Effect of Some Extrusion Variables on Rheological Properties and Physicochemical Changes of Cornmeal Extruded by Twin Screw Extruder

Abstract

The effect of extrusion variables, such as barrel temperature (100 to 170ºC), feed rate (100 to 500 g/min), feed moisture (20 to 40 g/100 g wet basis), screw speed rate (from 100 to 500 rpm), and slit die rheometer configuration (0.15 and 0.30 cm height) were studied using a co-rotating intermeshing twin-screw extruder coupled to a slit die rheometer on the rheological properties of yellow cornmeal. An increase in feed rate decreased WAI and WSI, but increased the viscosity values. The temperature interacts strongly with screw speed in affecting the WSI. The most important factor in starch degradation was the screw speed. Increasing the screw speed completely modifies the organised structure of starch (crystalline region)

Functional properties of corn and corn–lentil extrudates

“…Thus, the decreased specific mechanical energy is responsible for the lower WAI values of extrudates. This trend is in agreement with the twin screw extrusion of cornmeal reported previously (Chang, Martinez-Bustos, & Lara, 1998). The increase of legume proportion of extrudates led to decreased WAI.…”

“…The extruded melt in high feed rates is subjected to lower shear forces, which cause lesser degradation and therefore lower degree of cooking. The observed trend agrees with previous findings for corn meal extrusion, wheat-based and rice-based extrudates (Chang et al, 1998;Ding et al, 2005Ding et al, , 2006.…”

Structural and textural characterization of corn–lentil extruded snacks

“…The increased feed rate elevates the final viscosity of the product and results in more dense structures, which is consistent with this work. Similar results have been reported in past for corn, rice and bean-based extrudates (Chang et al, 1998(Chang et al, , 1999Ding et al, 2005;Ilo et al, 1996). Feed moisture content and material ratio affected significantly apparent density and expansion ratio.…”

Structural Properties of Corn-Legume Based Extrudates as a Function of Processing Conditions and Raw Material Characteristics

“…Exactly, a rise in feed rate leads to an increase of final viscosity and consequently porosity decreases. [6,26,31,33,34] Feed moisture content seems to have an influence to porosity; as it raised porosity decreased. Moisture content during extrusion provides the driving force for the expansion and also contributes to the rheological properties of the melt, which in turn affect expansion.…”