Modeling and comparison of extraction kinetics of 8 catechins, gallic acid and caffeine from representative white teas

- Extraction kinetics of typical ingredients in feature white tea.
- Structure transformation between epicatechins and trans-catechins.
- Peleg's modeling of extraction kinetics and condition optimization.

In this work extraction kinetics of typical ingredients in representative white teas was investigated. Aqueous extraction of 4 epicatechins (EGC, EC, EGCG, ECG), 4 trans-catechins (GC, C, GCG, CG), gallic acid (GA) and caffeine at 65 °C, 75 °C, 85 °C, 95 °C respectively from Fuding Silver Needle (FSN), Fuding White Peony (FWP), Zhenghe Silver Needle (ZSN) and Zhenghe White Peony (ZWP) was examined. The total catechins, gallic acid, caffeine, EGCG, epicatechins, trans-catechins were compared in terms of rate, peak value, peak time and the extraction kinetics at different temperatures. It is exhibited that the contents of 8 catechins in ZWP, ZSN and FSN follow the order of EGCG > ECG > GC > EGC > GCG > CG > EC > C, and that in FWP is EGCG > ECG > EGC > GC > EC > GCG > CG > C. Structural transformation from epicatechins to trans-catechins and dissociation of gallic acid were observed during extraction by data analysis. Extraction kinetics over 240 min period were successfully modeled using Peleg's model with low MSR (0-2.232) and high R2 adj (0.903-0.999). Optimal extraction conditions (FSN(43.3 min, 95 °C); FWP(43.3 min, 95 °C); ZSN(53.8 min, 95 °C); ZWP(41.5 min, 95 °C)) were suggested by Peleg's model. As a result, this study will facilitate quality control of white tea during processing.