MATHEMATICAL MODELLING OF VACUUM DRYING CHARACTERISTICS FOR MAHLAB PUREE

Mahlab has bitter taste, strong aroma and high anthocyanin content and it might be used for producing different fruit snack bars which the drying step is very important for the manufacture. In this article, mathematical modelling of the drying of mahlab puree in vacuum dryer at different temperatures is investigated. Thin-layer drying processes were performed using a temperature controlled vacuum drying oven at 50, 60 and 70°C under 50 mbar absolute pressure and the weight data were collected at certain time intervals. The drying curves were fitted to eight different drying models. In this curve fitting, nonlinear regression analysis was used to evaluate the parameters of the selected models. Additionally, effective diffusion coefficient was obtained from diffusion model of Fick and the activation energy was determined using Arrhenius equation. According to statistical analysis results for three drying temperatures, Midilli et al. drying model has shown a better fit to the experimental drying data of mahlab puree. The effective diffusion coefficients were found as 1.71x10-10, 6.21x10-10 and 8.64x10-10 m2/s at 50, 60, and 70oC, respectively. The activation energy that expresses the temperature dependency of the diffusion coefficients was calculated as 75.2 kJ/mol