Barrel temperature displayed a significant effect (p < 0.001) on
expansion ratio (Table 3). Increasing barrel temperature resulted
in an increase in expansion ratio (Fig. 2A and B). A similar relationship
between expansion and barrel temperature during extrusion
of starchy material was observed by other researchers (Mercier &
Feillet, 1975; Mercier, 1977; Owusu-Ansah, van de Voort, &
Stanley, 1983). An increase in barrel temperature would reduce
the viscosity of pea starch dough inside the extruder, resulting in
decreased shear rates. This would cause a reduction in the extent
of pea starch breakdown and, consequently, greater expansion.