Aflatoxin in Puerh: New results and reasons for concern?

[xiaobai]

A long time lurker here, I think I should begin by
apologizing for not registering earlier in this forum. As you know,
receiving is always easier than giving...

Anyway, this morning I had an "interesting" experience which encouraged
me to register and start participating. I am not sure whether the concern expressed below deserves the opening of a new topic, but I beg your understanding if you feel this should have been added to an already existing thread. Nevertheless, I would really welcome a fresh feedback from the teachat community on the topic discussed below.

The experience that I was referring to above is the finding of some white mold inside a a ripe puerh cake. Initially, I was pretty unconcerned as it was not the first time that I have seen (or read about) such a thing. Many people seem to believe that white mold is not a reason for concern, and so I did.

Yet, my wife always insists that we should quickly get rid of anything that is slightly covered by mold. And somehow this morning she motivated me to do a little bit of research on the Internet. Going beyond the standard gossip, one of the things I ended up reading was this:

http://www.tandfonline.com/doi/abs/10.1 ... L9Toy6UcZM

I managed to get a copy of the article thanks to one of my students, who is currently working at a richer University where they have subscription to the rather expensive Scientific Journals of Taylor & Francis' (unfortunately, the institution with which I am affiliated does not seem to be able to afford this particular one...). If you want to read it by yourselves, the article is available from me upon request through this Forum.

However, I can try to summarize my understanding of it (I should point out that I have Scientific training but not in this particular field...). The authors claim to have developed a new method (based on high-performance liquid chromatography, HPLC) to detect the presence of aflatoxins in puerh teas
(both raw and ripe). Now, here is their interesting result: Armed with this new method, they find a remarkable presence of Aflatoxins not only in shu (something that had been mentioned already in this forum) but also in sheng. In addition, they imply that other methods for measuring the levels of aflatoxin in tea may be flawed for they are not sufficiently sensitive to the presence of the toxins in tea.

Of course, this is not the only recent study about this. Here is another example:

http://www.lifescienceglobal.com/pms/in ... /view/2217

(This one seems to be freely accessible, though).

In a nutshell (and I do not want to sound like an alarmist as I have also accumulated quite a sizable stash of puerh like many other readers and I would be very worried knowing that is unsafe to drink), I think this kind of research is something we all should keep an eye on.

And here is something else for discussion: In the opinion of the experts in the Forum, what may be in sheng puerh that makes it susceptible to the growth of Aspergilus flavus (the main fungi responsible to the production of aflatoxins)? Does it have to do with the processing of the tea? Could this be found in other teas like green teas as well?

I look forward to reading teachatters' opinions.

[miig]

Hi there,
not too much I can contribute to this complicated subject, but I wanted to thany you for sharing this knowledge. Great reading, I'm looking forward to the ensuing discussion.

[Rui]

Thank you very much for the introduction to this topic. From now on I'll be keeping an eye for that white fungus type.

[xiaobai]

Let me add something that I just found after a more careful reading of the conclusions of the second article that I quoted in my first post above, which partly answers the question that I posted at the end:

Since fungi opt for living their entire lives within
plants, their metabolites and toxic products can easily
contaminate plant products and subsequently cause
intoxication. Pu-erh tea, especially the wet stored one,
is likely to be contaminated by fungi and their toxins,
because of its parasite-friendly processes of
production, storage, and transport. To investigate the
mycotoxin contamination in the wet stored Pu-erh tea,
we measured the concentrations of four types of
mycotoxins in 70 Pu-erh tea samples that were
randomly chosen from 12 stores in a tea market in
Guangzhou. Because people directly brew tea for
drinking, our measurements were based upon the
soaking solution of the tea samples. The purpose of
this study is to provide raw data to further support the
health management of Pu-erh tea.

Quoted from "Investigation for Pu-Erh Tea Contamination Caused by Mycotoxins in a Tea Market in Guangzhou", by J.-Y. Wu et al. Journal of Basic & Applied Sciences 10, 349-356 (2014).

I am inclined to think the main problem may not be with the processing but the environment of the tea trees. We tend to think that collecting leaves from the trees growing in such a natural environment as the mountains of South Yunnan brings the cleanest tea to our tea tables, but we should be reminded that extraction of resources from the wilderness is also quite often the source of many pathogens and toxins that are unwillingly introduced in human society.

[kyarazen]

there are many more methods to detect aflatoxin. i used to be involved in a project to develop a biosensor for it. way too many devices and test kits on the market now.

no guarantees that your white or yellow mold is aspergillus. the quick and dirty way is just to sent the sample to a lab for a quick PCR. the presence of the fungi does not indicate the presence of the toxin though.

most teas are not affected by this issue. aspergilli hates environments with under 10% water. most greens are kept/preserved at 3-4% water content. tieguanyin under traditional roasting is kept around 6%. not enough water for the fungi to grow and be happy.

sheng and shu pu-erh unfortunately have water contents above 10%, and if kept in high humidity it goes up to 16%+...

