Comparison of convective and infrared heating as means of drying pomegranate arils ( Punica granatum L.)

The purpose of this study is to compare convective and infrared heating as means of drying pomegranate arils. The drying process was conducted at 50, 60 and 70 °C. The minimal times required to reach 9 ± 0.2% moisture (mass/mass) starting from 78 ± 0.2% were 510 and 94 min respectively for convective and infrared drying. Calculation of aril effective diffusivity (D eff ) was based on Fick’s second law of diffusion. At all temperatures, D eff values ranged from 2.56·10–10 to 4.75·10–10 m 2 /s, and from 0.87·10–9 to 2.64·10–9 m 2 /s respectively for convective and infrared drying. Effective moisture diffusivity (D eff ) values were found to increase as temperature to increase. Pomegranate is one of the major sources of polyphenolic phytochemicals. Polyphenol stability might be affected by heat treatments that are required during drying. Based on the maximal total polyphenol content (205 ± 0.89 mg/100 g) of the dried product, the optimal temperature for infrared drying was 50 °C. This product also had an intense garnet-red color and a satisfactory rehydration capacity. Various models of drying kinetics were tested for conformity with the results obtained in this study. The model that best fit the drying data was the modified logistic model of Midilli et al., than other models.