Pu-Erh: Storing Tea Concept

The term "storing tea" is a colloquial expression that refers to the aging of Pu-erh tea, essentially its post-fermentation process. Strictly speaking, “storing tea” is not a standard term; it diverges significantly from the actual post-fermentation of Pu-erh tea, which is not merely a matter of storage. It is not a simple warehousing concept, but rather a specialised process akin to the conditions required for ageing wine in a cellar. This unique process is essentially aging, known in food chemistry as “post-maturation.”

“Post-maturation” in tea chemistry falls under the category of tea storage chemistry. For a long time, tea experts believed that only Pu-erh tea required aging and post-maturation, but it has since been discovered that other types of tea also undergo this process. “Post-maturation” refers to the quality change in tea as it transitions from slightly raw to good. For example, West Lake Longjing tea, when freshly made, exhibits a pronounced “green taste.” After one to two months of storage in a lime tank, this raw taste disappears, and the aroma becomes rich and fragrant. Of course, different tea types employ various aging methods, leading to different post-maturation effects. Aside from Pu-erh, Hunan black tea, and Guangxi Liu Bao tea, other types of tea generally have shorter aging periods aimed primarily at dissipating the “green taste,” revealing a normal tea aroma, enhancing smoothness, increasing the concentration of the brew, and clarifying the leaves.

It is worth noting a phenomenon in the tea community concerning the emergence of terms like “old green tea,” “old Oolong,” and “old red tea,” which reflect a misunderstanding of tea aging. The aging of green, Oolong, black, and yellow teas involves a “non-enzymatic oxidation” process that requires a shorter aging time. If aged too long, it leads to the auto-oxidation of polyphenols and catechins, with catechins dehydrogenating to form quinones, which polymerise into brown substances. The further oxidation of these intermediates can combine with amino acids and proteins, forming dark polymer compounds that dilute the tea’s flavour and diminish its astringency and freshness, thus reducing its quality, rendering it into aged tea. Since the initial processing of these teas involves high temperatures, their chemical components have already solidified. Further oxidation remains a “non-enzymatic oxidation” process, ultimately leading to “mould,” which is unsafe to consume and not a healthy beverage.

In contrast, Pu-erh tea's aging process is not “non-enzymatic oxidation,” but rather “enzymatic fermentation.”

“Enzymatic fermentation” utilises endogenous and exogenous enzymes (provided by specific environmental conditions) to deliberately degrade and condense the tea's polyphenolic substances, creating new compounds, leading to primary metabolic products and then secondary metabolic products, until the final products emerge. Therefore, the aging process requires a relatively high level of technical and environmental conditions, necessitating long aging times—twenty, thirty, or even fifty years. Perhaps it is precisely because of this lengthy duration that we often prefix “old” to Pu-erh tea and habitually refer to it as “old tea.”

However, “old tea” is not synonymous with aged Pu-erh tea. In recent years, many people have misunderstood “old tea” to mean that any Pu-erh tea stored for decades can be considered “old tea.” The reality is more complex; some Pu-erh teas that are twenty to thirty years old cannot be termed “old tea.” This usually arises from two main reasons:

1. The initial processing followed a “green tea mindset,” employing green tea techniques from selection to processing, resulting in a tea with the “appearance” of Pu-erh but lacking its “internal quality.” For example, transforming “sun-dried green” into “baked green” alters the processing; thus, even long storage cannot convert it into “old tea.” We often view this phenomenon as a “genetic defect,” categorising it as aged tea.

2. Oversimplifying the aging process of Pu-erh tea, lacking proper aging conditions, or improper storage results in unsatisfactory transformation, failing to meet the quality requirements for “old tea.” Such tea merely represents age but does not possess the quality of “old tea,” also falling under the concept of aged tea.

“Old tea” not only signifies age but also symbolises quality and stature, with high quality being paramount.

Let’s return to the original topic—“post-maturation.” It is essentially composed of two leading models: non-enzymatic oxidation and enzymatic fermentation.

Pu-erh tea falls under “enzymatic fermentation,” more accurately categorised as “multi-enzyme system enzymatic fermentation.”

You might ask, “What does ‘enzymatic fermentation’ bring to Pu-erh tea?” Answering this question also addresses another: Why do we store tea?

