Abstract:

Drying is a technique frequently used for agricultural food products to preserve them in long time periods. In this work, drying characteristics of Pomelo fruit (Citrus Maxima) peel for different drying techniques as microwave drying (MW), forced convection drying (FC) and freeze drying (FD) were determined. Experiments were conducted for two slab thicknesses (1 cm and 0.5 cm) in albedo part of the fruit peel. In addition, activation energy and effective diffusivity values also color properties were calculated for different drying techniques in both sizes. For FC, MW, and FD, drying times were determined as 34 min, 24 min, 410 min for thin slabs and 44 min, 30 min and 540 min for thick slabs, respectively. 0.5 cm thick peels had lower moisture content in a shorter drying period and when the slice thickness was reduced, the drying rate was increased nearly by 25%. By mathematical modelling with 11 different thin layer models, the best fitted kinetics models were found as Logarithmic, Diffusion Approach and Modified Henderson & Pabis models. At constant thickness, the highest effective diffusivity values were determined for the MW drying (1.925x10-8 for thin slab, 7.295x10-8 for thick slab). As for the color measurements, L*, a*, b* values generally have significant differences from fresh pomelo peel samples that the closest values to the fresh samples were obtained from freeze drying experiment. 

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