Pu'er tea
Pu'er or pu-erh is a variety of fermented tea traditionally produced in Yunnan Province, China. In the context of traditional Chinese tea production terminology, fermentation refers to microbial fermentation (called 'wet piling'), and is typically applied after the tea leaves have been sufficiently dried and rolled. As the tea undergoes controlled microbial fermentation, it also continues to oxidize, which is also controlled, until the desired flavors are reached. This process produces tea known as 黑茶 "hēichá" (lit. 'black tea') (which is different from the English-language "black tea" that is called 红茶 "hóngchá" (lit. 'red tea') in  Chinese). Pu'er falls under a larger category of fermented teas commonly translated as "dark teas". Two main styles of pu'er production exist: a traditional, longer production process known as "shēng" ("raw") pu'er; and a modern, accelerated production process known as "shóu" ("ripe") pu'er. Pu'er traditionally begins with a raw product called "rough" ("máo") "chá" (毛茶, lit. fuzzy/furry tea) and can be sold in this form or pressed into a number of shapes and sold as ""shēng chá" (生茶, lit. raw tea). Both of these forms then undergo the complex process of gradual fermentation and maturation with time. The "wòduī  (渥堆) fermentation process developed in 1973 by the Kunming Tea Factory created a new type of pu'er tea. This process involves an accelerated fermentation into shóu" (or "shú") "chá" (熟茶, lit. ripe tea) that is then stored loose or pressed into various shapes. The fermentation process was adopted at the Menghai Tea Factory shortly after and technically developed there. The legitimacy of shóu chá is disputed by some traditionalists when compared to the traditionally, longer-aged teas, such as shēng chá. All types of pu'er can be stored to mature (in non-airtight containers) before consumption, which is why it  is standard to label them, more so than most other types of tea, with the year and region of production. Name. "Pu'er" is the pinyin romanization of the Mandarin pronunciation of Chinese "Pu-erh" is a variant of the Wade-Giles romanization (properly "p‘u-êrh") of the same name. In Hong Kong the same Chinese characters are read as Bo-lei, and that is therefore a common alternative English term for this tea. The tea got its name from the ancient tea-trading town of Pu'er (普洱), located in today's Ning'er Town (宁洱镇) in Ning'er County, Pu'er prefecture-level  city of Yunnan. Pu'er County had its name changed into Simao, after Simao Town, the new county seat in 1950 following the Communist victory. The County of Simao became a prefecture level City and had its name changed to Pu'er in 2007. Although the urban center of the modern Pu'er City remained in Simao, the whole Pu'er region is now sometimes considered the appellation for pu'er proper. Pu'er, known in Chinese as a type of 'dark tea' (heicha) is known in Spanish as té rojo (red tea), while what in Chinese as 'red tea' (hongcha), is known in Spanish as  'té negro', i.e. black tea. History. Fermented tea leaves has a long history among ethnic groups in Southwest China. These crude teas were of various origins and were meant to be low cost. Darkened tea, or "hēichá", is still the major beverage for the ethnic groups in the southwestern borders and, until the early 1990s, was the third major tea category produced by China mainly for this market segment. There had been no standardized processing for the darkening of "hēichá" until the postwar years in the 1950s, when there was a sudden surge in demand in Hong Kong, perhaps because  of the concentration of refugees from the mainland. In the 1970s the improved process was taken back to Yunnan for further development, which has resulted in the various production styles variously referred to as "wòduī" today. This new process produced a finished product in a matter of months that many thought tasted similar to teas aged naturally for 10–15 years and so this period saw a demand-driven boom in the production of "hēichá" by the artificial ripening method. In recent decades, demand has come full circle and it has become more common again for "hēichá", including pu'er, to be  sold as the raw product without the artificial accelerated fermentation process. Pu'er tea processing, although straightforward, is complicated by the fact that the tea itself falls into two distinct categories: the "raw" shēngchá and the "ripe" shóuchá. All types of pu'er tea are created from "máochá" (毛 茶), a mostly unoxidized green tea processed from "Camellia sinensis" var. "assamica", which is the large leaf type of Chinese tea found in the mountains of