About Fermentation

Fermentation is a term that is of crucial importance in the context of tea processing. Fermentation, also referred to as oxidation or sometimes misleadingly as 'fermentation', encompasses the chemical change processes that occur when tea leaves come into contact with oxygen. In the world of tea, particularly Japanese tea, there are subtle but crucial differences in the way these processes are controlled and utilized.

In Japan, the concept of fermentation is often interpreted differently than in Western tea culture. While in traditional teas such as black and oolong tea, fermentation describes an oxidative ripening of the leaves in which the cell walls are broken down and the enzymes and polyphenols that emerge react with oxygen, Japanese tea production often aims to minimize or avoid these processes altogether in order to maintain a fresh, vibrant leaf color and a characteristic flavour profile.

Japanese green teas, such as the famous Sencha or the exquisite Gyokuro, undergo little to no fermentation, unlike their oxidized cousins. The essential step in the processing of these teas is the rapid steaming of the harvested tea leaves, a process that stops oxidation processes early and preserves the freshness and bright green color of the leaves. This steaming method differs significantly from the method often used in China, where the leaves are heated in pans. However, steaming produces a unique, sweet, umami flavor profile that is typical of Japanese teas.

However, some specialty teas deliberately use controlled fermentation processes, such as the lesser-known Japanese black tea called Kōcha, which has undergone a revitalization in recent years. Kōcha differs from its Chinese or Indian counterparts in that it has a more subtle, less oxidized note, often with nuances of honey and floral notes. The rarer oolong tea, which is not as common in Japan as in other Asian countries, also draws its appeal from deliberately stopped fermentation, which makes it softer and yet more complex in aroma.

One particular aspect of fermentation that is attracting increasing attention is biological fermentation, which is known in the context of post-fermented teas such as Pu-erh in China. Similar processes are rarely used in Japanese teas, although similar techniques are used experimentally in the production of classic Suntory Aged tea, which can lead to a subtle complexity in the flavor profile.

Overall, knowledge of fermentation is essential to understanding Japanese tea. Whether it is the gracefully bright Sencha or the mysteriously shaded Gyokuro - every Japanese tea tells of a masterful understanding of the chemical processes and the art of creating a highly individual and harmonious flavor profile through subtle control of the fermentation.