Influence of Fermentation Period on the Quality of Wild Yam (Discorea Villosa) Flour

Greater utilization of wild yam is limited due to the presence of some anti-nutritional factors. Submerged fermentation is a simple traditional method of detoxifying food substances. Yam slices were blanched and fermented at ambient condition with intermittent changing of water at three days interval for 15 days (0, 3, 6, 9, 12, and 15 days). Six samples obtained were dried at 60°C for 8 hours. The proximate compositions, anti-nutritional factors and functional properties were determined using standard methods. Data obtained were analysed using ANOVA. The proximate compositions of the samples were moisture (6.60-10.26%), protein (13.71-23.70%), fat (5.40-7.18%), crude fibre (2.61-9.60%), ash (0.50-3.17%) and carbohydrate contents (56.73-62.60%). The saponin, tannin, oxalate contents decreased from 3.47-2.20%, 0.36-0.20% and 0.001-0.002% respectively. Bulk density and water absorption capacity decreased from 6.43-4.80g/ml and 0.40-0.19g/ml respectively. The pasting properties obtained were peak viscosity (354.08 - 88.92 RVU), trough (70.00-277.58 RVU), set back (109.42-567.17 RVU), final viscosity (231.25 - 844.75 RVU), peak time (6.87 - 7.00 mins) and pasting temperature (52.55 - 84.70°C). Fermentation improved the yam flour quality and reduced its anti-nutritional factors, but should be limited twelve days due to decreasing functional properties, most especially the bulk density. Keywords: Wild yam, submerged fermentation, detoxification, functional properties, nutritional quality