The Chemistry of Time: Flavor Evolution and Functional Health Benefits in Aged Tea

Aged teas (dark, white, and heavily baked Oolong) undergo significant transformations during storage, yet the industry remains constrained by a lack of scientific standardization. This review dissects how storage conditions influence flavor, health benefits, and constituent changes. It further evaluates vintage prediction and accelerated aging technologies, proposing the integration of Industry 5.0 to modernize the sector. Mechanistically, aging is driven by enzymatic oxidation, nonenzymatic reactions, and microbial metabolism. The degradation of flavanols drives the reduction of bitterness and astringency, while the formation of polymeric catechins and N-ethyl-2-pyrrolidinone-substituted flavanols (EPSFs) serves as the key marker of aging. Additionally, the synergistic balance between methoxybenzenes and accumulating volatiles, such as woody/herbal compounds among others, drives the formation of the aged aroma. Regarding environmental factors, temperature, humidity, and microbial participation drive material transformation. While high-temperature/humidity environments can accelerate transformation, they may compromise quality. In terms of health benefits, components formed after aging (e.g., EPSFs and theabrownins) demonstrate advantages in regulating gut microbiota homeostasis and improving glucolipid metabolism. Notably, aging time is not linearly positively correlated with flavor and health benefits, but rather possesses an optimal window. Although vintage prediction models have been developed, their generalization ability across batches of teas remains to be improved. In terms of accelerated aging, ultraviolet radiation and high-voltage pulsed electric fields can induce sensory profiles closer to naturally aged tea in a shorter time than microbial inoculation and wet-heat treatments. Concurrently, the introduction of Industry 5.0 paradigms may provide potential for addressing vintage fraud, achieving precise quality control, and promoting green development in the industry.