Abstract:
The chemical composition of tea, especially its dry matter content, caffeine, and
polyphenols, has a significant impact on its quality. The purpose of this study was to
examine the dry matter content, caffeine concentration, and total polyphenol content
(TPC) of specific black tea grades that were gathered from two main Sri Lankan teagrowing
regions: Ruhuna (low-grown) and Dimbula (high-grown). Standard ISO
methods were used to analyze four tea grades (BOP, OP, Dust, PF1), with ten samples
per grade collected from different factories. Total polyphenol content was measured
by the Folin–Ciocalteu method (ISO 14502-1) and caffeine by UV-Visible
spectrophotometry (ISO 3103). Dry matter was determined by oven-drying at 105 °C.
Significant differences were observed across regions and grades, with Dimbula BOP
showing the highest polyphenol content (24.55 ± 1.81% DW). Low-grown tea showed
lower TPC with Ruhuna OP (18.31 ± 1.30% DW). Caffeine was highest in Ruhuna PF1
(879.39 ± 39.54 mg CE/L (Caffeine Equivalents)) and lowest in Ruhuna Dust
(504.11 ± 6.51 mg CE/L). Dry matter ranged from 91.65 ± 0.79% to 96.56 ± 0.95%,
indicating consistent processing. These results clearly show that high-grown and lowgrown
teas have very different chemical compositions. Analysis of variance (ANOVA)
was performed using Minitab (2022), revealing statistically significant differences in
total polyphenol content (TPC) and caffeine content across tea grades and regions (F =
4.96-8.17, p < 0.001).These differences are extremely useful for creating analytical
tools, particularly sensor-based devices like electronic tongues (E-tongues) that can
distinguish between different types of tea based on geographic location. The chemical
variations identified in this study represent strong identifiers that can be integrated
into equipment calibration and classification models, thereby enhancing tea
authenticity verification and quality control.
