Effect of Soybean Fortification on the Physicochemical and Sensory Properties of Fermented Maize Pap
B. C. Nwokeke *
Department of Food Science and Technology, University of Agriculture and Environmental Sciences, Umuagwo, Imo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Fermented maize pap (ogi or akamu) is a traditional cereal-based food widely consumed in Nigeria and other parts of West Africa. Although fermentation can improve cereal digestibility and sensory quality, maize pap remains predominantly carbohydrate-based and relatively limited in protein. Soybean (Glycine max L.) is a protein- and lipid-rich legume that can complement the amino-acid limitations of maize and modify the functional characteristics of cereal-based foods. This study evaluated the effect of graded soybean fortification on the proximate composition, flour yield, functional properties and sensory acceptability of fermented maize pap powder. Yellow maize was naturally fermented for 72 h and converted to pap powder, while soybean was soaked, dehulled, blanched, dried and milled separately. The resulting flours were blended at 100:0, 90:10, 80:20, 70:30, 60:40 and 50:50 maize:soybean ratios. Moisture, ash, crude fibre, fat, protein and carbohydrate were determined using standard procedures, while bulk density, water absorption capacity, pH, swelling index, solubility and flour yield were evaluated using established methods. Thirty semi-trained panellists evaluated reconstituted pap using a nine-point hedonic scale. Data were analysed by one-way analysis of variance and treatment means were separated at p < .05 using the least significant difference procedure. Soybean incorporation increased protein, fat and ash contents, with protein increasing from 8.80% in the control to 15.28% at 50% soybean. Fibre reached its maximum value at 40% soybean rather than increasing continuously. Water absorption capacity increased from 0.81 to 0.90 g/g, whereas swelling index and solubility decreased. Flour yield varied among formulations and was highest at 20% soybean. Overall acceptability was highest for the control (6.90) and 10% soybean blend (6.50); the 20% blend recorded 5.80 and was not statistically comparable with the control because the difference exceeded the reported LSD of 0.24. Thus, the study demonstrates that soybean fortification can improve the nutritional and selected functional properties of fermented maize pap but increasing soybean concentration can reduce sensory acceptance. A 10% soybean formulation provides the most conservative fortified option under a stated decision rule combining protein improvement with an overall acceptability score of at least 6.0.
Keywords: Fermented maize pap, composite flour, proximate composition, functional properties, sensory evaluation