Establishing a keemun black tea brewing control chart based on consumer acceptance via survival analysis and degree of satisfaction-difference method

Abstract

The optimization of brewing technique and brewing criteria for the globally popular Keemun black tea (KBT) has not been established. Herein, extraction yield (EY) and total dissolved solids (TDS) are employed as quality indicators to evaluate the quality of a cup of KBT. A KBT brewing control chart is designed with the “ideal” zone of EY defined from 3.50 to 6.50 g/g and that of TDS defined from 0.14 to 0.25 g/g, via survival analysis of tea consumers (n = 245). Thereafter, tea/water ratio is optimized to 1:45–1:20 g/mL via response surface methodology, and the brewing time is regulated to be within 16–38, 0–15 and 0–30 s to achieve the ideal quality KBT infusions freshly brewed for the first, second and third time, respectively, with the temperature controlled between 95°C and 100 °C. A relationship between consumer acceptance, quality indicators, and brewing parameters is visualized using the KBT brewing control chart. The KBT infusions located in the “ideal” zone and using optimized tea/water ratios are verified by consumers (n = 80) via the degree of satisfaction-difference method. The KBT brewing control chart is established in this study, and the brewing parameters are optimized as a useful reference for tea consumers when brewing KBT.