southern and western Yunnan (in contrast to the small leaf type of tea used for typical green, oolong, black, and yellow teas found in the other parts  of China). Máochá can be sold directly to market as loose leaf tea, compressed to produce "raw" "shēngchá", naturally aged and matured for several years before being compressed to also produce "raw" "shēngchá" or undergo wòduī ripening for several months prior to being compressed to produce "ripe" "shóuchá". While unaged and unprocessed, Máochá pǔ'ěr is similar to green tea. Two subtle differences worth noting are that pǔ'ěr is not produced from the small-leaf Chinese varietal but the broad-leaf varietal mostly found in the southern Chinese provinces and India. The second is that pǔ'ěr leaves are picked as one  bud and 3-4 leaves whilst green tea is picked as one bud and 1-2 leaves. This means that older leaves contribute to the qualities of pǔ'ěr tea. Ripened or aged raw pǔ'ěr has occasionally been mistakenly categorized as a subcategory of black tea due to the dark red color of its leaves and liquor. However, pǔ'ěr in both its ripened and aged forms has undergone secondary oxidization and fermentation caused both by organisms growing in the tea and free-radical oxidation, thus making it a unique type of tea. This divergence in production style not only makes the  flavor and texture of pu'er tea different but also results in a rather different chemical makeup of the resulting brewed liquor. The fermented dark tea, hēichá (黑茶), is one of the six classes of tea in China, and "pǔ'ěr" is classified as a dark tea (defined as fermented), something which is resented by some who argue for a separate category for "pǔ'ěr" tea. As of 2008, only the large-leaf variety from Yunnan can be called a "pǔ'ěr". Processing. Pu'er is typically made through two steps. First, all leaves must be roughly processed into "maocha" to stop oxidation. From there  it may be further processed by fermentation, or directly packaged. Summarising the steps: Both sheng and ripe pu'er can be shaped into cakes or bricks and aged with time. Section::::"Maocha" or rough tea. The intent of the "máochá " stage (青 毛 茶 or 毛 茶; literally, "light green rough tea" or "rough tea" respectively) is to dry the leaves and keep them from spoiling. It involves minimal processing and there is no fermentation involved. The first step in making raw or ripened pu'er is picking appropriate tender leaves. Plucked leaves are handled gingerly to prevent bruising and unwanted oxidation. It  is optional to wilt/wither the leaves after picking and it depends on the tea processor, as drying occurs at various stages of processing. If so, the leaves would be spread out in the sun, weather permitting, or a ventilated space to wilt and remove some of the water content. On overcast or rainy days, the leaves will be wilted by light heating, a slight difference in processing that will affect the quality of the resulting "maocha" and pu'er. The leaves are then dry-roasted using a large wok in a process called "killing the green" (殺 青; pinyin: "shā  qīng"), which arrests most enzyme activity in the leaf and prevents full oxidation. After pan-roasting, the leaves are rolled, rubbed, and shaped into strands through several steps to lightly bruise the tea and then left to dry in the sun. Unlike green tea produced in China which is dried with hot air after the pan-frying stage to completely kill enzyme activity, leaves used in the production of pu'er are not air-dried after pan-roasting, which leaves a small amount of enzymes which contribute a minor amount of oxidation to the leaves during sun-drying. The bruising of  the tea is also important in helping this minimal oxidation to occur, and both of these steps are significant in contributing to the unique characteristics of pu'er tea. Once dry, "máochá " can be sent directly to the factory to be pressed into raw pu'er, or to undergo further processing to make fermented or ripened pu'er. Sometimes "Mao Cha" is sold directly as loose-leaf "raw" Sheng Cha or it can be matured in loose-leaf form, requiring only two to three years due to the faster rate of natural fermentation in an uncompressed state. This tea is then pressed into  numerous shapes and sold as a more matured "raw" Sheng Cha. Pressing. To produce pu'er, many additional steps are needed prior to the actual pressing of the tea. First, a specific quantity of dry "máochá" or ripened tea leaves pertaining to the final weight of the "bingcha" is weighed out. The dry tea is then lightly steamed in perforated cans to soften and make it more tacky. This will allow it to hold together and not