Modeling of polyphenols extraction process from green tea and the effect of temperature on the process

Two mathematical models of polyphenols extraction from green tea leaves were tested: Peleg’s model and First-order model. Thermodynamical parameters of the process were determined.
For the Peleg’s model we got the following analytical equation: Ct= t/(0.2570207+0.0324377*t). Ct is a concentration of polyphenols in extract at the time t. For the First-order model analytical equation describing the extraction process was as follows: Ct=23.09278*(1-exp(-0.1418264*t)). Goodness of fit of the both models were high but the first-order model prognosed equilibrium concentration of polyphenols in tea infusion with much more precisely than the Peleg’s model. Activation energy for the First-order model was equal to 2798 j/mol. Entropy change (ΔS) of this process was equal to 52 (J, (mol, K−1)), and enthalpy change (ΔH) was equal to 16304 (Jmol−1). The ΔG value gradually decreased as the extraction temperature increased, indicating that increasing the extraction temperature can make the extraction easier. First Order Model of tea polyphenols extraction was shown to be well describing the process. The most useful conditions for polyphenols extraction from green tea leaves were 70 ℃ and 20 min.