[xiaobai]

Kyarazen,

Your answer is in line with what Akira Hojo told me this morning when I contacted him (as one of my most responsible puerh providers) concerning this problem. He has also a long experience working in the Spice industry with the problem posed by mycotoxins. He emphasized that he very closely monitors the humidity levels in his puerhs, I believe for the reasons that you stated.

Yet, I think no everybody has easy access to PCR equipment in the event he or she finds mold on her favorite sheng or shu.

And when shopping, I think we all have had the experience of being treated by a vendor to some aged puerh that tasted humid and musty because of the so-called "traditional storage conditions". In such a situation, it is hard to send a sample for analysis before deciding to buy or not.

[kyarazen]

yeap most wouldnt have access to a pcr machine. i vaguely remembered someone in TC whom was rather "peeved" at my suggestion of PCR. but seriously, without scientific analysis, a photo of a mold is as good as fortune telling/astrology.

it really still depend on the vendor and the consumer. a dead serious vendor whom would procure large amounts of tea for resale, collection, investment, will probably be wise enough to send something for a lab test, heavy metal content, pesticide content, whether certain mycotoxins are present (for shu at least, sheng is not much an issue sometimes).

the local food safety regulatory agencies do require testings on many foods, but "tea" falls into a grey area

Kyarazen,

Your answer is in line with what Akira Hojo told me this morning when I contacted him (as one of my most responsible puerh providers) concerning this problem. He has also a long experience working in the Spice industry with the problem posed by mycotoxins. He emphasized that he very closely monitors the humidity levels in his puerhs, I believe for the reasons that you stated.

Yet, I think no everybody has easy access to PCR equipment in the event he or she finds mold on her favorite sheng or shu.

And when shopping, I think we all have had the experience of being treated by a vendor to some aged puerh that tasted humid and musty because of the so-called "traditional storage conditions". In such a situation, it is hard to send a sample for analysis before deciding to buy or not.

[xiaobai]

Kyarazen,

No, I am not going to get annoyed by the suggestion of using PCR to test my mold (although, to tell the truth, my research field is theoretical in nature and I very rarely visit any lab...)

However, the point is not whether the mold in my puerh cake or in your cake is good, bad, or it has produced aflatoxin or any other mycotoxin. It is clear that we are not going to scientifically determine that by showing some pictures on this Forum.

The issue raised by the articles that I quoted is whether the presence of mycotoxins is a unavoidable phenomenon in Puerh tea or not. I think one needs to read those works carefully, extract his/her own conclusions, and contrast them with his/her own experience, and if this can be of any use to others, share it on this Forum. This is the reason why I decided to register and open this thread.

Of course, it is also important to recall that no scientific study is the last word on anything and that there are also recent studies pointing in more positive directions, e.g.

http://www.ncbi.nlm.nih.gov/pubmed/23573983

As to me, for the moment, I think I will probably spend more time in the green/oolong section of my tea closet...

[bob]

Thank you for the info! Very interesting.

It would be great if somebody compared freshly made plantation puerh with freshly made wild old tree puerh (from the same local region). If the plantation tea would show significantly less toxins, then the price of gushu might finally come down a bit...

[Evan Draper]

Welcome to the boards--quite a magnificent introduction! I think this will just confirm my anti-shu bias, thank you very much.

[Evan Draper]

And what manner of xiaobai are you? Not a xiaobailian, I hope....

[xiaobai]

Evan,

You should look at the data in the article by W. Li and coworkers before
drawing your conclusions. They tested both sheng and shu, and indeed, the levels of aflatoxin in both kinds of teas are comparable.

For instance, a sheng from a factory in Xishuangbana contained
6.74 ppb (ppb = parts per billion or micrograms/kg) of AFG1
(one of the four types of aflatoxin). On the other hand,
a shu from another factory from the same region of Yunnan
contained only 0.345 ppb of AFG1. The US limit is, I think,
0.5 ppb.

In general, looking at the data in the article, it seems that
shu contains indeed lower amount of aflatoxins than sheng,
at least the shu from those 30 factories tested all over Yunnan.

PS.: No, I am not a Xiaobailian... the name was not chosen with that
meaning in mind...

[Evan Draper]

You intimated that the access to the article was prohibitive, so I didn't try. I was basing my reaction on this passage from the abstract:

The results revealed that Pu-erh teas from Yunnan, China, contained aflatoxins, especially AFB1 (8.333 μg/kg in raw and 20.149 μg/kg in ripe tea).

I presumed those were the median/mean figures, and so assumed ripe was worse generally, willfully ignoring any nuances of range. Because I am not gonna stop drinking sheng...

[BW85]

I presumed those were the median/mean figures, and so assumed ripe was worse generally, willfully ignoring any nuances of range. Because I am not gonna stop drinking sheng...

I'm with this guy

[xiaobai]

There goes the table with the Aflatoxin data for sheng... I will post the table for shu later. The data are in parts per billion or microgram/kg. There is a substantial difference between ELISA and HPLC, as the former method is considered less reliable.

Key: The tea companies A–C were from Xishuangbana, D–F from Lincang, G–I from Dali, J–L from Baoshan, and M–O from Pu-erh. The numbers 1 and 2 represent raw and ripe Pu-erh tea, respectively.