Effect of protein, moisture content and barrel temperature on the physicochemical characteristics of pea flour extrudates

The effects of protein content (6%, 12% or 18%, db), moisture content (15%, 18% or 21%, wb), temperature (set temperature of the final barrel section—100, 120 or 140 °C) and a leavening agent (0.5% sodium bicarbonate) on the direct expansion characteristics of pea flour were determined with a twin-screw, co-rotating extruder. The various levels of protein were obtained by blending air-classified pea starch (6% protein, 85% starch) and pea flour (24% protein, 56% starch). Extrusion of pea flour containing 6% protein and 15% moisture at a set temperature of 120 °C resulted in expansion indices (EIs) of 3.3 and 3.6, respectively, in the absence or presence of the leavening agent. EI decreased, and extrudate bulk, particle densities and hardness increased with increase in protein or moisture content. Lysine losses were proportionally lower at higher protein and moisture contents.