Evaluation of snack foods from barley–tomato pomace blends by extrusion processing

Blends of barley flour and tomato pomace were processed in a co-rotating twin-screw extruder. Experimental design with die temperature (140–160 °C), screw speed (150–200 rpm) and tomato pomace level (2–10%) as independent variables produced 20 different combinations that were studied using response surface methodology to investigate the effect of these variables on system parameters (SME, die melt temperature and die pressure) and product responses (expansion, bulk density, water absorption and solubility indices, texture and color). Extrudate from five experiments within 20 samples was selected for sensory evaluation in terms of color, texture, taste, off-odor and overall acceptability. Regression equations describing the effect of each variable on the system parameters and product responses were obtained. The system parameters and product responses were most affected by changes in temperature, pomace level and to a lesser extent by screw speed. Extrudates with 2% and 10% tomato pomace levels extruded at 160 °C and 200 rpm had higher preference levels for parameters of color, texture, taste and overall acceptability. The results suggest that tomato pomace can be extruded with barley flour into an acceptable and nutritional snack.