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An Exploration of Anthraquinone in Tea

“是薬三分毒 – Medicine is three parts poison“

Background Information

I think by around 2016 or 2017 there started to be talk about a kind of organic (phenolic) compound called anthraquinone (AQ) in tea, etc. As important secondary metabolites, anthraquinones are found in a wide variety of plants, fruits, flowers and fungi, including tea, coffee, senna, rhubarb, aloe, lichens, etc. Fabaceae (pea family), Liliaceae (lily family), Polygonaceae (buckwheat family), and Rhamnaceae families. There are around 200 compounds that are found in plants that belong to this class of compound.

They are common in the human diet and have a variety of biological activities including anticancer, antibacterial, and antioxidant activities that reduce disease risk. Rhubarb (Da Huang/大黄), for example, first documented in Shen Nong’s ‘’Herbal Classic’, the dried roots and rhizomes of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf., Rheum undulatum, or Rheum officinale Bail is one of the most commonly used herbs in the Chinese Pharmacopoeia to “eliminate heat, cool blood, disperse blood stasis” etc.

There are various isomers of AQ but the most important are 9,10 Anthraquinone (Anthracene-9,10 – dione).

Chemical structure of relevant anthraquinones from mdpi.com

The biological activity of anthraquinones depends on the substitution pattern of their hydroxyl groups (OH) on the anthraquinone ring structure. The chemical formula of AQ is C14H8O2.

Uses

Anthraquinones are the main active constituents in a number of herbal remedies and, as mentioned above, Traditional Chinese Medicine, they have anti-inflammatory, antioxidant, antibacterial, antiviral, anti-osteoporosis, and anti-tumor properties and have a stimulating laxative effects on the large intestine (by increasing fluid in the colon and enhancing peristalsis).  At high doses anthraquinone-rich herbs are gastrointestinal irritants, causing symptoms of toxicity.

Apart from its pharmacological uses, AQs are used for dyes, pigments, in chemotherapy drugs, and as a catalyst in paper making. It is also used as a bird repellent. It shows low mammalian toxicity but there are some concerns regarding its potential to bio-accumulate. No serious risks to human health have been reported but it is moderately toxic to birds, most aquatic organisms and earthworms.

Risks

Typical of many plant-based, naturally occurring compounds, AQ has a down side as well as an up. In Chinese there is an expression: ‘是薬三分毒 shi yao san fen du’ or ‘Medicine is three parts poison’. On the one hand having anti-inflammatory, antioxidant, anti-cancer, etc. properties, Anthraquinone is now understood to have potential carcinogenic risks. The maximum residue limit (MRL) of AQ in tea set by the European Union is 0.02 mg/kg. Previously it was 0.01 mg/kg. Japan has not set a specific limit other than to say it ‘must not be detected’. Detectable levels of AQ are rather common, including in Japanese teas.*

Sources in in Tea

The consensus is that the AQ in tea likely has a few specific origins. The first is environmental, which is a fairly broad definition that might include AQ ‘contamination’ in the air or water from nearby industry, traffic pollution or burning on agricultural land, forest fires, etc. This could therefor affect the fresh leaves and also the dried leaves through the drying process if the tea is sun dried.

The second possibility is in the ‘fixing/sha qing‘ process of tea making or in the drying process if tea, like black tea, is oven dried. Research has found that the AQ content of tea processed in different ways can vary considerably.

Tea Processing

Processing of tea. Most tea is ‘fixed’ using some form of heat, either hand fried in a wok or in a mechanised process – a machine driven rotating drum – with some kind of heat source underneath. Also as part of the wilting step in black tea processing, heated air coming from furnaces that are used for drying tea can be sent up to wilting troughs toward the end of the withering process.

Some research has found that ‘coal’ fired fixing compared with fixing using an electric heat source in green tea processing, saw increased AQ levels of 4.3 to 23.9 times, far exceeding the EU’s 0.02 mg/kg, The same trend was observed in Wulong tea processing using coal heat. The steps with direct contact between tea leaves and fumes, such as fixation and drying, are considered as the main steps of AQ production in tea processing. The levels of AQ increased with the rising contact time, suggesting that high levels of AQ pollutant in tea may be derived from the fumes caused by coal/char/charcoal or other organic matter combustion.

It was also found that different types of tea, with their different processing methods, produced different levels of AQ.

“9,10-Anthraquinone is produced by a reaction between benzoquinone and crotonaldehyde. On the other hand, emodin and physcion are two hydroxyanthraquinones produced by fungi and have been found in microbial fermented teas, including Pu-erh and Fuzhuan brick teas. The ingestion of hydroxyanthraquinones have been shown to have both beneficial and deleterious effects. The safety dosage range and the time of administration required for a satisfactory benefit/risk balance of both anthraquinones are still unknown.”

