Does Pu'er tea have a shelf life?

Pu'er tea has a rich taste and high nutritional value. It is the first choice for many tea lovers and the best choice for giving as a gift. In response to market demand, many Pu'er tea producers make the tea into tea bags and dry tea to make it easier to sell. But the taste is also somewhat different from that of new tea. If it is well maintained, it may have an unexpectedly pure fragrance. So, does Pu'er tea have an optimal shelf life?

1. Does Pu'er tea have a shelf life?

All food has a shelf life, but almost everyone knows that Pu'er tea becomes more fragrant with age and is known as a "drinkable antique." Most people believe that Pu'er tea has the characteristic of "better taste as it ages", which means that as long as it is stored properly, the longer the Pu'er tea is stored, the better it tastes, so it can be preserved forever. Some people simply say: Pu'er tea has no shelf life.

Regarding the shelf life of Pu'er tea, what does the national standard stipulate?

From the definition of Pu'er tea itself: Pu'er tea is a loose tea or compressed tea with post-fermentation made from large-leaf sun-dried green tea produced in a specific area of ​​Yunnan. Therefore, the national standard also gives a shelf life label based on the characteristics of Pu'er tea, which means that it can be stored for a long time under an environment that meets the GB/T22111-2008 implementation standard.

However, long-term storage does not mean permanent storage

In 1963, the Palace Museum in Beijing was processing the tribute tea of ​​the Qing Palace and found more than 2 tons of aged tea in the tea warehouse, including some Pu'er tea. Wang Yufeng mentioned in his article "Pu'er Tea and the Qing Dynasty": "On October 23, 1963, by chance, I saw these aged tribute teas in a Beijing tea factory. The Pu'er tea balls were as big as watermelons (slightly flat), and as small as tennis balls or ping-pong balls. The tea was brown-black in color, not moldy or rotten, and well preserved." At that time, an expert took some tribute tea for trial brewing, and the comment was: "The soup has color, but the tea leaves are old and light."

There is no uniform standard in the industry for the post-aging life of Pu'er tea. Generally speaking, the conversion in an environment with high temperature and high humidity is much faster than that in an environment with low temperature and low humidity. The tea soup of new tea is yellow-green with a strong green taste. Depending on the raw materials, it may have sweetness or bitterness, which is normal.

After the new tea is stored for 3 to 10 years, the tea soup changes subtly, becoming more yellow and red, the green taste is no longer so strong, there is a faint fragrance, and the bitterness is also reduced. The transformation will produce obvious effects, roughly within 10 to 20 years, the tea soup will undergo obvious changes, the yellow color will fade to red and it will become thick and smooth, the green taste will be gone, the honey sweet fragrance will be obvious, and the aged aroma will begin to show. The bitterness of the tea soup almost disappears, even if there is any, it will dissipate very quickly, and the leaf bottom will turn from yellow to yellow with brown.

After 20 years, it can be considered to be in the late stage of transformation. The tea soup is deep red and as beautiful as the best red wine, with a strong fruity sour taste and full of aged aroma without any bitterness. The soup is smooth and thick and melts in the mouth. The tea cake is dark brown and shiny, and the leaf bottom is light brown.

The above Pu'er aging process has been fully verified in reality. From this perspective, Pu'er tea becomes more fragrant and charming as it ages. Under the premise of good storage, tea with a history of 20 to 30 years has a full aroma of aged and fruity flavor, the soup is as red and thick as red wine, and it has a beautiful golden ring when poured into the cup. It is also comfortable to drink, and the taste and body sensation are in a relatively good state, but the tea aroma is very light. As for old tea that is sixty or seventy years old, even if it is well stored, it is inevitable that it will approach the carbonization state.

The Institute of Industrial Science of the Chinese Academy of Agricultural Sciences, the Modern Research Center for Traditional Chinese Medicine of Peking University, China Agricultural University, Southwest University, Kunming Institute of Botany of the Chinese Academy of Sciences, Pu'er Tea College of Yunnan Agricultural University and other seven institutions carried out the "Key Technology Research Project of Pu'er Tea" and proposed that the concept that Pu'er tea "becomes more fragrant as it ages" is not entirely correct. "This statement is unscientific. Pu'er tea takes a certain amount of time to go through a series of production processes such as production and fermentation. Generally speaking, the concept of 'the older the Pu'er tea, the better it tastes' is applicable within the ten-year shelf life, but this statement is not applicable beyond this shelf life. Pu'er tea matures quickly now, and it also has a certain shelf life. Although this shelf life has not yet been determined, it will still be bad after the shelf life is exceeded."

In response to the research result that "the best shelf life is only 10 years", senior tea drinkers in the industry believe that good tea with proper storage methods can be stored for 30 to 40 years!" "How long can Pu'er tea be stored?" and "When is it best to drink?" all vary from tea to tea and from person to person.

2. Is Pu'er Ripe Tea fully fermented or post-fermented?

Chinese tea is divided into six major categories according to the degree of "fermentation" and comprehensive production methods. But the word "fermentation" here is completely different from the microbial fermentation of Pu'er ripe tea. The fermentation process of Pu'er ripe tea is more like yogurt, soy sauce, vinegar and other fermented foods that are processed using beneficial microorganisms and have unique flavors and special functions.

In tea, the same green leaf is processed into green tea, black tea, oolong tea, etc. through controlled biological oxidation, a process also known as "fermentation". This process is more like a series of enzymatic reactions and should perhaps be called "biological oxidation." The "biological oxidation" of tea is a series of oxidation processes of tea polyphenols promoted by oxidases present in the cell walls after the cell walls are damaged. Depending on the degree of oxidation of polyphenols, they are divided into "full fermentation", "semi-fermentation" and "light fermentation". In black tea, when the degree of oxidation of polyphenols is very high, it is called "fully fermented". No other type of tea has as high a degree of polyphenol oxidation as black tea, which means that only black tea is fully fermented tea.

The fermentation process of Pu'er ripe tea is also accompanied by enzymatic reactions. According to the popular understanding of the degree of fermentation, it is generally around 70%. However, the biggest feature of Pu'er ripe tea is the post-fermentation process, that is, a series of oxidation and microbial fermentation processes are still going on after it is made into the finished product. Therefore, from this point of view, Pu'er ripe tea is a post-fermented tea.