The effect of extrusion variables on bean extrudate’s BD is shown in
Table 1. There was significant difference in BD based on moisture
content (p ¼ 0.040); BD was generally higher for extrusion at
36 g/100g moisture content (MC-2).Perez-Navarrete et al. (2006)
reported that higher moisture content creates a lubricating effect
in the extruder barrel, which lowers friction and increases vaporization
of superheated water as the extrudate exits the die, both of
which can interfere with product expansion and bulk density.
Barrel temperature (BT-1 or BT-2) and screw speed (SS-1, SS-2, or
SS-3) showed no clear trends and had minimal effect on BD of bean
extrudates; whereas, feed rate at higher BT-2 showed some
significant differences in BD of extruded samples.Edwards, Becker,
Mossman, Gray, and Whitehand (1994) indicated that bulk density
considers sample weight and the three dimensional changes of the
extrudate resulting from expansion at the die and is generally
inversely proportional to expansion ratio