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Functional instant tea from black tea waste fiber: effects of extraction conditions on bioactive composition and in
Neriman Ezgi Cifte1, Gokhan Gorgisen2, Emre Taskın3
1Department of Food Engineering, Middle East Technical University, Ankara, Türkiye.
Introduction:
Black tea processing generates large amounts of waste fiber that still retains considerable levels of bioactive compounds. In this study, black tea waste fiber was valorized for the production of instant tea powders, and the influence of extraction conditions on both bioactive composition and anticancer activity was investigated.
Methods:
Instant tea powders were produced using hot extraction (100 °C, 6 min) and cold extraction (25 °C, 2 h). Catechins, gallic acid, caffeine, theanine, theaflavin and thearubigins were quantified. Anticancer activity was evaluated by the MTT assay using prostate cancer cell lines (PC3, 22Rv1 and LNCaP), glioblastoma cell lines (U87MG and A172) and the breast cancer cell line MCF7.
Results:
Hot extraction resulted in significantly higher levels of catechins, condensed phenolics and theanine (p < 0.05). In contrast, the extended extraction time applied in the cold method partially compensated for mass transfer limitations in the extraction of gallic acid and caffeine. The anticancer potential of the instant teas was evaluated in vitro using prostate cancer cell lines (PC3, 22Rv1, and LNCaP), glioblastoma cells (U87MG and A172), and breast cancer cells (MCF7). The hot-extracted instant tea infusion inhibited the proliferation of prostate cancer cells in a concentration-dependent manner (p < 0.05). Hot-extracted instant tea showed a particularly strong cytotoxic effect on U87MG glioblastoma cells, reducing cell viability to 2.7% at 1.25 mg/mL, whereas A172 cells exhibited greater resistance. In contrast, cold-extracted samples demonstrated stronger inhibitory effects on MCF7 breast cancer cells (p < 0.05).
Discussion:
These findings demonstrate that black tea waste fiber can serve as a valuable raw material for functional instant tea production and highlight the importance of extraction conditions in shaping both the bioactive profile and biological activity of instant tea products derived from tea processing residues.
