ISOTERMAS DE DESSORÇÃO E CINÉTICA DE SECAGEM DE SEMENTES DE PIMENTA DEDO DE MOÇA (Capsicum baccatum var. pendulum)

Abstract

Dedo de Moça pepper seeds (Capsicum baccatum var. pendulum) are rich in vitamins and medicinal compounds. Furthermore, they play a relevant role in food supplements and in cosmetic and pharmaceutical industries. Studies show that the drying process of these seeds reduces the amount of water at suitable levels, aiming to prolong their lifespan and maintain their physical, chemical, and nutritional characteristics. This paper aimed to study the isotherms of desorption and the drying kinetics of Dedo de Moça pepper seeds, by simulating mathematical model adjustments to experimental data, under different temperatures and water contents. Thermodynamic properties related to temperature and water content were also evaluated. Static gravimetric method with saturated saline solutions was used under air-controlled temperatures at 30 °C, 40 °C, 50 °C, and 60 °C and equilibrium relative humidity from 11,22% to 97,26% to obtain the isotherms of desorption. Seeds were weighed daily until they reached a constant mass. Mathematical models were adjusted to the experimental data by nonlinear regression analysis by the Gauss Newton method. Drying kinetics was carried out by gravimetric analysis of samples, also under air temperatures at 30 °C, 40 °C, 50 °C, and 60 °C. Mathematical drying models were also adjusted to the experimental data by nonlinear regression. The significance of the regression parameters by the t test at 5% probability of significance, the magnitude of the determination coefficient (R²), the relative mean error value (P) the mean estimated error value (SE), Akaike criterion (AIC), Schwarz Bayesian criterion (BIC), and the behavior of the waste distribution were considered to select the models. The Halsey model was the one that best fit the isotherms of desorption, with R2 values ranging from 92.75% to 99.01%, P values ranging from 0.49 to 1.97, and SE values ranging from 0.007 to 0.03. The integral isosteric heat of desorption showed behavior inversely proportional to the water content in the seeds after the experiment, with values from 2365.59 to 2736.26 kJ kg-1The Medill model was the one that showed the best adjustments for representation of seed drying kinetics of Dedo de Moça pepper seeds considering the statistical criteria. The effective diffusion coefficient increased with the elevation of drying air temperature, ranging from 0.751 10-10 to 2.882 10-10 m2s-1. The activation energy value was 39.02 kJ mol-1. The increase in drying air temperature caused a decrease in enthalpy and entropy values and an increase in Gibbs free energy values.