ABSTRACT
The cooking of food in an extruder has been previously described as a series of chemical and physical changes occurring because of heating and shearing during the time of passage through the extruder. An examination of the factors which effect the residence time distributions for isothermal Newtonian flow is helpful in understanding the effects of extrusion variables and the screw geometry. The combination of the strain and residence time distribution gives a unique parameter, the weighted average total strain which can be related to mixing. A dye was injected into the dough as an impulse and the relative color intensity was measured in the extrudate as a function of time. Mixing is important within the food extruder to assure uniformity of the extrudate. Residence time data were obtained by D. Bigg and S. Middleman by using a red food coloring dissolved in the liquids being extruded.
