Effects Of Twin Screw Extrusion Cooking On The Nutrients, Antinutrients And Sensory Attributes Of Broad Bean (Vicia Faba) And Ighu Flour Blends

ABSTRACT

 Effects of Twin screw extrusion of the flour blends of Broad beans (Vicia faba) and Ighu were studied. Ighu ( pregelatinized shredded Cassava) and Broad beans were size reduced into coarse and flour forms respectively. The Ighu : Broad beans blends were moistened to a feed moisture contents of 16, 20 and 24% respectively, mixed using a Hobart mixer and extruded in a commercial scale co-rotating twin screw extruder (Model SLG 65, China) at a screw speed of 0 to 200 rpm and die diameters of 1.5, 3.0 and 6.0 mm respectively. A Box Behnken Design expert‘s response surface was employed to investigate the effects of the three independent process variables (Die size, Feed moisture and Feed composition) on the product‘s responses (Functional, Nutritients, Anti-nutritients and Sensory properties) at three levels each. The Proximate composition, nutrients and anti-nutrient factors were analysed. Functional and Sensory analyses were also carried out on the raw before extrusion and on the extrudates. Optimization results showed that the optimal values for Proximate composition (Crude Protein, Moisture Content, Fat, Crude Fibre, Ash and Carbohydrates) were 14.27, 13.40, 3.24, 0.79 , 1.52 and 82.05 % respectively. The Amino acid profile of the raw blends increased as the proportion of Broad beans increased in the blends before extrusion. Extrusion cooking altered the quantity of the amino acids but all appeared in the extrudates. The optimal value for the minerals (Potassium and Sodium) were 11.63mg/100g and 37.46mg/100g, respectively. The minimum value for the anti-nutrients (HCN, TAN and HAEM) were 0.02mg/kg, 4.29% and 6.90Hu/g, respectively. The optimal value (16.17 %) of Nitrogen Solubility Index (NSI) was obtained at 2.95mm Die diameter and 21.41% Feed moisture. Significant (p < 0.05) differences existed in the linear and quadratic effects on NSI of the extrudates. The optimal expansion ratio of 3.95 % occurred at 2.41mm Die diameter, 17.62 % Feed moisture and 36.89 % Feed composition. The Sensory evaluation results of the extrudates showed that there were significant (p < 0.05) differences in the linear effect of feed moisture and quadratic effects of die diameter and feed composition on the extrudate‘s texture. The mean values of the samples in terms of texture were between 4.33 and 6.86 which implies that extrusion cooking had a positive (much like) effect on the texture of the extrudates. It was only linear effects of feed moisture that had a significant (p < 0.05) difference on general acceptability of the extrudates.