Mass Transfer Kinetics of Combined Infrared-Hot Air Drying of Pumpkin

Pumpkin is a good source of carotene, water-soluble vitamins and amino acids. Pumpkin can be processed into flour which has a longer shelf-life. Pumpkin flour is used because of its highly-desirable flavour, sweetness and deep yellow orange –red colour. In this study, kinetic modeling of pumpkin drying in an infrared-hot air dryer was investigated.
The effect of radiation lamp power at three levels of 204, 238 and 272W, hot air temperature at three levels of 55, 65 and 75 °C and samples thickness at two levels of 0.5 and 0.7 cm on time and drying kinetics and moisture diffusion coefficient during drying of pumpkin in a completely randomized design were evaluated.
The effect of radiation power and hot air temperature on the drying process of pumpkin is significant. Increase in infrared lamp power from 204 to 272 W and increase in hot air temperature from 55 to75°C reduced pumpkin drying time 15.05 and 37.43 %, respectively. Effective diffusivity coefficient of pumpkin moisture was between 9.2×10-10 to 3.3×10-9 m2/s.
272 W power, 75 °C temperature and 0.5 cm thickness were the best condition for drying of pumpkin. The effects of infrared heat power and hot air temperature on effective diffusivity coefficient changes were investigated and it was found that the effective diffusivity coefficient increased by increasing heat source power and air temperature. In modeling of pumpkin drying process, Newton model is a better match with the experimental results as compared to other models.