Goishi tea
ingredient / ingredient-goishi-cha
碁石茶 / Goishi-cha (goishi tea)
Goishi tea is a post-fermented tea transmitted in Otoyo, Nagaoka District, Kochi Prefecture. It is made by mold-inoculating steamed tea leaves (aerobic fermentation), pickling them in a tea cask for lactic acid fermentation (anaerobic fermentation), then sun-drying and cutting them. The name is described as coming from the cut leaves becoming black and rounded and looking like arranged go stones.
Photographs (captions in Japanese)
Goishi-cha, a post-fermented tea from Otoyo Town, Nagaoka District, Kochi Prefecture. A photograph of dried, cut blocks of tea leaves: steamed leaves are left to develop mold (aerobic fermentation), then lactic-acid fermented (anaerobic fermentation) in a tea barrel, and dried in the sun.
Shown: No applicable taxon (blocks of Goishi-cha tea leaves)Part / state: Cut and dried blocks of Goishi-cha tea leaves
Photo: Asset utilitist / CC0 1.0 / original image / ledger's original image
Scope and provenance of the photo
Identification: Identified as labelled in the source. The source description is only "Goishi-cha tea leaves", with no scientific name. A group of related photographs by the same uploader was posted in May–June 2026 under CC0.
Image shown: After obtaining the full-size file from Wikimedia Commons, NIGAMI LAB reduced it to about 2400 px on the long side with sips. No cropping or color changes. For display, a WebP capped at 1200 px wide is served; the ledger's original image can be checked from the link above.
On this page (7 sections)
Reading the bitterness
Goishi-cha is a post-fermented tea transmitted in Otoyo, Nagaoka District, Kochi Prefecture. It is made by mold-inoculating steamed tea leaves (aerobic fermentation), then pickling them in a tea cask for lactic acid fermentation (anaerobic fermentation), and sun-drying and cutting them. Ueda (2015) cites an HPLC analysis of hot-water extracts reporting that the total of major catechins and gallic acid in goishi-cha was approximately 1/7 that in green tea and about half that in oolong and black tea. Catechins are involved in tea astringency, and goishi-cha after two-stage fermentation is described as mild in astringency. The original 2002 paper was not confirmed; this is a secondary citation by Ueda (2015).
The record described as the oldest surviving record of goishi-cha is the 1745 (Enkyō 2) statement 『長岡郡豊永郷 碁石茶 六蔵茶とあわせ茶高30斤入り3154丸』 (in translation: "Nagaoka District, Toyonaga Township, goishi-cha; together with Rokuzo tea, tea total 30 kin, 3154 balls") in a work by Anyoji Kamaro, and the statement 『茶 韭生郷 大抜茶 本川郷 碁石茶』 (in translation: "Tea: Niu Township, Ōnuki tea; Motokawa Township, goishi-cha") in 『南路志』 (in translation: "Nanroshi"), compiled around 1815. From these, Ueda (2015) considers that goishi-cha was already being produced before 1745. The cited Edo-period sources themselves were not confirmed in this investigation; this is a secondary citation by Ueda (2015).
Ueda (2015) measured goishi-cha against green tea, black tea, hojicha, coffee, and red wine using a taste-sensor radar chart comprising astringency, bitterness, umami, sourness, bitter aftertaste, astringent aftertaste, and umami aftertaste. Goishi-cha was reported to have weaker astringency and umami and stronger sourness than the other teas and coffee; this pattern was extremely similar to red wine among the compared drinks. The panel size and number of repetitions are not given, and this was a comparison of a single sample.
A 1987 report analyzing aroma compounds in hot-water extracts of goishi-cha and Awa-bancha by GC identified 12 new compounds (2 esters, 5 alcohols, 4 phenols, and acetoin) and described a shared aroma pattern considered characteristic of 『漬物茶』 (in translation: "pickled tea"). Only the abstract was confirmed; it does not mention bitterness or astringency, and sample numbers and production details were not confirmed.
Sources for this overview
Checked for this overview: The cited HPLC-analysis results by Ueda (2015) were confirmed. / The 1745 historical statement and the quoted passage from 『南路志』 (in translation: "Nanroshi") were confirmed. / The taste-sensor radar-chart measurement results were confirmed.
Checked for this overview: The abstract description of aroma-compound identification by GC was confirmed.
Hypotheses and recipe candidates for this entry are on the Japanese page.
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (2)
Scope: A comparison of hot-water extracts across several teas including goishicha
Note: As described by Ukeda (2015); the original is given as Moriyama, Katayama, Nakabayashi, Ukeda, and Sawamura, Nippon Shokuhin Kagaku Kogaku Kaishi 49, 679 (2002). The primary source (the 2002 paper) itself was not checked this time, so it is included as a secondary citation.
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ingredient-goishi-cha —has_composition→ (the claim sentence above)Sensory (1)
Scope: Taste-sensor comparison of Goishicha (sample of unspecified origin) against 6 reference beverages
Note: A taste-sensor measurement performed by Ukeda (2015) himself. No mention of panel size or number of replicates. This is a comparison of single samples, and is not generalized to tea types in general, pu-erh tea included.
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ingredient-goishi-cha —has_sensory_attribute→ (the claim sentence above)Culture (1)
Scope: Otoyo, Kochi Prefecture
Note: As recorded by Ukeda (2015). The works cited as the source, 『土佐幽考』 (in translation: "Tosa Yuko") (of the Tani Taizan school) and 『南路志』 (in translation: "Nanroshi"), have not themselves been checked this time, and are included here as a secondary citation via Ukeda (2015).
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ingredient-goishi-cha —has_historical_origin→ (the claim sentence above)