One of the first “serious” tea books I read cover to cover was The Story of Tea: A Cultural History and Drinking Guide, co-authored by Mary Lou and Robert J. Heiss. To this day, it remains one of my favorite books about tea. The book combines a lot of factual information (“serious” stuff) along with the authors’ travel and cultural narratives from tea-sourcing trips.
I remember initially skimming through the book and pausing as I read a pretty bold statement about tea oxidation vs. fermentation during the processing of tea. The advice was if you were shopping for tea and went into a shop that talked about tea fermentation to run out of the shop as quickly as possible. The point was that teas may oxidize during processing, but there was no such thing as tea fermentation and if the tea shop was using the term fermentation, any tea advice they gave was suspect at best.
The statement made sense as fermentation is driven by the use or introduction of a micro-organism, for example, yeast. Oxidation refers to tea enzymes being broken down and/or tannins being transformed or released during shaping and heating tea leaves during processing. Therefore, to these unscientific ears, oxidation sounded like the best descriptive term related to tea. The only teas for which I can see fermentation wiggle-room are pu-erh teas since the added step in their production of introducing moisture to partially oxidized tea leaves results in fermentation caused by micro-organisms.
Objective distinctions aside, “fermentation” historically and in many current writings on tea continues to be used – why? This is a point for discussion. I have no definitive answer to share; the case for “oxidation” has been made and the defense rests.
This post was first published 11 March 2013.
I too am a big fan of Mary Lou and Robert and thoroughly enjoy and value their book. I use it frequently as a reference.
I agree with your issue about oxidation. I believe pu-erh is truly a fermented tea. It functions as an excellent digestive aide for that very reason.
In my experience, I’ve only heard oxidation spoken of as opposed to fermentation – must mean I’ve only encountered more serious tea shop owners:) I look forward to hearing what others have experienced.
Guy,
Thanks for the shout-out for The Story of Tea. Mary Lou and I find tea to be as fascinating today as ever and we are happy that so many tea enthusiasts have found our book helpful.
And thank you for posting on the topic of oxidation and fermentation. I feel as strongly today as I did when we wrote our book about this tea production misspeak that still recurs to this day. It is very difficult today to argue making an error regarding these terms as being a ‘bad translation’, as the terms oxidation and fermentation are well-known and clearly defined.
However, for those who have not read our book, The Story of Tea, A Cultural History and Drinking Guide (Ten Speed Press 2007), I feel it is very important to clarify the point that you have raised regarding what I wrote.
Whereas clearly the category of dark tea (Pu-erh, Heicha, etc ) utilize both oxidation and fermentation in their processing, my statements alluded to in your post do not clarify this.
The exact quotation, below, is very specifically in regards to black tea only, and is in the section on Black Tea in Chapter 3, on page 84:
“Black tea is not fermented, it is oxidized; the most common error found in discussing or describing black tea is the improper use of the terms fermented and fermentation as a phase in the production of this class of tea. …. If you visit a teashop or website and there is any mention of ‘fermentation’ in reference to the production of black tea, run – do not walk – to another tea vendor!”
Further, as part of this discussion of oxidation and fermentation in the various types of tea, your readers may be interested in an article that Aaron asked me to write for Issue 2 of The Leaf on this very topic:
http://the-leaf.org/issue%202/wp-content/uploads/2008/03/oxidation-fermentation-in-tea-manufacture-single-page-layout.pdf
Tea knowledge is certainly an on-going process and I thank you for continuing to bring important topics to the attention of tea enthusiasts.
Robert J Heiss
Great article Robert, thanks for the link.
It’s great to see this topic come up again, I work for a tea brand training key food & beverage accounts in our local market on the broad subject of tea. As a primarily Ceylon Tea company I put a lot of focus on Black Tea so make a point of explaining this common confusion.
The example I use for oxidation is the browning of an eaten apple core through the disruption of it’s cell structure and release of enzymes reacting with oxygen.
Wonderful to see you posting a reply here Robert, big fan of the book :)
Jonathan
Thank you, for bringing this subject up. I find it most frustrating, when I hear so call tea experts/sommeliers use the word fermented in the context of black tea. Well done.
Here in Taiwan, it’s the same issue. People are just not used to saying “oxidized”, and “fermented” is what is commonly used – even among professionals.
I think in the Chinese language it is more a matter of terminology being misused rather than a misunderstanding of the processing of tea. But nevertheless, the point remains.
In translating a booklet published by the Lugu Farmers’ Association in the heart of Dong Ding Oolong tea country, I pointed this out to my friend and teacher many years ago. Consequently, he changed the word in the Chinese text from fermented to oxidized. Ever since, when he gives educational presentations on tea, he elucidates the differences in the terms and points out that “oxidation” is the accurate way to describe the process.