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Comment by JasonCEC | Hacker News Reader

I work with tea both professionally[0] and semi-professionally[1] and will clarify that:

- this is for commercial tea, not specialty or "ceremony" grade tea

- all of the big commodity houses, blending houses, brand buyers, etc have their own modifications on the standard, and this ISO tea prep standard is most definitely not the "standard"

- From elsewhere in the thread: all great tea can be brewed with boiling water. The idea that green tea (or any other type of whole leaf tea) should be brewed with something under ~100C is a technique used by merchants to sell you bad tea.

[0] www.gastrograph.com

[1] teatechnique.org/

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> From elsewhere in the thread: all great tea can be brewed with boiling water. The idea that green tea (or any other type of whole leaf tea) should be brewed with something under ~100C is a technique used by merchants to sell you bad tea.

Is this "can be brewed" as in you will end up with a beverage that is drinkable, or that you think that in general green tea is fine to be brewed at 100C. The former I can understand (especially with cheap bagged green tea) but I'd be very surprised at the later considering that goes against pretty all modern and traditional guidance I've heard or read.

Tl;dr: yes, use boiling water on very high end Chinese green tea for best results.

Longer Explanation:

In the Chinese tea tradition, water temperature is referred to by the size of bubbles during boiling (crab eyes = small bubbles (cooler) vs fish eyes = large bubbles (hotter)).

In theory, all water at boil is 100°c, but in practice, there is often a temperature gradient within a kettle and only the gas (the bubbles) is at exactly 100°c (assuming you're at sea level), which is why even some culinary recipes will call for a "rolling boil".

In any case, the strength of the stream when pouring will have a greater effect on the resulting flavor profile of very good green tea than the variation in bubble size, as bubble size is a variance of ~2°c while water can lose up to 5°c in a high slow pour.

Thus, boiling water at crab eyes with a thin slow (but not high) pour is the method used for high end Chinese green tea amongst high level Chinese tea practitioners.

What about high end Japanese green tea? Are they the same?

They are not! Sencha should be brewed with off-boiling water, anywhere from 85 - 95°c (which is still a higher temperature than low end sencha).

What accounts for this difference?

High-end sencha is steam processed at a lower temperature. Steam only gets to ~100°c depending on altitude and that is the highest temperature it is exposed to throughout its production.

High-end Chinese green tea is partially processed in a wok to denature the oxidizing enzymes. The saying for Chinese tea is that "tea remembers the heat of the wok", which is the pan frying process at upwards of ~200°c.

So all wok processed green tea can be brewed with hotter water than steam processed green tea.

Okay, I'm familiar with measuring temperature by the eyes and I get your point (which essentially seems to be the same as traditional guidance i.e. don't steep the tea in boiling water. You're just accounting for the variance in temperature from boiling and pouring) but I'm not sure I follow how this means merchants are trying to sell you bad tea.

Plus there doesn't account for other green teas that aren't poured in accordance with Chinese tea ceremony, such as the Nepalese green I had earlier today.

That is only partially correct;

Yes, the general idea is to adjust your boil and pour method for the type of tea you're brewing, but that is true for all tea. Water will lose the same heat under the same conditions whether you're brewing oolong or green tea.

To summarize the points addressed here:

- High-end Chinese green tea can be brewed with "boiling water" just as oolong or black tea can; the adjustments are within the range used for other classes of tea.

- Merchants recommending cooler water for green tea do so to reduce the astringency and/or grassy flavor found in lower quality tea.

- Nepal does not have a historical tea tradition and the cultivation of Nepalese green tea is a modern development. Nepal inherited its tea habits from India whom had it imposed on them by the British who stole the seeds from China. While Nepal produces good tea on par with Darjeeling, it does not compare to the highest end Chinese green teas, which are an order of magnitude more expensive, if not more.

I was under the impression that this document exists to have -a- standard such that if followed before performing some sort of experiment whether directly tea related or not, you could more easily exclude preparation differences as a confounder when comparing results with people who'd also followed the document.

Certainly this is how the old coworker who had a paper copy pinned up behind their desk explained it to me, and that understanding was why they found its existence so amusing even if their preferred cuppa's preparation process was substantially different.

This could of course be entirely wrong but seeing the paper copy pinned to the wall always did make me smile.

You are correct;

My point was that outside of the most commodity level tea sourcing, no one uses these "standards".

This is not used for tea sourcing. The document explicitly states its purpose as being for the preparation of tea for sensory tests. It has nothing to do with brewing tea for enjoyment.

Sensory testing (which is what is what I and my company specialize in) is a large component of tea sourcing and absolutely part of the process.

To illustrate this:

Just as coffee has "cupping", a method of preparation used for sourcing and evaluation but which no consumer would ever use to prepare coffee for enjoyment....

Commodity tea has this ISO standard (also called cupping).

The reason that this method, over a method that results in a better tasting cup is used, is because commodity tea is selected via flaw minimization and consistency testing.

That's precisely what I explained, yes.

I'm unsure why you presented the entire point of the conversation as if it was a gotcha, but assuming it was a genuine mistake I can only suggest that you read my comment again.

I made the other comment about not using boiling water. I've also run a tea shop and have imported very high quality tea. I've tried green and white teas with boiling water and they definitely did not taste as good as with 70-80 C water. At boiling temperatures they taste somewhat burnt and astringent.

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