Effect of Fruit Thickness on Microwave Drying Characteristics of Myrtus communis L.

Myrtus communis L. (Myrtle) is an evergreen shrub and its fruit is used in traditional medicine in hypoglycemic, oral, and stomach disease therapy. To the best of our knowledge, there is no report on microwave drying of it. Therefore, this study is aimed to evaluate the effect of microwave power and fruit thickness on drying kinetics, effective moisture diffusivity, activation energy, specific energy consumption, and quality characteristics of Myrtus communis L.. Thus, four thicknesses (5, 7, 9, and 11 mm) of the fruit were dried at microwave power levels of 450, 600, and 750 W. The kinetics study revealed that the Midilli et al. model exhibited the best microwave drying behavior of the samples. Moreover, increasing microwave power and decreasing fruit thickness resulted in a substantial (P 0.05) reduction in drying time and an increase in drying rate. Fruit thickness also showed a significant effect (P 0.05) on effective moisture diffusivity and specific energy consumption, which ranged from 0.453×10-7 to 8.91×10-7m2/s and 6.98 to 18.13 MJ/kg water, respectively.  In addition, the less fruit thickness, the more moisture diffusivity, and the less activation energy. The calculated activation energies were in the range of 11.46 to 21.76 W/g. Moreover, as the thickness of the fruit was reduced and the microwave power was increased, the shrinkage ratio of the samples was reduced and their rehydration abilities were enhanced. Finally, it was determined that a microwave power of 750 W and a fruit thickness of 5 mm made better results in terms of quantity and quality parameters. a significant effect (P 0.05) on effective moisture diffusivity and specific energy consumption, which ranged from 0.453×10-7 to 8.91×10-7 m2/s and 6.98 to 18.13 MJ/kg water, respectively. In addition, the less fruit thickness, the more moisture diffusivity, and the less activation energy. The calculated activation energies were in the range of 11.46 to 21.76 W/g. Moreover, as the thickness of the fruit was reduced and the microwave power was increased, the shrinkage ratio of the samples was reduced and their rehydration abilities were enhanced. Finally, it was determined that a microwave power of 750 W and a fruit thickness of 5 mm made better results in terms of quantity and quality parameters.