Este trabalho visa caracterizar a cinética de secagem de feijão carioca, cultivar BRS Estilo e Canadense e ajustar diferentes modelos matemáticos. O produto foi submetido à secagem em estufa nas temperaturas de 35, 55 e 65 ºC. Amostras foram colocadas em bandejas de metal com fundo telado, em três repetições. Durante o processo de secagem, as bandejas com as amostras foram pesadas periodicamente, até que atingisse a massa constante. Os modelos matemáticos foram ajustados aos dados utilizando o software Statistica 12.0, e os parâmetros para selecionar o melhor modelo foram: o coeficiente de determinação ajustado, o erro médio relativo e o erro médio estimado.
Spirulina platensis is a blue-green multicellular photosynthetic cyanobacterium and it is used in many countries as human and animal feed. The aim of this work is to determine and set kinetics drying for S. platensis at different temperatures (30, 40, 50 and 60°C). A completely randomized design was adopted and the treatments were the drying temperatures. S. platensis was furnished by the company, Brasil Vital, located in Anápolis-Goiás. The initial water content from the product was determined according to analytical norm from Association of Official Analytical Chemists (AOAC). The product was subjected to drying in a heater at temperatures of 30, 40, 50 and 60°C. The samples were placed on stainless steel removable trays with background screen; they consisted of three replications. The temperature and relative humidity from the air in the environment were monitored with a thermo-hygrometer. During the process of drying, the trays with samples were periodically weighed to obtain a constant weight. Afterwards, the math models were set on the experimental drying data, using Statistica 12.0 software. The criteria for the selection of the estimative statistics were: R 2 close to 100%, P < 10% and SE close to zero. The effective diffusion coefficient was obtained from the mathematical model of liquid diffusion. One can conclude that the necessary time for S. platensis to reach constant weight was 7.00, 4.58, 3.83, and 3.25 h, at temperatures of 30, 40, 50, and 60°C, respectively. The recommended model used to predict the drying phenomenon for S. platensis was the Midilli Mathematical model at temperatures of 30, 40, and 50°C, and the model Approach of Diffusion at temperature of 60°C. The diffusion coefficient increased with increased temperature; its values were from 3.343 × 10-8 to 14.881 × 10-8 m 2 s-1 at temperature ranging from 30 to 60°C. It activates energy for liquid diffusion at 39.52 kJ.mol-1 .
The present study aimed to determine and model the physical (orthogonal axes, circularity, sphericity and apparent specific mass), thermal (thermal conductivity, specific heat and thermal diffusivity) and aerodynamic properties (thermal experimental speed) of beans grains with different water contents. BRS cultivar were used as test crop and properties were investigated with seven water contents (32.9; 28.1; 24.9; 21.9; 18.9; 16.2; 13.6% dry based .b.). After data collection, mathematical models were set as experimental data. At the moment of choosing the best model, the following were taken into account: the adjusted coefficient of determination (R²) and average relative error (P). The outcome analysis showed that the orthogonal axes and beans grain circularity are directly proportional to water content reduction. Apparent specific mass decreased and sphericity remained constant, with increase in water content. Thermal conductivity, specific heat and thermal diffusivity decreased by 22.7; 12.7; 14.3%, respectively, when water content decreased from 32.9 to 13.6% d.b. The experimental terminal speed was increased by 15.3% when water content increased.
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