The influence of specific mechanical energy on cornmeal viscosity measuredby an on-line system during twin-screw extrusion

The influence of specific mechanical energy (SME) on cornmeal viscosity dur ing the twin-screw extrusion at feed moisture contents of 25 and 30% and sc rew speeds in the range from 100 to 500 rpm was measured. Cornmeal was extr uded in a co-rotating, intermeshing twin-screw coupled ro a slit die rheome ter. One approach to the on-line rheological measurement is to use a slit d ie with the extruder. In the present work it was show that sheer viscosity decreased as a function of SME. The viscosity of cornmeal at the exit die w as influenced by screw speed, rate of total mass flow, mass temperature ins ide the extruder and SME. An increase in screw speed resulted in an increas e in SME and a decrease in viscosity. A reduction in slit die height and an increase in screw speed and mass temperature led to a remarkable macromole cular degradation of the starch, as evidenced by the decrease in viscosity.