Thin layer drying of tomato slices using a combined infrared-vacuum dryer

In this study, drying kinetic of tomato slice in a combined infrared-vacuum dryer was investigated. The effects of infrared lamp power at three levels (300, 350 and 400 W) and pressure of vacuum oven at three levels (6, 16 and 26 kPa) on drying time and moisture diffusion coefficients during drying process of tomato were evaluated. The results showed that the effects of infrared lamp power and pressure on the drying process of tomato were significant (p<0.05). With increase in infrared lamp power from 300 to 400 W, drying time of tomato 42.86 percent reduced. In addition, decreasing in vacuum oven pressure from 26 to 6 kPa reduced 40.00 percent of drying time. The effects of infrared heat power and vacuum oven pressure on effective diffusivity coefficient of tomato were investigated and the results showed that the effective diffusivity coefficient was increased with increasing heat source power and decreasing of pressure. Moisture effective diffusivity coefficient of tomato was between 5.00×10-10 - 2.38×10-9 m2/s. In fitting of tomato drying process data, the quadratic model, compared to other models, with the highest R2 and the lowest error, had closer results to the experimental data. According to the results obtained in this study, the use of this dryer is recommended for the drying of tomato slice.