MOISTURE ADSORPTION ISOTHERMS AND DRYING KINETIC OF PERSIAN CLOVER (Trifolium resupinatum L.) AND ARROWLEAF CLOVER (Trifolium vesiculosum) SEEDS

Resumo

The aim of this work was to obtain adsorption isotherms and to study the drying kinetics of persian clover (Trifolium resupinatum L.) and arrowleaf clover (Trifolium vesiculosum) seeds. The equilibrium moisture content and the moisture adsorption behavior were found by isotherms curves at 40, 45 and 50 ºC, and the Peleg model was the most suitable. The drying kinetics was determined by thin layer assays in an air parallel flow dryer at all three temperatures. In addition, the predominance of the falling drying rate period for the two species of seeds was observed, and the critical moisture content values were approximately of 0.20 and 0.25 g_water g_{dry matter}^-1 for persian clover and arrowleaf clover seeds, respectively. The effective diffusivity values were estimated in ranges of values of 3.61×10^-11 – 6.81×10^-11 m² s^-1 for persian clover and 6.76×10^-11 – 1.15×10^-10 m²s^-1 for arrowleaf clover seeds and the temperature effect was expressed by an Arrhenius relation. Thus, drying kinetics confirmed the greater difficulty in moisture removal from the arrowleaf clover seeds, compared to the persian clover seeds drying, in agreement with the results obtained through adsorption isotherms.