starch in a Single‐Screw Extruder

Authors:
  • VDV. J. Davidson
    V. J. Davidson
  • DPD. Paton
    D. Paton
  • LDL L Diosady
    L L Diosady
  • LRL. J. Rubin
    L. J. Rubin
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Abstract
The effect of extrusion cooking in a single screw extruder on the molecular weight distribution of wheat starch was correlated to the starch melt rheology. A simple first‐order model has been developed which defines the extent of mechanical degradation of the amylopectin component as a function of nominal shear stress and residence time in the extruder. A limited set of experimental observations were used to test the model. Iso‐shear stress curves were calculated for the experimental range of conditions. The curves can be used, in conjunction with estimates of the residence time, to calculate equivalent processing conditions, and to predict the extent of amylopectin degradation. The model may allow the use of small extruders to determine fundamental process parameters for full scale extrusion.