“Tea oil” refers to the yellow spots that appear on the cotton paper of Pu'er tea after it has been stored for a certain period. It is composed of two substances: Pectin seepage. As Pu'er tea ages, its cell walls break down, and pectic substances seep out, being absorbed by the packaging paper, forming the “oily stains” we see. Volatile oil condensation. According to scientific research: “Pu'er tea contains over 50 volatile oils, primarily alcohols, acids, aldehydes, aromatics, and esters, which influence the aroma of Pu'er tea. Both raw and ripe Pu'er teas contain similar volatile oil components, and the presence of tea oil is a natural occurrence during storage.”

It is normal for any Pu'er tea to contain some pectin and volatile oils, so seepage is a common occurrence. The presence of tea oil indicates rich internal qualities and does not signify “poor quality” or “improper storage.”

The appearance of tea oil in aged Pu'er tea can be attributed to several reasons:

First reason

The tea is stored for a long time in an environment with high temperatures (around 40°C) or experiences seasonal changes leading to alternating dry and humid conditions. This is also a significant factor in the seepage of tea oil. When the weather is dry, the seepage stops. However, when humidity increases again and the outer packaging becomes damp, the areas on the paper where the oil content is higher become more compatible, causing the oil to seep out faster and more easily, eventually forming multiple tea stains.

Second reason

The tea itself contains abundant internal substances, making pectic matter more likely to seep out. As Pu'er tea naturally ages and transforms, its cellular structure gradually breaks down, releasing this oil over time. This also indirectly reflects the ongoing transformation of the tea.

Third reason

Pu'er tea pieces are stacked together, causing the tea oil to seep onto the cotton paper due to the pressure between the cakes. Additionally, the early tea papers were made of pure cotton, thin, and without sizing, which had good absorbency. Therefore, once the tea oil seeps out, it is easily absorbed by the paper.

Fourth reason

Not only in aged tea but also in some new teas, small amounts of tea oil may appear because the tea leaves are still alive. During transportation, when new teas are compressed under weight, their internal substances seep out, forming tea oil.

From the above, the appearance of tea oil in Pu'er tea is a normal phenomenon that occurs during production, fermentation, storage, and transportation. It cannot be linked to the quality of the tea and does not indicate any defects.

When tea enthusiasts purchase tea, if they encounter tea oil on Pu'er tea cakes, there's no need to worry. If the storage conditions are proper, they can buy with confidence; they can also carefully smell the aroma of the tea cake, observe the brightness and luster of the tea cake surface and tea strips. If necessary, brewing the tea provides even greater reassurance.