The beauty of post-fermented Japanese teas

Updated: Sep 14

It has been a while since I discovered Ishizuchi Kurocha,(石鎚黒茶) also known as Tengu Kurocha, a post-fermented Japanese tea. Even though the word used to describe it translates into black tea, the truth is it is a dark tea instead of a black one.



But this is not the only post-fermented tea that Japan has to offer, goishicha (碁石茶) or awabancha (阿波晩茶) fall into the same category.


Finally, after a lot of work & effort, I received some samples of post-fermented Japanese teas. I had a great time tasting them so I wanted to share my thoughts with you.


I am certain I don't really know all the types of dark teas being made in Japan, I always end discovering a new type I have never heard of before while doing research to write blog articles. For example, looking for information to write an article about bancha teas, I found a new type of post-fermented Japanese tea, Toyama Kurocha, also known as Asahi Kurocha, & used in the preparation of batabatacha (バタバタ黒茶 ) Now I will have to find a way to get a sample.


What's post-fermented tea?


Before I explain more in detail each type of Japanese dark tea I have tasted, I would like to provide you with some background information about dark teas, what they are & where they can be found.


Fermented or post-fermented teas are also known as dark teas & pretty common in China. They have undergone microbial fermentation for a given period of time, some of them are left to ferment for several months. That's the case of heicha (黑茶), as this type of tea is known in China. Notice that the kanji used in this word are dark/black & tea.


Apart from China & Japan, Myanmar also produces a type of dark tea known as laphet. Byeongcha (병차)& Doncha (돈차) are the Korean versions of the dark tea.


How is post-fermented tea produced?


There are different ways to produce this type of tea, usually, they are classified by their production method.


Piling method: Chinese dark teas & Toyama Kurocha are produced in this way, in a pile under rather dry conditions the naturally occurring bacteria take care of the fermentation process.


Pickling method: Awabancha falls into this category, it is fermented in a rather humid environment where the lactic bacteria develops conferring the tea leaves their characteristic pickled flavour.


Piling & pickling method: a combination of both methods, it is used in the goishicha & Ishizuchi Kurocha production. Both dark teas undergo a two-step post-fermentation process.


Why are these types of post-fermented teas produced?


One of the reasons for producing dark tea is its usage as a source of micro-nutrient food. Some studies have found a number of beneficial microorganisms & components in post-fermented teas.


For example, a study found that Toyama Kurocha has a high amount of B12 content & Ishizuchi Kurocha is rich in gamma-aminobutyric acid.


Another reason is preservation. Post-fermentation transforms the tea leaves components in a way that allows them to age without rooting. The older the tea becomes, the better its taste.


The most interesting reason is for investment. By allowing the fermented teas to age, their value increases considerably. Some well preserved & aged pu-erh teas can cost a pretty penny.


Ok, so tell me more about the dark Japanese teas!


I received a 10 grams sample each of goishicha, awabancha & Ishizuchi Kurocha. A short description of each of them can be found here.


Goishicha: is produced in Kochi using the piling & pickling method, its name derives from its go piece shape once is cut.


1st step: aerobic fermentation


All the parts of the plant harvested in late summer are used, from leaves to branches. They are steamed inside a wooden barrel, then piled up & left to ferment aerobically covered by straw mats for up to 10 days.


The liquid from the steaming is saved for the second step.


2nd step: anaerobic fermentation


After the aerobic fermentation is over, the leaves are layered inside a wooden barrel, covered by heavy stones & left to ferment anaerobically for about three weeks up to a month.


The liquid collected during the steaming process is added to the barrel together with the leaves.


3rd step: drying


Once the lactic bacteria has finished doing its magic, the uniform mass is divided into rectangular thick pieces, extracted from the barrels, then shaped like go pieces using a tool similar to a cleaver & left to dry under the sun for three days.


Finally, we can enjoy a nice brew!


I had tasted this type of tea before during my Japanese tea training. These are the tasting notes I remembered:


Liquor smell: acidic, funky, a bit of putting Liquor colour: yellowish

Goishicha tea liquor looks golden to reddish brown

Liquor taste: milky, smooth, brothy, slightly salty


Since I was able to brew it from the comfort of my home this time, I was able to perform a full evaluation. However, I will still have to sit down & go through a more thorough tasting session. This is what I observed:


Dry leaves aspect: compact, squared, pressed, partially dark in colour, dry, mat


Dry leaves smell: salty, brothy, a bit like soy sauce with a hint of caramel mixed with vine leaves


Wet leaves smell: salty, brothy, like pickled vegetables, cornichons or olives


Liquor smell: mildly salty & brothy Liquor colour: goes from golden to reddish-brown

Liquor taste: salty, like pickles, tons of pickles with a mild sour note


Brewing parameters: 100 degrees Celsius, 150 ml, 1 full square


1st infusion: 1 minute, salty, pickles-like, brothy, full-bodied, if you have ever tasted the brine from olives, this is a similar taste but much milder


2nd infusion: 3 minutes, brothy, salty, milder pickle-like flavour


3rd/4th infusions: 5 minutes, still salty but milder & smoother


At this point, the parts of the leaves were all over the place since the layering falls apart, I didn't try to get more brews but I ice brewed the leaves, the liquor tasted really nice & smooth yet a bit salty still.


