ABSTRACT

The drying characteristics of Dioscorea bulbifera flour at different drying temperatures (55°C, 65°C, 75°C, 85°C and 95°C) and varied drying time (60 minutes, 80 minutes, 100 minutes, 120 minutes and 140 minutes) at a constant air velocity of 1.0 m/s were investigated. The moisture content of the dried flours ranged from 5.76 to 8.31%, 5.11 to 7.76%, 4.60 to 7.27%, 4.11 to 6.81% and 3.55 to 6.20% for samples dried at 55, 65, 75, 85 and 95˚C for between 60 to 140 minutes respectively. The ash content of the dried flours ranged from 2.64 to 2.87 %, 2.66 to 2.90%, 2.70 to 2.94%, 2.75 to 2.99% and 2.81 to 3.03% for samples dried at 55, 65, 75, 85 and 95˚C for between 60 to 140 minutes respectively. The protein content of flours dried between 55 to 95˚C ranged from 7.05 to 7.17% (60 minutes), 7.02 to 7.16% (80 minutes), 6.97 to 7.11% (100 minutes), 6.91 to 7.06% (120 minutes) and 6.85 to 7.00% (140 minutes) respectively. The fat content of the flours was quite low with the control recording 1.54% while those of the dried flours ranged from 1.36 to 1.51% (60 minutes), 1.32 to 1.49% (80 minutes), 1.27 to 1.47% (100 minutes), 1.23 to 1.44% (120 minutes) and 1.18 to 1.40% (140 minutes) respectively. The crude fibre content of the control was obtained as 1.28% and it was significantly (p<0.05) lower than those of the dried flours which ranged from 1.29 to 1.36 (60 minutes), 1.30 to 1.37% (80 minutes), 1.32 to 1.40% (100 minutes), 1.35 to 1.44% (120 minutes) and 1.37 to 1.47% (140 minutes). The carbohydrate content was observed to increase in the dry flour, ranging from 79.08 to 81.16%, 80.00 to 82.27%, 80.65 to 82.88%, 81.22 to 83.41% and 81.66 to 83.92% in flours dried at 55, 65, 75, 85 and 95˚C (for 60 to 140 minutes). WAC ranged between 2.70 to 3.38 ml/g, 2.73 to 3.42ml/g, 2.78 to 3.47ml/g, 2.88 to 3.60ml/g and 2.96 to 3.73ml/g in flours dried at 55, 65, 75, 85 and 95˚C at intervals of 60 to 140 minutes respectively. OAC ranged between 2.35 to 2.56 ml/g, 2.38 to 2.63ml/g, 2.44 to 2.71ml/g, 2.50 to 2.76ml/g and 2.56 to 2.84 ml/g for flours dried at 55, 65, 75, 85 and 95˚C at intervals of 60 to 140 minutes respectively. Gelatinization temperature increased from 72.10 to 73.70°C, 72.20 to 73.90°C, 72.40 to 74.20°C, 72.60 to 74.60°C and 72.90 to 75.10°C for flours dried at 55, 65, 75, 85 and 95˚C for intervals of 60 to 140 minutes, respectively, while pH values ranged from 6.30 to 6.50, 6.00 to 6.40, 5.60 to 6.20, 5.30 to 6.00 and 4.90 to 5.80 in flours dried at 55, 65, 75, 85 and 95˚C for intervals of 60 to 140 minutes, respectively. Generally, the dried D. bulbifera flours were found to be of good quality nutrient and could serve as good ingredients in infant food formulation.