Revista Ciência Agronômica
On-line version ISSN 1806-6690
SOUSA, Kelly Aparecida de; RESENDE, Osvaldo; CHAVES, Tarcísio Honório and COSTA, Lílian Moreira. The drying kinetics of forage turnips (Raphanus sativus L.). Rev. Ciênc. Agron. [online]. 2011, vol.42, n.4, pp.883-892. ISSN 1806-6690. http://dx.doi.org/10.1590/S1806-66902011000400009.
A study aimed at determining the best mathematical model to describe the drying of forage-turnip seeds, along with the diffusion coefficient and activation energy under different air-conditions, was carried out in a randomized design with four replications. Seeds were harvested, having a moisture content of 0.36 (decimal bs) and then dried to 0.09 (decimal bs) in an experimental dryer at controlled temperatures of 30; 40; 50; 60 and 70 °C and relative humidities of 47.3; 26.2; 12.0; 10.1 and 5.1%, respectively. The effective coefficient of diffusion was calculated by F-test variance analysis and regression, adopting a 5% level of probability. The conclusion was reached that among the models analyzed, that of Midilli best fit the drying curves of forage-turnip seeds. The effective diffusion coefficient increases with temperature, with values of between 3.23 x 10-11 and 10.42 x 10-11 m2 s-1 for a temperature range of from 30 to 70 °C. The relationship between the coefficient of diffusion and drying temperature can be described by the Arrhenius equation which gives an activation energy of 24.78 kJ mol-1 for liquid diffusion in the drying process of forage-turnip seeds.
Keywords : Drying curves; Brassicaceae; Oilseed; Forage turnips.