Research on Humans

Firstly, to date, there is no proof of a connection between AQ and cancer in tea drinking humans.

In a US National Library of Medicine report on rats published in 2012 they stated：

“No studies of human cancer were identified that evaluated exposure to anthraquinone per se;
however, a series of publications on dye and resin workers in the USA, who were exposed to anthraquinone, was available. These workers were potentially exposed to anthraquinone during its production or its use to manufacture anthraquinone intermediates. Effect estimates were reported for subjects who worked in anthraquinone production areas, but they were also exposed to other chemicals, and effects specific for exposure to anthraquinone were not analysed. A study of substituted anthraquinone dyestuff workers in Scotland (United Kingdom) was also available; however, it was unclear whether anthraquinone was used to produce the intermediates in this study”

The same report stated：

”Currently, there is insufficient evidence that human exposure to AQ causes cancer. A case–control study by Barbone et al. (Citation1992) observed a 2.5-fold increased risk of lung cancer in subjects from AQ dye-producing areas. However, there is no direct evidence from this study that AQ causes cancer. In addition, Wei et al. (Citation2010) found that DNA oxidative damage in the human body is linked to AQ exposure. The International Agency for Research on Cancer has classified AQ as a possible carcinogen to humans (Group 2B) (International Agency for Research on Cancer (IARC), Citation2013). AQ is commonly found in the natural environment and has been detected in the air (Albinet et al., Citation2006; Cautreels et al., Citation1977), water (Akiyama et al., Citation1980; Q. Liu et al., Citation2021; Meijers & Leer, Citation1976) and soil (Rodgers-Vieira et al., Citation2015), as well as in herbs, spices, coffee, tea and other foods (Díaz-Galiano et al., Citation2021). Apart from these, AQ also occurs naturally in the seeds used to produce cassia gum (World Health Organization (WHO), Citation2010). Humans can be exposed to AQ through the above pathways”

Research on Rats

The National Library of Medicine report describes research done on rats where AQ was administered orally:

“Groups of 50 male and 50 female F344/N rats were fed diets containing 469, 938 or 1875 ppm anthraquinone for 105 weeks. Further groups of 60 males and 60 females received 0 or 3750 ppm anthraquinone for the same period. These dietary concentrations resulted in average daily doses of approximately 20, 45, 90 and 180 and 25, 50, 100 and 200 mg/kg bw anthraquinone for males and females in the 469-, 938-, 1875- and 3750-ppm groups, respectively. At 2 years, animals in the highest-dose group weighed less than those in the control group.”

After 2 years rats in all groups had ‘significant levels of adenoma or carcinoma, ….. papillomas’ affecting the kidney and bladder.

In another study from 2022, “Acute and Subchronic Oral Toxicity of Anthraquinone in Sprague Dawley Rats” research was conducted on groups of 10 male and 10 female rats by giving them doses of AQ (gravage) of 0, 1.36, 5.44, 21.76, and 174.08 mg/kg bw, 7 days a week for 90 days followed by a recovery period of 28 days. They concluded that the ‘no observed adverse effect level’ (NOAEL) for anthraquinone in rats was 1.36 mg/kg bw and the ‘lowest observed adverse effect level’ (LOAEL) was 5.44 mg/kg bw.

Research on Tea

In a report “Anthraquinone in Chinese tea: concentration and health risk assessment” published in 2024 it states:

“The concentration levels of AQ in tea varied by different types of tea, different packaging types, different sale spots and different tea-producing areas. The results of the deterministic assessment show that the health risks associated with daily exposure to AQ via tea consumption are low in different populations in China. For the general population, the mean daily exposure of AQ via tea consumption was (2.50 × 10−4) µg/kg body weight (BW), 0.0037% of the acceptable daily intake of AQ (6.8 µg/kg BW). In the different sex-age groups, the highest mean daily exposure of AQ via tea consumption was found in the male group aged ≥ 60 years, which was (2.84 × 10−4) µg/kg BW. The high consumer exposure (95th percentile, P95) was found in the female group aged ≥ 60 years, which was (9.36 × 10−4) µg/kg BW. Green tea is the main type of tea with AQ exposure by Chinese tea consumers.“

They also say:

