## 3 Results and Discussion
### Convective and Infrared Drying
#### 3.1.2 Effective Moisture Diffusivity of Convective and Infrared Drying of Terebinth  
Investigation of the effects of temperature and infrared power on the \(D_{\mathit{eff}}\) of treebinth indicated that a rise in the temperature of the CV dryer and the power of the IR dryer can significantly enhance the \(D_{\mathit{eff}}\). Statistical analysis revealed that the reciprocal effects of dryer type and pretreatment were significant for the \(D_{\mathit{eff}}\) parameter (Table 2). The highest \(D_{\mathit{eff}}\) (9.77 \(\times 10^{-9}\) m\({}^{2}\)/s) was achieved under MW pretreatment at 750 W using an IR dryer, while the lowest (6.53 \(\times 10^{-10}\) m\({}^{2}\)/s) was observed in the CV dryer at 50 \({}^{\circ}\)C in the control sample. The results showed an increment in the \(D_{\mathit{eff}}\) with increasing the temperature in all cases. The reason is that the temperature elevation led to enhanced molecular motion and surface suction caused more water molecules to leave the product (increased mass transfer) and consequently reduced the drying time and incremented the \(D_{\mathit{eff}}\)[33]. With increasing IR power, the \(D_{\mathit{eff}}\) also increased as the IR ray's penetration into the material led to the oscillation of water molecules and increased the internal vapor pressure. In this case, the molecules will need less energy to transfer from the porous material, therefore a rise in IR power will enhance the \(D_{\mathit{eff}}\)[7]. These results are in line with the reports by other researchers such as [PERSON] et al. [19] for drying walnuts in the IR power range of 500-1500 W, [PERSON] et al. [36] for button mushroom slices in the IR power range of 150-375 W, and [PERSON] et al. [7] for jujube fruit in the IR power range of 62-125 W.  
At constant temperature and IR power, the \(D_{\mathit{eff}}\) showed an increment in the pretreatment mode (MW, US, and BL) as compared to the control. Variations and decreases in textural density and integrity after pretreatments promoted the moisture migration from the center to the surface, hence, the moisture will rapidly leave the product [17]. A comparison of different pretreatments (in both dryers) indicated that the MW and US pretreatment had the most and the least effects on the \(D_{\mathit{eff}}\). Microwaves make the product porous [37] and by increasing the thickness and inflating the product, opened the capillary tubes and facilitated the moisture transfer and consequently shortened the drying time compared to other pretreatments (US and BL). On the other hand, MW pretreatment enhances the sample heating due to the increase in the polarization of water molecules, followed by volumetric heating and heat generation inside the sample, which leads to a large pressure difference between the center and the surface. As a result, the texture of the product is more destroyed in the microwave pretreatment, promoting moisture loss during drying while rising the moisture diffusion coefficient [14]. The results also showed that the blanching pretreatment increased the moisture diffusion more than ultrasonic pretreatment. The reason is that blanching degrades the cell membrane resistance due to high temperature, hence, moisture can be transferred from the inside of the product to the outside at higher rates. This increased the diffusion coefficient of the product compared to the US treatment. Similarly, in a study on cranberry snacks in a microwave-vacuum dryer with ultrasonic and blanching pretreatment, it was found that the use of different pretreatments enhanced the \(D_{\mathit{eff}}\) compared to the control samples [17]. [PERSON] et al. [35] dried apple slices by microwave-vacuum dryer using different pretreatments (US, BL, and osmotic dehydration) and determined the value of \(D_{\mathit{eff}}\) in the range of 1.64-3.46 \(\times\) 10\({}^{-8}\) m\({}^{2}\)/s. This indicates that the use of different pretreatments enhanced the \(D_{\mathit{eff}}\). [PERSON] et al.