The effect of boiling and soaking time on the chemical and functional properties of wild bitter yam
Chika Ada Ugwuanyi, Ifeyinwa Sabina Asogwa, Jane Chinyelu Ani
The effect of boiling and soaking time on the chemical composition and functional properties of wild bitter yam (WBY) was investigated. Wild bitter yam samples was peeled, washed and randomly divided into 4 lots. The first lot was the un-boiled and un-soaked samples which served as control while the remaining 3 lots were cooked in boiling water for varying length of time; 20, 30 and 40 minutes, respectively. The boiled lots were allowed to cool, shredded into three well labeled bowls. The strips from each boiled lot were washed 4 times in water tuber ratio of 2:1, respectively and each lot was split into 2 sub-lots. The sub-lots were soaked in water at water tuber ratio of 2:1 for 14 and 16 hours, respectively, washed 5 times, drained and sun-dried. The dried strips were milled and packaged in an airtight plastic container to give a total of 6 WBY samples. The samples were evaluated for chemical composition and functional properties. The proximate composition of the WBY samples varied from 8.57–12.84% for moisture, protein 7.00–8.93%, fiber 2.17–2.36%, fat 1.10–1.17%, ash 1.68–1.93% and carbohydrate 75.05–77.03%. The phytochemcial contents ranged from 0.41–0.48% for alkaloid, flavonoid 0.23–0.30%, tannin 0.14–0.18%, saponin 0.18–0.35%, phenol 0.52–0.61%, oxalate 0.21–0.37% and dioscorine 326.87–304.35mg/100g. There was a general decrease in the phytochemcial contents of the yam samples with increasing boiling and soaking time The functional properties of WBY samples varied from 0.43–0.50g/cm3 for bulk density, water absorption capacity 5.05–7.10g/g and oil absorption capacity 6.55–7.83g/g. Boiling WBY for 30 minutes and soaking for 14 hours was able to reduce the toxic dioscorine to safe levels while still retaining the nutrients.