Response surface methodology was used to optimize the pretreatments before solar cabinet drying of bitter gourd slices (6-7 mm thick). Central composite design (CCD) was used to conduct the experiments which consisted thirteen experiments with two variables, viz., blanching time (1-5 min) and potassium metabisulfite (KMS) (0.2-0.5 %). After the pretreatments, the bitter gourd slices were dried up to 6 % (Approx.) moisture content (d.b) in solar cabinet dryer at air temperature, relative humidity and air velocity in the range 38 to 62°C, 45 to 55 % and 0.9 to 1 m/s, respectively. The responses taken were chlorophyll retention (mg/100g of dried sample) and texture (hardness) of dehydrated bitter gourd slices. The optimum process condition was found at 4.24 min blanching time and 0.49 % KMS which resulted in 20.15 mg/100g chlorophyll retention and 340.55 g hardness. Some selected quality attributes of solar cabinet dried bitter gourd slices pretreated with the optimized combination of blanching time and KMS were compared with the quality of freeze and open sun dried samples and it was found that quality of solar cabinet dried product was falling in between open sun and freeze dried products. Also, the drying data of bitter gourd slices obtained during solar cabinet, freeze and open sun drying were analyzed and drying constants as well as moisture diffusivity were calculated.
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