Fluid Dynamic Investigation of the Extrusion Process in Cereals Production and Analysis of the Parameters that Affect Product Quality

Extrusion cooking of cereals regards a wide range of food products (snack-foods, baby-foods, cereals for breakfast and pasta). Extrusion of cereals is a complex process, because it involves chemical and physical transformations: molecular modifications (gelatinization) and structural properties alteration (hardness, elasticity, color, etc.). In this work, an investigation on the extrusion cooking process for cereals in a twin-screw extruder was carried out, using a finite-element fluid dynamics model. Several numerical tests were carried out, varying temperature, screw rotation velocity and extruder’s geometry. Fluid dynamic parameters inside the extruder, as shear rate and residence time, were analyzed. The extruder characterized by a more complex geometry allows to obtain higher values of shear rate and residence time and, consequently, high degree of gelatinization and cooking of material.