“Our study found that the total detection rate of AQ in 1573 tea samples was 60.97%, indicating that AQ contamination was prevalent in the Chinese commercial tea samples. The mean concentration was 0.0170 mg/kg, which did not exceed the MRLs set by the EU. Among the different types of tea, this study confirmed the findings of Yuan et al. (Citation2020) and He et al. (Citation2019), who found that dark tea had the highest over-standard rate of all types of tea. These results are most likely related to the unique production process of dark tea-pile fermentation, which is more complicated than other types of tea (Yuan et al., Citation2020). Some studies have shown that the concentration of chemicals in dark tea may also be related to its high maturity (Yang et al., Citation2012) and aging time (Liang et al., Citation2022; Liang et al., Citation2023). In addition, what is surprising is that the mean concentration of AQ in white tea in this study was higher than in other types of tea, this result can be explained by the following fact that domestic sales of white tea in China are small. Therefore, for a result with statistically significant differences in the detection rate, over-standard rate and concentration, the white tea sample collected in this study was too small“

Furthermore:

“From a producing and processing perspective, studies have demonstrated that smoke from wood fire or coal may be one of the sources of AQ contamination in tea. AQ can also be a process contaminant, the chemical reactions between crotonaldehyde and hydroquinone during tea processing also may be a potential pathway for the endogenous formation of AQ in tea“.

“The results of the exposure assessment showed that the mean daily exposure and consumers at the P95th percentile daily exposure of AQ via tea consumption in the general population were (2.50 × 10−4) µg/kg bw and (8.41 × 10−4) µg/kg bw, respectively. Furthermore, our study found that the health risks associated with exposure to AQ via tea consumption are extremely low for the general population and the different sex-age groups“.

Some sums

Let’s say a lab rat weighs 445g (F344/N) and is fed 90mg/kg body-weight of AQ (taking the figures from above) then the daily dose would be 40mg/day. If the rat was given only 20mg/kg-bw daily (the lowest dosage in the research), the daily dose would be 8.9mg daily.

If we relate that to a 60kg human:

i) If we calculate what the equivalent dosage for a human being would be, using the lowest dosage rate (20mg/kg/day), it would result in the consumption of 2696mg per day of AQ.

X=20 x 60/0.445 = 2696mg per day

ii) At the higher rate in the example (90mg/kg/day) it would result in the consumption of 12134mg of AQ per day.

Let’s imagine those levels of AQ are consumed entirely from tea – on the assumption that all the anthraquinone in the tea would be transferred to the broth and was then consumed – taking the EU MRL of 0.02mg/kg:

At the lowest dosage, it would look like this:

2696/0.02 = 134,800kg. i.e. 134 metric tons. That’s every day for two years in order to get to the same equivalent level of intake.

If we take the figures from the second research paper, using the NOAEL of 1.36mg/kg bw:

For a 60kg human, the ‘no observed adverse effect level’ would be 81.6mg daily. Using our previous example of tea containing 0.02mg of AQ per kg of tea, one would need to consume 4 tons of tea daily:

X=1.36 x 60 = 81.6mg per day

So 81.6/0.02 = 4080kg. That’s four tons.

Using the ‘acceptable daily AQ intake of 6.8 µg/kg BW’ (for which I have to acknowledge a caveat since I don’t know how it was derived at) for a 60kg human, that would calculate out as 6.8×60/0.02, we get 8,160kg. Eight tons.

You get the idea..

To look at it from another angle – if one drank 10 different teas (each of 8g all with the same 0.02mg/kg limit) , 80g of tea all together, every day, one would imbibe:

80/1000 x 0.02 = 0.0016mg of AQ per day. That would be 0.008 % of the minimum dosage used in the first experiment, or 0.12% of the NOAEL limit referred to in the second research paper. Or, if we take the ‘acceptable daily intake’ referred to above we get: 0.0016/6.8 = 0.0235%.

That’s not to dismiss the potential risks of excessive consumption of anything. And not to doubt that there are risks involved, but it’s important to keep it in perspective.

And remember too that this 0.02mg/kg MRL (originally 0.01mg/kg), was set by the EU, which has still failed to include glyphosate in any standard testing protocol. A conspiracy theorist might, over a cup of tea, be forgiven for wondering whether, if anthraquinone was made by Monsanto, we would even be considering it.

Conclusions

For anyone concerned about buying selling tea within the EU this might be an issue as it may be that some teas would not pass EU testing requirements. Personally, I am rather more concerned to avoid agro-chemical residues. By that I mean that, whilst most definitely doing my best to avoid tea that won’t meet EU criteria, I do not consider AQ levels to be a priority. If a tea is good and chemical free, yet may still have some detected level of AQ, I may well go ahead with it anyway.

