Why does my tea foam?

Is tea supposed to foam? If your tea builds some foam you may wonder what happened. Is it still safe to drink it?
In this post you’ll learn what this foam is, some ways to prevent it and why you don’t need to worry too much about it.

You do everything right to make yourself a nice cup or pot of tea: you choose a good tea, pour some water in the proper temperature…
only to find that the surface has an unexpected layer of white foam!
Did I miss to rinse the dishwasher?”, ”Was my tea treated with harsh chemicals or pesticides?”, you may think.
Well, actually, you did nothing wrong and your tea didn’t turn bad.

Is tea supposed to foam?

Yes, it isn’t unusual for tea to foam because it contains saponins.
Saponins are chemicals that produce soap-like foam when added to water.

While there are manmade saponins (for example the ones used to make detergents or soap), they also occur naturally in a wide range of plants, like in tea plants.

Tea also has tannins that may also produce some foam.

That’s why it’s absolutely normal if your tea builds some foam on top.

In fact, the traditional preparation of matcha takes advantage of this saponin content: matcha is whisked to form a foamy layer that makes it taste milder.

Whisking matcha
The traditional preparation of matcha involves whisking to foam the tea

Why is my green tea foaming?

Tea leaves naturally contains saponins and tannins, both natural, bitter compounds that produce foam when mixed with water.
Because of this, tea, both green tea and black tea, may form some foam.
Since black tea contains more saponins and tannins than other tea varieties, they often produce more foam.

In China, where tea foam is sometimes desired, some types of tea are processed so they produce more foam.

Also, broken tea leaves may produce more foam.

But tea foam on its own isn’t a red flag: it doesn’t mean the tea was treated with pesticides nor it makes your tea taste worse.

TIP: if your tea has foam and it tastes bad, check if you are steeping the tea for too long or if the water temperature is too high.

Can I drink tea with foam?

Yes, the tiny bubbles that may appear on the top of tea come due to the natural saponins and tannins content of tea.
Many foods contain saponins and tannins and they are considered safe for humans:

Saponins

Not only are saponins considered safe; they may offer some health benefits like lowering cholesterol levels, acting as an antioxidant, expectorant and the anti‑inflammatory.

Other common food that contain saponins are for example beans, legumes (also peanuts), garlic, asparagus, spinach or red wine.

Tannins

Tannins are phytochemicals that belongs to the group of polyphenols.
You may have heard of the benefits of polyphenols, which are similar to them of saponins: they are known for having antioxidant and anti-inflammatory effects.

Downsides of saponins and tannins

Since we’ve seen the benefits of these natural components of tea, let’s also disclose that they may also have some potential downsides:

Saponins and tannins were originally evolved as a defense system from the plants, so they are poisonous for some herbivore insects.
Also people with sensitivities may get also some discomfort like nausea or stomach ache from tannins, specially if drinking tea with an empty stomach.

The tannins content of tea varies depending on the sort (black tea has the highest levels; green the lowest).
However, regular tea leaves have a quite low saponins content (0,1%).

Can I prevent tea from foaming?

Some people say tea foams more when you use mineral rich, hard water, as it happens with tea cum (that oily looking film that sometimes forms on the top of tea).
But in my experience, this isn’t the case at all: you may use the same type of tea, water and anyway get more or less foam (or even don’t foam at all).

The first time I noticed foam on my tea was as I was cold brewing an organic green tea. I had already prepared the same tea several times without getting any foam:

The tea and the water (a store-bought, very soft water) were the same, but for some reason, this time the tea produced quite a lot of foam…

At first I was a little bit alarmed, until I read on many tea forums from Japan that this foam is not only harmless but also quite normal.

However, I forgot to take pictures of that foamy tea.
And interestingly enough, after that I wasn’t able to get the foam again as I tried to replicate it to illustrate this post

At least at first.

Then I remembered that the day I got the foam, I was in a rush, so I poured the water quite carelessly, opposed to how I normally do when preparing my best teas (slowly).

I then tried 2 different things to make tea with foam:

  1. Poured the water from a height (and also, in a big stream)
  2. I shook vigurously some tea in a bottle

Both produced the kind of foam I casually got the first time.

And actually, it makes sense: when we want to foam soap, we mix the soap with some water and also air.

So, my theory is that if you want to avoid your tea from foaming, you should pour the water carefully (and also don’t shake it if you are putting it in a bottle).

What does it mean if there’s bubbles in your tea?

We’ve seen it’s quite natural for tea to form what’s called “tea foam”.

And as tea drinking has such a long tradition, it’s easy to imagine there are more than one saying about its foam:

  • In ancient China, this foam layer was considered a treasure.
  • In England, some say that bubbles in the cup mean imminent love, every bubble symbolizing a kiss. Others say that bubbles in your tea means money is coming to you.

This makes tea foam more fun, right?

TRIVIA:
Since we are talking about bubbles in tea, nowadays the term “bubble tea” is commonly used for boba tea (milk tea with tapioca balls).
But did you know that the “bubble” in the name doesn’t come from the small tapioca pearls, but rather from the fact that the tea was originally prepared shaking it (thus it formed tiny bubbles)?

Conclusion

Tea naturally contains saponins and tannins, which may produce some foam.
This foam is safe for humans and the compounds that produce them may even offer some interesting health benefits.
So, the next time you see some foam on your tea don’t worry and just enjoy your cup of tea!
However, if you want to prevent foam in your tea, try by pouring the water slowly. While this isn’t a guarantee you won’t get foam, it usually helps.

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One Comment

  1. How interesting to learn about the benefits of saponin and tannins! I had never thought much about them, and now I’m glad knowing they are responsible for the foam and that I don’t have to worry about it. Thank you!

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