Nutritional composition and sensoric acceptability of wheat bread supplemented with soybean flour, maize bran and maize germ
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Bread consumption and other bakery products such as cookies and cakes prepared from solely wheat flour have remained popular in Uganda. The low protein and fibre content of wheat flour and its associated high cost are the major concerns in its utilization as ingredient in bakery and confectionery industries. The removal of bran and germ during the processing of wheat flour leads to the drastic reduction in the nutritional density and fibre content. In this study, four composite breads were formulated with wheat flour (60-90%), soybean flour (5-15%), maize bran (4-15%), and maize germ (1-10%). Bread prepared with 100% wheat was the control. Proximate composition was determined using standard methods. Aflatoxin was determined using LC-MS/MS. The crumb hardness was determined using Stable texture analyzer. Sensory evaluation was carried out using Hedonic nine point scale. There were significant (p< 0.05) differences in protein, crude fibre, ash, fat, total energy, iron and calcium. The protein content increased with increase in blending and varied from 8.53 to10.97%. The crude fibre content ranged between 4.33 and 5.80%, the fat, ash, energy, iron and calcium were in the range of 1.36–4.76, 1.09–1.92%, 718.67–1105kj/100g, 2.30–2.80 and 31.40–46.30mg/100g respectively. There were significant differences in bread loaf weight and loaf specific volume among the bread samples (p< 0.05). The weight loaf of composite bread increased with increasing blending level and ranged between 441g and 487g. The loaf specific volume of bread decreased from 3.58 to 1.88 as the proportion of soybean, maize bran and maize germ flours was increased. The mean aflatoxin levels in the bread were below 0.005μg/kg which is lower than FDA/WHO, EU and UNBS regulatory limits of 20, 4 and 10ppb respectively. Bread with substitution level (80% wheat, 8% soy 10% maize bran 2% maize germ, (T3)) had the lowest crumb hardness whereas substitution level (60% wheat, 15% soy, 15% maize bran, 10% maize germ, (T5)) had the highest crumb hardness. Sensory properties of the composite bread were significantly (p< 0.05) affected by blending ratio. Mean scores of general appearance, colour, aroma, taste and overall acceptability were in the range of 6.71-7.46, 6.54-7.26, 5.71-7.14, 5.71-6.83, and 5.74-7.06 respectively. Sensory analysis showed that the bread processed from the formulation of 80% wheat, 8% soybean flour, 10% maize bran and 2% maize germ had the highest overall acceptability. The results have demonstrated that soy flour, maize bran and germ can be incorporated in the formulations for bread production with promising results.