One Green Tea is not like Another
In Lesson 2 of our Tea ABC, we have established a list of the factors that make up the difference between individual teas in your cup. One of these factors, tea processing, is the subject of our lesson 8. In sub-chapters 8.1. and 8.2., we got to know the basic distinction of 6 different tea processing categories. Accordingly, this lesson 8.3 now takes a closer look at the first, simplest – and oldest – of these processing categories, namely the processing of green tea.
Because even one green tea is not like another. Rather, depending on origin, terroir, cultivar, cultivation, picking, and: processing, green tea comes in a virtually infinite number of variations. At this, the differences in processing arise from variations of the individual basic processing steps of green tea. For example, we find completely different designs when comparing the processing of green tea in Japan with that of Chinese green teas. In turn, other green tea producing countries usually take orientation at one of these two approaches.
In the following, let’s take a closer look at each of the basic steps of green tea processing. At this, we will pay attention to variations and highlight the fundamental differences between the Chinese and Japanese approaches.
First of all, the withering, whether outdoor under the sun or in the shade of the factory hall, is actually NOT a characteristic processing step for green tea! In contrary, the processing of green tea is in fact even characterized by the lack this processing step. Because the withering of freshly picked tea leaves always comes with oxidation processes, while the missing of oxidation processes in processing is the hallmark of green tea par excellence. So why do I still talk about the withering of tea leaves in connection with green tea processing? Well, because one withering is not like another, too…
One of the main purposes of the withering is that the tea leaves gain suppleness through the loss of water during this process. This considerably facilitates or even enables the ensuing processing step of rolling the leaves. Furthermore, the withering also has a significant effect on the taste of the resulting tea. In particular, the process reduces the tea’s astringency considerably. And with this, we’re already at the first important difference between Chinese and Japanese green tea processing.
For many Chinese green tea varieties, the withering of tea leaves is considered a process in favor of a desirable flavor change of the resulting tea. In order for the green tea to still be a green tea, it is important to limit incipient oxidation processes to a minimum. This is done by relatively cool ambient temperatures and largely blocking the air circulation. For example through piling the tea leaves in a withering trough.
Incidentally, a certain inevitability of oxidation processes already results from the distance between tea garden and tea factory. The tea leaves always have to travel this distance before they can proceed to the next processing step. Accordingly, a slightly – up to about 10% – oxidized tea still goes as a green tea.
In Japan, one considers the changes in taste that green tea undergoes by initial withering of the tea leaves to be rather undesirable. If intentional withering takes place at all, then in a cool environment with minimal air circulation. Often this step is completely eliminated in the processing of green tea in Japan. Thus, the proximity of the tea garden to the tea factory becomes an important factor. As to that, we even find mobile processing units here, allowing for the next processing step, fixation, to take place directly at the tea garden.
Fixation (Oxidation Stop)
The most defining feature of green tea processing is the abolition of oxidation processes in the freshly picked tea leaf at the earliest possible point. This is done through heating the tea leaves as soon as possible after picking. Or after a withering process without significant accompanying oxidation processes, in favor of the accompanying changes in taste.
Purpose of the oxidation stop is to “fixate” the green tea leaves in their actual (fresh) state. To this end, the heat causes a degeneration of the enzymes in the tea leaf. As a result, these no longer react with the oxygen from the air. The exact method of this fixation (also: “kill green”) has a variety of different traditions in China. Of these, only one has prevailed in Japan.
The most ancient method of fixating green tea leaves is steaming with hot steam. Like almost everything that has to do with tea, the method originates from China. There, it was the predominant method during the times of the Tang dynasty (617-907 AD). Due to changed taste preferences, the trend in China changed in the direction of roasting the tea leaves in a wok pan by the time of the Ming dynasty (1368-1644) . Later, the method of roasting green tea leaves in the oven (“baking”) came about.
The traditional method of roasting tea leaves by hand in the hot wok pan is today only found at smaller family and artisan farms. Keeping the tea leaves moving so that they are heated evenly is an art in itself. People not mastering this technique will eventually find some of the tea leaves burned, while another part won’t have completed the oxidation stop yet.
In today’s modern, commercial (mass) tea processing in China, machines and devices are used that are basically based on one of the two principle methods, roasting or baking. Modern fixation furnaces usually use air circulation systems, while roasting devices usually have a rotation system. In both cases, the movement of the tea leaves serves the purpose of uniform heat application to the tea leaves.
In Japan, the introduction of tea cultivation and the entry of tea culture into Japanese society date back to the times of the Chinese Tang and Ming dynasties. Along with the tea, traveling monks also brought the knowledge of its processing from China to Japan. There, the steaming of the green tea leaves, which used to be common in China at that time, is the predominant fixation method until today.
Anyone with experience with some different green teas probably knows the four typical forms that green tea leaves can get from rolling. This would be once the thin needle shape, then the also elongated curly shape, third the snail-like or spherical shape and finally the flat-pressed shape. Examples of acicular rolled green teas would be the Japanese Sencha tea or the Chinese Anji Bai Cha. Then, a typical curly green tea is Mao Feng. An exemplary specimen of the snail shape is Bi Luo Chun, and the best known example of a granule-shape green tea is the “Gunpowder”. A special case is the flat-pressed shape, which – of course – does not come about by rolling in the narrow sense of that word. Well-known examples include the Long Jing and Tai Ping Hou Kui green teas.
However, the rolling of the tea leaves does not only serve aesthetic purposes. Rather, it is an extremely sensitive process that has a significant impact on the taste of the resulting tea. In fact, it is a question of permanently removing remaining cell walls and structures and promoting the even distribution of the juices in the tea leaf. The resulting shape receives permanent consolidation in the subsequent processing step, the drying.
During the previous processing steps, the green tea leaves have continuously lost moisture. In the interest of good preservability and the lasting preservation of taste and aroma, it is necessary that no more than a minimum residual moisture remains in the leaves. Therefore, at the end of the processing (not only) of green tea is a final drying step. There are three basic types: roast drying, oven drying and sun drying.
For the traditional roasting in the wok pan, there are of course modern industrial equivalents today. The same applies to the oven drying. Sun drying, on the other hand, is to a certain extent a special case. For example, it is still characteristic for green tea from large-leaved tea trees in Yunnan. The resulting green tea has much in common with the basis for the production of Pu-erh tea, namely “maocha”.
As we have seen, even with the “simplest” tea processing category, that of green tea, tea processing is anything but easy. First, there are many possible occasions for mistakes. Then, you can hardly make up for a mistake once made in this process. However, the processes of the next processing category, the oolong tea, which we will discuss in the following lesson 8.4., are even more complex than that.
One more thing, on my own account…
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