Effect Of Blend Ratio And Extrusion Operating Conditions On Product Quality Of Sorghumsoybean Extrudate

In this work, the effects of full fat soybean flour addition and extrusion operating conditionsrn(barrel temperature and feed moisture) on quality characteristics of sorghum flour extrudatesrnwere studied, with the objective of developing ready-to-eat extruded product. A pilot scale twinrnscrew food extruder was used for the extrusion. Full factorial design was employed to investigaternthe effect of blend ratio (95:05, 90:10 and 85:15 sorghum and soybean respectively), barrelrntemperature (120, 135 and 150 °C) and feed moisture levels (14, 16 and 18%) on the physicalrn(radial expansion ratio and bulk density) and functional (water absorption index and waterrnsolubility index) properties of the extrudates. Maximum radial expansion ratio (two times) andrnminimum bulk density extrudate was obtained at 90:10 blend ratio. In addition to this lowerrnblend ratio (95:05) registered lower water absorption index and higher water solubility index.rnTaking into consideration the extrusion operating conditions, increasing barrel temperaturern(120-150 °C) and feed moisture (14-18%) decreased the radial expansion ratio and waterrnsolubility index while increasing the water absorption index. Later on, the results of the sensoryrnevaluation (color, flavor, texture and overall acceptability) revealed that increased blend ratio,rnbarrel temperature and feed moisture content decreased the level of acceptance yet the resultsrnalso showed that the extruded product from 90:10 blend ratio, 120 °C barrel temperature andrn14% feed moisture is still an acceptable product with an overall acceptability of 7.1. It was thenrndemonstrated from the optimization result that it is possible to produce good extruded product.rnThe extruded product from 91.8:8.2 (sorghum and soybean respectively), 120 °C barrelrntemperature and 14% feed moisture was selected as best formulation to yield a protein richrnextruded product with desirable attributes like higher radial expansion ratio (2.02), lower bulkrndensity (0.072), higher water absorption index (4.53) and higher sensory acceptability (7.327).rnKey words: Sorghum flour, Soybean flour, Extrusion cooking, Fullfactorial

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