Effect of processing methods on the proximate composition of African yam bean (Sphenostylis stenocarpa) flours and sensory characteristics of their gruels

Abstract

Background: African yam bean (AYB) could be processed into value added food products. Processing however affects the chemical, sensory and functional properties of the foods. Objectives: This work determined the effect of processing methods on the proximate composition of African yam bean ( Sphenostylis stenocarpa ) flour and the sensory properties of its gruels. Methods: Six kilogram of African yam bean seeds were sorted and divided into 4 portions of 1.5kg each. One portion was washed and fermented without lime for 24h, sundried for 72h and roasted (F24R). The second portion was washed, fermented with lime juice for 24h, sundried for 72h and roasted (FL24R). The third portion was washed, fermented with lime for 48h, sundried for 72h and roasted (FL48R). The last portion was washed, dried and roasted (OR) (the control). The samples were milled into flours and analyzed for proximate composition. Gruels were prepared with the flours and analyzed for their sensory properties. Statistical Packages for Social Sciences (SPSS) was used to analyze the data obtained. Results: Sample F24R had the highest protein content (33.08%) while FL24R had the least protein content (20.96%) and was followed by FL48R (27.86%). The fat content of FL48R, F24R and OR were 3.68%, 4.90% and 5.49%, respectively. Sample FL24R had higher ash content (4.08%) than the other samples. The control (OR) on the other hand, had the highest fibre content of 6.31%. The fibre contents (4.16% - 4.28%) of the other samples were not significantly (p>0.05) different. FL24R had carbohydrate level of 62.26% which was significantly (p<0.05) different from those of the other samples. F24R had the least carbohydrate level of 54.63%. The gruel prepared from FL48R was preferred in colour (6.53) while the gruel from FL24R had the highest score for flavour (6.57). The consistency of all the gruels were similar (6.87, 6.17, 6.13, 6.97) and not significantly different (p>0.05). Conclusion: Alkaline fermentation combined with roasting improved nutrient contents of AYB. Keywords : African Yam bean Flour, Sensory Characteristics, Proximate Composition, and Processing Methods.