Time's impact on Tea quality is a complex interplay of factors, where even slight changes in conditions can have butterfly-effect-like ripples that manifest as unexpected sensations upon tasting. Ancient wisdom largely prescribed low temperatures, avoidance of light, sealed storage, and dryness—conditions that, through centuries of trial and error, were found to generally improve the tea. Modern scientific research reveals that the storage conditions of tea are akin to a chemical game, with complex physical and chemical changes affecting the tea's quality to varying degrees. The main influencing factors can be summarized as moisture, temperature, oxygen, and lighting conditions.

1. The Relationship Between Light and Pu'er Tea Quality

Storing Pu'er tea away from light is a concept that has only emerged in recent years; it was not previously emphasized. Light has strong penetrating power and promotes oxidation, while ultraviolet rays directly affect enzyme activity, making it essential to avoid exposure during Pu'er tea storage.

Leaving a single cake of Pu'er tea exposed to indirect natural or artificial light will result in noticeable off-flavors within a year, which some refer to as a “sun Odor,” similar to the “rancid” taste that aged bacon acquires. If a single cake is placed in an area occasionally exposed to sunlight, it will develop off-flavors in just three months and lose its aroma quickly. Many tea sellers and buyers are unaware of this principle, leading to stacks of tea cakes displayed in shops—a situation that can be described as a waste of good Pu'er tea.

So, what is the proper way to store Pu'er tea? For home storage, using cardboard boxes is recommended. In tea shops, minimize the amount of tea stored on shelves, keeping only necessary samples.

Additionally, buyers should avoid purchasing sample teas from shop shelves, and sellers should not serve these samples to customers, as the tea may have already changed flavor or gone bad.

2. The Relationship Between Humidity and Pu'er Tea Quality

Excessive humidity is the primary enemy of stored Pu'er tea. Misled by the fermentation process, many believed that microbial activity was essential for the transformation of Pu'er tea, which requires warm and humid conditions. Consequently, some stored their Pu'er tea in environments with humidity levels exceeding 80%, or even added extra moisture to their storage rooms.

While increased humidity does promote microbial growth and accelerate the reddening of the tea liquor, it does not lead to high-quality Pu'er tea that improves with age.

Pu'er tea undergoes normal transformation utilizing the approximately 9% cellular moisture present after sun-drying. External moisture does not contribute positively to the aging process.

Observations indicate that the optimal range for aroma release in Pu'er tea is between 45% and 65% humidity. Above 70%, the air absorbs much of the released aroma, accelerating its release and hindering the development of the desired aging characteristics. Beyond 80%, microorganisms multiply more rapidly, causing external decomposition and potentially leading to spoilage. Therefore, maintaining a humidity level below 65% is ideal for storing Pu'er tea.

3. The Relationship Between Temperature and Pu'er Tea Quality

Temperature either slows down or accelerates the transformation of Pu'er tea. Enzyme activity is at its best between 20°C and 45°C, with temperatures below 20°C slowing down the process.

Higher temperatures (30°C-45°C) speed up the transformation, but if combined with high humidity (over 80%), they can foster microbial growth, accelerating fermentation and spoilage.

Some claim that high temperatures can cause the tea to become acidic, but this is not observed in practice. Given that natural high temperatures typically do not exceed 40°C, no acidification occurs. Instead, raw tea shows less change, while the fermentation taste in Pu'er tea becomes less pronounced, and the aroma significantly improves. Therefore, when storing tea, there is no need to artificially raise the temperature. If possible, slightly increasing the temperature in winter would be beneficial.

4. The Relationship Between Sealing and Pu'er Tea Quality

Influenced by traditional fermentation practices, it has been commonly advocated that storing tea requires relatively high humidity and ventilation.

However, did you know that ventilation is actually the enemy of the aging process in Pu'er tea? If tea is stored with good ventilation and humidity above 70%, the aroma will continuously dissipate, leaving very little after a few years.

Ventilation and the aging process are contradictory. Excessive sealing slows down the transformation, while ventilated storage prevents the tea from aging well. Whether to ventilate the storage room depends on the desired outcome. To obtain tea that improves with age, the storage area should be sealed. If the goal is faster transformation and a redder liquor without concern for improved aging, then ventilation or even adding moisture is acceptable.