As observed from the literature, not much effort is made on increasing the content of healthy components of total polyphenols in teas by using post-treatment technologies based on nanoparticles (NPs). In this work, we report a new strategy on the green preparation of Au NPs from bulk Au sheets by employing a thermal reduction method in a solution containing chitosan (Ch) and trisodium citrate. The synthesized Au NPs are innovatively applicable for treating commercial teas at room and elevated temperatures for increasing the contents of their healthy components. Encouragingly, the content of the total polyphenols in the treated teas, including less oxidized oolong tea and fully oxidized black tea, can be significantly increased by ca. 100% and 30%, respectively, compared to corresponding untreated teas. In addition, the ability to scavenge free hydroxyl radicals for oolong tea can be enhanced by ca. 20% after the Au NPs-treatment. These results suggest that this alternative approach based on prepared Au NPs promises the availability of healthier teas.
