Translated Article – Sealed Pu’er Storage Comparison Experiment

This article was retrieved here. All the usual caveats of my previously translated articles still apply here~ Please don’t shoot the messenger. For this one I will add a quick personal note:

For anybody that somehow has not heard about sealed storage in the West, the first place you should absolutely go to find information is Marco’s blog. There you will find solid information and well-kept data on far more variables than in the piece translated below.

For this particular article, there is missing information on what I would imagine are important variables – such as temperature levels not being recorded (at least in the article) for us to view. It also may be important to consider that the tea used was unpressed, and only one particular tea was used for the experiment. While the findings should be interesting to compare to other folks out there conducting similar experiments, this isolated experiment cannot be representative of any conclusive “best-practices.” One interesting piece about this particular experiment is that it was conducted over four years, which is a considerable chunk of time compared to other more fledgling experiments.

With that out of the way, let us begin:

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Despite the fact that there is constantly a push from many people to encourage people to “drink” pu’er, and to avoid hyping and investing/storing pu’er tea, the reality of pu’er is that it can be stored for long periods of time and can potentially through this process increase in value. This naturally makes pu’er tea a very suitable commodity for investment and collection. Teas from 2005 of high quality and a certain level of notoriety have essentially risen 20 times their original price, with some selections exceeding 100 times their original value. Pu’er investment and collection has a very large space for value increase; however, a prerequisite for this is reliable storage.  With poor storage, it doesn’t matter how long a tea has been age,d if it tastes bad, it has lost room for significant value increase.

There are essentially a few primary methods of tea storage: Natural Storage, Wet Storage, Sealed Storage with controlled humidity, and sealed storage with constant and consistent temperature and humidity.

Wet Storage (濕倉)

Wet storage refers to a human controlled environment in which tea is subjected to high temperature and high humidity, and provided adequate conditions for microbial activity. These parameters encourage must faster fermentation (in general 2 to 5 years).  General examples of this type of storage are sheet iron containment rooms, where water is added to the floor space, or caverns. Wet storage fermentation is similar in nature to how ripe pu’er is produced, the important concept is that through the enzymatic breakdown of tea leaves, the tea will have reduced levels of bitterness and astringency, and the resulting liquor will redden. In general the fermentation level of wet stored pu’er is lower than that of ripe pu’er.

Disadvantages of wet storage: When the wet storage process is complete, tea is noticeably covered in a frosty white cover of mold. When smelled, it has a distinct mildew-like scent, and drinking the tea very easily causes a dry throat (鎖喉) and is bitter. If during the fermentation process any harmful mildews or other microorganisms appear, the tea cannot be consumed.  

The benefits of wet storage is that tea can rapidly reduce bitterness and astringency, while changing liquor color, and due to the fact that the fermentation level is lower than that of ripe tea, with sufficient time being released from its wet storage (ten years or more),  after this successful “removal process” (退倉), this throat drying will fall away, and tea will have a vibrant red color, be sweet and smooth, have huigan, and have a much more lively taste than ripe tea. After the year 2000, wet storage was largely rejected as a storage style.

Natural Storage (自然倉)

Natural storage indicates that tea has not been disturbed by human intervention. It has been stored under natural conditions. During the 90s, natural storage was the most popular storage style. The thought was that for post-fermentation, oxygen and a certain level of humidity was needed, and that “there is no threshold to be crossed as far as pu’er storage is concerned. any place where people can reside, so can tea.” Because of the influence of this outlook, home storage started to become a widespread phenomenon. Since natural storage can avoid mold growth on tea, some people believed this to be “dry storage” (乾倉). In reality, these natural storage conditions cannot be called dry storage.

The benefits of natural storage: Natural storage’s most shining advantage is that it has a very low cost. There is no need for dedicated, specialized storage, no need for any particular equipment, and any place one desires to put tea can become a storage location.

The cons of negative storage: The quality of the storage is completely dependent on the storage environment’s climate conditions. High temperature and humid environments will more easily ferment the tea, lose fragrance, or even affect taste quality. Low temperature and low humidity environments will slow a tea’s aging. In most places (this is written geographically form an Asian perspective) when the rainy season arrives, indoor humidity trends high. When humidity is high, tea leaves will absorb excess water and will lead to fermentation affecting quality, and potentially will produce off flavors. The second problem with natural storage is that fragrance will very quickly leave the tea – within two or three years, there will be essentially no fragrance left to the tea leaf.  The third problem with this storage style is that the active enzymes within the tea leaves will quickly diminish, causing the tea’s later aging to have a lower “power source” to draw from. Any random so-called “dry stored” natural tea storage, with 10 to 20 years on it, despite having liquor that shows redder than before due to oxidation, will struggle to rid itself of bitterness and astringency. The general “special qualities” of this storage type are: Red liquor, no fragrance, and bitter/astringent tea.

