PEER-REVIEWED ARTICLE bioresources.com Sadaka (2022). “Short-grain rice drying kinetics,” BioResources 17(3), 4001-4017. 4001 Determination of Short-Grain Rough Rice Drying Kinetics Under Isothermal Conditions Using an Integrated Model Sammy Sadaka The constants of the drying kinetics models of short-grain rough rice were determined under isothermal conditions between a temperature of 40 °C and 100 °C. The initial moisture content of the rough rice was 28.2% dry basis. The results revealed that increasing the drying temperature and drying duration decreased the moisture content of the rough rice. The lowest rough rice moisture content (15.58% dry basis) was achieved at a drying temperature of 100 °C and a drying duration of 6 h. Four well-known models, i.e., Page, Newton, Logarithmic, and Henderson and Pabis, were evaluated. The models were evaluated based on the highest coefficient of determination value; the lowest root means square error, and the Chi- square value. The Page and Logarithmic models fit four and three cases of the seven drying curves, respectively, among the four evaluated models. Accordingly, combining the Page and Logarithmic models in an integrated model resulted in a model that fits all the seven studied curves. Furthermore, increasing the air temperature from 40 °C to 100 °C increased the moisture diffusivity from 1.5517 × 10 -9 m 2 /s to 4.2698 × 10 -9 m 2 /s. As a result, the activation energy value reached 16.43 kJ/mol for short-grain rough rice under the studied drying conditions. DOI: 10.15376/biores.17.3.4001-4017 Keywords: Short-grain rough rice; Drying kinetics; Thermal diffusivity; Activation energy Contact information: Biological and Agricultural Engineering Department, University of Arkansas - Division of Agriculture, Little Rock 72204 Arkansas; Corresponding author: ssadaka@uada.edu INTRODUCTION The grain drying process is estimated to consume 10% to 15% of the total energy requirements of all the food industries in developed countries (Klemeš et al. 2008). There are more than 200 types of dryers that can be used for drying agricultural products (Klemeš et al. 2008). The efficiency of the drying process is affected by drying features, i.e., the drying temperature, air velocity, relative humidity, retention time, and pressure. Therefore, it is essential to study the drying kinetics of each particular product to analyze the drying behavior of agricultural products. The drying conditions, type of dryer, and material characteristics influence drying kinetics. Over time, the models developed to explore the drying process using the developed dryers have been used in calculations involving the design and construction of new drying systems. Additionally, optimization of the drying process and the description of the entire drying behavior, including the combined macroscopic and microscopic medium heat and mass transfer, have been performed. Therefore, the drying kinetics models are important in deciding the ideal drying conditions, essential parameters for equipment design, process optimization, product quality improvement, energy, exergy analysis, and process automation and control (Giri and Prasad 2007; Erbay and Icier 2010).