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A Discussion of Aging Tea; from Science to Spirit

Article by Aaron Fisher; Photo and Cham Kam Pong

Mr. Fisher was born in the U.S. He studied philosophy and anthropology. Afterwards he traveled extensively, living in India, China, and Japan, before finally settling in Taiwan. He was first introduced to tea by a Chinese friend in the 90's and fell in love instantly. Since then he's developed a passion for the Leaf that motivated much of his travel and study over the last years. It is an infatuation he wishes to unreservedly share. Nowadays, he divides his time between the school he founded, writing, painting and drinking tea.

There is something magical about the way that teas change when they are aged. I used to think that only Puerh tea could be fermented, improving over time; I have since found that almost any tea gets better with time. I have had old jasmine teas, oolongs, and even green teas. The latter seems to take a lot longer to change, and isn't usually kept for so long because I think a big part of what makes green tea so enjoyable is its freshness. Still, there is a mystical way in which teas wizen with age, becoming deeper, stronger and richer in flavor and Qi. And while many of the aged teas I've had were rewarding, no tea on Earth transforms as much as Puerh.

There is a part of this change that will forever remain magical, and a part of me likes it that way. My Western mind, however, is always curious, hoping to understand as much as I can intellectually. I was therefore very excited when I met a biology professor at my local university who is also a tea lover. We had some very interesting conversation and he even showed me some slides of tea cells, which I had never before seen. Nevertheless, as I began to piece together more and more about the process of aging tea, I still feel like I need to say that being able to analyze, measure and understand something intellectually doesn't make it any less magnificent. If scientists one day explain why yogis can control their body temperature, go without sleep, or why Indians can bathe and drink in the Ganges without getting sick; or even why there are lights above certain temples in the Himalayas that I've seen— any explanation wouldn't diminish the power, magic or mystery of these phenomena. I feel the same about Puerh. I may learn more about the chemical changes that occur over time as it ferments, but what of the way in which it accumulates Qi, becoming wiser? Zhou Yu always says that one would be a fool to spend thousands of dollars on old tea simply because you like the flavor; their value lies in their health benefits, and the comfortable relaxation and Qi they bring to a tea session.

As I talked with professor Yang, I began to understand more and more about what is happening to Puerh as it ages. I had studied some of this with one of my teachers, Huang Chan Fang, but these recent conversations and the slides Mr. Yang kindly showed me seemed to bring it all together.In order to understand what is going on as Puerh ages,it is important to first explore a bit of biology:

The main difference between plant and animal cells is that plant cells need to retain nutrients and moisture more efficiently, and consequently have very thick layers of cellulose that surrounds the cell walls. Each wall then has small valve-like openings through which gas and nutrients are exchanged. The organization of the cells themselves is also much more stratified and impenetrable than animal tissue. The leaves of a plant or tree are especially impervious, as they are protected by a waxy cuticle that is padded by tightly-packed epidermal cells. The leaf breathes - exchanges gas - through microscopic openings on the bottom called "stomata". The moisture and nutrients in all of the cells are therefore protected within and without: within each cell by a thick wall, and the tissue itself by a thick, waxy skin covering the outside of the leaf.

When we brew tea, it is the oils and nutrients within the cells that provide all the flavor and aroma - the essence of the tea itself. Consequently, the processing of tea is in part about breaking and/or bruising the cellular structure of the leaf so that it will release its inner oils and nutrients. There are many different methods of tea production used to break down enough of these barriers. Sometimes the tea is kneaded, as with oolongs and Puerhs, to break down the cellular structure; while other times the cells are left intact. This will affect the flavor, strength and patience of a tea.