Sealed Storage with constant/consistent humidity and temperature (密封恆溫恆濕倉)

Sealed storage with consistent temp and humidity has undergone human intervention and control, controlling an entire storage area at the desired levels of humidity and temperature of its owner.

The Disadvantages of this sealed storage: One, maintenance cost is high, and tea – being thought of as a plant – under normal conditions generally undergoes some variation of humidity and temperature change. Whether complete control of humidity and temperature will benefit a tea is still uncertain, we will still have to wait for future observations.

The Advantages: You can relatively easily protect a tea’s fragrance and active enzymes, guaranteeing that the tea will maintain its fragrance through its continued change. Additionally, there are no conditions that could cause off-flavors to occur.

Sealed Storage with controlled humidity (密封控濕倉)

This storage style indicates an environment where humans control how sealed a tea is, as well as how much humidity it is exposed to. Tea is sealed in a container without exposure to light or excess humidity. The tea is sealed, storage sealed, a dehumidifier is introduced, and any excess humidity beyond 70%RH is removed, keeping the tea below this 70%RH cap.

The cons of this storage: A storage area must be specially dedicated to tea. Again, there are cost for the equipment needed to manage storage.

The pros of this storage: This storage style can maintain a tea’s fragrance long-term, and within a certain range of time will allow tea to increase fragrance through storage. Because it can maintain enzyme activity, tea can continue to change, and bitterness and astringency will reduce, liquor will redden, and tea will not any produce off flavors related to the aging process.

Pu’er sealing experiment

Sealing tea inevitably runs into the question of oxygen’s contribution to aging. According to the generally accepted understanding of the tea fermentation (aging) process, pu’er tea must have some level of oxygen and water in order to age, thus air exchange is needed for storage. However, in actuality, many people storing tea have already discovered that too much airflow in storage reduces a tea’s fragrance within a few years despite the liquor reddening, and bitterness and astringency do not easily fall off. It appears that what pu’er truly relies on for continued aging is microbial activity – this falls under an outside influence – the other thing pu’er tea relies on is the enzymatic activity within the tea leaf. This can be considered an internal influence. After a tea has been sealed under a controlled level of humidity, the tea does not need any more microbial fermentation, the tea is primarily relying on the enzymatic activity brought by the tea leaf itself to promote further aging.

What will happen to sealed tea, assuming the above points about enzymatic activity, within a sealed environment with no oxygen? In order to explore this question, the writer of this article began an experiment with sealed storage in 2013.

Experimental Methods:

The author obtained unpressed (散茶) Jingmai gushu material, all material being of the same year and the same producer, and sorted the material into 4 equal portions. One portion was vacuum sealed, one portion was sealed in a sealed bag (not mentioned but very likely mylar), one was sealed in a sealed bag with oxygen added periodically, and the final portion was naturally stored with no seal. All four samples of tea were placed in a storage unit with dehumidification. After four years, 3 grams of each tea was steeped in a 150ml vessel for five minutes. The results were as follows:

Vacuum Sealed Tea: This sample had the most significant change in color. The liquor displayed a bright bronze color. The tea’s fragrance had kept the best – The dry tea had a clear fragrance stronger than that of new tea even. The fragrance of the liquor was also quite noticeable. The tea remained quite bitter. Of the four, this tea was the most bitter.

Sealed (not vacuum sealed): The tea’s color changed well, a nice bronze color. The tea’s fragrance kept well. The dry leaf had a strong scent, again much more than that of new tea. The tea’s liquor had considerable fragrance. This sample’s fragrance came in second to the vacuum sealed tea. Bitterness and astringency reduced.

Sealed with oxygen added: This tea also had a bronze color, but inferior to the two previously mentioned samples. The tea was fragrant, but very obviously had reduced fragrance compared to the previous two. Bitterness and astringency were reduced. The bitterness and astringency levels were lower than the vacuum sealed sample, and at a similar level to the sealed-not-vacuumed sample.

Natural Storage No Seal: Bronze color in liquor, similar to that of the sealed tea with oxygen added. The tea leaf basically had no fragrance left. There was a slight taste change related to aging. Bitterness/astringency was reduced, however, the degree of reduction was inferior to the sealed teas.

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Due to the fact that this experiment was conducted over only four years, no absolute conclusions can be made. As far as the results from this isolated experiment are concerned, there are some relatively obvious phenomenon observed.

First, vacuum sealed tea can preserve a tea’s characteristics extremely well. This is an ideal way to store tea samples. Because harshness does not reduce well, it does not appear ideal for pu’er tea storage.

Second, oxygen’s role in pu’er aging did not show any significant signs. Natural storage and sealed-with-oxygen-added teas did not have any obvious advantages compared to the vacuum sealed and sealed (with no periodic oxygen added) samples.

Third, sealed storage not only preserves tea fragrance; additionally, it seems to enhance the fragrance’s display.

Fourth, sealed storage, under the effects of internal enzymatic activity does not appear to hinder the change of color (liquor) or reduction of harshness, suggesting that tea can rely primarily on its inherent enzymatic activity to age.