Selective adsorption of metabolites by different size of TiO₂ nano particles from tea infusion

Tea is rich in catechins, amino acids, and carbohydrates, which are the main flavor components of tea. However, excessive amount of catechins contribute to the bitter and astringent tastes of tea, thereby affecting the quality of tea. In this study, TiO₂ was employed as an adsorbent material to investigate its adsorption properties for different structural types of main flavor compounds in tea infusion. The results found that anatase-type TiO₂ had strong adsorption capacity for tea polyphenols, and its adsorption amount relied on the surface area of TiO₂ particles. After the addition of 60 nm TiO₂, the total catechins content in tea infusion decreased from 813.78 to 93.16 μg/mL. Meanwhile, the content of theanine and monosaccharides, the umami and sweet compounds of tea, was not affected. These results indicated that TiO₂ could serve as an adsorbent to exclusively remove the bitter tasting component catechins from tea and enhance their taste profile.