The Influence of Water’s PH on Tea Liquor

Why did the green tea I brewed this time become red or light brown after a while? The most common responses are that you used too many tea leaves, you brewed it for too long, the water temperature was too high, and the tea leaves had gone bad. What else will you think of after discovering that these are not the causes of the changing of the tea liquor?

By chance, our drinking water in the tea room was replaced by a bucket of mineral water. It was no longer the purified water commonly used before. On this particular day, we received feedback regarding Premium Dragon Well Long Jing Green Tea from a tea friend that his tea liquor is red and tasteless. As usual, we took out the same batch of Premium Dragon Well Long Jing Green Tea samples and prepared to brew it with Gaiwan method. We made the first infusion, and the color and taste is stronger than before. However, when I was about to make the second infusion, we found that the tea from the first infusion turned light brown. What’s happening? We’ve kept every batch of green tea samples in the refrigerator for half a year. The green tea cannot oxidize or degrade. We proceeded to brew for the third and fourth infusions and had the same results. The tea liquor was first yellow-green, but quickly became light brown. The tea is tasteless, too.

One by one, we all started to check. The tea was 4g, the Gaiwan held 110ml, and the water temperature was 85°C. The tea has been kept sealed in the refrigerator, and the color of the tea remains the same. At the moment, our colleague was brewing last year’s Premium Dragon Well Long Jing Green Tea with her mug. Her tea was even not kept in a refrigerator, and the color of her tea liquor was normal. There’s no way this year’s tea went bad.

We decied to brew her Longjing again with Gaiwan. This time, her tea liquor changed too. We were shocked, and the only difference was water. In the past, we used the purified water, but this time we replaced it with a bucket of mineral water.

We rebrewed the same batch of Longjing using our previous water, tea leaves, water temperature, Gaiwan, and brewing time. This time, the liquid has a regular yellow-green color. And there is no discoloration.

Everyone was shocked. We used to respond to consumer letters but never considered water. Different water produces different tea liquid, therefore the color and flavor are fundamentally different.

We purchased PH testing paper (also known as litmus paper) to measure the PH-value of these two types of water. We may use PH to quickly determine if an aqueous solution is acidic, basic, or neutral.

Finally, we discovered that the PH value of mineral water is 8, while the PH value of our purified water is 6. So, it demonstrates that the higher the pH of the water, the darker the tea liquid produced.

We checked several sources and discovered that the pH of water and mineral ions influences the solubility of soluble components in tea, particularly mineral ions. Mineral water’s high ionic strength inhibits the dissolution of soluble compounds. From this angle, there is less disintegration, and the tea liquid color appears to be lighter. However, the mineral water that is often appealing is generally alkaline. Both mineral ions and alkaline pH increase polyphenol oxidation. In other words, when tea is brewed with mineral water, the polyphenols oxidize more quickly and the color darkens.

All in all, water is the mother of tea. The varying acidity and mineral content can alter the color and flavor of tea.