FERMENTATION AND TEA

Let’s dive into a topic that can get a little confusing: fermentation and tea.

In Japan, the green tea everyone knows is classified as a “non-fermented tea.” In the West, the most popular black tea is labeled as a “fermented tea.” And in China and Taiwan, oolong is described as a “semi-fermented tea.”

But here’s the twist: in strict scientific terms, none of these involve fermentation. What’s actually happening is oxidation. Fermentation is a chemical reaction carried out by microorganisms for human benefit, yet in the processes that transform fresh leaves into green tea → oolong → black tea, microorganisms play no role at all.
So what is happening? It’s the enzymatic oxidation driven by compounds naturally present in the tea leaf.

Inside tea leaves is an enzyme called polyphenol oxidase (PPO). When the leaf is damaged, PPO mixes with polyphenols such as catechins, triggering an oxidative reaction that produces the tea’s aroma and color. This process is sometimes referred to as “enzymatic fermentation,” and it’s essential for making both oolong and black tea.

But then comes the question: Are there teas that involve genuine microbial fermentation?
The answer is... yes!

• Chinese dark teas, such as Pu-erh from Yunnan
• Lahpet, a traditional fermented tea-leaf pickle enjoyed for centuries in the mountains of Myanmar and Laos
• Japan’s traditional lactic-fermented teas, including Awa Bancha and Ishizuchi Black Tea from the mountain regions of Shikoku

All are deeply rooted in local cultures and burst with individuality.