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In this study, a mathematical model to simulate the drying of shelled corn in a continuous plug-flow fluidised bed dryer is presented. Equipment and material models were applied to describe the process. The equipment model was based on the differential equations obtained by applying mass and energy balances to each element of the dryer. In the case of the material model, mass and heat transfer rates in a single isolated particle were considered. Calculation results were verified by comparison with experimental data from the literature. There was a very good agreement between experimental data and simulation. The effects of gas temperature and velocity, particle diameter, dry solid flow and solid temperature on the drying process were investigated. It was found that the changes in gas velocity, dry solids flow and the solid temperature had essentially no effect on the drying process.

RESUMENEste estudio se basó en la producción de harina de papa para puré instantáneo, utilizando las variedades de papas nacionales Provento y Granola. Para ello, se determinó el porcentaje de humedad de las papas, resultando la variedad Granola con el menor rango de humedad y mayor contenido de materia seca. Adicionalmente, se estudió la efectividad de los tratamientos fisicoquímicos (temperatura, reducción de oxígeno atmosférico y uso de reactivos químicos) para la inhibición de la enzima Polifenoloxidasa en el tubérculo. Los resultados mostraron que los tratamientos térmicos, sin uso de agentes químicos, fueron la mejor opción para la inhibición enzimática. La determinación de las curvas de secado de la pasta de papa, con tratamiento previo, se llevó a cabo en un secador de túnel a 60 ºC y una velocidad de aire de 0.2 m/s. Los pre-tratamientos incluyeron escaldado, cocción y el uso de ácido ascórbico y metabisulfito de sodio. Los resultados indicaron que con la aplicación del tratamiento térmico al tubérculo fue suficiente para evitar el pardeamiento enzimático y además, se logra un menor tiempo de secado. Los datos experimentales fueron evaluados usando el modelo de Midilli observándose un buen ajuste con un R 2 > 0.99. Además, se comprobó que el método más óptimo para la producción de harina de papa involucra las siguientes etapas: cocción, enfriamiento y reducción de tamaño en seco. Esto garantiza una harina, que según los resultados de poder de hinchamiento, solubilidad en agua y absorción de agua, alcanza las características de almidón instantáneo lo cual favorece la formación de un puré de manera rápida. Los rendimientos en la producción de harina oscilan entre 12.55-14.09% para la Granola y entre 11.18-15.58% para la provento en base húmeda.Palabras clave: Harina de papa; Inhibición enzimática; Papa granola y provento; Curvas de secado; modelo de Midilli ABSTRACTIn this study, potatoes flour for instant purée was produced using national potato varieties Provento and Granola. For this, the moisture content of potatoes was determined; the results showed that the Granola variety has lower moisture range and higher dry matter. Also, the effectiveness of physicochemical treatments (temperature, reduction of atmospheric oxygen and the use of chemical reagents) was studied for inhibition of polyphenol oxidase enzyme in the potatoes. The results showed that heat treatments, without the use of chemical agents, were the best choice for enzyme inhibition. The determination of the drying curves for potato paste, with pretreatment, was conducted in a drying tunnel at 60 ° C and an air velocity of 0.2 m/s. The pre-treatments include blanching, cooking, and the use of ascorbic acid and sodium metabisulfite. The results indicated that the applying heat treatment to potatoes was sufficient to prevent enzymatic browning and also, a lower drying time is achieved. Experimental data were evaluated using Midilli model, showing a good fit with an R 2 > 0.99. Also, it was found that the optimal method for the preparation of p...

In this study, an antioxidant-rich extract was obtained by leaching Moringa oleifera leaves. The activity of the extract against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical was measured by determining a second-order rate constant (k2). The reaction between the mixture of antioxidants in the extract and the DPPH was monitored by measuring the absorbance at 517 nm in 30-second intervals for a period of 600 s. The absorbance exhibited a rapid decay within the first 100 s, followed by a slower decay. The absorbance data were fitted to a bi-exponential model. The curve fitting showed a linear relationship between the initial concentration of antioxidants and the reaction rate with the coefficient of determination values greater than 0.9979. The k2 value was 0.0870 ± 0.0007 mg/mL.