Valorization of Black Tea Waste Fibers into Instant Teas and Characterization of Their Bioactive Profile and Physicochemical Properties

Instant teas including their herbal derivatives, ginger and sage, from black tea waste fiber were produced to find an effective strategy to valorize massive tea waste. Brewing parameters for waste fiber were optimized to maximize extraction yield considering the hot and cold brewing processes based on the water-to-tea ratio (30:1 mL/g), particle size range (the average of 19.39 μm), brewing temperature, and time (100 °C for 6 min and 25 °C for 2 h). Despite the improving effect of hot brewing on the extraction of catechins, including the most abundant epicatechin, theaflavin, thearubigins, theanine, antioxidant capacity, and total phenolic contents of instant teas, cold brewing proved its potential in gallic acid and caffeine extraction. In addition to hygroscopicity and color, morphologies of the powders were evaluated for interpretation of the solubility and turbidity of instant tea infusions. This study offers an innovative waste utilization strategy and will promote further study on the cold extraction of other foods.