Evaluation of Drying Kinetics and Activation Energy of Oyster Mushroom (<i>Pleurotus ostreatus</i>)

Abstract

Oyster mushroom (Pleurotus ostreatus) is a fungus which easily deteriorates after harvest and hence, there is need to make it stable by  reducing its moisture content to a lower level after harvest. In this study, fresh oyster mushrooms were dried using three modes of  drying: sun at an average temperature of 32^oC, solar at an average temperature of 40^oC and tunnel dryer at 50^oC. Kinetics of moisture  drying was modelled using Fick’s second law of diffusion which is generally applicable to thin-layer drying of agricultural products. Six  models namely Henderson and Pabis, Logarithms, Newton, Page, Two Terms and Midilli Kucuk were employed for the drying kinetics.  Nonlinear regression analysis was carried out using Statistical Package for Social Scientist (SPSS 16.0 version) to fit the experimental data.  The reliability of the models was tested using some statistical criteria such as coefficient of determination (R²), reduced chi- square  (χ2), Mean Bias Error (MBE) and Root Mean Square Error (RMSE). The model which had the best fit was chosen to represent the drying  behaviour of oyster mushroom. The drying pattern was observed to be in the single falling rate period in the entire drying modes. The  values of R2 ranged from 0. 0.933-0.988, χ2 (2.4E-06-0.044), MBE (-7.6E-4-0.044) and RMSE (7.8E-4-0.201). Effective moisture diffusivity for  samples dried in the sun, solar and tunnel were 1.19 E-11m²/s, 1.21 E-11m² /s and 1.59 E-11m²/s, respectively. Two Term model best  described drying behavior of oyster mushroom during tunnel drying and the activation energy of the model was 64.9kJ/mol.