Abstract

The objective of this study was to evaluate the drying kinetics of Pequi pulp (Caryocar brasiliense Cambess) at temperatures of 40, 50 and 60°C, and the thermodynamic properties for this process. Eleven mathematical models commonly used to represent the drying process of agricultural products were fitted to experimental data. The Fick's second law was used to determine the diffusion coefficients of Pequi fruits through the drying kinetics. The model of Midilli best represented the drying process of Pequi pulp. The calculated effective diffusivity was 4.69988 × 10^-14, 5.277436 × 10^-14 and 5.609491 × 10^-14 (m²s^-1) for temperatures of 40, 50 and 60°C, respectively, and the energy activation for the process was 7694.94 J mol^-1. The enthalpy decreased with increasing temperature, with values ​​of 5091.41, 5008.27 and 4925.13 (Jmol^-1) for temperatures of 40, 50 and 60°C, respectively. The entropy values ​​found were -251.01, -250.38 and -250.05 (J.Mol^-1K^-1) for the same temperatures. The values ​​obtained from the Gibbs free energy for the drying of Pequi pulp increased with increasing temperature. The obtained data were consistent to the drying process, and the mathematical equations were effective to explain the migration of water within the product.

Key words: Effective diffusivity, drying models, enthalpy, entropy, Gibbs free energy.