crumble during compression. A ticket, called a ""nèi fēi"" (内 飞) or additional adornments, such as colored ribbons, are placed on or in the  midst of the leaves and inverted into a cloth bag or wrapped in cloth. The pouch of tea is gathered inside the cloth bag and wrung into a ball, with the extra cloth tied or coiled around itself. This coil or knot is what produces the dimpled indentation at the reverse side of a tea cake when pressed. Depending on the shape of the pu'er being produced, a cotton bag may or may not be used. For instance, brick or square teas often are not compressed using bags. Pressing can be done by: Pressed pu'er is removed from the cloth  bag and placed on latticed shelves, where they are allowed to air dry, which may take several weeks or months, depending on the wetness of the pressed cakes. The pu'er cakes are then individually wrapped by hand, and packed. Fermentation. Pu'er is a microbially fermented tea obtained through the action of molds, bacteria and yeasts on the harvested leaves of the tea plant. It is thus truly a fermented tea, whereas teas known in the west as black teas (known in China as Red teas) have only undergone large-scale oxidation through naturally occurring tea plant enzymes. Mislabelling the oxidation  process as fermentation and thus naming black teas, such as Assam, Darjeeling or Keemun, as fermented teas has long been a source of confusion. Only tea such as pu'er, that has undergone microbial processing, can correctly be called a fermented tea. Pu'er undergoes what is known as a solid-state fermentation where water activity is low to negligible. Both endo-oxidation (enzymes derived from the tea-leaves themselves) and exo-oxidation (microbial catalysed) of tea polyphenols occurs. The microbes are also responsible for metabolising the carbohydrates and amino acids present in the tea leaves. Although the microbes responsible have proved  highly variable from region to region and even factory to factory, the key organism found and responsible for almost all pu'er fermentation has been identified in numerous studies as "Aspergillus niger", with some highlighting the possibility of ochratoxins produced by the metabolism of some strains of "A.niger" having a potentially harmful effect through consumption of pu'er tea. This notion has recently been refuted through a systematic chromosome analysis of the species attributed to many East Asian fermentations, including those that involve pu'er, where the authors have reclassified the organisms involved as "Aspergillus luchuensis". It is apparent that this species does  not have the gene sequence for coding ochratoxin and thus pu'er tea should be considered safe for human consumption. Ripe and raw pu'er. "Ripened" Shu Cha (熟茶) tea is pressed "maocha" that has been specially processed to imitate aged "raw" Sheng Cha tea. Although it is also known in English as cooked pu'er, the process does not actually employ cooking to imitate the aging process. The term may be due to inaccurate translation, as "shóu" (熟) means both "fully cooked" and "fully ripened". The process used to convert "máochá" into ripened pu'er manipulates conditions to approximate the result of the  aging process by prolonged bacterial and fungal fermentation in a warm humid environment under controlled conditions, a technique called "Wò Duī" (渥 堆, "wet piling" in English), which involves piling, dampening, and turning the tea leaves in a manner much akin to composting. The piling, wetting, and mixing of the piled "máochá" ensures even fermentation. The bacterial and fungal cultures found in the fermenting piles were found to vary widely from factory to factory throughout Yunnan, consisting of multiple strains of "Aspergillus" spp., "Penicillium" spp., yeasts, and a wide range of other microflora. Control over the multiple variables in the  ripening process, particularly humidity and the growth of "Aspergillus" spp., is key in producing ripened pu'er of high quality. Poor control in fermentation/oxidation process can result in bad ripened pu'er, characterized by badly decomposed leaves and an aroma and texture reminiscent of compost. The ripening process typically takes between 45 and 60 days on average. The "Wò Duī" process was first developed in 1973 by Menghai Tea Factory and Kunming Tea Factory to imitate the flavor and color of aged raw pu'er, and was an adaptation of wet storage techniques used by merchants to artificially simulate ageing of their  teas. Mass production of ripened pu'er began in 1975. It can be consumed without further aging, or it can be stored further to "air out" some of the less savory