With tea making, there are limits to what one can do as there are many factors which are beyond one’s control: if people in Myanmar or Thailand, or over the other side of the mountain, are burning rice stubble during tea season there’s not too much one can do about it. Most contemporary hand frying set-ups have a wall between the side of the stove where the wok is, and where the tea is fried, and the side where the wood is added to the fire. As long as chimneys are well made – tall enough with good draw – there is limited chance of smoke from the burning wood getting into the tea. Making sure frying woks are regularly cleaned and rinsed during the tea frying process (to avoid any buildup of residues) and hands/gloves are clean are practical step that may help minimise the potential for AQ in the tea. Machine frying using a rolling drum (滚筒/gun tong) or a thing called a ‘chao tian guo‘/朝天锅 (think of something like a cement mixer with the revolving drum made of cast iron on better models, or otherwise steel). In earlier times gun tong were wood fired but now, like chao tian guo are more likely to be heated by electricity or bottled gas, but the result is not the same as hand frying in a wok, so they are often used for larger quantities of tea and ‘small tree tea’, etc. but are still not often used for premium old or ancient tree teas.

‘Wu Long’ Puer. Rolling, Rolling, Rolling

A while back I saw the term ‘Wu Long’ Puer recently re-appeared on the English language internet, so I thought it worth revisiting this old topic as it comes up from time to time. I’m not sure when was the first time it was raised on the internet but I remember seeing something from maybe 2005 or 06. It seemed like it could be an appropriate coda to my previous post about processing tea and the implications for ageing.

To be clear, this is an English language term with, as far as I know, no Chinese equivalent. So it’s describing something which is described in a different way in Chinese. The idea seemed to be formulated from the perception that there was a new style of Puer tea that had been oxidised in a way that a ‘traditional’ Sheng Puer wasn’t.

The suggestion was that the tea had been rolled more (more heavily/longer?) with the effect that the tea flavour steeped out much more quickly and the tea had qualities which were reminiscent of Wulong tea.

My guess at this point is that that’s a misunderstanding. I think it’s not likely to have the effect that some folks have suggested. Rolling more heavily, rolling twice, etc. are not new, and whilst, of course, bruising the leaves more is going to break down more of the cell walls and may well result in more oxidation, I somehow doubt it would produce the effect talked about.

If anything, over the last ten years or so, there has been a trend toward lighter rolling, 抛跳/pao tiao, rather than tighter, originally driven, it seems, by Taiwanese demand. People coming to Yunnan and demanding tea that was rolled in a way that they thought looked better. Some tea farmers have told me that Taiwanese customers wanted them to roll straight – backwards and forwards – as opposed to a circular motion to create rolled leaves that were more needle shaped. Less twisted. This is not standard Puer fare. Traditionally, if anything, people rolled tea more tightly pre 2000s, so this doesn’t easily fit with the proposition that post 2000s Puer was rolled more, creating an ‘Wu Long’ type flavour/aroma.

At least, if additional or heavier rolling is a factor, it’s more likely that any extra rolling in tandem with other factors produced the result talked about. Sure, it’s difficult, I haven’t drunk the tea that someone else drank that made them think it had been ‘wulonged’, but the variables in tea making are not infinite.

Another factor with heavier rolling is that the flavours will be steeped out more quickly, so the tea will be less ‘nai pao’ / 耐泡 and the flavour in the early steeps more intense. This is also another reason why there has been a trend to lighter rolling: to make early steeps less intense and to have the tea steep more slowly.

Of course, if other things are done in the processing of Puer, to reduce bitterness and astringency for example, then heavier rolling is not going to produce such a marked effect, and the tea will generally have poorer structure, and steepability.

The only time I have heard a term in Chinese which I would say is referring to the same thing was many years ago when someone referred to a raw Puer as ‘fa jiao cha’/发酵茶/fermented tea. As now, the understanding was that it was tea that had been processed in such a way as to cause it to ferment in a way similar to other types of fermented tea: Wu Long, black tea, etc. and not proper Puer processing.

But even fairly excessive wilting – with autumn tea this is not that uncommon, where the tea is picked in the afternoon and then left overnight to be fired early the next morning – if the tea leaves are piled at a correct depth, it will not on its own produce an ‘Wu Long’ kind of fermentation. So it seems that it’s more likely a combination of factors of which excessive wilting may be a part.

One thing that can cause a light ‘fermented’ aroma is if the sha qing is not done well, or a combination of tan qing and sha qing are not managed properly, which can result in the stems of the tea leaves, which typically have more moisture in them, not being ‘fired’ properly, and enzyme activity not being arrested sufficiently. The result being that once the tea comes out of the pan it continues to ferment, producing an aroma in the dry tea that is reminiscent of a fermented tea -‘hong shu wei/红薯味/sweet potato taste, as some people call it. Personally, I wouldn’t think it was similar to Wulong, but who knows.

On Processing Raw Puer Tea

Several years ago I received an email from someone expressing some nervousness about buying young Puer tea because they were concerned about how it would age, which is fair enough, but then they said they were concerned they might purchase in error some ‘western boutique puer’. Since then I have been slowly trying to formulate a response.

