The intermittent drying characteristics of an Iranian popular paddy rice variety were experimentally investigated to determine the drying kinetics and obtain the effective moisture diffusivity. A lab-scale fluidized bed dryer was designed and constructed to enable obtaining the required results while controlling critical drying parameters. The effects of drying temperature and tempering period on drying kinetics and moisture diffusivity were studied. The results showed a significant effect on drying performance and effective moisture diffusivity by adding tempering stage. Drying rate improved sharply by implementing the tempering stage, increase of drying air temperature as well as the tempering duration. Several thin layer drying models were fitted separately to experimental data of each drying stages namely pre-tempering and post-tempering and suitability of these models were examined using the statistical analysis. The Midilli and Tow-Term model were found to be the most appropriate one for the first and second drying stages, respectively.

The drying characteristics of mallow (Malva sylvestris L. ) in a microwave dryer were examined at different microwave power levels. To dry 30 g of mallow leaves, microwave power levels of 360, 450, 540, 720, and 900 W were used. The initial moisture content of samples was 6. 31± 0. 01 g water/ g dry base. To determine the kinetic parameters, which were calculated by comparing the ratio of the difference between the initial and final moisture contents to the equilibrium moisture content, experimental data were fitted to seven distinct models. At various microwave power levels, the moisture diffusivity and energy consumption were measured. Based on the results, increasing microwave power from 360 to 900 W resulted in a drying time reduction between 14 and 5 minutes. A comparison of the proposed models demonstrated that the logarithmic model (MR= a. exp(-k. t)+b) provided the best fit because it had the highest coefficient of determination (R2), the lowest sum of squared errors (SSE), and the lowest root mean square error (RMSE). This model can therefore be used to estimate the moisture content of mallow leaves during microwave drying. Also, the maximum and minimum energy consumptions for drying with 360 W and 720 W microwaves were 84. 0 and 67. 5 W. h, respectively. Moreover, the effective diffusivity of mallow leaves varied from 1. 098×10− 10 to 3. 532×10− 10 m2/s for different microwave powers.

In this study, microwave drying conditions of quince pomace optimized with respect to quality attributes (moisture content, color change and consumer acceptance). Response surface methodology (RSM) technique was used to develop models to respond to the microwave power (100, 2000, 300 W), and microwave time (5, 10, 15 min). The models obtained from the responses were adequate and acceptable because the coefficient of determination R2 of the models was relatively high. Microwave power of 200W and microwave time of 8 minutes were concluded as the optimum conditions prior to air-drying at 50°C. To describe the drying process, the experimental data for moisture loss was converted to moisture ratios. The effective moisture diffusivity increased with increase in microwave power and its values varied from 1.83-4.87×10-9 m2/s. Using an exponential expression based on Arrhenius equation the activation energy and was found to be 16.41 W/mm.

Background: Drying is one of the oldest methods that humans have employed to preserve and store foods. Today, this method is being widely utilized, as such there have been great advances in the production of dried fruits. Materials and Methods: In this study, different drying methods including sun drying, oven at different temperatures (70, 80, 90 or 100 °C), and microwave were used to dry “Ohadi” pistachio cultivar. In this respect, the effect of these methods on drying kinetics and the duration of drying was investigated. Results: The results showed a meaningful difference (p<0.05) between the drying methods. The results also demonstrated that the microwave method accelerates the drying process. The results of the drying methods on qualitative characteristics of the pistachio such as changes in color parameters showed that the application of the microwave method increases color changes. Based on the results of the modeling for pistachio drying, Newton model was the most suitable model for describing the drying process of pistachio layers at 70°C oven, binomial model was the most suitable model for describing drying process of pistachio layers by oven at of 80, 90 and 100 °C. Conclusions: The Page model was the most suitable model for describing the drying process of pistachio layers by microwave, and the Wang and Singh model was selected as the most suitable model for describing the drying process of pistachio layers by sun drying method.