Effect of drying conditions on energy utilization during cocoyam drying

Cocoyam samples soaked in sodium metabisulphite (SM) and water blanched (WB) were oven dried at 50, 60 and 70° C and microwave power levels of 385, 540 and 700 W while untreated samples were sun dried. The effect of drying on selected properties of cocoyam was studied. The drying time generally reduced with increase in drying temperature and power level used. The use of SM pretreatment resulted in lower drying times compared with WB pretreatment. Effective moisture diffusivity values (Deff) for all the drying conditions varied from 5.27 x 10-8 to 2.07 x 10-6 m2/s and SM samples had higher values than WB samples.  Activation energy values for oven drying were 37.41 KJ/mol and 61.79 KJ/mol and that for microwave drying were 38.59 and 41.91W/g for SM and WB samples respectively.  The energy consumption varied from 125.1 to 142.8 kWh and 308 to 396.7 Wh while that of specific energy requirement varied from 86.2 to 106.5 kWh/kg and 1.49 to 2.03 KJ/kg water for oven drying and microwave drying respectively