Development of flaxseed fortified rice - corn flour blend based extruded product by response surface methodology.

Flaxseed imparted the evidence of health benefits in human being. Response surface methodology (RSM) was employed to develop flaxseed fortified rice - corn flour blend based extruded product using twin screw extruder. The effect of roasted flaxseed flour (RFF) fortification (15-25 %), moisture content of feed (12-16 %, wb), extruder barrel temperature (120-140 °C) and screw speed (300-330 RPM) on expansion ratio (ER), breaking strength (BS), bulk density (BD) and overall acceptability (OAA) score of extrudates were investigated using central composite rotatable design (CCRD). Increased RFF level decreased the ER and OAA score significantly while increased BS and BD of extrudates (p < 0.01). Moisture content of extruder feed was positively related to ER (p < 0.01) and OAA (p < 0.05) and negatively related to BD (p < 0.01). Extruder barrel temperature was found to be negatively related to ER and OAA (p < 0.05) and positively related to BD (p < 0.1). Quadratic effect of screw speed was significantly positively related to ER (p < 0.01), BS (p < 0.05) and negatively related to BD (p < 0.01). 15 % RFF fortification with rice flour, 16 % moisture content (wb) of extruder feed, 120 °C extruder barrel temperature and 330 RPM of screw speed gave an optimized product of high desirability with corresponding responses as 3.08 ER, 0.53 kgf BS, 0.106 g.cm(-3) BD and 7.86 OAA.