Effect of Different Processing Methods On the Chemical Composition of African Yam Bean (Sphenostylis Stenocarpa) Flours and Organoleptic Characteristics of Their Gruels.

ABSTRACT The aim of this study was to determine the effect of different processing methods on the chemical composition of African yam bean (Sphenostylis stenocarpa) flours and the organoleptic properties of it’s gruels. The seeds of cream coloured African yam bean (AYB) and lime were purchased from Oye Igbo-Eze and Ogige Nsukka markets, respectively in Enugu State, Nigeria. The seeds were sorted and divided into 4 equal portions of 1.5kg each. One portion was washed and fermented in tap water at a seed- water ratio of 1:3 (w/v), for 24h. The second portion was fermented in tap water (1:3 w/v) containing 30 tablespoonful of freshly squeezed lime for 24h. The third portion was fermented in tap water containing lime (30 tablespoonful of lime) (1:3 w/v) for 48h. They were separately sundried for 72h and roasted in a hot sauce pan until cracking. The fourth portion (control) was washed, drained and roasted in a hot sauce until cracking. The AYB samples were separately milled into fine flours and stored in separate airtight containers for chemical analysis and gruel preparations. The flour samples were chemically analyzed for proximate, phytate, tannins, oxalates, saponins, trypsin inhibitors, raffinose, stachyose, hemagglutinins and hydrogen cyanide composition using standard laboratory methods. A nine point hedonic scale was used to collect data on sensory and acceptability tests of the gruels. Means and standard deviations were calculated and least significance difference test was used to separate means. The sample that was fermented in tap water containing lime for 48h ranked best generally. The moisture levels for the flours ranged from 3.60-5.00%, protein 19.96-31.87%, fat 3.54-5.23%, ash 2.99-3.89%, crude fibre 4.00-6.01% and carbohydrate 52.72-62.32%. The anti-nutrient values for the flours were: phytate 2.63-2.97mg/g, tannins 0.02-0.04mg/g, trypsin inhibitors 0.45- 0.53mg/g, oxalate 0.01-0.03mg/g, the samples had the same saponin level of 0.01mg/100g. Raffinose contents of the samples ranged from 8.25mg-9.22/100g and stachyose (8.48- 6.76mg /100g). heamagglutinins ranged from 4.87 – 6.70 mg/100g and hydrogen cyanide ranged from 0.22-0.28mg/g. In the organoleptic studies, the sample that was fermented for 48h was most preferred over others in terms of colour (6.53), the sample that was fermented in lime water for 24h ranked best for flavor (6.57) and the sample that was only roasted ranked best for general acceptability (6.03).