Tea polyphenols at the sensory-functional interface: Bitterness, astringency, bioactivity and modulation through macromolecular interactions

Tea polyphenols, especially catechins, contribute to bitterness and astringency while also being widely investigated for potential health-related bioactivities. This sensory-functional tension affects consumer acceptance, product formulation and the development of tea-based functional foods. Although sensory studies and health-oriented studies have both advanced, their relationship remains insufficiently examined. This review examines them through a polyphenol-macromolecule interaction framework. In the oral cavity, such interactions help explain salivary protein aggregation, lubrication loss and astringent mouthfeel. In digestive and systemic settings, related binding events may contribute to enzyme modulation, membrane association, nutrient bioaccessibility and other biological activities. Of particular interest is the galloyl group, which has been associated with interactions with biological targets while also increasing bitter taste receptor activation and binding to salivary proteins. These effects are conditional rather than fixed, because processing, formulation, fermentation and aging can redirect polyphenol structure, availability and interaction behavior. This review integrates evidence on molecular perception, sensory evaluation, matrix effects, health-related activity and transformation strategies, and considers how bitterness and astringency might be reduced without eliminating the compounds with potential bioactivity.