Effects of Extrusion Process Parameters on a Cereal-Based Ready-to-Eat Expanded Product Formulated with Carrot Pomace

The effects of extrusion process parameters, i.e., screw speed (300500 rpm), die temperature (120-180 degrees C), feed moisture content (14-20%), and sample formulation (60-80% rice flour/10-30% pulse flour [red lentil]/10% carrot pomace), on the functional (bulk density [BD], expansion ratio [ER], water absorption index [WAI], and water solubility index [WSI], physical (hardness and overall acceptability [OA]), and system (specific mechanical energy [SME]) properties of an expanded rice-based snack product were investigated. The experiments were planned using a Box-Behnken design, and the extrusion process parameters were optimized for maximum ER, WAI, and OA and minimum BD, WSI, SME, and hardness within the experimental range using response surface methodology. Analysis of variance (ANOVA) revealed the higher significant (P <= 0.05) effects of feed moisture content on functional properties and of die temperature on physical properties, followed by the effect of screw speed on system properties compared with other extrusion parameters. Among the process parameters studied, sample formulation demonstrated a significantly lower effect on the response variables studied. The optimal extrusion process parameters obtained were an 80:10:10 (rice flour/pulse flour/carrot pomace powder) sample formulation, 14% feed moisture content, 323 rpm screw speed, and 120 degrees C die temperature.