Bioactive Compounds, Phytochemical and Microbiological Profile of Fermented Tea: A Comprehensive Review

ABSTRACT Tea, which is made from Camellia sinensis leaves, is a largely consumed drink and occupies a significant position in artistic practices, trade, and human diet. Among different processing styles, fermentation serves as the crucial process determining tea's biochemical composition, functional properties, and sensory characteristics. As opposed to straightforward oxidation, fermentation involves enzymatic as well as microbial transformations that vastly alter polyphenols, catechins, flavonoids, alkaloids, amino acids, and other components of tea. Similar changes produce unique flavor and aroma characteristics while, at the same time, adding tea's bioactivity. Data have proved that fermented teas, for example, Pu‐erh, dark tea, and kombucha, are richer in antioxidants, antimicrobials, and anti‐inflammatory agents than their unfermented counterparts. Also, microbial fermentation enriches tea with probiotics and bioactive metabolites that contribute to better gut health, lipid regulation, and protection against oxidative stress‐ related diseases. These health‐ promoting metabolites are particularly applicable in the modern environment, where consumers are increasingly preferring natural, functional properties with added nutritive value. Beyond physiological benefits, fermentation also enhances sensory appeal by developing complex flavors and aromas that increase consumer acceptance. The significance of fermentation is not limited to conventional tea species but also applies to new functional tea‐ grounded products, in which the optimization of fermentation conditions, including microbial strains, duration of fermentation, temperature, and oxygen content, becomes crucial factors for product quality. The recent progress in biotechnology, genomics, and metabolomics also offers opportunities into the microbial ecology and metabolic pathways responsible for the tea fermentation, creating room for invention and better fermentation approaches. This review evaluates the available information on how fermentation affects the chemical composition, functional properties, and sensory quality of tea. It also emphasizes how judiciously optimized fermentation can open up new directions for designing value‐added tea that adds to world demand for safe, sustainable, and health‐ promoting drinks.