DEVELOPMENT AND EVALUATION OF EXTRUDED READY-TO-EAT SNACK FROM OPTIMISED RICE, KERSTINGS GROUNDNUT AND LEMON POMACE COMPOSITES FLOURS

Abstract

Composite flour comprising Rice, Kersting’s groundnut and Lemon pomace were produced in this study. The proximate composition and functional properties of the composite flours were optimized using response surface methodology which generated 16 experimental runs. The optimum blends(75.00 g rice flour, 20.00 g Kersting’s groundnut flour and 5.00 g lemon pomace; 82.28 g rice flour, 10.00 g Kersting’s groundnut flour and 7.71g lemon pomace; and 77.40 g rice flour, 12.55 g Kersting’s groundnut flour and 10.00 g lemon pomace) based on protein, fiber contents and functional properties were subjected to further analyses (antioxidant, minerals, anti-nutritional, pasting, in-vitro carbohydrate and protein digestibilities, mixograph). The overall best blend was selected for extrusion. The extrusion process was optimized using Central Composite Design. The variables were (moisture content, screwspeed and temperature) while the dependent variables were (lateral expansion, residence time, water absorption capacity and water solubility index). The microbial analysis as well as the sensory evaluation of the extrudate were also evaluated. Results showed that the protein ranged from 7.51 to 12.99 g/100g; crude fibre 2.52 – 3.78 g/100g and ash 1.00 – 1.81 g/100g. Addition of Kersting’s groundnut had positive effect on the protein while lemon pomace had positive effect on the fibre. The functional properties showed that water absorption capacity ranged from (2.80 -3.80 g/100g), water solubility index(8.00 – 9.50%),oil absorption capacity (1.20 – 1.60 g/100g), dispersibility (72.20 – 84.80%) and swelling capacity (14.00 – 19.00 g/ml). Pasting characteristics showed that runs 7 had the highest effect on the peak viscosity, trough and final viscosity. The blend with higher lemon pomace of (10.00 g) had the best calcium, iron, potassium and magnesium contents, blend with highest Kersting’s groundnut (20.00 g) had the best zinc content. Blends with highest lemon pomace (10.00 g) had the overall best antioxidant characteristics. The anti-nutrients in the blends were generally low and safe for human consumption. The mixograph show that the composite flour are not suitable for bread production which buttress the result of the pasting analysis. The blends produced composite flour with lysine, tryptophan and methionine that are 43.2% essential amino acid components. The optimum blends for extrusion was 97 oC barrel temperature 12% moisture and 90 rpm screw speed which presents the best throughput , lateral expansion, water absorption index and water solubility index. All the extrudate had high general acceptability between 68 and 82 h.The study has shown that composite flour consisting of Rice flour (75.00 g), Kersting’s Groundnut flour (20.00 g) and Lemon Pomace (5.00 g) had good and acceptable protein, crude fiber and mineral contents