How do I brew Goishicha?

Use A few squares (3–5g) per 400–500ml of leaf to 90–100°C (194–212°F) water and steep Simmer 3–5 minutes. Most quality Goishicha can be re-steeped for 1–2 (often boiled).

Does Goishicha contain caffeine?

Goishicha is a dark tea and is rated "low" caffeine. See the chemistry section on this page for cited ranges.

Where does Goishicha come from?

Goishicha is produced in Japan, specifically in the Kochi region.

Goishicha

碁石茶 · /go-EE-shee-cha/

One of only two truly fermented teas in Japan - a rare Shikoku heirloom that undergoes both mold and lactic acid fermentation, producing a uniquely sour, probiotic-rich tea.

Type: Dark Tea
Origin: Japan · Kochi
Oxidation: post-fermented
Caffeine: low
Brew temp: 90–100°C
Brew time: 2–3 min
Flavor notes: sour, pickled, earthy
Harvest: Made from mature summer leaves, then fermented and dried over the following weeks.

History

Goishicha is one of Japan's rarest teas - a doubly-fermented 'dark tea' made for centuries in the mountain village of Otoyo in Kochi Prefecture, on the island of Shikoku. Its name means 'go stone tea': after fermentation the tea is pressed into sheets and cut into small squares that resemble the black stones used in the board game Go. Historically it was traded across the Seto Inland Sea, where it was prized not as a drink to sip but as the base for 'cha-gayu', a savory tea-rice porridge eaten daily in the Setouchi region. By the late 20th century only a handful of farming families still made it, and Goishicha survives today thanks to a small local cooperative that keeps the tradition alive.

Processing

Steps: Steam → Mold ferment → Pack & lactic ferment → Press → Cut into squares → Sun-dry

Goishicha is made from mature summer leaves and undergoes two separate fermentations - one of only a few teas in the world to do so. The leaves are first steamed, then piled and covered to encourage an aerobic mold fermentation (driven by Aspergillus) over about a week. The molded tea is then packed tightly into wooden vats, weighted down, and left to undergo an anaerobic lactic-acid fermentation for two to three weeks. The resulting mass is pressed into thick sheets, cut into small squares, and dried in the sun. It is the lactic stage that gives Goishicha its signature sourness.

Tasting Notes

First time? Expect something genuinely sour and pickled rather than a typical 'tea' flavor - it is closer to a fermented drink, and is wonderful cooked with rice.

Appearance

Sold as small, dark, pressed squares - the 'go stones' that give the tea its name. The brewed liquor is a clear amber to orange-brown, lighter than its earthy reputation suggests.

Aroma

Tangy and pickled, like sour plum or fermented vegetables, over a quiet base of damp wood and earth. The sourness is clean rather than musty.

Taste

Distinctly sour and tart up front - closer to a fermented drink than a typical tea - mellowing into a soft, clean earthiness with very little bitterness or astringency. Low in caffeine and gentle on the stomach, it is refreshing served hot or cold and is traditionally cooked with rice into porridge. The lactic tang is unlike anything in mainstream tea.

Brewing Guide

Western Style

Leaf: A few squares (3–5g) per 400–500ml
Water: 90–100°C (194–212°F)
Time: Simmer 3–5 minutes
Infusions: 1–2 (often boiled)

Step-by-step

Boil, don't just steep. Drop a few squares into a pot of water and bring to a gentle simmer for several minutes - Goishicha is traditionally decocted rather than infused. Tip: Start light; the sourness builds quickly with longer boiling.
Serve hot or chilled. Pour off the amber liquor and drink as is, or chill it for a refreshing summer drink. Tip: It keeps its character well even after cooling.
Try cha-gayu. Use the brewed tea to cook rice into a savory porridge - the dish Goishicha was historically made for. Tip: This is the most authentic way to experience the tea.

Health Benefits

Produced by lactic-acid bacteria, giving it a naturally probiotic character
Very low in caffeine - suitable for evening drinking
Gentle and easy on the stomach
Long used in the Setouchi region as the base for nourishing tea-rice porridge (cha-gayu)
Contains organic acids and polyphenols developed during double fermentation

Food Pairings

Rice - especially cooked into traditional cha-gayu tea porridge
Pickled vegetables (tsukemono), which echo the tea's lactic tang
Grilled or salted fish
Light, savory Japanese home cooking
Umeboshi (pickled plum)

Buying Guide

What to look for

Genuine Otoyo, Kochi Prefecture origin - true Goishicha is made in only one place
Firm, dark, evenly-pressed squares
A clean, sour-pickled aroma without harsh mustiness
Information about the producing cooperative or family

Quality indicators

Otoyo-cho, Kochi (Shikoku) provenance
Traditional two-stage mold-and-lactic fermentation
Recognized as a designated traditional product
Small-batch, hand-made production

Price range: $15–40 for a small pack - genuinely scarce because very few producers remain

Storage: Already fully fermented and dried; store in a cool, dry place away from odors. It keeps well and does not require the active aging of pu-erh.

Fun Facts

The name 'Goishicha' means 'go stone tea' - the dried squares look like the black stones used in the ancient board game Go.
It is one of only a tiny number of teas in the world to undergo both a mold fermentation and a lactic-acid fermentation.
Traditionally Goishicha was rarely drunk on its own - it was cooked with rice into a daily porridge called cha-gayu.
Production once nearly died out entirely, surviving thanks to a small cooperative in the village of Otoyo.