Low-grade black teas are often machine-harvested and then torn up by other machines, called CTC or Crush, Tear, and Curl' and then completely oxidized so that they release all of their nutrients in a single steeping, which is why most tea bags cannot be resteeped. White, yellow and green teas are not manufactured in these ways, and therefore brew a light, subtle liquor. White and yellow teas are traditionally just steamed and dried, the difference being that yellow teas are covered with a cloth while steaming to seal in the aroma, and therefore have almost no cellular breakdown. The fact that they are composed exclusively of buds also contributes to the fact that the cells of the leaves are still firm and strong, which means the resulting tea is even lighter.

It is also important to understand the difference between oxidation and fermentation in order to further clarify what is happening to tea as it ages. Using my wise friend Bob Heiss' definition of oxidation as "a biochemical, enzymatic activity during which oxygen is absorbed by and subsequently causes changes to the host physical matter" we can begin to discuss the way it affects tea processing. Oxidation occurs naturally or is controlled by the producer. Natural oxidation is what happens when the leaves are left to wither in open air, or as Bob Heiss reminds me also the way in which a cut apple turns brown when left on the counter. Controlled oxidation is a big part of processing oolong, black and Puerh teas. The teas are moved in and out of doors as they absorb oxygen. In the production of some black teas, oxidation chambers are sometimes used, with humidified, oxygen-rich air pumped in through vents. The oxidation is then arrested in the case of oolong, white, green and yellow teas by frying, steaming, roasting or meticulous drying techniques. With green, yellow and white teas, the manufacturer will arrest the oxidation immediately, though some natural oxidization is inevitable, whereas oolong is allowed to oxidize to a huge variety of degrees depending on the tea, region and tradition of manufacturing methodology. Many tight-rolled oolongs in Taiwan and Fujian are hardly oxidized at all, while others like Wuyi Rock Teas, Dan Cong and Bai Hao Oolong are more heavily oxidized.

As teas wither and begin their natural or controlled oxidation, several complex chemical changes are occurring that will change the flavor. Oxygen combined with techniques of rolling, shaking, frying, roasting, etc. are all changing the leaves at a cellular level, as well as breaking down the thick cell walls so that the nutrients of the tea can come out when it comes into contact with hot water. Oolongs, Puerhs and black teas that haven't been chopped up will often release their essence slowly over many steepings, and the higher quality the leaf, the hotter the water we'll use to dig down into the leaves for their inner spirit.Creen. yellow and white teas, on the other hand, don't really break down at the cellular level and therefore arc just scalded by hotter temperatures, responding better to lower temperatures for longer steepings. They also won't last nearly as long.

Though often confused for oxidation, especially since there is only one Chinese term, fermentation is a different process. Fermentation is the breakdown of complex molecules in any organic compound under the influence of a 'ferment', which is usually some form of bacteria - the microbial changes that occur as organic molecules are aged, in other words. The term applies to curd, yoghurt, cheese, alcohol, etc. You might regard oxidation as a part of the processing of tea, and fermentation as the changes that occur as it is aged post-processing. Normally, many foods and beverages arc best fermented in the absence of oxygen, in fact. Puerh tea is a unique exception to that rule. Oolong teas, however, are often stored in jars sealed with wax to keep oxygen out, and the resulting changes are therefore very different.


There is no tea on Earth like Puerh, as it comes from the Eden of all tea gardens, and old trees that are themselves descendents of the first ever tea. Though many Puerh plantations have began recently to respond to the growing popularity of this genre of tea, Puerh was traditionally harvested from large trees grown in small gardens deep in the mountain forests of Yunnan, hardly distinguishable from the surrounding trees and undergrowth. As we'll soon see,the "ageability" of these plantation teas is suspect, since a big part of why Puerh changes so drastically is in the trees themselves.

More than any other kind of tea, Puerh tea is covered in microbes and bacteria. Since it comes from trees in the jungle, the leaves themselves are covered in thousands of kinds of bacteria, many found in other fermented products like yoghurt. Puerh is then processed rather simply, in a tradition dating back thousands of years. It is withered, then fried when the oxidation has reached the desired stage, kneaded to break down the cells and then dried, traditionally in the sun.