It got my interest because I had never heard the term. I looked on line and the only reference I came up with was on ‘A Tea Addict’s Journal’ from a few years prior, also questioning the meaning of the term.

Since I’d never seen ’boutique’ being used as an adjective before I was curious and decided to check my Larousse. It’s a bit out of date, so I double-checked on-line to confirm my understanding, which is that in French, ’boutique’ simply means a shop. More often than not, selling expensive clothing and accessories, etc. predominantly aimed at women. Almost by definition small scale, as opposed to ‘les grands magasins‘.  In English, the meaning is similar to the French: a small, specialised, and probably expensive, shop.

In French it’s only a noun. There are plenty of other words in French to describe what I guess the adjective ’boutique’ is trying to express in this case in English: chi chi, chic, bijou, mignon,  maybe. What the shop sells is not ’boutique’ as in: ‘I bought a boutique little handbag in that shop in the Marais the other day‘.

The idea that something, for which one might create the adjective ’boutique’, would be inferior also doesn’t quite fit since ’boutique’ generally implies the opposite: quality. So it’s not a particularly good choice of word to denote something inferior, or even ‘fashionable’ (if implying that the object in question has a limited shelf-life. But, if we’re being sarcastic, why not?

My french friends, I supposed, could reasonably call their tea shop a ’boutique de thé’, if they wanted to peddle it’s smallness and class.

It’s another of those words like sommelier which has been purloined. Call me old fashioned, but I reckon there’s no such thing as a ‘tea sommelier‘ in French. A sommelier is a wine waiter/ress or wine steward. Nothing more, nothing less. Come to think of it, I’m not even sure what a ‘tea sommelier’s job might be: stocking teas and pairing them with food maybe?

So what, having got all that out of the way, is ‘western boutique Puer’ really referring to?  I thought it might have made sense if it was referring to small scale, expensive Puer made for niche markets, or something. The author of the term seemed to think it referred to tea processed in such a way as to make the tea more accessible/appealing to Westerners, (although he seemed unsure exactly how that was done) but in so doing, the tea was somehow rendered unsuitable for ageing, 

That’s not a new idea. In Chinese people refer to ‘市场茶/shi chang cha‘. Tea that is made ‘for the market’, i.e. made to be sold and drunk, not to be stored. But I find it hard to imagine that any Western tea makers/merchants would be doing that: intentionally producing tea that was not going to age well.  I’m also not sure many people would go out of their way to do that with old or ancient tea tree tea. It doesn’t make much sense, particularly given the current cost of fresh tea leaves. Generally, tea from ancient or old tea gardens is already very drinkable but I guess folks might do it with bush tea. It could well happen unwittingly however.

The other thing I have trouble imagining is that any Chinese Puer producers would go out of their way to make tea specifically for a Western market, given the size of that market compared to the domestic one. But if there is someone somewhere doing that, then what are they doing?

Raw or ‘sheng’ Puer processing looks pretty straight forward: the leaves are picked, maybe spread out in the shade for some time, ‘fried’, rolled and then sun dried. It doesn’t look like rocket science. But within that process there are a whole bunch of factors that can be varied, intentionally or not, to produce different outcomes.

The basic variables are:

LeavesGoing into the wok most people would agree leaves should not be ‘over-wilted’, say, 2-4 hours tan qing time.*
SizeA larger wok is generally better, and maybe thicker. Say 90 -100cm diameter, Set at an angle on the oven for ease of use. Too small a wok means holds heat less well and the amount of tea that can be processed is small, so overall less consistent result.**
AmountThe ideal amount of fresh leaves to put into the wok at one time is mostly determined by the size of the wok, but say about 6kg in a 90-100cm wok) †
TemperatureThe ideal temperature of the wok surface is probably around 250°C in the middle portion of the wok. It will be a little cooler toward the edges, but after firing a couple of woks of tea, it should be quite uniform. Most people will agree that the temperature of the wok needs to be quite high at the outset. The first few minutes is key. What happens after that is of some debate. ††
HandlingThe method and speed of handling the leaves in the pan is the ‘art’ of firing tea. The leaves must be turned uniformly (relaxed and steady): inside out as well as top to bottom to avoid leaves in the middle being ‘steamed’ without coming into contact with the wok’s surface. Movement controls the speed at which the tea dries out and one must avoid tea leaves drying out before they are ‘cooked’.
The leaves must be shaken out intermittently in the pan to help release moisture and help bring out the fragrance but must be done judiciously. (Too much shaking will dry the leaves more quickly).‡
TimeDepending on all of the above the length of frying time might be around 12-20 minutes.
CoolingAfter the leaves are taken out of the wok they need to cool before rolling. This is generally done by shaking them out onto a bamboo mat or ‘bo ji’ and leaving them to cool after that. The contentious practice of putting the leaves in a heap when they’re still hot is discussed below.
The basic variables are listed above.

