ABSTRACT
Food extrusion has developed rapidly during the past 40 years with applications being continually expanded to new areas of food processing. Beginning in the late 1940s, a variety of extrusion models were developed which described the fundamentals of the fluid and heat transport in the extrusion of thermal plastics. Despite the many complexities when biopolymeric food systems are extruded, the application of the simplified extrusion theory has been successfully applied and provides considerable insight into the measured effects of changing screw geometry and extruder operating conditions. In a cooking extruder, flow would have to be characterized as nonisothermal and non-Newtonian. The cause of the leakage flow is the cross channel pressure gradient which occurs due to the circulation of the dough within the channel. To analyze the flow through the grooves in the barrel, assumptions similar to those required to develop the equation for flow in the channel of the screw are required.
