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Blog 154: Wuyi Oolong: “White Foam” Means Good Quality??

What’s the ultimate definition of a good Wuyi oolong?

We’ll never get a perfect answer for an open-ended question like this.

For example, what defines a good car? Different car enthusiasts would have different answers. Some might say the absolute top speed should be the most important criteria; other might say that the level of comfort is more important.

When it comes to tea, the definition of “good” is subjective as well.

While finding the absolute “perfect tea” is impossible, experienced tea makers still manage to put together a list of qualities a good tea should have. For instance, in Wuyi oolong, a good tea needs to have a distinct set of floral and fruity aromas, a taste profile based on the respective cultivar characteristics, clear and transparent tea soup, etc…

But of course, sometimes we come across some bizarre claims such as “the white foam on tea soup indicates a good Wuyi oolong”.

Is this claim true? Today, let’s discuss this “white foam”.

What is the white foam?

When we infuse a Wuyi oolong with hot water, some white bubble would appear on the surface of the tea soup. Normally, an experienced tea drinker would use the lid of the the Gaiwan to clear the bubbles.

These bubbles, or the “white foam”, are the result of a nutrient substance called tea saponin. Tea saponin can be found in the root, stem, leaves and seeds of a tea plant. As a natural substance, tea saponin can generate long-lasting bubbles in water.

Tea saponin is quite active. According to our research, in water temperature between 20℃/68℉ to 90℃/195℉, tea saponin’s ability to generate white bubbles rise nearly perpendicularly.

Characteristics of tea saponin

To generate white bubbles, there are three major preconditions needed.

First, tea leaves must have tea saponin. Of course, as long as it’s a normal tea product, it should have some tea saponin content.

Second, some vibration is needed. When dry leaves are infused, leaves would clash with each other. Subsequently, leaves generate some vibration. Stronger the vibration, higher the probability of developing more bubbles, and vice versa.

Third, the water temperature must be high enough. Higher the water temperature, more bubbles generated.

Therefore, almost all Wuyi oolong, regardless good or bad quality, can generate white bubbles. Obviously, “white foam/bubbles means good quality is unsound.

Bitterness is tea saponin’s theme

The bitter taste of tea saponin is similar to caffeine. However, bitterness is never the criteria of a good Wuyi oolong. A good Wuyi oolong should be aromatic, clear, pleasant, and alive.

If “a good Wuyi oolong has more white bubbles” is true, then tea saponin content should be as high as possible. As a result, tea should definitely taste bitterer.

Is a bitter tea really a good tea? Of course not.

One more thing…

In ancient times, “tea form” was regarded as a sign of good quality. There were many poems praising the beauty of tea foam. (such as 《荈赋》written between 266-316: “惟兹初成,沫沈华浮。焕如积雪,晔若春敷)

Nonetheless, modern tea-making and tea-drinking has an entirely different system. Tea foam is no longer regarded as a sign of quality.

We hope you enjoyed today’s blog. As always, if you have questions or suggestions, please leave a comment, tweet us @valleybrooktea or email the author directly at Please also follow us on Instagram @valleybrooktea and join our mail list to get our daily tea updates and our latest promotions!

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