Effect of Thermal Processing Treatments on the Proximate, Functional and Pasting Properties of African Yam Bean (Sphenostylis stenocarpa) Seed Flours

Abstract

The study was designed to evaluate the effect of thermal processing treatments on the proximate composition, functional and pasting properties of African yam bean seed flours. The African yam bean seeds were sorted, cleaned and divided into five equal lots of one kilogram each. Four lots were processed into boiled, blanched, roasted and autoclaved African yam bean flours, while the last lot was processed raw and used as control. The flour samples obtained were analyzed for proximate composition, functional and pasting properties using standard methods. The proximate composition of the samples revealed that the flours had a range of 6.14-11.24 % moisture, 8.18-14.37 % crude protein, 3.06-4.61 % fat, 2.04-3.32 % ash, 3.18- 3.56 % crude fibre, 62.90 -76.98 % carbohydrate and 350.57 - 368.50 kJ/100g energy, respectively. The functional properties of the flours equally revealed that the bulk density, water absorption, oil absorption, swelling, emulsification and foam capacities of the samples ranged from 0.43-0.68 mg/mL, 0.48-0.76 %, 0.45-1.57 %, 2.32-2.72 %, 1.27-2.69 % and 1.43-1.86 %, respectively. The pasting properties of the samples also showed that the trough, breakdown, setback and final viscosities as well as the peak time and pasting temperature of the flours were significantly (p <0.05) higher in blanched and roasted African yam bean flours compared to the samples processed by boiling and autoclaving treatments. However, the study showed that the processed African yam bean flours could be used as nutrient dense and functional ingredients in the formulation of a variety of novel food products for children, adolescents, and adults especially in Nigeria and other developing countries where the problem of protein-energy malnutrition is prevalent than the raw sample.