Mung bean protein enhances the expansion of corn starch during twin-screw extrusion

This study examined the effects of the inclusion of mung bean protein (MBP) on the direct expansion characteristics of corn starch during twin-screw extrusion. Six blends of corn starch and MBP isolate (0%, 5%, 10%, 15%, 20%, and 25% w/w) were hydrated to three different moisture contents (MCs) (16%, 19%, and 21% w.b.). The blends were extruded using a twin-screw extruder at three screw speeds (SSs) (300, 400, and 500 rpm). The resulting extrudates were evaluated for their water solubility index, water absorption index, expansion ratio (ER), true density, unit density, and porosity. As the protein content increased, the porosity of the extrudates increased. The ER of all extrudates ranged from 2.90 to 5.46, with the largest ER observed at an SS of 400 rpm, an MC of 19%, and 25% MBP inclusion. The porosity of the extrudates ranged from 1.79% to 11.42%. SS and protein content had a significant impact (p < 0.05) on the porosity and ER of the extrudate.