flavors and aromas acquired during fermentation. The tea is sold both in flattened and loose form. Some tea collectors believe "ripened" Shu Cha should not be aged for more than a decade. Wet pile fermented pu'er has higher levels of caffeine and much higher levels of gallic acid compared with traditionally aged raw pu'er. Additionally, traditionally aged pu'er has higher levels of the antioxidant and carcinogen-trapping epigallocatechin gallate as  well as (+)-catechin, (–)-epicatechin, (–)-epigallocatechin, gallocatechin gallate, and epicatechin gallate than wet pile fermented pu'er. Finally, wet pile fermented puer has much lower total levels for all catechins than traditional pu'er and other teas except for black tea which also has low total catechins. Classification. Aside from vintage year, pu'er tea can be classified in a variety of ways: by shape, processing method, region, cultivation, grade, and season. Shape. Pu'er is compressed into a variety of shapes. Other lesser seen forms include: stacked "melon pagodas", pillars, calabashes, "yuanbao", and small tea bricks (2–5 cm in width). Pu'er is also  compressed into the hollow centers of bamboo stems or packed and bound into a ball inside the peel of various citrus fruits ("Xiaoqinggan") or sold as nuggets ("Suiyinzi" 碎银子 or "fossilized tea" 茶化石) or bundles ("Laotoucha" 老头茶). Process and oxidation. Pu'er teas are often collectively classified in Western tea markets as post-fermentation, and in Eastern markets as black teas, but there is general confusion due to improper use of the terms "oxidation" and "fermentation". Typically black tea is termed "fully fermented", which is incorrect as the process used to create black tea is oxidation and does not involve microbial  activity. Black teas are fully oxidized, green teas are unoxidized, and Oolong teas are partially oxidized to varying degrees. All pu'er teas undergo some oxidation during sun drying and then become either: According to the production process, four main types of pu'er are commonly available on the market: Flavour. Ripe pu'er is often described by its multiple layers of aroma: "duiwei" (堆味) or fermented flavour, "cangwei" (仓味) or storage flavour, "xingwei" (腥味) or fish flavour and "meiwei" (霉味) moldy flavour. The storage locations (Yunnan, Canton or Hong Kong) and storing conditions (wet vs dry storage) will result in distinct flavours . The aromas can be annotated as camphora (樟香), ginseng (参香), jujube (枣香), costus (木香), minty (荷香) or very aged (陈香). Raw pu'er is often distinguished by its floral (花香), grassy (草香), fresh (清香), herbal (药香), fruity (水果) or honey（蜜香）aroma. Some pu'er are flavour infused, for example Sticky rice pu'er ("Nuomixiang", 糯米香) are infused with leaves of Semnostachya menglaensis native to Mengla, which gives it a young rice flavour. Bamboo roasted pu'er is encased in bamboo tubes and underwent a smoking process. Tangerine pu'er ("Xiaoqinggan", 小青柑) were made from small green tangerine stuffed with tea. Flower-infused pu'er are made in  the form of tea balls (龙珠) or tea cakes. Regions. Yunnan. Pu'er is produced in almost every county and prefecture in the province. Proper pu'er is sometimes considered to be limited to that produced in Pu'er City. Six Great Tea Mountains. The best known pu'er areas are the Six Great Tea Mountains (), a group of mountains in Xishuangbanna, Yunnan, renowned for their climates and environments, which not only provide excellent growing conditions for pu'er, but also produce unique taste profiles (akin to terroir in wine) in the produced pu'er tea. Over the course of history, the designated mountains for the  tea mountains have either been changed or listed differently. In the Qing dynasty government records for Pu'er (普洱府志), the oldest historically designated mountains were said to be named after six commemorative items left in the mountains by Zhuge Liang, and using the Chinese characters of the native languages (Hani and Tai) of the region. These mountains are all located northeast of the Lancang River (Mekong) in relatively close proximity to one another. The mountains' names, in the Standard Chinese character pronunciation are: Southwest of the river there are also nine lesser known tea mountains, which are isolated by the river . They are: For various reasons, around the end of the Qing dynasty and at the beginning of the ROC period (the early twentieth century), tea production in these mountains dropped drastically, either due to large forest fires, overharvesting, prohibitive imperial taxes, or general neglect. To revitalize tea production in the area, the Chinese government in 1962 selected