Preparation and Characterization of Theasinensin A-Enriched Instant Black Tea

Instant black tea is widely used in both the food and pharmaceutical industries. However, traditional water-mediated preparation leads to the loss of theasinensin A (TSA), a characteristic compound of black tea. This study aimed to optimize the preparation of instant black tea using TSA content as the primary quality indicator. Through response surface methodology, the ideal extraction parameters were identified as 49% ethanol (v/v), extraction at 70 °C for 41 min, and a material-to-liquid ratio of 1:60 g/mL. Under these optimized conditions, the TSA content reached a maximum of 456.05 ± 4.45 mg per 100 g of instant tea powder, with the predictive model showing high accuracy (only 0.3% deviation from experimental values). The resulting instant black tea presented as a dark yellow powder, yielding a dark brownish-red infusion with a characteristically strong, thick, and astringent flavor profile. Compositional analyses indicated that the proposed preparation produced an instant tea with a high total polyphenol content, particularly rich in TSA. These findings provide a theoretical foundation for developing functionally enriched instant tea, offering promising potential for nutraceutical and specialized food applications.