Functional Properties of Flours from Fresh and Boiled Wild Yam Dioscorea praehensilis Tubers

Abstract

The aim of this study was to evaluate the effect of boiling time on functional properties of flour from the wild yam Dioscorea praehensilis tuber. For this purpose, six (6) flours were produced with different boiling times of the wild yam tubers: 5 min (YT5), 10 min (YT10), 20 min (YT20), 30 min (YT30) and 40 minutes (YT40); the raw tuber flour (YT0) was used as reference control. Slower wettability registered for raw flour (116.33s) significantly (p<0.05) change with boiling as wettability of boiled tubers flours ranged from 25.32 s (YT5) to 33.5 s (YT40). The densities paste clarity and Water Absorption capacity significantly (p<0.05) increased with the boiling. But there were significantly (p<0.05) decrease in water solubility index (WSI) (from 19.45 % to 16.45 %), dispersibility (from 82.03 % to 74.2) and foam capacity (from 86.02 to 11.79 %). The foam stability increased from raw to the boiled tuber. Parameter like least gelation concentration (LGC) remained constant (at 6 g/ml) from raw to boiled tubers and increased to 8 g/ml only at the longer boiling time (30 min and 40 min). The highest emulsion capacity was registered at 20 min while the highest), water absorption capacity (WAC) was registered at 10 min. The swelling power and solubility increased significantly from 70° to 95° C with the highest values in swelling power for YT5. The highest solubility value was registered at 70° C for YT5. Turbidity values ranged from 1.6 to 2.8 with higher values for YT0 and lower values for YT40. Four oil types were tested for Oil Absorption Capacity (OAC). Highest OAC values were obtained in boiled flours with unrefined palm oil (all values higher than 180 %) followed by refined palm oil (values ranged 166.5 to 185 %). These results showed that the boiling and the boiling time induced significant changes in functional properties of flour from the wild yam Dioscorea praehensilis tuber.