a new group of six great tea mountains that were named based on the more important tea-producing mountains at the time, including Youle mountain from the original six. Other areas of Yunnan. Many other areas of Yunnan also produce pu'er tea. Yunnan  prefectures that are major producers of pu'er include Lincang, Dehong, Simao, Xishuangbanna, and Wenshan. Other notable tea mountains famous in Yunnan include among others: Region is only one factor in assessing a pu'er tea, and pu'er from any region of Yunnan can be as prized as any from the Six Great Tea Mountains if it meets other criteria, such as being wild growth, hand-processed tea. Other provinces. While Yunnan produces the majority of pu'er, other regions of China, including Hunan and Guangdong, have also produced the tea. The Guangyun Gong cake, for example, although the early productions were composed  of pure Yunnan "máochá", after the ‘60s the cakes featured a blend of Yunnan and Guangdong "máochá", and the most recent production of these cakes contains mostly from the latter. In late 2008, the Chinese government approved a standard declaring pu'er tea as a "product with geographical indications", which would restrict the naming of tea as pu'er to tea produced within specific regions of the Yunnan province. The standard has been disputed, particularly by producers from Guangdong. Fermented tea in the pu'er style made outside of Yunnan is often branded as "dark tea" in light of this standard. Other regions . In addition to China, border regions touching Yunnan in Vietnam, Laos, and Burma are also known to produce pu'er tea, though little of this makes its way to the Chinese or international markets. Cultivation. The method of cultivation can have as much of an effect on the final product as region or grade. There are three widely used methods of cultivation for pu'er: Determining whether or not a tea is wild is a challenging task, made more difficult through the inconsistent and unclear terminology and labeling in Chinese. Terms like "yěshēng" (野 生; literally "wild" or "uncultivated"), "qiáomù" (乔 木 ; literally "tall tree"), "yěshēng qiáomù" (野 生 乔 木; literally "uncultivated trees"), and "gǔshù" are found on the labels of cakes of both wild and "wild arbor" variety, and on blended cakes, which contain leaves from tea plants of various cultivations. These inconsistent and often misleading labels can easily confuse uninitiated tea buyers regardless of their grasp of the Chinese language. As well, the lack of specific information about tea leaf sources in the printed wrappers and identifiers that come with the pu'er cake makes identification of the tea a difficult task. Pu'er journals and similar annual guides such as  The Profound World of Chi Tse, "Pu-erh Yearbook", and "Pu-erh Teapot Magazine" contain credible sources for leaf information. Tea factories are generally honest about their leaf sources, but someone without access to tea factory or other information is often at the mercy of the middlemen or vendor. Many pu'er aficionados seek out and maintain relationships with vendors who they feel they can trust to help mitigate the issue of finding the "truth" of the leaves. Even in the best of circumstances, when a journal, factory information, and trustworthy vendor all align to assure a tea's genuinely wild  leaf, fakes teas are common and make the issue even more complicated. Because collectors often doubt the reliability of written information, some believe certain physical aspects of the leaf can point to its cultivation. For example, drinkers cite the evidence of a truly wild old tree in a menthol effect ("camphor" in tea specialist terminology) supposedly caused by the Camphor laurel trees that grow amongst wild tea trees in Yunnan's tea forests. As well, the presence of thick veins and sawtooth-edged on the leaves along with camphor flavor elements are taken as signifiers of wild tea. Grade. Pu'er  can be sorted into ten or more grades. Generally, grades are determined by leaf size and quality, with higher numbered grades meaning older/larger, broken, or less tender leaves. Grading is rarely consistent between factories, and first grade tea leaves may not necessarily produce first grade cakes. Different grades have different flavors; many bricks blend several grades chosen to balance flavors and strength. Season. Harvest season also plays an important role in the flavor of pu'er. Spring tea is the most highly valued, followed by fall tea, and finally summer tea. Only rarely is pu'er produced in winter months, and  often this is what is called "early spring" tea, as harvest and production follows the