Journal of Tea Science Research, 2025, Vol.15, No.1, 21-29 http://hortherbpublisher.com/index.php/jtsr 23 ultrasound-assisted extraction have enhanced yield, selectivity, and efficiency. For example, mechanochemical pre-treatment enables effective separation of caffeine and polyphenols and deep eutectic solvents enable simultaneous extraction and selective partitioning of theanine, catechins, and caffeine from tea residues (Yang et al., 2024). Ultrasound-assisted extraction and other recent technologies (microwave, pressurized liquid, supercritical fluid) also optimize the recovery of these bioactives, justifying their use in functional foods, beverages, and nutraceuticals (Li et al., 2022; Ashraf et al., 2023; Raghunath et al., 2023) (Figure 1). The polyphenol to caffeine ratio also provides the optimal balance between the stimulant and relaxing properties of tea products (Kim et al., 2025). Figure 1 Food applications of L-theanine (Adopted from Li et al., 2022) 3.2 Progress in the development of functional tea beverages Functional tea beverages are a rapidly expanding market, capitalizing on the health-promoting potential of tea bioactives. Advances in extraction and formulation technology have enabled the manufacturing of low-caffeine, high-theanine products and polyphenol-enriched beverages for targeted health benefits (Allameh and Orsat, 2024; Liang et al., 2024; Kim et al., 2025) (Figure 2). The use of pruned tea biomass and tea waste as a raw material for new foods and beverages and ingredients is also gaining ground, promoting sustainability and resource efficiency (Liang et al., 2024). The optimization of the ratio of polyphenol to caffeine is being used to tailor beverages to arousal or relaxation response (Huda et al., 2024; Kim et al., 2025). 3.3 Exploration of tea components in “Medicine-Food Homologous” products and health foods Tea components, especially L-theanine, polyphenols, and caffeine, have been increasingly involved in "medicine-food homologous" food—food that is both therapeutically active and nutritional (Wei et al., 2022). L-theanine, for instance, was demonstrated to possess antioxidant, neuroprotective, and mood-altering activities, which promote its role in functional foods and dietary supplements (Li et al., 2022). Meta-analyses establish that theanine and theanine-caffeine combinations can enhance cognition, mood, and sleep in healthy humans (Payne et al., 2025). The results form the basis for developing tea-based health foods for stress alleviation, cognition improvement, and sleep modulation.
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