Effects of brewing conditions on the sensory and chemical properties of Turkish black tea and their interrelationships

Abstract

This study investigated the effects of different brewing conditions on the sensory and chemical properties of Turkish black tea and examined the relationships among the related parameters. The brewing variables evaluated were teapot type, brewing method, teapot spout condition, brewing time, and brewing water temperature. The brewed tea samples were evaluated by seven trained panelists for colour, astringency, and flavour and analysed for major chemical quality parameters, including total phenolic content (TPC), caffeine, theaflavins (TF), thearubigins (TR), brew colour indices, and L*a*b values. A total of 2,688 cups of brewed black tea were prepared, of which 672 were control and 2,016 were test samples, and were evaluated by seven trained panelists. Among the sensory attributes, colour was the most responsive parameter, being significantly affected by teapot type and brewing water temperature (p < 0.01), whereas astringency and flavour were not significantly influenced by the tested brewing conditions. In the chemical analyses, brewing water temperature was the most influential factor, significantly affecting TPC, caffeine, TF, TR, total colour in the brew, brightness in the brew, and a* (p < 0.01). Teapot type, brewing method, teapot spout condition, and brewing time also showed selective effects on specific chemical variables. Correlation analysis further showed that sensory colour was positively associated with TPC, caffeine, TF, TR, brightness in the brew, and total colour in the brew (p < 0.01), whereas astringency and flavour showed limited or no direct associations with the analysed chemical parameters. By examining Turkish-style brewing variables together with sensory and chemical profiling, this study provides novel evidence on sensory-chemical relationships in black tea and offers practical guidance for optimising brewing conditions in research and traditional tea preparation.