weather pattern rather than strict monthly guidelines. Tea factories. Factories are generally responsible for the production of pu'er teas. While some individuals oversee small-scale production of high-quality tea, such as the Xizihao and Yanqinghao brands, the majority of tea on the market is compressed by factories or tea groups. Until recently factories were all state-owned and under the supervision of the "China National Native Produce & Animal Byproducts Import & Export Corporation" (CNNP), Yunnan Tea Branch. Kunming Tea Factory, Menghai Tea Factory, Pu'er Tea  Factory and Xiaguan Tea Factory are the most notable of these state-owned factories. While CNNP still operates today, few factories are state-owned, and CNNP contracts out much production to privately owned factories. Different tea factories have earned good reputations. Menghai Tea Factory and Xiaguan Tea Factory, which date from the 1940s, have enjoyed good reputations, but in the twenty-first century face competition from many of the newly emerging private factories. For example, Haiwan Tea Factory, founded by former Menghai Factory owner Zhou Bing Liang in 1999, has a good reputation, as do Changtai Tea Group, Mengku Tea  Company, and other new tea makers formed in the 1990s. However, due to production inconsistencies and variations in manufacturing techniques, the reputation of a tea company or factory can vary depending on the year or the specific cakes produced during a year. The producing factory is often the first or second item listed when referencing a pu'er cake, the other being the year of production. Recipes. Tea factories, particularly formerly government-owned factories, produce many cakes using recipes for tea blends, indicated by a four-digit "recipe number". The first two digits of recipe numbers represent the year the recipe  was first produced, the third digit represents the grade of leaves used in the recipe, and the last digit represents the factory. The number 7542, for example, would denote a recipe from 19"75" using "fourth"-grade tea leaf made by Menghai Tea Factory (represented by "2"). Tea of all shapes can be made by numbered recipe. Not all recipes are numbered, and not all cakes are made by recipe. The term "recipe," it should be added, does not always indicate consistency, as the quality of some recipes change from year-to-year, as do the contents of the cake. Perhaps only  the factories producing the recipes really know what makes them consistent enough to label by these numbers. Occasionally, a three digit code is attached to the recipe number by hyphenation. The first digit of this code represents the year the cake was produced, and the other two numbers indicate the production number within that year. For instance, the seven digit sequence "8653-602", would indicate the "second" production in 200"6" of factory recipe 8653. Some productions of cakes are valued over others because production numbers can indicate if a tea was produced earlier or later in a season/year. This  information allows one to be able to single out tea cakes produced using a better batch of "máochá". Tea packaging. Pu'er tea is specially packaged for trade, identification, and storage. These attributes are used by tea drinkers and collectors to determine the authenticity of the pu'er tea. Individual cakes. Pu'er tea cakes, or "bĭngchá", are almost always sold with a: Recently, "nèi fēi" have become more important in identifying and preventing counterfeits. Menghai Tea Factory in particular has begun microprinting and embossing their tickets in an effort to curb the growth of counterfeit teas found in the marketplace in the  late 1990s and early 2000s. Some "nèi fēi" also include vintage year and are production-specific to help identify the cake and prevent counterfeiting through a surfeit of different brand labels. Counterfeit pu'er is common. The practices include claiming the tea is older than it actually is, misidentifying the origin of the leaf as Yunnan instead of a non-Yunnan region, labeling terrace tea as forest tea, and selling green tea instead of raw pu'er. The interpretation of the packing of pu'er is usually dependent on the consumer's knowledge and negotiation between the consumer and trader. Wholesale. When bought  in large quantities, pu'er tea is generally sold in stacks, referred to as a "tǒng" (筒), which are wrapped in bamboo shoot husks, bamboo stem husks, or coarse paper. Some tongs of vintage pu'er will contain a "tǒng piào" (筒 票), or tong ticket, but it is less common to find them in productions past the year 2000. The number of "bǐngchá" in a "tǒng" varies depending on the weight