Effect of feed moisture and extrusion temperature on protein digestibility and extrusion behaviour of lentil and horsegram

Abstract

Effect of extrusion temperature (ET) and feed moisture (FM) on in vitro protein digestibility, protein thermal stability and extrudate characteristics of lentil and horsegram was evaluated. Thermal stability of different polypeptides (PPs) present in both the pulses varied as a function of FM and ET. PPs degradation increased with decrease in FM and increase in ET. Low molecular weight PPs between 13 and 30 kDa of lentils and 37 kDa of horsegram were highly thermo stable and were not affected during extrusion. PPs of 81, 35, 31, 29 and 14 kDa of lentils and PPs of 81 and 78 kDa present in horsegram were thermo labile. Expansion ratio (ER) and lightness (L*) of extrudates from both the pulses increased with increase in ET and decrease in FM. Lentil extrudates expanded more and were lighter than horsegram extrudates. Oil absorption capacity increased with increase in FM whereas, water absorption capacity decreased with increase in both ET and FM. Foaming capacity of extrudated flours from both the pulses increased whereas viscosity and in vitro protein digestibility decreased with increase in FM and decrease in ET.