Kinetics and Thermodynamics of Total Polyphenolic Compounds Microwave Assisted Extraction from the Roots of Ximeniaamericana (Olacaceae)

In this study the effect of temperature, kinetic and thermodynamic parameters of the total polyphenolics microwave assisted extraction (MAE) process of the roots of Ximeniaamericana were evaluated for different temperatures. The total polyphenolic content increased with increasing irradiation extraction time and temperature. The highest extraction temperature and longest irradiation extraction time of 80C and 120 sec resulted in the highest total polyphenolic of 5013.07 11.25 g GAE/g. DW. The kinetics of the microwave assisted extraction process was tested by pseudo- first-order, pseudo-second order and Ficks Law. It was shown that extraction of total polyphenolic of Ximeniaamericana roots could be described by the pseudo-second order kinetic model. Besides that, the result of the initial microwave assisted extraction rate (h) calculated at each microwave temperature show that the initial rate at 80C extraction temperature was almost six times higher than that of 30C; the effective diffusion coefficients (Deff) identified for different temperatures (303353K: Deff ranged from 2.215 10-13 to 7.232 10-13 m2/s) increased with increasing temperature; The dependence of the mass transfer coefficient of the microwave assisted extraction process on temperature verified by using Arrhenius model in its linearized form show a value of activation energy Eaof 14.436 kJ/mol with a high determination coefficient (R2 = 0.859, Pless than0.05). The thermodynamic study shows that the variations of enthalpy and entropy were positive; indicating that the process was endothermic and irreversible while Gibbs free energy was negative, indicating that extraction was spontaneous and thermodynamically favorablewith exception to extraction at 30 and 60 C.