The answer is simple—Pu-erh tea possesses the aging mechanism of “the longer, the better,” which is its post-maturation effect.

What does “the longer, the better” mean?

“The longer, the better” is a vivid description of the aging process of Pu-erh tea. “The longer” refers to the concept of time, while “the better” pertains to quality. The aging process of Pu-erh tea represents the final stage of processing, key to enhancing or recreating its quality.

Many people doubt the notion of “the longer, the better.” They argue that all teas do not improve with age and may lose their flavour over time. They question if such tea can still be considered tea. Claiming that Pu-erh tea can be stored long-term while its quality improves is seen as misleading, aimed at encouraging consumers to stockpile tea. This perspective effectively transforms Pu-erh tea into an investment tool, altering the intrinsic value of the tea itself.

Critics of the idea of “the longer, the better” primarily stem from a literal misunderstanding of the term. They assume that if it means “the longer, the better,” the aroma should match that of green tea or even Oolong tea. According to this understanding, Pu-erh tea not only lacks the “fresh aroma” of green tea but also does not possess the “unique aroma” of Oolong tea. Moreover, in terms of aromatic compounds, Pu-erh tea does not improve with age; rather, its aroma may become weaker. Many “old Pu-erh teas” even have very faint aromas, which seems to indicate that the idea of “the longer, the better” is unfounded.

Conversely, those within the Pu-erh community argue that the notion of “the longer, the better” should not be taken at face value; it encompasses two aspects. First, after aging, Pu-erh tea indeed exhibits aromatic compounds such as camphor, orchid, and jujube fragrances, unique to Pu-erh and significantly different from the aromas of green or Oolong teas, making simple comparisons inappropriate. Second, the phrase represents a figurative description of the aging process of Pu-erh tea, where “the better” not only refers to aroma but broadly encompasses the concept of quality.

Which viewpoint is more convincing?

In tasting green tea, we often employ “sensory evaluation” methods, such as assessing the shape of the dry leaves, the colour of the brewed tea, the appearance of the wet leaves, and the flavour and aroma of the brew. This evaluation primarily relies on visual observation, tasting, and experience—one of the oldest and most fundamental methods for tea assessment. However, human senses, unlike chemical analytical instruments, cannot reliably detect and differentiate the presence and concentrations of the hundreds of compounds within the tea, which inevitably leads to errors in the evaluation process; sometimes, these discrepancies can be quite significant.

Human sensory perception is influenced not only by sight, smell, hearing, touch, and taste but also by individual differences, tea-drinking habits, preferences, mood, health status, and environmental factors like climate. Therefore, without chemical analysis and supporting data, the judgments derived can only be categorised as subjective speculation. Thus, whether for green tea, Oolong tea, Pu-erh tea, or other types, there are currently no qualitative or quantitative standards regarding the flavours and aromas of tea, nor established quality standards or product testing criteria. Many research findings remain in exploratory and verification stages. This explains why critics of “the longer, the better” in Pu-erh tea have yet to present any chemical analysis reports on aromatic compounds or other constituents of aged Pu-erh tea, which would substantiate claims of “lack of flavour” or “lack of drinking value.”

In fact, the concept of “the longer, the better” in Pu-erh tea transcends mere taste and aroma; it primarily refers to the quality aspect, forming the “lifeline” of Pu-erh tea’s intrinsic value.

We understand that, after undergoing a specialised processing technique and reaching packaging completion, Pu-erh tea has not yet finalised its product form; it requires an aging process. In this regard, Pu-erh tea shares remarkable similarities with spirits and wines. These beverages, after distillation, immediately enter the aging stage, with some requiring ten or twenty years or even longer before they can be marketed. The aging of Pu-erh tea is subject to even stricter time requirements compared to other spirits, as evidenced by the tradition of “grandfathers making tea, grandchildren selling tea,” which underscores that the aging time of Pu-erh tea far exceeds that of other alcoholic beverages.

The necessity for aging in Pu-erh tea arises from its fermentation process; all pre-fermentation steps are preparations for fermentation, while the true fermentation occurs during aging. Consequently, some refer to this aging phase as the natural fermentation (or post-fermentation) stage. In the case of ripe Pu-erh tea, although it undergoes artificial piling fermentation, it still requires a period of aging post-piling