Determinação de parâmetros de transferência de massa e de propriedades termodinâmicas na secagem curcuma longa L. usando a técnica de refractance window

Abstract

The Curcuma Longa L. rhizomes (CL) presents a significant amount of starchy, lipids, vitamins, minerals and important bioactive compounds. The CL is an aromatic spice with natural dye action. However, these rhizomes are perishable, requiring dehydration treatment. The drying by Refractance Window (RW) is a very effective technique in the dehydration process. As far as we know, no information about dehydration or parameters prediction of mass transfer and thermodynamics of CL using this technique is available in literature. Thus, this study had as objective to determinate mass transfer parameters and thermodynamics properties that control the dehydration process of the Curcuma Longa L. by Refractance Window in different temperatures. (70, 80, 90° C), through applicability of the analytical model developed by Dincer e Dost (1995). It was observed that the dehydration process of the samples occurred in a small period. The unity content in natura was 80.71±1.12% (b.u) and of the dry product varied from 20.81 to 17.34% (b.u). The CL samples submitted to drying with exhaustion obtained a small influence on the drying fees when compared to the samples with no exhaustion. According to the model of Dincer & Dost, diffusivity of moisture varied from 5.21 × 107 m².s-1 to 12.89 × 107m².s-1 without exhaustion and 7.89 × 107 m².s-1 a 19.67 × 107m².s-1 with exhaustion and the mass transfer coefficient varied in the range of 9.79 × 105 to 6.73 × 105 m.s-1 without the exhaustion and 8.86 × 105 a 0.51 × 105 m.s-1 with exhaustion. All the entropy values (ΔS) obtained related to the drying of the CL by RW were negative (ΔS < 0). The study showed that the exhaustion system had a small influence on the mass transfer flee during the drying of the CL sample. The thermodynamics properties pointed to a nom spontaneous process with positive values of enthalpy and free energy of Gibbs, and negative values of entropy.