Controlling microbes in your Pu-erh cave.

[SlowOx]

I listened to a podcast today. A tea shop owner explained that people collect pu-erh to age at home and I'm not convinced pu-erh cakes really age in a home cave. After aging shu and sheng pu-erh for at least 5 years, The only difference I can see is a lack of vitality the tea once held. Humidity certainly brought some aromas but no noticeable aging occurred.
Does anyone have any information on some of the microbes found in pu-erh and whether or not they are anaerobic or aerobic? The reason that I ask is because if some of these microbes are aerobic, how is it that a cake of pu-erh can age since it is so compact? It stands that only the surface would be able to age if oxygen doesn't penetrate through into the tea.

Loose-leaf sheng pu-erh, however, is a completely different beast IMO.

Thoughts/info?

[entropyembrace]

You should understand that shu and sheng are actually very different. Shu puerh is composted in large piles with abundant moisture, heat and very little oxygen. The microbes involved in shu production are mostly anaerobes and facilitative anaerobes. This is done quickly, fully fermented shu puerh is sold the same year as the leaves are harvested.

Sheng pu-erh is usually pressed into shapes before it's aged and is stored in stacks of cakes bundled together in tongs, tongs bundled into larger packages in warehouses. There's less water, less heat and lots more oxygen because it's not composting in massive piles. Oxygen is a very small molecule and I would be very surprised if it can't penetrate into a puerh cake. There's also not enough microbial activity inside each cake to deplete it there. This really takes time to age the tea will continue to transform over decades. I've heard even tea from the 80s is not in the final stages of maturity yet.

That said...traditionally stored sheng puerh comes from Hong Kong it is very hot and very humid there compared to probably anywhere in the United States. Additionally for the early stages it's kept in conditions which are above the ambient humidity. I really doubt your home cave is as hot and humid as a Hong Kong warehouse and even there after 5 years the cake is not aged yet.

[SlowOx]

The microbes involved in shu production are mostly anaerobes and facilitative anaerobes.

Do you know what microbes these are? Also, would sheng carry different microbes?

[entropyembrace]

The microbes involved in shu production are mostly anaerobes and facilitative anaerobes.

Do you know what microbes these are? Also, would sheng carry different microbes?

many different bacteria most of them not yet identified specifically; it is a complex community including:
Actinobacteria, Proteobacteria, Firmicutes...

also Ascomycota (yeasts, molds)

but also lesser numbers of representatives from many other phyla.

Bacillus coagulans was identified specifically in one study as the dominant species in pile fermented tea

yeasts belonging to the genus Saccharomyces were also identified as the most common Eukaryote in another study...

and yes the community of bacteria and other microbes on sheng puerh is almost certainly going to be different. They saw the community change in shu puerh throughout the process of pile fermentation so it's extremely unlikely that the microbial community in sheng would be the same when it's such a different environment.

http://www.ncbi.nlm.nih.gov/pubmed/23591759
http://www.ncbi.nlm.nih.gov/pubmed/23553377

Identifying exactly what the composition of puerh microbial communities are is just getting started. You'd better get a doctorate in microbiology in China if you really want to know.

[SlowOx]

and yes the community of bacteria and other microbes on sheng puerh is almost certainly going to be different.

First of all, thank you for providing some info and feedback here. Really cool finds there!

I wonder why producers of Shu pu-erh wouldn't inoculate their tea with similar microflora that spontaneously occurs on sheng pu-erh.

To the books!

[entropyembrace]

and yes the community of bacteria and other microbes on sheng puerh is almost certainly going to be different.

First of all, thank you for providing some info and feedback here. Really cool finds there!

I wonder why producers of Shu pu-erh wouldn't inoculate their tea with similar microflora that spontaneously occurs on sheng pu-erh.

To the books!

it's difficult to correctly identify the species which provide the greatest influence on the characteristics of aged tea, then to culture them to inoculate the fermentation piles with but there is some experimentation going in that direction: http://www.ncbi.nlm.nih.gov/pubmed/20471594

[SlowOx]

it's difficult to correctly identify the species which provide the greatest influence on the characteristics of aged tea, then to culture them to inoculate the fermentation piles with but there is some experimentation going in that direction

Another wonderful resource! I'm paying quite a bit for these articles. Thus proceeds the passion!

I've cultivated spores in my own lab before, this may or may not be too different. I'm going to start experimenting with cultivating bacteria found on a Menghai 86 loose Sheng. It's the best pu-erh I've ever had so far. (I haven't had a whole lot)

[xiaobai]

If I were you I would be very careful when planning to inoculate your sheng cakes with strains of mycotoxin producing molds, like the ones that have been detected on some wet-storage cakes from certain tea markets:

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

If you accidentally cultivate and manipulate the bad strains of molds such like aspergillus flavus or ochraceous, as well as some species of penicillium, you may be at risk of damaging your internal organs or even suffering aspergillosis, which is not a nice thing to be exposed to (it can even kill you ):

http://en.wikipedia.org/wiki/Aspergillosis

Use care here. Some of the stuff on your puerh is coming from ecosystems that are far removed from human society and it is not necessarily beneficial to us when cultivated as a hobby.

[bannacha]

I had a class about tea aging at National Taiwan University. It was given by a researcher from the Tea Research and Extension Station, the main tea research body in Taiwan.

