Mathematical modeling and thermodynamic properties in drying okra

Abstract

Okra is a vegetable that stands out agronomically due to its fast vegetative cycle, of high yield, besides presenting considerable nutritional value. Due to its composition and to be consumed still green, its useful life is quite short, requiring some conservation process to maintain acceptability. In this sense, the objective was to dry the okra in slices, approximately 2 mm thick, at temperatures of 50, 60, 70 and 80 ° C, adjust mathematical models to the experimental data and determine the diffusion coefficients, activation energy and thermodynamic properties. It was observed that the increase in drying temperature at 30 ° C reduced the total process time by 50.55%. Among the mathematical models tested, the Midilli model presented the best parameters of adjustments to the experimental data. The effective diffusion coefficients increased with increasing temperature, in the order of 10-11 m2 s-1, and their dependence on temperature was described by the Arrhenius Equation, which indicated an activation energy of 26.12 kJ mol^-1. The enthalpy and entropy values ​​decreased with the increase of the drying temperature, while the Gibbs free energy was increased in the temperature range evaluated.