PRODUCTION AND QUALITY EVALUATION OF BISCUITS FROM WHEAT (TRITICUM AESTIVUM) SWEET POTATOES (IPOMOEA BATATAS) AND SOYBEAN (GLYCINE MAX) FLOURS

Abstract: The purpose of this research work was to evaluate flours made from Wheat (Triticum aestivum), Sweet Potatoes (Ipomoea batatas) and Soybean (Glycine max), their blends and biscuits. Flours were produced from wheat, yellow fleshed sweet potato and soybean and blended into different ratios of 100:0:0 (WSS100), 75:20:5 (WSS75), 50:40:10 (WSS50), 25:60:15(WSS25) and 0:80:20 (WSS0). The flours were evaluated for proximate, functional and pasting properties while the biscuits were evaluated for proximate, Physical properties, and mineral properties using standard methods while sensory composition of the biscuit was determined using 20 semi-trained panelists. The results of the proximate composition of the flours showed that soybean had the highest protein (39.09%), fats (28.02%), crude fiber (5.01%), ash (2.19%) and energy content (491Kcal) while sweet potato had the highest carbohydrates (83.77%) and moisture content (8.91%). Partially substituting wheat flour with sweet potato and soybean flour had a significant increase in the functional properties of the flour blends except for swelling capacity (72.50% - 62.30%) and bulk density (10.01% – 7.6g/ml) which had a significant decrease. The pasting properties of the flour blends decreased significantly with substitution in all the parameters except for the peak time (5.21mins – 6.07mins) and pasting temperature (57.12 oC – 67.27oC) which increased significantly. For the biscuits, there was a significant increase in their physical properties except for thickness (10.0 – 8.0mm) which decreased significantly. There was significant increase in the proximate composition of the biscuits with substitution except for the carbohydrate (75.61- 63.24%). The mineral content of the biscuits also increased significantly with substitution except for iron ( 5.81 – 3.40mg/100g) and zinc (2.13 – 1.52mg/100g) which had a significant decrease (p<0.5) with substitution. The biscuits from Sample WSS50 (50% wheat flour, 40% sweet potato flour and 10% soybean flour) were preferred in terms of taste, flavour, colour and overall acceptability while sample WSS25 (25% wheat flour, 60% sweet potato flour and 15% soybean flour) was preferred in terms of texture. Based on the findings of this research work, substituting wheat with sweet potatoes and soybeans in biscuit formulation and the likes will improve their nutritional quality, functional properties, physical and chemical properties, sensory and overall acceptability. This will also reduce the over dependence on wheat flour which is usually imported hence reducing the burden of importation which will lead to improved economy.