S.: Dehydration Dynamics of Potatoes in Superheated Steam and Hot Air

Superheated-steam at atmospheric pressure is an alternative drying medium for dehydrating materials insensitive to temperature equal to or above 100°C. This research compared the dehydration characteristics, temperature histories, drying rates, and overall moisture diffusivities of cylindrical potato samples exposed to superheated steam and hot air at 125, 145, and 165°C. A small amount of moisture (0.18 to 0.47 kg/kg db, dry basis) dependent on the steam temperature was gained from steam condensation on the sample surface during the warm-up period from the superheated-steam. The temperature of the drying medium had a greater effect on the drying rate, overall moisture diffusivity, and consequently dehydration time for the superheated-steam dehydration than for the hot-air dehydration. Increasing the temperature from 125 to 165°C decreased the dehydration time by 60 and 24 % for the superheated-steam and hot-air dehydration, respectively. A constant-rate drying period was only observed wit