She explained that the microflora on the pu-erh cakes changes a lot over time and according to the storage environment. The pH of tea changes as it ages: it starts high, decreases and increases again after a couple of year. This is due to the oxidation of different compounds.

Two factors contribute to aging: microbial activity and enzymatic oxidation. When tea is dry stored (leaf water content <7%), microbial activity is not very important, most of the change is due to enzymatic activity. The tea won't have wet-storage flavor. Between 7% and 12% of leaf water content, microorganisms make a significant contribution to the taste of tea, it is typically tea stored in Hong Kong, Taiwan and Guangdong. Over 12%, more mold is able to grow and the tea will become undrinkable, it will rot.

Two main parameters control which species will be able to grow: pH and water activity. This explains why the microflora is dynamic and also why the taste of pu-erh tea can change significantly with the weather.

Hope this helps.

[xiaobai]

I had a class about tea aging at National Taiwan University. It was given by a researcher from the Tea Research and Extension Station, the main tea research body in Taiwan.

She explained that the microflora on the pu-erh cakes changes a lot over time and according to the storage environment. The pH of tea changes as it ages: it starts high, decreases and increases again after a couple of year. This is due to the oxidation of different compounds.

Two factors contribute to aging: microbial activity and enzymatic oxidation. When tea is dry stored (leaf water content <7%), microbial activity is not very important, most of the change is due to enzymatic activity. The tea won't have wet-storage flavor. Between 7% and 12% of leaf water content, microorganisms make a significant contribution to the taste of tea, it is typically tea stored in Hong Kong, Taiwan and Guangdong. Over 12%, more mold is able to grow and the tea will become undrinkable, it will rot.

That's very interesting and useful information. Thanks for sharing, Bannacha.

I have one question: Did the researcher explain which kind of
microorganisms contribute significantly to the flavor of tea when the moisture of the dried leaves is between 7% and 12%? Is it bacteria or mostly mold?

From my exchanges with some tea vendors with expertise on the issue of mycotoxins in foodstuff, I learned that the presence in puerh of A. flavus and other mycotoxin-producing molds does not necessarily imply that they have produced the toxins. The latter are produced about the time when the molds grow their spores.

However, this indicates that, in order to assess the safety of a certain aged puerhs what are needed are tests that detect the toxins rather than the molds themselves.

[Cwyn]

Here is an article http://www.researchgate.net/publication ... af_extract

I'm certain factory puerh is enhanced, since the research directions now are all about enhancing both the flavor and properties that lower cholesterol, promote weight loss etc. . If you read the Journal of Yunnan Agricultural U there are lots of articles.

You don't need to over think this too much because it isn't high tech. Shou is made on a cement floor, sprayed with water and covered with a tarp. This past winter I changed over sheng to shou using crock fermentation, using an old farm stoneware bowl. Same process as sauerkraut. I learned a lot and am experimenting with samples in small crocks. It is all in my blog at deathbytea.blogspot.com Just buy some cheap sheng or use free samples you get with your tea orders and try adding humidity to see what happens. You don't need to go so far as making shou, but you can see how the tea opens up with added humidity. This helps to learn to compensate for your environmental conditions.

The process of aging sheng is no different, bacteria and molds are no different, just at lower levels. When shou is done, after six months the bacteria level returns to the baseline level.

[bannacha]

I can't find the researcher's powerpoint, the aging is caused mostly by mold, but bacteria also play a part. It should also depend on the level of wetness, bacteria requires a more humidity than mold in order to be able to grow.

As you can see here: http://www.ncbi.nlm.nih.gov/pubmed/23957415
The main mold growing on pu-erh tea comes from the Aspergillus and Penicillium genus.

Dear Cwyn, do you have papers that compare the microflora in Shou during fermentation and aged Sheng? I would be surprised to find the same ecosystem in both, different species will compete better in different environments. If there were no major differences what would explain the diversity of tastes among Shou?

Another question: during the Shou fermentation process, do the tea enzymes play a significant role or is it mostly microorganisms that changes tea?

[entropyembrace]

I can't find the researcher's powerpoint, the aging is caused mostly by mold, but bacteria also play a part. It should also depend on the level of wetness, bacteria requires a more humidity than mold in order to be able to grow.

As you can see here: http://www.ncbi.nlm.nih.gov/pubmed/23957415
The main mold growing on pu-erh tea comes from the Aspergillus and Penicillium genus.

This paper (or one similar? Im not signed in to the library proxy to look) is referenced in the introduction of one of the papers I posted earlier (Lyu et al 2013). They suggested that Aspergillus and Penicillium being identified as the most abundant organisms is an artifact of Tian et al using a culture dependent method. This is pretty reasonable considering less than 1% of the diversity of microbial life can actually be cultured at all.

[kyarazen]

decidedly it is still between "fermentation" and "oxidation"

a reminder that some herbs, i.e. lian qiao, mandarin peel, chinese bergamot are "aged" but not fermented

[Evan Draper]

Between 7% and 12% of leaf water content,

Thanks much for this. Can you say more about leaf water content and how it is measured? How is this related to relative humidity? I have heard people mention leaf water content thresholds in the context of the end product of manufacturing (or re-roasting) but I would have a hard time knowing how to create a storage environment based on those criteria. (Me, I just aim for 75% relative humidity....) Ox, what're your humidity levels?