Besides the fact that it comes from trees, Puerh is also different from other teas because it is compressed. People often ask why it is that compressed teas ferment differently than loose-leaf Puerh. The reason is that the dried, finished tea called "mao cha" is compressed using steam. The humid steam rooms in which this is done are themselves treasure troves of bacteria.

These bacteria and other microbes are then compressed into the cake, along with the other natural bacteria that was already present on the leaves in the jungle gardens. Traditional factories compressed their teas on the mountain where they were grown, using the same water for steam and the same air. Modern factories transport the mao cha great distances and it often sits for some time waiting for its turn in a large production schedule, which is obviously inferior to the age-old methods. The cakes are then dried, but never completely. Some moisture is trapped in the cake, which is the perfect environment for the bacteria and microbes to do their work.

Newborn Puerh is astringent and strong, often bitter. It is also unhealthy for the stomach, and 'cool' in the Chinese medicinal system, which isn't good for most people's constitution. This kind of drink is only suitable for those with heavy, rich and oily diets, like the Tibetans who have traditionally drunk such Puerh to supplement their all-meat diets.

It is amazing to see some people drinking gallons of Newborn Puerh, much of which is grown on the pesticide-covered plantations rather than the traditional "old-growth" gardens, and though they might grow to appreciate the rich, astringent flavor, the tea is most likely harming their stomachs and kidneys. Aged Puerh, on the other hand, is smooth, woody and sweet with hints of plum, orchids, camphor or other rich flavors. Its nature is 'warm', comforting the body and opening up the flow of Qi.

I looked at slides of newborn and aged Puerh with professor Yang and was amazed to see that the cells of the aged Puerh were completely broken down, muddled and flat while the newborn teas cells were relatively still intact, though the damage from the kneading was evident when we compared it to a look at a fresh, untouched leaf.

Though I have had some great aged oolongs, I think one difference between them and the Puerh-leagues apart-lies in the fact that Puerh is exposed to oxygen throughout its fermentation. This keeps the bacteria in the tea active, making the changes over time much more pronounced than with oolong teas.

Puerh tea needs some humidity, oxygen and natural warmth throughout its storage. Traditionally it was always kept in southern China, Taiwan and Hong Kong as the seasonal fluctuations in humidity were ideal: in spring the tea absorbs moisture, in summer the heat increases the microbial activity, and then in autumn and winter the humidity drops significantly over time which allows the tea time to rest before repeating the process again. I've noticed these changes in my own collection simply by the strength and variation in odors that the tea releases throughout these seasons.

Recently, many collectors have began to focus and promote different storage methods. This is in part due to the popularity of Puerh, and the fact that more people have began to study and verify different aspects of storage, as well as the increased distribution of information in magazines such as this. Still, all of the famous vintages of Puerh were not stored with such hypersensitivity. Of course, tea shop owners—primarily in Hong Kong—viewed their Puerh as a financial investment and didn't just toss it anywhere; but neither did they monitor the humidity, build special shelving units or scrutinize, analyze or measure any other aspect of the tea as it changed over time.

The changes that occur in Puerh, and other teas over time, do so naturally. They are not manmade. Traditional warehouse owners would check on their tea but once or twice a year, move it around, sweep and dust, I have been to large warehouses in Hong Kong and Taiwan that still store very old, very expensive teas in wood crates scattered about over a huge room, without any meticulous organization, humidity gauges or other methods of analyzing this or that. The first intentional experiments in "dry storage" occurred in the late eighties or nineties, and any older dry-stored tea was done so accidentally, like one fifties tea I had that had been stored on the 22nd floor and was therefore drier. The desire for dry-stored tea is a very modern fad, related to misinformation, and in part the newborn markets in some parts of China that didn't ever have access to aged tea and so promoted the idea that a lot of Puerh was "moldy", "musty", etc. - thereby teaching customers that it is better to by their newborn teas. Some oolong vendors in Taiwan also promoted the idea that Puerh was unhealthy or distasteful because of these reasons. Studies, like the one conducted in the first issue of this magazine, have concluded that all of the mold present in Puerh tea is completely destroyed by water at temperatures of 80 degrees or higher.

