Influence of the drying temperature of menina brasileira pumpkin slices in the kinetic and thermodynamic parameters

Abstract

Pumpkin has great nutritional interest due to its content of carbohydrates, fibers, carotenoids and phenolic compounds. The menina brasileira pumpkin is commonly found in Brazil and has great susceptibility to degradation due to its high moisture content, which promotes the modification of the physical-chemical and sensory characteristics, increasing the proliferation of microorganisms and the disposal of this food. Therefore, this work aims to perform the convective drying of slices of menina brasileira pumpkin pulp at temperatures of 50, 60, 70 and 80 ºC, evaluating by means of empirical and semi-empirical mathematical models the effects in relation to drying kinetics and the thermodynamic parameters of the process. The drying kinetics was obtained by successive weighing of menina brasileira pumpkin slices allocated in a tray dryer adjusted to an air speed of 1 m s^-1. The kinetic data were adjusted to six mathematical models and the Second Fick's Law was used to determine the diffusivity coefficient of the material. Thermodynamic parameters were determined from the Arrhenius equation. It was observed that the increase in temperature reduced the drying time from 360 min to 180 min, increasing the effective diffusivity from 1.3526x10^-9 to 1.9352x10^-9. In addition, the Cavalcanti-Mata and Valcam models represented in a predictive and accurate way the behavior of the experimental data at all temperatures evaluated. Finally, from the thermodynamic parameters, it was possible to state that the dehydration process is endothermic and does not occur spontaneously.