Abstract:
There is an increasing demand for variety in food products, mankind rely on very limited number of crops to meet the needs of staple diets on a very limited number of major non-food crops to meet the associated needs, the functionality of wheat-morama bean composite flour for food applications was thus investigated. Morama bean (Tylosema esculentum) was shelled and milled into flour. Part of the morama bean flour was defatted using n-hexane. Wheat flour (both hard and soft) was substituted with defatted and full fat morama bean flour at varying levels and their physico-functional and pasting properties determined. The design of the study followed a 2 X 2 X 4 factorial design for morama bean flour (full fat and defatted), wheat flour type (soft and hard) and morama bean flour substitution level in composite flour (10, 20, 30 and 40%). The least gelation concentrations of the wheat-morama composites were quite low with some composites gelling at 4%. The functionality of the composite flours was significantly influenced by the particles size distribution of the morama bean flour. Defatted morama bean flour had a similar particle size distribution as the soft wheat flour. Full fat morama bean flour generally had larger particle sizes due to the presence of fat. At 70°C, water absorption capacity of the composite flours decreased with increasing morama bean flour (full fat or defatted) concentration. The functionality of the composite flours was more influenced by morama bean flour (defatted or full fat) level than by wheat type (soft or hard wheat). Incorporation of morama bean flour (both defatted and full fat) to wheat reduced the pasting indices of peak viscosity, breakdown and setback even when as little as 5% of full fat morama bean flour was added. At 40% morama level of substitution the composite flour did not show meaningful pasting profile.
At 30°C the water sorption behavior of the composite flours was influenced by the amount and type of morama bean flour. The equilibrium moisture content of composite flour with defatted morama bean flour was more sensitive to increasing water activity, indicating the possibility of it being less stable due to moisture absorption during storage than full –fat morama flour composites. Monolayer values of the composite flour were influenced by the level of morama bean flour (full fat and defatted). The GAB model was the better model in describing the relationship between water activity and moisture content of soft wheat-morama bean flour, as compared to the BET model. Consumer preference tests data showed that twenty (20) percent substitution of soft wheat with full fat morama bean flour was the preferred composite flour for making biscuits. The successful application of morama bean flour in food systems will enhance its utilization and improve food and nutrition security.