The fact is that all old tea was wet-stored, some of it very much so as it was placed in basements under hills in Hong Kong to accelerate the aging process. "Wet-stored", however, does not always mean a conscientious effort to speed up the aging process. By definition wet-stored tea just means that it was stored in a location with higher than normal humidity (normal being 70-85%, depending who you ask), which sometimes can be the same tea stored on a different shelf - higher or lower, closer or further from the door. It doesn't always happen intentionally. It was often just a part of the natural aging process, not a trick or scheme to make teas seem older. Though such fraudulence did occur, it didn't happen often long ago when Puerh wasn't worth very much. Most of that began after Puerh tea became so popular.

My teacher Huan Chan Fang always says that if you don't like wet-stored Puerh, then you must really hate Ripe (shou) tea, since it is the wettest of the wet. Ripe Puerh was invented to try to reproduce the affects of aging Puerh during the processing itself - artificially fermenting the tea, in other words. The tea is piled in heaps, sometimes moistened and then often covered with thermal blankets, which is why it is sometimes called "cooked" Puerh. The intense heat, moisture and bacteria then ferment the tea partially or completely, depending on the duration. Rather than mimicking the qualities of aged Raw (sheng) Puerh, the manufacturers who invented Ripe tea succeeded only in making a new genre of tea, to be evaluated with its own criteria.

One should be willing to try all kinds of Puerh, wet and dry. Often times, the mustiness in wet tea is enjoyable. Even otherwise, it usually washes off after a couple steepings. Furthermore, as Zhou Yu mentioned above, most people who spend large amounts of money on aged Puerh are doing so for the warm feeling and Qi it brings to the body, more so than the flavors. Of course, I am not arguing that dry-stored tea is worse than wet-stored. My point is that I have had atrocious dry-stored tea and plenty of superb wet-stored tea. Usually, if a tea is very, very old then we want the driest, cleanest example. But when the tea isn't quite as old, wetter storage means the astringency and 'cool' nature will be gone, replaced by the rich woody flavors and warm feeling of old Puerhs.

I myself have a very large collection of newborn tea from the 80's, 90's and some from post 2000. While I do watch it, my philosophy is more about letting Nature do its work, the way tea was traditionally stored.

As I am still young, I put most of my tea in cardboard boxes to slow the process down a bit. I check on them every few months to make sure nothing is severely wrong, in which case I might move them. I clean the storage room once a year. Beyond that, very little of what is happening to them has anything to do with me. I don't monitor the oxygen, humidity, etc. I think that if Nature made all the great teas from the Antique and Masterpiece Eras, she'll do fine with my humble collection. In fact, as far as the Qi is concerned, I have a feeling that the less human interaction the better. I have had teas stored in con-trolled, manmade environments using humidifiers, etc. and they were all vastly inferior to the ones stored naturally.

Drinking aged teas assures that they were harvested at a time before there was pesticide, when all Puerh was organic, and most were harvested from the great tea trees that first established its legacy in the world of tea. The changes then that occur over time are amazing, both on the cellular level as the tea breaks down and all the oils release, making the tea rich and full of the essence of Nature, as well as in the spiritual sense, as aged teas accumulate greater concentrations of Qi so conducive to meditation and mental health. Learning from great teachers like Huang Chan Fang and professor Yang has more than satisfied my intellectual thirst. I feel like I have begun to understand the changes happening in teas as they are processed, oxidized and fermented. I'm sure I still have a lot left to learn, but most of this is about satisfying our curiosity enough to let go and enjoy the moment of tea. I think it is healthy to maintain a balance between how much we learn and discuss about tea and how much we simply sit back and enjoy. As I sip a well-aged Puerh and relax, the science is secondary to the wonderful, magical flavors and the comfort and well-being that soon follows.