Effect of different pretreatments and temperature on drying characteristics of sweet Potato

Abstract

In this study slices of sweet potato were pretreated with different pretreatments such as; 0.1% w/v potassium metabisulfite (KMS), 1% w/v calcium chloride (CaCl2) and blanching at 80 °C for 5 min. Pretreated sweet potato slices were dried in a mechanical tray dryer at 50, 55, 60 and 65 °C and their drying characteristics such as moisture content, drying rate, moisture diffusivity and rehydration ratio were studied. The initial moisture content of raw sweet potato was found 246.02 per cent (db). The initial moisture content of pretreated sweet potato slices ranged between 240.68 to 260.35 (db) and final moisture content was found ranged from 6.01 to 7.33 per cent (db) at temperature 50, 55, 60 and 65 °C. The CaCl2 pretreated sample taken less drying time and higher drying rate as compared with kms, hot water blaching and control samples. Moisture diffusivity ranged from 1.1 10-8 to 2.92 10-8 m2/s as the drying temperature increased from 50 to 65 °C. It was found that Moisture diffusivity and rehydration ratio increased with increase in drying air temperature.