Abstract

The effect of feed moisture, screw speed and barrel temperature on cooking characteristics of re-fabricated rice grains was investigated in a co-rotating twin-screw extruder using response surface methodology. The rice flour obtained from broken rice (< 1/8th of actual kernel size) of PR-116 after mixing with structural components was used in the study. The screw speed was set at five levels between 49 and 150 rpm, barrel temperature between 59 and 110°C and feed moisture between 31 and 45%. All cooking parameters of the re-fabricated rice grains evaluated—Kernel length before cooking (KLBC), kernel length after cooking (KLAC), volume expansion ratio (VER), water uptake (WU) and cooking coefficient (CC) –were significantly (P<0.01) affected by the three process variables. Barrel temperature was the most significant variable with quadratic effect on KLAC and WU. Response surface regression models were established to correlate the cooking parameters of re-fabricated rice grains to the process variables. The optimized extrusion conditions for preparation of re-fabricated grains were 38% moisture content, 130 rpm screw speed and 89°C barrel temperature. Understanding the effect of process variables on the cooking properties and optimization of extrusion conditions was deemed useful for the development of re-fabricated rice.