Improved yam-baobab-tamarind flour blends and its potential use in extrusion cooking

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This project was aimed at determining the physicochemical properties of water yam- baobab-tamarind flour composites and its potential use in extrusion cooking. Proximate and mineral composition of Baobab (B), Yam (Y), and Tamarind (T) were determined. Six blends of composite flours in the proportions of 0:0:100, 0:40:60, 40:0:60, 30:10:60, 10:30:60 and 20:20:60 (B: T: Y) were formulated and colour, physicochemical, pasting properties were determined. Two of the flour blends were used as trial samples and extruded at 300 rpm feed speed, temperature of 200°C and screw speed of 1200rpm. Sensory evaluation, physicochemical properties, colour, pasting properties and expansion ratio of the extruded products were assessed. Proximate composition of B, Y and T were comparable to literature, however, the mineral compositions were low. Moisture content, pH, water binding capacity, swelling power and bulk density values obtained were in the range of 3.01-5.61%, 3.90-5.39, 87.50-132.50%, 201.43-237.95% and 0.74-0.93g/ml, respectively for flour blends. Peak, minimum, cooling end, final, breakdown and setback viscosities were in the range of 2.50-291.00bu, 2.20-289.50bu, 11.00- 455.00bu, 10-440bu, 0.00-20.50bu and 69.50-148.00bu respectively. The addition of tamarind and baobab flours improved upon the physicochemical and pasting properties. The flours could be used for drinks, puddings, sauces, ice-creams, pastries and yoghurts depending on the desirable characterictsic of the flour blends. The L*valuesof composite flours was in the range of 84.67-85.49 as compared to water yam flour (100Y) which was 85.73. Generally the l, a, b values for extrudates were lower than the flour composites which resulted in a lower value of hue for extrudates. The bulk density and expansion ratio of extruded snacks were low: the values were 0.24g/cm3 and 0.19g/cm3; 3.45 and 4.15 for E5 (10B:30T: 100Y) and E6 (20B:20T: 60Y) respectively. Sensory evaluation results revealed that panellists preferred extrudates with higher tamarind kernel powder substitution (E5). Generally pasting analysis showed that the extruded composite flours (E6) had low viscosity values. The values were 14.67bu, 5.33bu, 14.33bu, 7.67bu and 8.33bu for peak, minimum, final, breakdown and setback viscoties respectively. This study has revealed that as tamarind and baobab flours were added to yam flour there was improvement in the physicochemical and pasting properties of flour blends as compared to yam flour only. These composite flours can be used in various food applications. It was demonstrated that incorporation of tamarind and baobab into water yam flour for development of low temperature extruded snacks has great potential as a ready to eat snack.
A thesis submitted to the Department of Food Science and Technology, College of Science, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree Master of Philosophy (Food Science and Technology).