*Some people say best not to wilt at all. Others will tell you several hours is OK.

** In the last few years there has been a trend for thicker woks. Some folks are now saying that whilst they hold the heat better, they are less responsive to changes in temperature so maybe not ideal. Managing the fire under the wok is as important as master the frying of tea. There is room for a little leeway, but not too much.

† Personal choice is dictated to some extent by physical stature, strength etc. Once the leaves start to loose moisture in the pan they become rather more difficult to handle. This is when it becomes easy to burn them.

†† There are many different opinions about wok temperature but generally speaking, lots of people tend not to like tea that they say has been ‘men chao’d/闷炒 at lower temperature. There is however, in tandem with the handling of the leaves, a fairly broad range of acceptable-ness. In any case, the ultimate aim is to arrest enzyme activity without killing them off completely as it is the enzymes that are going to kickstart the ‘fermentation/oxidation’ process later.

‡ If you’ve seen any of those videos of folks frantically throwing leaves high up into the back of the pan, you know what it doesn’t look like.

There is, what I think most people would agree, a range of acceptable variations in processing factors listed above that are still detectable in a newly made tea, but after it’s been stored for some time are rather harder to perceive. A friend of mine reckons ‘In the first four years, you drink the craftsmanship, after that you drink the tea.’ A clumsy translation, but you get the idea: Initially, various aspects of the tea-making process might be more to the fore, but after say, ten years, they will have receded somewhat, and what you’re left with is the basic quality of the original material. So if it was good, and hasn’t been damaged in the processing or subsequent storage, it should still be good.

The two things that people new to Puer tea might be drawn in by are fragrance and sweetness, and they may have trouble with bitterness and astringency. There are a couple of things folks could be doing to augment the former and reduce the latter during processing. Currently there are three things that people might be doing which are arguably detrimental to the tea, but will help reduce bitterness and astringency and can make Puer tea more fragrant in the short-term.

Wilting. This is an old contention: Some people say that ‘wilting’ was never per-se part of Puer tea processing, but, whatever you call it, or whether you give it a name or not, it’s something that typically has happened (see here, and here). From when the leaves are picked to when they go in the wok, the time, and the way they were handled, can vary considerably.

The length of time is important. It could be anything from an hour to several hours. Everything, including the leaves themselves and the way they are handled during that time , the weather, the altitude, can affect the degree of wilting. There could be times when leaves are wilted more than is desirable because of factors largely outside the producers control, but for sure there are some producers who will deliberately wilt for a longer period with the aim of reducing the astringency and bitterness – generally at the customer’s request. Over the last 10 years or more wilting troughs have become more common. They are not native to Yunnan Puer tea making, but have been used in the production of green tea. They aren’t inherently evil. If leaves are put on a wilting platform rather than on a bamboo mat on the ground, air will pass under the leaves as well as over them so they will lose moisture more quickly. Hence, the time they are left like that should be shorter. Most wilting troughs are equipped with a fan at one end which when turned on will blow air into the tunnel underneath which will then be blown up through the leaves, thus increasing the rate of wilting. Some producers don’t use the fan, some do, some say they only use it with summer tea. So it’s something to watch out for. There’s really no need to use a fan with spring or autumn tea. 

Tea that has been ‘over-wilted’ is probably fairly obvious; it can be quite smooth, fragrant and sweet, but in my experience, somehow lacks structure/backbone/body/vitality. It’s good to be vigilant in any situation, particularly where wilting troughs are present, simply because it’s probably easier to exceed an ideal resting time for fresh leaves before frying. If fresh leaves are put on bamboo mats on an earth or concrete floor, they’re not going to loose moisture very quickly, so an hour or two either side of ‘the ideal’ will probably not make too much difference. The supposed aim of the ‘tan qing‘ process is for the moisture content in the leaves to be reduced a little (typically said to be about 10%).

