Interaction mechanism of theaflavin and various proteins on influence of tea cream formation: A study on spectroscopic measurements and molecular docking

In black tea beverage, the interaction between theaflavins (TFs) and proteins may lead to the precipitates' formation, affecting its clarity and shelf life. This study investigated interactions between TF and five exogenous proteins (fl-lactoglobulin (fl-Lg), zein, soy protein isolate, gelatin and collagen) by spectrometry measurements. The technique for order preference by similarity to an ideal solution (TOPSIS) was applied to select the optimal protein and TF concentration to prepare a high-TF tea beverage with high clarity. The results showed TF interact with forementioned proteins via static quenching process and the optimal combination was fl-Lg:200 mg/L and TF:200 mg/L. Noticeably, the selected TF concentration (200 mg/L) was 1.5 times higher than that of commercial tea beverage (80 mg/L). To obtain further insight of fl-Lg-TF complexes, UV-visible absorption and Circular dichroism spectroscopy were used to investigate the secondary structures changes in fl-Lg and molecular docking demonstrated the binding modes and main interaction forces of TF-fl-Lg.