Quality assessment and modeling of microwave-convective drying of lemon slices

Juice production is the most important process used for citrus fruits. However, drying process applied in the production of powders, flakes, and slices is also of great importance. Drying behavior of lemon slices was investigated using convective (50, 55 and 60 °C inlet air temperatures), microwave (specific power of 0.97 W g−1), and combined microwave-convective (specific powers of 0.97 and 2.04 W g−1 assisted with 50, 55 and 60 °C inlet air temperatures) dehydration methods. The quality was assessed in terms of L∗ a∗ b∗, total color difference (ΔE), chroma, Hue angle, and rehydration capacity measurements. In addition to higher drying rate, the quality parameters for microwave-convective treatments were significantly higher than those for other methods. Drying kinetic curves indicated a constant rate period followed by a falling rate period in both convective and microwave drying methods. However, for microwave-convective treatments a falling rate period was observed with the exception of a very short accelerating period at the start. Mathematical modeling of the drying kinetics was conducted by applying the commonly used drying models to the experimental data. According to the statistical parameters, Midilli et al. model presented the best prediction for the drying kinetics.