Selection of the Best Kinetic Model in Drying of Button Mushroom by Infrared System

Button mushroom (Agaricus bisporus) is a high nutritional valuefood that is allocated about 40% of the mushroom market share and contains 32.5 % protein, 1.6 % fat, 9.2 % fibre, 7.5 % ash, 6.8 % moisture and 42.4% carbohydrate according to dry basis. Button mushroom is highly perishable product that shelf-life at 4 °C is up to 8 days. In this research, to increase the shelf life of button mushroom and producing high quality product, infrared (IR) dryer was used and mass transfer kinetics of the samples was measured.

In this study, drying of button mushroom in an infrared dryer at irradiation power of 150, 250 and 375 W and distance of 5, 10, 15 and 20 cm was investigated. The effect of lamp power and distance of sample from radiator on time and drying rate, and moisture diffusion coefficients were evaluated in a factorial experiment based on completely randomized design. For drying kinetics modeling, the 9 mathematical models including, Fick's Diffusion, Approximation of diffusion, Page, Modified Page –II, Newton, Midilli, Logarithmic, Verma and Two term were evaluated and the best model with the highest correlation coefficient and the lowest standard error was selected.

The results showed that the effect of lamp power and distance on the drying process of button mushroom is significant. Increase in infrared lamp power from 150 to 375 W, and decrease in the distance of lamp from sample from 20 to 5 cm reduced drying time button mushrooms 56.6 and 55.3 %, respectively. The maximum drying time was related to the power of 150 watts and the 20 cm lamp distance, which took 190 minutes to complete the process. Also, the lowest drying time is related to 375 W power and 5 cm lamp distance, which recorded time for this treatment was 30 minutes. By increasing the lamp power and reducing the irradiation lamp distance in the drying process of button mushroom, the effective moisture diffusivity coefficient had an increasing trend. By increasing the lamp power from 150 to 375 W, the effective moisture diffusivity coefficient increased from 3.8×10-9 m2s-1 to 11.0×10-9 m2s-1 (at a distance of 5 cm from the lamp). By increasing the sample distance from 250 W lamp, from 5 to 20 cm, the effective moisture diffusivity coefficient for a button mushroom decreased from 7.0×10-9 m2s-1 to 2.2×10-9 m2s-1.

Effective diffusivity coefficient of button mushroom moisture was between 1.2×10-9 to 11.0×10-9 m2/s. In modeling of mushroom drying process, Page model has better match with the experimental results compared with other models.