Reanalyze Previous Data to Develop a Universal Kinetic Model for Grain Sorghum Drying Process

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Abstract. Sadaka and Atungulu (2018) determined the drying kinetic models of grain sorghum. They used a thermogravimetric analyzer (TGA) to dry sorghum under isothermal conditions. The grain sorghum kernels were placed in the TGA under isothermal drying conditions, i.e., 40, 50, 60, 70, 80, 90, and 100oC. The changes in the sample weight were determined from the TGA. The moisture ratios and the derivative of the weight loss curves were determined. Four well-known models, namely the Page model, Newton model, Logarithmic model, and Henderson model, were tested. The authors stated that the Page model was the best fit for 71.4% of the drying curves, whereas the Logarithmic and Henderson models were the best fit for 28.6% of the studied cases. They did not conclude a single model that could fit all the studied cases. Accordingly, the goals of this paper were: (1) to study the effects of analyzing the same data using the modified Page model and (2) to test a newly developed universal model, namely the Sadaka model for the drying process of grain sorghum. The highest drying rate of 0.0208 mg/min was achieved at the drying temperature of 100oC and the beginning of the experiment. Increasing the drying duration showed a negative effect on the drying rate for all tested temperature levels. The drying constant of all the tested models (ko) increased with increasing the drying duration with the page model showing the highest effect. The modified Page model did not contribute any additional best fit model case to the previous results. The newly developed model known here as the Sadaka model showed the best fit model (with R2 between 0.9939 and 0.9983) for all the previously studied cases. The newly developed model needs to be continuously tested.