Foam ?


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Foam ?

Postby David R. » Nov 17th, '12, 12:38

When rinsing the leaves, some teas make more foam than others. Sometimes, when there is a lot, I can't help wondering if this is a bad sign or not. But the truth is that I have no idea what is actually going on. Does anyone have an explanation ?
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Re: Foam ?

Postby Drax » Nov 17th, '12, 13:29

I'll be curious what traditional views of tea will say on the topic, but from a scientific standpoint, I think it's difficult to determine good or bad.

For example, saponins are a naturally occurring plant chemical that can cause a soapy or foamy appearance in liquid solutions. They are a combination of sugars and sapogenins (the latter of which are derived from isoprene usually; biochemical pathways similar to hormones). How do these things alter the taste, texture of the tea? I don't know...! :D

And of course, there could be other non-saponins causing the foam, so that's a consideration as well.
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Re: Foam ?

Postby David R. » Nov 18th, '12, 04:43

Thanks Drax.
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Re: Foam ?

Postby HifideliTea » Nov 19th, '12, 04:05

Perhaps some of the many factors:

1) Temperature of the water
I am drinking a 92 raw yiwu today and it is flat, no sweetness at all, lots of aged temple taste (sandalwood incense and camphor pillars). I remembered that when I rinsed the first flush this morning, there was a lot of foam, and the water was not really hot (too lazy to reboil).

2) Sweetness of the teas
Sugar creates foam in teas?

3) Speed and height at which one pours the hot water to the teas
The higher and the faster the hot water is poured into the tea will cause foaming.
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Re: Foam ?

Postby tingjunkie » Nov 23rd, '12, 10:42

Can't comment on the chemistry or science, but the traditional wisdom assumes the foam carries the dirty stuff you don't want to drink, and that's why you're supposed to swipe it off with the gaiwan/teapot lid and get rid of it.
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Re: Foam ?

Postby David R. » Nov 24th, '12, 12:19

tingjunkie wrote:Can't comment on the chemistry or science, but the traditional wisdom assumes the foam carries the dirty stuff you don't want to drink, and that's why you're supposed to swipe it off with the gaiwan/teapot lid and get rid of it.


Thanks. I do that, but I recently encountered a puerh which was still giving me bubbles after many brews. This is like the 8th brew or so :

Image.
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Re: Foam ?

Postby wyardley » Nov 24th, '12, 13:23

The foam from the first round or two should be skimmed. I thin later on, though, it's just the saponins in the tea.
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Re: Foam ?

Postby tingjunkie » Nov 25th, '12, 01:32

Yep, bubbles and foam are different things. Just do the rinse and maybe first infusion, and don't sweat it. :wink:
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Re: Foam ?

Postby David R. » Nov 25th, '12, 08:21

Thanks you everyone ! :)
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Re: Foam ?

Postby needaTEAcher » Dec 1st, '12, 20:45

tingjunkie wrote:Can't comment on the chemistry or science, but the traditional wisdom assumes the foam carries the dirty stuff you don't want to drink, and that's why you're supposed to swipe it off with the gaiwan/teapot lid and get rid of it.


My teacher calls it "the breath of microbes", though from where I am sitting, I can't help but imagine millions of little critters drowning in a sea of boiling doom!

I am reading a book on tea and teaware from China, with English alongside the Chinese. They talk a bit about the foam, saying that in competitions way back when foam color and consistency were among the aspects judged. Apparently, white foam is a good thing, though I have never noticed a different color.
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Re: Foam ?

Postby brandon » Dec 1st, '12, 23:05

You were reading about a head of foam on whipped tea being judged, not saponin. Pretty sure the OP question has nothing to do with microbes, though. You can get this on Yancha straight from the roasting, or sealed in vacuum for years, just for example.
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Re: Foam ?

Postby Evan Draper » May 29th, '13, 16:15

I got yer dirty bubbles right here!
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Re: Foam ?

Postby gingkoseto » May 29th, '13, 19:13

Pectin contents in tea can cause foam, bubble, "tea pearl", whatever you call it. It's also responsible for some of the smooth, sticky mouth feel of a good tea. Tea with abundant organic fertilization (from nature or human given) tends to have more pectin than tea cultivated with synthesized fertilizer (which doesn't have the rich carbon-containing nutrients for pectin synthesis).

Tea dust and debris in tea could also cause foam/bubble kind of thing at the beginning of the session. But if it lasts till later infusions, I think it's more likely due to the good stuff in tea - and of course depending on how the tea tastes and feels in your mouth.
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Re: Foam ?

Postby wyardley » May 29th, '13, 21:00

The recommendation I received (from Michael at Tea Gallery, if memory serves) was to skim during the rinse, but not in later infusions. The reasoning was similar to what Gingko said - that is, the first infusion may contain some dust / impurities, but bubbles in later infusions are actually desirable.

Whether or not skimming the rinse actually removes anything objectionable from the tea is anyone's guess - I think you will be hard-pressed to find any actual research about this. Personally, I'm not that squeamish, but I also doubt that the rinse will really remove much in the way of dirt or impurities. I do it anyway, just because that's how I was taught.
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Re: Foam ?

Postby Evan Draper » May 31st, '13, 15:25

gingkoseto wrote:Pectin contents

Gingko, can you cite some stuff about pectin in tea? Never heard it mentioned before. I can see that pectin would increase viscosity, but I don't see how it would produce bubbles. Perhaps pectin is the glycoside moiety of tea saponin, and perhaps I'm talking through my hat.
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