of individual "bǐngchá". For instance one "tǒng" can contain: Twelve "tǒng" are referred to as being one "jiàn" (件), although some producers/factories vary how many "tǒng" equal one "jiàn . A jiàn" of tea, which is bound together in a loose bamboo basket, will usually have a large "batch ticket" (大 票; pinyin: "dàpiào") affixed to its side that will indicate information such as the batch number of the tea in a season, the production quantities, tea type, and the factory where it was produced. Aging and storage. Pu'er teas of all varieties, shapes, and cultivation can be aged to improve their flavor, but the tea's physical properties will affect the speed of aging as well as its quality. These properties include: Just as important as the tea's  properties, environmental factors for the tea's storage also affect how quickly and successfully a tea ages. They include: When preserved as part of a "tong", the material of the "tong" wrapper, whether it is made of bamboo shoot husks, bamboo leaves, or thick paper, can also affect the quality of the aging process. The packaging methods change the environmental factors and may even contribute to the taste of the tea itself. Age is not the sole factor in determining pu'er quality. Similar to aging wine, the tea reaches a peak with age and can degrade in quality afterwards. Due  to the many recipes and different processing methods used in the production of different batches of pu'er, the optimal age for each tea will vary. Some may take 10 years while others 20 or 30+ years. It is important to check the status of ageing for your teacakes to know when they have peaked so that proper care can be given to halt the ageing process. Raw pu'er. Over time, raw pu'er acquires an earthy flavor due to slow oxidation and other, possibly microbial processes. However, this oxidation is not analogous to the oxidation that results in green, oolong , or black tea, because the process is not catalyzed by the plant's own enzymes but rather by fungal, bacterial, or autooxidation influences. Pu'er flavors can change dramatically over the course of the aging process, resulting in a brew tasting strongly earthy but clean and smooth, reminiscent of the smell of rich garden soil or an autumn leaf pile, sometimes with roasted or sweet undertones. Because of its ability to age without losing "quality", well aged good pu'er gains value over time in the same way that aged roasted oolong does. Raw pu'er can undergo "wet storage" ("shīcāng", 湿仓) and  dry storage ("gāncāng" 干仓), with teas that have undergone the latter ageing more slowly, but thought to show more complexity. Dry storage involves keeping the tea in "comfortable" temperature and humidity, thus allowing the tea to age slowly. Wet or "humid" storage refers to the storage of pu'er tea in humid environments, such as those found naturally in Hong Kong, Guangzhou and, to a lesser extent, Taiwan. The practice of "Pen Shui" 喷 水 involves spraying the tea with water and allowing it dry off in a humid environment. This process speeds up oxidation and microbial conversion, which only loosely  mimics the quality of natural dry storage aged pu'er. "Pen Shui" 喷 水 pu'er not only does not acquire the nuances of slow aging, it can also be hazardous to drink because of mold, yeast, and bacteria cultures. Pu'er properly stored in different environments can develop different tastes at different rates due to environmental differences in ambient humidity, temperature, and odors. For instance, similar batches of pu'er stored in the different environments of Yunnan, Guangzhou and Hong Kong are known to age very differently. Because the process of aging pu'er is lengthy, and teas may change owners several times, a  batch of pu'er may undergo different aging conditions, even swapping wet and dry storage conditions, which can drastically alter its flavor. Raw pu'er can be ruined by storage at very high temperatures, or exposure to direct contact with sunlight, heavy air flow, liquid water, or unpleasant smells. Although low to moderate air flow is important for producing a good-quality aged raw pu'er, it is generally agreed by most collectors and connoisseurs that raw pu'er tea cakes older than 30 years should not be further exposed to "open" air since it would result in the loss of flavors or degradation  in mouthfeel. The tea should instead be preserved by wrapping or hermetically sealing it in plastic wrapping or ideally glass. Ripe pu'er. Since the ripening process was developed to imitate aged raw pu'er, many arguments surround the idea of whether aging ripened pu'er is desirable. Mostly, the issue rests on whether