Frying. Frying times can also vary considerably. This again depends on the state of the leaves, the temperature/nature of the wok (material, size, thickness, age, etc.), and the desired outcome. For some years there have been producers who fry tea for longer periods, as much as 35 or 40 minutes, toward the end of the frying the temperature of the wok is reduced and the tea is alternately left in a pile in the wok for a minute maybe and then shaken out. The process is typically repeated several times. Some people will even begin rolling the tea whilst it’s still in the pan, so once it comes out it needs little if any rolling. The stated aim of this is to make sure that leaf stems are properly fried to reduce any redness that may otherwise occur once dry, but it can also elevate the fragrance and reduce astringency. It’s not to everybody’s taste, and I personally don’t like tea like that, even though it initially can seem quite palatable. It’s a style of frying that I was first aware of in the He kai-Ban Zhang area around 2008/2009 which seems to have spread to other areas, albeit on a limited scale. It would certainly make sense that frying for a longer period of time, even at reduced temperatures, is going to be detrimental to the tea, but to what extent and whether it renders it unworthy of drinking five or ten years down the line, I’m not sure.

At the other end of the ‘sha qing’/杀青 spectrum you have the theory that tea should be fried just enough to reduce the moisture content sufficiently (a typical test is to take a leaf and bend the stem. If it doesn’t break, the tea is ‘done’). So it could be as short as 10 or 12 minutes. The idea here is that you preserve as much as possible of the constituents in the leaf on the understanding that the flavour will be more fulsome and the tea will age better. One ‘rule of thumb’ that one hears is that tea should be fried until the first time the fragrance comes out. That is enough. The theory being you want to seal things in, not let them out.

Another contentious element that many people now consider as detrimental is ‘ti xiang’/提香/enhancing the fragrance. This is done by shaking out the leaves more towards the end of the frying, and doing it beyond what is necessary to release moisture. Because of this, the tea dries out rather more than it would ideally. The aim of this step is to increase the fragrance of the tea, but Puer tea is not typically very fragrant when it’s young. It is generally understood that with raw Puer the fragrance will improve as the tea ages, and any attempts in the processing to artificially augment the fragrance are in error because once the tea has dried out to that extent it will not age well.

Some people are rejecting the ‘hand fried’ approach and using a ‘gun tong’/滚筒, a rotating drum fryer with hot air being passed through it. The argument is that the tea can be fried more evenly and more quickly at a higher temperature, producing a tea that is nearer the ideal described above. To do this in a wok takes a lot of skill and effort so is harder to maintain. The downside is that the person doing the frying still needs to be very skilled, as controlling the temperature, speed of rotation and time are all critical and a minor loss of focus could produce a less than optimal tea.

In recent years there have been other trends. One is ‘bao fa’/爆发: frying tea very quickly at a very high temperature, perhaps in an attempt to try and get closer to the ‘gun tong’ experience, but using this method it is very easy to produce tea that has a ‘dou xiang’/豆香, a beany fragrance, more reminiscent of a green tea. Not Puer tea. Folks doing this are sometimes working in teams so that people can rest between ‘fries’ as it is quite physically demanding.

At the other end of the ‘sha qing’ spectrum, there are folks who have been experimenting with low temperature firing with extended frying times.

The other thing that has been around for a while, is that when tea is taken out of the wok it is not immediately shaken out to cool before rolling, but is put in a small pile for some time (and occasionally even covered with cloth or sacking): it seems like times can vary from a few minutes to rather longer. The stated aim of this step is also to make sure the thicker stems are ‘cooked’ and increase fragrance/reduce astringency. This is a technique loosely borrowed from Yellow tea processing though the times may be rather shorter than those used for Yellow tea.

It seems very likely that this will have a deleterious effect on the tea’s ageing potential as the leaves are still at high temperature and are basically going to continue to oxidise/ferment – ‘cook’ if you will – when left in a pile for some time. It may be a question of degree, and a relatively short period of time may have a minimal impact on the tea’s ageing potential. Typical Puer processing, as mentioned above, is for the leaves to be shaken out immediately on leaving the wok to allow them to cool in readiness for rolling.

It is this last technique, [coupled with the practice of ‘ti xiang’ (they are not necessarily used in tandem)] which seems likely to have the most impact on a tea’s ageing potential and conversely, is not always so obvious in a new tea, though the colour of the broth will generally be deeper than one might usually expect.

Of course, there are always folks experimenting and trying to find new ways to tweak old practices. That’s surely not anything new. So there’s always going to be something to watch out for and learn from.

In 2021 it seems like we’ve been through a whole cycle (though it maybe hasn’t finished yet). There are people who were trying various ways of making tea some years back, who are now saying that that tea has not aged as well as they hoped and are again reviewing their methods and returning to what are understood to be ‘traditional’, or slightly modified ‘traditional’ processing techniques.

So what’s the conclusion?