I also tried using half a square, later on, similar taste, milder & way smoother. Starting by using just half a square would be my recommended dosage, to begin with.


I didn't try cold brewing or boiling it this time, but it can be used that way as well, both are in my list of brewing methods to try next.


Ishizuchi Kurocha: is made in Ehime & takes its name from the mountain Ishizuchi. Shoots from tall tea trees harvested in summer are used to produce this tea. The leaves fall off during the steaming process.

1 step: aerobic fermentation


The leaves are washed & steamed before they placed inside wooden crates where they are left to ferment for up to a week.


2nd step: anaerobic fermentation


Then the leaves are hand-rolled & placed in plastic bags for them to undergo the anaerobic fermentation process which lasts up to three weeks. All the oxygen is extracted from the bags. Pichia manshurica is the name of the yeast that plays a role during the second fermentation process.


3rd step: sun-drying


Once ready, the tea leaves are placed under the sun. And there you have it, some nice dark tea from Ishizuchi is ready to be consumed.

Some people say it smells like GABA, the truth is, I can't remember what GABA smells like unfortunately. But definitely, this is due to its high levels of gamma-aminobutyric acid.


This was my first time tasting Ishizuchi Kurocha, a super rare type of Japanese tea that almost went extinct. Thanks to the effort of some inhabitants from the area who learnt the manufacturing process from the last farmer making this type of tea, the trade has been preserved.

I will still need to perform a much more thorough review, yet these are my tasting notes.

Ishizuchi Kurocha golden liquor

Dry leaves aspect: golden dark green, dry, crispy, broken


Dry leaves smell: exactly like vine leaves in brine with a hint of hay


Wet leaves smell: vine leaves, mild acidity


Liquor smell: slightly salty, brothy


Liquor taste: pleasant, umami-rich, smooth, brothy, leafy


Brewing parameters: 100 degrees Celsius, 150 ml water, 2 grams


1st brew: 60 seconds, mild, slightly salty, smooth, mild sour undernotes


2nd brew: 2 minutes, full-bodied, umami-rich, dolma


3rd/4th brews: 4 minutes, same taste but a bit milder


After this, the leaves still hold strong yet I used them to ice brewing, delicious, smooth, slightly salty liquor. I would normally use 3 grams but I only have a small sample so I am rationing it a bit until I get more.


As with the goishicha, I haven't cold-brewed or boiled the leaves yet, this has now become part of my next brewing mission.


Awabancha (organic): another type of dark tea from Japan, is made in Tokushima. Mature tea leaves harvested mid-summer, mostly from zairai, are used to produce awabancha.


1st step: anaerobic fermentation


The leaves are boiled for around 10 minutes before being rolled & placed inside plastic barrels covered by big leaves from a different plant & a heavy stones, in order to undergo their fermentation process, which can last bet a week to a month.


Some liquid from the boiling may be added to the barrels to aid the fermentation of the leaves.


Lactobacillus Plantarum is a type of bacterias that can prolifer in such tannic environment.


2nd step: sun-drying


Once ready, the leaves are left to dry under the sun for 24 hours, after that, they can be consumed. Nice & dandy.


I had also tried this type of tea during my training, I was surprised because its flavour was quite different from what I remembered.


These are my previous tasting notes:


Liquor smell: acidic, funky, off-putting, acrid


Liquor taste: brothy, sour, acidic


Again, this time I was able to taste it at home, at my own pace, with my tools, my own brewing parameters & also way more knowledge about teas than a couple of years ago.


Dry leaves aspect: partially broken, dry, crispy, light golden olive green in colour


Dry leaves smell: nice & pleasant smell similar to the vine leaves used to make dolma close to what Ishizuchi Kurocha smells like but the hint of hay is more noticeable.


Wet leaves smell: salty, leafy, vine-like

Awabancha liquor is a bit yellowish

Liquor smell: salty, brothy

Liquor taste: leafy with a hint of saltiness


Brewing parameters: 100 degrees Celsius, 150 ml, 2 grams


1st infusion: 1 minute, salty, smooth, vine leaves, hay


2nd infusion: 3 minutes, slightly salty, smoother, still leafy, hay


3rd/4th infusions: still salty but milder & smoother


I used the spent leaves for ice brewing as well, (yes, I know, I love it far too much) & I got a really smooth liquor. Definitely a nice rare treat.


I truly enjoyed all of them & definitely I can't wait to get larger quantities so I can share them with you all. My top favourite this time was awabancha due to its amazing, well rounded yet complex flavour.


Would you recommend them?


Yes, absolutely! Their smell, taste & appearance are so different from the traditional than they can easily be drunk in combination with other types of teas.


I particularly enjoyed pairing them with sweets since they offered a great flavour range & a perfect pairing for cakes, mousses, pannacottas & similar treats.


Have you tried any of them before? If you haven't, would you like to? What are your thoughts? Share your comments below!

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Keep sipping on great organic whole leaf Japanese teas! Until next Monday!

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