Abstract
This research study was aimed to develop nutritious and sensorial acceptable teff based expanded product through optimization of extrusion process parameters. The experimental study was performed using response surface methodology face centered central composite design. Teff, maize and decorticated lentil composite flour was extruded through twin screw food extruder at different barrel temperature (120, 140, 160°C), feed moisture content (14, 17, 20%) and blend ratio BR 1 (70T:20M:10L), BR 2 (60T:25M:15L) and BR3 (50T:30M:20L) at constant screw speed (340 rpm). The physical, functional, textural and sensory characteristics of extrudates were inspected and their responses were examined. Maximum expansion ratio (4.85), maximum water absorption index (7.80), minimum hardness (13.49 N/g) and minimum bulk density (0.108 g/cm 3 )were found at 140°C barrel temperature, 14% feed moisture content with blend ratio of 60% Teff, 25% Maize and 15% Lentil (60T:25M:15L). Acceptable extrudates with added vanilla powder additive were significantly (p<0.05) better in colour, flavor, crispiness and overall acceptability. The model developed could be used for designing of extrusion process parameters in order to get extrudates with desirable characteristics.
Highlights
Extrusion cooking is a process of forcing a material to flow under a different temperature, pressure and feed moisture content through a shaped hole at a predetermined rate to achieve different extruded products
Water Absorption Index (WAI) (%): The supernatant preserved from WAI measurement was evaporated at 96oC temperature for overnight
With increasing the barrel temperature, the expansion ratio was increased till maximum value was achieved and slightly decreased with further increasing in temperature beyond its optimum value
Summary
Extrusion cooking is a process of forcing a material to flow under a different temperature, pressure and feed moisture content through a shaped hole (die) at a predetermined rate to achieve different extruded products. Several products are developed by extrusion i.e., pasta, breakfast cereals, bread crumbs, biscuits, crackers, baby foods, snack foods, confectionery items, texturized vegetable protein, modified starch, pet foods, dried soups and dry beverage mixes (Chang and Ng, 2009). The extruded products which are high in fiber content could be improved in its overall nutritional content and taste by incorporation of protein rich ingredients. Incorporation of legume flour has positive impact on levels of proteins and dietary fiber of extruded snacks (Berrios, 2006). In developing countries such as Ethiopia, where many people can hardly afford high protein foods due to their relative expensive costs. There is urgent need for cheaper foods rich in protein for individuals, taking into consideration their age, sex, physical activity and physiological needs
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