The Importance of Compression Processing in Tea Cake Production

Various teas such as raw Pu-erh tea, ripe Pu-erh tea, and white tea are processed into compressed tea cakes. Typically, the production of tea cakes is thought to focus on shape and firmness, with little impact on quality. However, in reality, the compression process significantly affects tea quality. Therefore, the compression process is an important part of tea production and requires carefully managed operations. In this article, we introduce several important points in tea cake processing.

Compressed Tea Was Developed for Easy Transportation

In Yunnan Province, the production area of Pu-erh tea, Pu-erh tea was an important commodity in foreign trade. Yunnan Province had the Ancient Tea Horse Road, a historical trade route through which Pu-erh tea was exported to neighboring countries, where tea and horses were bartered. Mules were mainly used for transportation, but loose tea was very bulky and took up large volumes, so compression was developed to facilitate transport. There are theories that compression was done to facilitate aging, but I believe this is a retroactive explanation. Pu-erh tea was originally positioned as "tea from the borderlands" and was not a delicate tea with subtle aged flavors at that time.

The basic compression process is as follows:

1. Weighing tea leaves based on the size of the tea cake
2. Placing the weighed tea leaves in a metal cylinder and passing steam through them to soften the leaves
3. Placing the softened tea leaves in a cloth mold for shaping
4. Compression using various methods such as vises, large stones, or people standing on top
5. Drying

However, the compression method differs between raw Pu-erh tea and ripe Pu-erh tea. Raw Pu-erh tea retains its components intact and has very high viscosity, allowing for manual compression. The pressure applied during compression is relatively light, resulting in relatively loose compression. In contrast, ripe Pu-erh tea is produced through microbial fermentation, so the tea after fermentation has no viscosity and has a dry, crumbly texture. Therefore, if compression is performed manually as with raw Pu-erh tea, the tea leaves will crumble. For this reason, ripe Pu-erh tea compression is performed using powerful hydraulic press equipment. Consequently, tea cake processing of ripe Pu-erh tea requires a factory of substantial scale.

Importance of Steam Heat Energy Passed Through Tea Leaves

There are two factors that significantly affect quality in tea cake processing. First, the initial process involves the magnitude of thermal energy from the steam passed through the tea leaves. As you can see in the video above, steam is used to soften the tea leaves, and the output (temperature) of this steam dramatically changes the final result. Many processors use powerful steam to soften the tea leaves more quickly. However, when this powerful steam is used, the tea leaves are exposed to high temperatures, resulting in a flavor similar to steamed green tea. The high-temperature steam causes oxidative decomposition of chlorophyll in the tea leaves, releasing magnesium that was bound to chlorophyll, resulting in tea with bitterness. Therefore, steam temperature control is very important, and processing tea leaves at the appropriate temperature ensures desirable flavor and quality. In the video above, gentle steam is passed through, and a two-tier cylinder system is used to minimize heat damage from steam. In some factories, it is not uncommon to apply steam so strong that it makes a hissing sound.

Importance of Tea Cake Drying Method

Next, equally important as steam is the drying method for tea cakes after compression. There are mainly two methods for drying tea: using a drying machine and natural drying. The method using a drying machine and natural drying produce completely different product results, and there are also significant differences in how the tea changes during aging. The drying method varies depending on the policy of the compression processor and the preferences of the buyers making requests, but which method is best varies from person to person, and everyone has different reasoning. Based on years of experience, we have adopted natural drying. The reason is that we do not want to change the components contained in the tea leaves by applying as little heat as possible during drying. Tea compression work is performed in-house by many Pu-erh tea production factories of a certain scale. However, different methods are used in each factory regarding how steam is passed through and drying methods, and ideal factories that do meticulous work are very rare. Previously, to find an ideal tea cake production factory, we received information from many acquaintances in Yunnan Province and visited numerous processors. As a result, we were able to meet the specialized tea cake processing company we currently work with. They provide excellent care for tea and consistently deliver satisfactory work. They can also control the moisture content of the finished tea cakes as desired, eliminating concerns about mold that might occur during transportation. At our shop, we procure Pu-erh tea and white tea in loose tea form from various producers and send them to the tea cake processing specialist factory. By establishing this workflow, we have been able to entrust tea cake processing with confidence in recent years.

For more on how raw Pu-erh is made, see What Is Raw Pu-erh Tea?.