aging ripened pu'er will, for better or worse, alter the flavor of the tea. It is often recommended to age ripened pu'er to air out the unpleasant musty flavors and odors formed due to maocha fermentation. However, some collectors argue that keeping ripened pu'er longer than 10 to 15  years makes little sense, stating that the tea will not develop further and possibly lose its desirable flavors. Others note that their experience has taught them that ripened pu'er indeed does take on nuances through aging, and point to side-by-side taste comparisons of ripened pu'er of different ages. Aging the tea increases its value, but may be unprofitable. Vintaging. The common misconception is that all types of pu'er tea will improve in taste—and therefore gain in value—as they get older. Many different factors play into what makes a tea ideal for aging and the aging process  itself. Further, ripe (shu) pu'er will not evolve as dramatically as raw (sheng) pu'er will over time due to secondary oxidation and fermentation. As with aging wine, only finely made and properly stored teas will improve and increase in value. Similarly, only a small percentage of teas will improve over a long period of time. From 2008 Pu'er prices dropped dramatically. Investment-grade Pu'er did not drop as much as the more common varieties. Many producers made large losses, and some decided to leave the industry altogether. Preparation. Preparation of "pu'er" involves first separating a portion of the compressed tea  for brewing. This can be done by flaking off pieces of the cake or by steaming the entire cake until it is soft from heat and hydration. A "pu'erh knife", which is similar to an oyster knife or a rigid letter opener, is used to pry large horizontal flakes of tea off the cake to minimize leaf breakage. Smaller cakes such as "tuocha" or mushroom "pu'erh" are often steamed until they can be rubbed apart and then dried. In both cases, a vertical sampling of the cake should be obtained since the quality of the leaves in a cake usually  varies between the surface and the center. "Pu'erh" is commonly brewed in the Gongfu style using "Yixing teaware" or a gaiwan, a Chinese brewing vessel consisting of bowl, lid, and saucer. Optimum water temperatures are generally regarded to be in the range of 85-99 °C depending on the quality and processing of the "pu'erh". The leaves are traditionally given one or more "rinses" before the first infusion, involving exposing them to hot water for 2–5 seconds and subsequently discarding the extract produced. This is done to saturate the leaf with water and allow it to decompress, as well  as remove any small leaf particles that could adversely affect the outcome of the first infusion. The first infusion is steeped for 12 to 30 seconds, followed by later infusions repeatedly increasing by 2–10 seconds. The prolonged steeping sometimes used in the west can produce dark, bitter, and unpleasant brews. Quality aged "pu'erh" can yield many more infusions, with different flavor nuances when brewed in the traditional Gongfu method. Because of the prolonged fermentation in ripened "pu'erh" and slow oxidization of aged raw "pu'erh", these teas often lack the bitter, astringent properties of other teas, and can be brewed much  stronger and repeatedly, with some claiming 20 or more infusions of tea from one pot of leaves. On the other hand, young raw "pu'erh" is known and expected to be strong and aromatic, yet very bitter and somewhat astringent when brewed, since these characteristics are believed to produce better aged raw "pu'erh". Judging quality. Quality of the tea can be determined through inspecting the dried leaves, the tea liquor, or the spent tea leaves. The "true" quality of a specific batch of "pu'erh" can ultimately only be revealed when the tea is brewed and tasted. Although not concrete and sometimes  dependent on preference, there are several general indicators of quality: Practices. In Cantonese, the tea is called "po-lay" (). It is often drunk during dim sum meals, as it is believed to help with digestion. It is not uncommon to add dried osmanthus flowers, pomelo rinds, or chrysanthemum flowers into brewing pu'er tea in order to add a light, fresh fragrance to the tea liquor. Pu'er with chrysanthemum is the most common pairing, and referred as "guk pou" or "guk bou" (菊 普; ; pinyin: jú pǔ). Sometimes wolfberries are brewed with the tea, plumping in the process. Research. There is  no evidence that consuming pu'er tea promotes loss of body weight in humans. Popular culture. In the Japanese manga Dragon Ball, the name of the character Pu'ar is a pun on pu'er tea.