water quality
If you don't know much about the water used for brewing tea, just choose qualified purified water; do not use alkaline mineral water .
(The water quality of commercially available mineral water varies depending on the water source and the brand. So-called "high-quality mineral water" may cause loss of functional components and inhibition of aroma in tea.)
Generally, soft water is used to brew "fragrant tea", while hard water is used to brew "aged tea" .
Step 1: The Effects of Alkaline Water on Tea
1. Effects on the color of tea liquor
green tea:
Under alkaline conditions, chlorophyll is easily destroyed (chlorophyll stability decreases at pH > 8.0) , causing the tea liquor color to easily change from bright green to yellow or dark yellow, resulting in turbidity , especially noticeable when brewed at high temperatures. Flavonoids (such as catechins) in green tea are easily oxidized in an alkaline environment, exacerbating the darkening of the tea liquor color.
black tea:
Theaflavins (bright orange-yellow) are easily oxidized to thearubigins (dark red) under alkaline conditions, and further generate dark brown, causing the soup color to change from bright red to dark and lose its transparency .
Other types of tea:
The color of oolong tea, white tea, and yellow tea may be darker due to alkaline water. The color of black tea (such as ripe Pu-erh) will become more turbid, and the color stability of aged aroma substances will also be affected .
2. Impact on taste and texture
Analysis reveals differences:
Tea polyphenols and caffeine: lead to insufficient concentration and bland taste . An alkaline environment inhibits the dissolution of tea polyphenols (bitter substances) and caffeine, reducing the bitterness of the tea soup.
Amino acids and sugars: Disruption of amino acid structure reduces the freshness and crispness.
Mineral influence: Alkaline hard water (containing more calcium and magnesium ions) combines with tea polyphenols to form insoluble precipitates (such as "cloudiness after cooling"), resulting in cloudy tea soup and a rough taste .
Balance of taste: It significantly affects the "richness" of tea soup for teas that rely on polyphenols to support their taste (such as raw Pu-erh tea and high-roasted rock tea), with no noticeable aftertaste and an overall taste that is bland and coarse .
3. Effects on aroma
Volatile aromatic substances: An alkaline environment may accelerate the degradation or transformation of aromatic substances (such as aldehydes and alcohols), resulting in a single aroma profile, especially in light-aroma teas (such as jasmine tea and Anji white tea), where the floral fragrance dissipates easily and may even develop a "mushy" taste.
Aged aroma and woody aroma: For fermented teas such as black tea and aged Pu'er, alkaline water may slightly highlight the aged aroma (pH>8.0) and suppress the fruity or honey aroma.
Step 2: The adaptability of different types of tea to water quality
1. The interaction between the physicochemical properties of water and tea components
- Hard water (>120 mg/L CaCO₃) : Calcium ions combine with tea polyphenols to form precipitates, reducing the astringency of tea soup (EGCG binding rate can reach 23%), but losing antioxidant activity (Food Chemistry, 2018); Magnesium ions promote caffeine dissolution, and every 1 mg/L increase in magnesium can increase the caffeine concentration by 0.8% (Journal of Agricultural and Food Chemistry, 2020).
- Soft water (<60 mg/L CaCO₃) : Theaflavin dissolution rate increased by 12%, and the brightness of the tea soup increased (L* value increased by 3.2), but the amino acid extraction efficiency decreased (Food Research International, 2019).
2. Supported by scientific experimental data
- Longjing green tea brewing experiment (TDS = 50 vs 300mg/L) : The amino acid content of the tea soup in the soft water group (1.2mg/mL) was significantly higher than that in the hard water group (0.8mg/mL), but the caffeine content was 18% lower (China Tea Processing, 2021); Sensory evaluation showed that the freshness score of the soft water group was 1.7 points higher (out of 9), while the body of the hard water group was 0.9 points higher.
- Research on water quality suitability for Wuyi rock tea : Water containing trace amounts of sulfate (20-50 mg/L) can increase the dissolution of cinnamaldehyde, a characteristic aroma compound of cinnamon, by 24% (GC-MS detection), and significantly enhance the rocky aroma (Tea Science, 2020).
3. Water quality selection recommendations (based on tea)
| Tea | Ideal TDS | Recommended pH | Key ion requirements |
| FTL Green Tea | 30-80mg/L | 6.8 | Ca²⁺＜15mg/L, Mg²⁺＜5mg/L |
| FTL Oolong Tea | 80-150mg/L | 7 | HCO₃⁻ 40-60mg/L |
| FTL Black Tea | 100-200mg/L | 6.8 | K⁺ 2-5mg/L, SiO₂ 10-15mg/L |
| FTL Pu-erh Tea | 50-120mg/L | 6.8 | Fe³⁺ < 0.1 mg/L |
4. Examples of the impact of special water quality
London tap water (high hardness) : When brewing black tea, the formation of oxalool-calcium complexes leads to "cold turbidity" appearing 30 minutes earlier, with the turbidity (NTU) of the tea reaching 12.5, which is significantly higher than that of the soft water group (NTU = 4.3) (Food Hydrocolloids, 2019).
Kagoshima hot spring water (containing sulfur) : Sulfides react with theaflavins to form methyl flavonoids, which reduces the umami intensity of sencha by 37% (*Journal of the Japanese Institute of Food Science and Technology, 2022).
The quality of water from a particular source can enhance the color, aroma, and flavor of local tea, but using local water requires systematic professional knowledge and is very costly. For non-professionals, mastering the basic principles of "soft and clean water + temperature control" is far more practical than pursuing famous springs from their place of origin.
The precise matching of water and tea is essentially a dialogue of geographical genes, which needs to be built on a multidisciplinary system of geology, food chemistry, heat transfer and other disciplines, and cannot be covered in just a few lines of web pages.
The UK-based AquaSim laboratory has simulated 12 core indicators of Tiger Spring water. However, it lacks the original spring's microbial community (such as Nocardia tea-loving bacteria), resulting in a 27% difference in post-fermentation flavor. In addition, the operation is complex: it requires mastering the "listening to the spring while boiling water" method (stopping the fire immediately when the water first boils), and a temperature error of more than 3°C will disrupt the flavor balance.