EFFECT OF PRETREATMENTS ON AIR-DRYING PATTERN AND COLOR OF DRIED PUMPKIN (CUCURBITA MAXIMA) SLICES

Effect of pretreatments on air-drying pattern and color of pumpkin slices was investigated. Fresh, sulfited (1,000 ppm), blanched (100C for 3 min) and osmotically pretreated pumpkins (40, 50 and 60 degrees Brix) were air dried at 50-80C. Moisture transfer from fresh and pretreated pumpkin was modeled using Fick's diffusion model, and effective moisture diffusivity (m(2)/s) was calculated. Moisture ratio decreased with increased drying temperature and time. No constant drying rate period was observed in the drying process. Pre-osmosed pumpkin recorded lower moisture contents and drying rate. Effective moisture diffusivity was in the range of 6.50 E-10-2.45 E-09 m2/s. Arrhenius relation with activation energy for moisture diffusion of 24.49-43.27 kJ/mol expressed the effect of temperature on moisture diffusivity. L*, a*, b*, color intensity (Delta E) and chroma (Delta C) values of dried pumpkin increased with increase in drying temperature from 50 to 60C.