Key Points
- Researchers found that increasing HCO₃⁻ concentrations in brewing water transformed the chestnut-like aroma of green tea into a sweeter, cooked off-flavor, especially under high-temperature and prolonged infusion conditions.
- The study reinforced that both cations and anions in water—particularly total ion concentration—affect tea infusion quality.
- Higher ion levels correlate with diminished aroma purity, increased astringency, and degraded freshness due to chemical interactions with tea constituents such as catechins and theaflavins.
- These findings provide actionable guidance for selecting water sources in tea preparation and processing. Avoiding water with high HCO₃⁻ content can help maintain the aroma quality of green tea, with applications in both traditional brewing and industrial tea product formulation.
A team of researchers representing the Chinese Academy of Agricultural Sciences, Huazhong Agricultural University, and Xinyang Agriculture and Forestry University investigated the effect of hydrogen carbonate (HCO3−) on the aroma quality of green tea through a combined approach of sensory evaluation, headspace solid-phase microextraction, and gas chromatography-mass spectrometry (GC-MS) techniques. The findings will provide a basis for selecting ion indicators in water used for brewing tea as well as create a theoretical foundation for further in-depth studies on the mechanism of how brewing water affects the release of aroma in tea infusion. A paper based on this work was published in Food Chemistry: X (1).
Researchers have delved deep into exploring the effects of water's physicochemical characteristics to determine how water quality influences the taste and quality of tea infusion. Their findings reveal that pH level, mineralization, and hardness emerge as pivotal factors which contribute to the varying qualities of the finished product (2). These properties are intimately tied to the composition and concentration of ions present in water. Therefore, fundamental differences in the flavor profile of tea infused with various types of drinking water ultimately stems from the disparities in ionic compositions (3).
Studies concentrating on the ions in water have shown that the content and composition of ions in water will affect the quality of tea infusion, with the total ion content exhibiting a negative correlation with the quality of tea infusion (4). When there is a higher concentration of cations (a positively charged ion with fewer electrons than protons [5]) or anions (a negatively charged ion with more electrons than protons [5]) in the water, it leads to a decrease in the purity of aroma, an increase in a dull, overcooked flavor, a notable rise in astringency, and a decline in freshness and mellowness of the brewed tea, with specific concentration thresholds producing these effects varying depending on the type of ion involved (6).
Research on the impact of cations in water on the quality of tea infusion has found that their presence may promote the self-association of major flavor components in tea infusion, such as caffeine, polyphenols, and theaflavins, and result in the formation of tea cream (7). Cations in water were also found to accelerate the oxidative degradation of catechins during tea brewing, which further affected the flavor quality of the tea infusion, as well as influence the aroma quality by altering the content and proportion of aroma components (8–10). However, there is a lack of research on anions, which also significantly influence the flavor and quality of tea infusion, thus inspiring this study.
GC–MS conditions were as follows: inlet temperature 250 °C; high purity helium (99.999%) as carrier gas, flow rate of 1.0 mL/min; splitless injection. Temperature program: initial temperature 40 °C for 2 min; increased to 120 °C at a rate of 4 °C/min; rising to 260 °C at a rate of 30 °C/min; hold for 5 min. Mass spectra was recorded in electron impact (EI) ionization mode at 70 eV. The quadrupole mass detector, ion source and transfer line temperatures were set, respectively, at 150, 230, and 280 °C. The MS scan range was set at 30–350 amu.
The researchers determined that HCO3− in water exhibited a dose-dependent influence on the aroma quality of tea infusion, transforming the chestnut-like aroma into a sweeter, cooked off-flavor. The experimental results confirmed that water characterized by high HCO3− content was found to be unsuitable for green tea brewing. This effect was particularly evident under high-temperature conditions compared to room temperature, and it intensified over time. The presence of HCO3− in water changed the concentration of aroma components in tea infusion, resulting in a significant reduction in key compounds like β-ionone and dimethyl sulfide, which subsequently decreased the overall aroma quality. HCO3− also decreased the content of EGCG in tea infusion while increasing the content of GCG, and these changes were closely correlated with alterations in key aroma substances. The researchers believe that their study provides actionable insights for tea industry applications, enabling both smarter water source selection for differentiated tea varieties and quality enhancement in processed tea products like concentrates and extracts (1).
References
- Zhang, M.; Li, M.; Wang, F. et al. Effect of Hydrogen Carbonate in Brewing Water on the Aroma of Tea Infusions. Food Chem. X 2025, 29, 102758. DOI: 10.1016/j.fochx.2025.102758
- Xu, Y. Q.; Zou, C.; Gao, Y. et al. Effect of the Type of Brewing Water on the Chemical Composition, Sensory Quality and Antioxidant Capacity of Chinese Teas. Food Chem. 2017, 236,142-151. DOI: 10.1016/j.foodchem.2016.11.110
- Zhang, H. H.; Jiang, Y. L.; Lv, Y. J. et al. Effect of Water Quality on the Main Components in Fuding White Tea Infusions. J. Food Sci. Technol.2017,54 (5), 1206-1211. DOI: 10.1007/s13197-017-2571-2
- Cao, Q. Q.; Wang, F.; Wang, J. Q. et al. Effects of Brewing Water on the Sensory Attributes and Physicochemical Properties of Tea Infusions. Food Chem. 2021,364. DOI: 10.1016/j.foodchem.2021.130235
- Ion. Wikipedia. https://en.wikipedia.org/wiki/Ion (accessed 2025-07-23)
- Zhang, M. M.; Yin, J. F. Research Progress on the Effects of Ions in Water on Flavor of Tea Infusion. China Tea2023, 45 (08), 1-9, 17.
- Yin, J. F.; Xu, Y. Q.; Yuan, H. B. et al. Cream Formation and Main Chemical Components of Green Tea Infusions Processed from Different Parts of New Shoots. Food Chem. 2009, 114 (2), 665-670. DOI: 10.1016/j.foodchem.2008.10.004
- Yin, J. F.; Zhang, Y. N.; Du, Q. Z. et al. Effect of Ca2+ Concentration on the Tastes from the Main Chemicals in Green Tea Infusions. Food Res. Int.2014, 62, 941-946. DOI: 10.1016/j.foodres.2014.05.016
- Bai, F. Q.; Chen, G. J.; Niu, H. L. et al. The Types of Brewing Water Affect Tea Infusion Flavor by Changing the Tea Mineral Dissolution. Food Chem. X 2023, 100681. DOI: 10.1016/j.fochx.2023.100681
- Y.F. Ren, Z.H. Ye, X.Q. Liu, et al. Surface-Enhanced Raman Spectroscopy-Based Metabolomics for the Discrimination of Keemun Black Teas Coupled with Chemometrics. LWT 2023,181, 114742. DOI: 10.1016/j.lwt.2023.114742