There are certainly things people are doing to try to make young Puer more appealing, particularly to new Puer drinkers and some of that tea will surely end up in the Western market, but it may not all be bad. The factors discussed above are variables that can affect the tea’s quality and ageing potential, but their effects need to be seen as a whole, on a spectrum. We can’t say for sure which of any one of them on it’s own, in whatever degree, will definitely render a tea useless for ageing. Experimenting with the tea making process is also clearly not something new: the sheer variety of types of tea in China alone is testimony to that. Awareness of that fact should be enough to keep the consumer safe from erring too far from the well worn path of conventional Puer processing. Other factors such as the region, the ‘terroir‘, the season, the age of trees, etc. will also impact the ageing potential of any tea, and much as is the case with red wines, it’s not every year, grand cru or not, that produces a wine that’s equally good for ageing. So unless one is sure of what one’s doing, buy in small quantities, drink with awareness. Be skeptical, without being doctrinaire, and be prepared for some regrets: both for what you did and didn’t buy.

Autumn

It was nearly the end of October and it had been raining pretty much solidly for three days.

Ten day forecast for Jinghong

And the same for Menghai.

I had thought it might ease up and was contemplating starting to look for some Autumn tea, which can sometimes be quite good, but the rainy season effectively didn’t stop. I called a couple of tea farmers in the Yiwu area who said there was little to no tea. Even if daytime temperatures are fairly high, overnight temperatures can drop considerably.

Early November and more rain on the way.

Once that happens, old tea trees stop flushing. So that was the end of that. It’s been the wettest Autumn since I’ve been in Xishuangbanna, which is nine years.

It’s bad news for tea farmers because, whilst Autumn tea doesn’t fetch Spring tea prices, and the volume is somewhat less, it means a portion of their annual income has just disappeared.

 

Nan Nuo Shan’s ‘Cha Wang Shu’

Anyone who goes to Nan Nuo Shan will have heard about, or visited ‘Cha Wang Shu’, the ‘King of Tea Trees’ that is between Ban Po Lao Zhai and Ya Kou Zhai. It is estimated to be 800 years old or more, but apart from carbon dating, there appears to be no sure-fire way to tell a tea trees age as they do not have rings that can be counted in the way that most other trees do. Locally, there are only word-of-mouth assessments of age, ‘so-and-so’s grandfather says it was yea big when he was a boy’ or something akin to that. Or otherwise by comparison with a tree of known age.

Carbon dating has been used to establish the age of some tea trees. And so to the apocryphal tale of the original Nan Nuo Shan ‘Cha Wang Shu‘. It was growing a little way below Shi Tou Zhai, and had attracted a lot of interest from scientists. As early as the beginning of the 1950’s Yunnan College of Agriculture researchers were exploring the varieties of tea tree in this area. The story is that local hunters who were familiar with the area would act as guides to take researchers deep into the forest. On one such trip in late 1951 a tea tree that was 8.8 metres tall with a girth of 0.83 metres was found. A couple of years later, one Zhou Peng Ju from Yunnan Agricultural College Research Department came to examine the tree, and over the ensuing years an increasing number of botanists and specialists came to examine the tree. Eventually it was established that the tree was a cultivated variety of tea tree.

According to one version of the sequence of events, as more and more people came to visit the tree, the surrounding environment was badly affected and the tree itself was also damaged, and by the mid 1990’s the tree died.

The local version of the story is that scientists came and took samples for examination by drilling into the trunk of the tree, which lead to the death of the King of Tea Trees.

This photo, with the tea tree behind, from the famous visit in 1985, is about all the evidence that remains on Nan Nuo Shan.

nan nuo shan cha wang shu

Zeng Wei Ran and colleagues visit the tree in 1985.

 

Some Old Tea Tree Gardens (and some lessons on transliteration)

Last week, I had a few days’ trip in the SFTM area. The weather was good – dry, warm in the day, cool at night – and I got to re-visit some places and also go to a couple of new places.

I’ve been trying to get to Ma Pia (吗叭/ma ba in Chinese) for a couple of years. I think it was the autumn before last, I was with some friends in Ding Jia Zhai who had just come back from Ma Pia with some tea. One of them had a couple of pictures on his mobile phone. The tea wasn’t up to much – there were some problems with processing – but the trees looked interesting.

Laos China border region

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New Home

So here is HM in a new home. It’s been a while. I just realised, when moving things around, how long the hiatus has been. I’ve been busy with other things, but I’m hoping to still find time to keep this more contemporary.

Spring is still a little while away, but Spring Festival is round the corner – The Year of the Goat. A wooden goat at that. I just got back from a month or so of travelling to rain and some fairly cold weather. Already, I heard a couple of folks wondering about how so much rain early in the new year might affect tea, but it’s early yet. No point in worrying about what hasn’t happened.

In my explorations of the last year I’ve happened on a couple of interesting tea gardens, not well known – one pretty much unknown – from which I’m planning to source tea this Spring.

I’m getting ready to go and check out the tea gardens again and will post a couple of photos when I get back.