Abstract
Green tea has traditionally been evaluated based on low-molecular-weight constituents such as catechins, caffeine, and theanine. However, tea leaves are structurally organized matrices comprising cellulose, hemicellulose, pectin, heterogeneous tea polysaccharides, proteins, and associated phenolic compounds. This natural polymer matrix regulates water penetration, swelling, diffusion, extraction, structural disruption, molecular interactions, and the gastrointestinal release of bioactive compounds. This review integrates green tea processing, brewing, matcha micronization, polymer-polyphenol interactions, and digestion from a matrix-centered perspective. Conventional green tea infusion is considered an extraction-based system in which soluble compounds are transferred into the beverage, while most of the insoluble cell-wall matrix remains in the spent leaves. In contrast, matcha is a whole-leaf particulate system in which both soluble constituents and the polymer-rich solid matrix are ingested. Particle size affects the accessibility and digestive release of polyphenols and polysaccharides, although finer particles do not necessarily provide greater bioaccessibility. Interactions between catechins and cell-wall polysaccharides, tea polysaccharides, and proteins may further influence their stability, solubility, aggregation, and release during digestion. Unreleased matrix-associated polyphenols may reach the colon and undergo microbial transformation, but direct evidence in matcha remains limited. A conceptual framework linking processing, matrix structure, molecular interactions, digestion, and bioaccessibility is proposed. Future research should directly compare infusions and matcha from identical raw materials and apply standardized gastrointestinal digestion,…
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