Freeze Drying Process of Kiwi Slices With Various Thicknesses And Investigation Drying Characteristic of Process

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In the study, the kiwi fruit was sliced into various thicknesses as 5 mm and 7 mm, and those sliced specimens were put in the freeze-drying device. the mass losses of the specimens were measured and saved during the drying process and kinetic drying models were performed using those measurements. The mass losses of each kiwi slices in 100 g mass were measured every two hours in the experiment lasting 14 hours in total and moisture ratios (MR) were calculated as well. Considering the experimental results, 8 different kinetics drying models were performed using MATLAB software. As a result, the lowest reduced chi-square (X2) values for 5 mm and 7 mm thicknesses were calculated about 8.261x10-6 and 1.705x10-5 respectively, the root means square error values (RMSE) were about 0.002865 and 0.004146, respectively. Also, the coefficient of determination (R2) for both thicknesses was calculated as 0.9999 which was the highest result closest to 1. Among the 8 different kinetic drying models, the Logarithmic model was chosen as a proper kinetic drying model for kiwi products. When the moisture contents and drying rates were considered it was seen that the drying rate of kiwi slices with 7 mm thickness exhibited slow behavior because of the higher moisture content. Besides, it was determined that the effective diffusivity coefficients for specimens with 5 mm and 7 mm thickness were calculated as 2.25 × 10-10 m2/s and 3.28 × 10-10 m2/s respectively.