Effect of Different Pretreatments and Air Temperatures on Drying Characteristics of Kachri (Cucumis callosus) Dried in Heat Pump Dryer

Abstract

Kachri (Cucumis callosus) is an underutilized fruit of India widely found in the western part of Rajasthan during the rainy season. In this study kachri fruit slices were pretreated with different pretreatments such as hot water blanching, 0.1% w/v potassium metabisulfite (KMS) and 0.1% w/v magnesium oxide (MgO) at 800C for 3 min. Pretreated samples were dried in a heat pump dryer at 40, 50 and 600C and their drying characteristics such as moisture content, drying rate, moisture diffusivity and rehydration ratio were studied. The initial moisture content of control kachri was 893.04% (db) and for the pretreated sample, it was 906.75% (db) and the final moisture content was found 4 to 6% (db) for all the treatments. The KMS treated sample took less drying time and a higher drying rate followed by MgO, hot water blanching and control. Moisture diffusivity ranged from 1.90 × 10-07 to 8.28 × 10-07 m2/s as the temperature increased from 40 to 600C. The value of the rehydration ratio ranged from 2.1 to 5.03. It was found that both rehydration ratio and moisture diffusivity values increased with an increase in drying air temperature.