碁石茶 (Goishi-cha)

Goishi-cha is one of only ~3 post-fermented Japanese teas; Otoyo cooperative has held the production protocol for 400+ years; Japan-domestic intangible cultural heritage.
Caffeine very low (0.5-1.5%); polyphenol 8-15%; characteristic lactic-acid bacteria (Lactobacillus plantarum) fermentation profile.
Boutique tea retail, fermented-tea collector market, traditional-craft amenity sets.
Rare double-fermented post-fermented tea produced exclusively in Otoyo, Kochi Prefecture. Distinguished by its black-stone-like compressed cubes (the 'goishi' name references Go board stones), goishi-cha is one of only a handful of post-fermented teas in the world (alongside Chinese pu-erh and Japan's awa-bancha and ishizuchi-kurocha). Production is controlled by a small Otoyo cooperative — annual output is limited to less than 10 tonnes. Functional positioning targets the lactic-acid bacteria fermentation profile and resulting low-caffeine / high-polyphenol balance. Niche but increasingly sought by tea collectors and natural-fermentation enthusiasts in export markets.
| Jepang | Food product; specific Otoyo cooperative production; intangible cultural heritage status |
|---|---|
| Uni Eropa | Food import; CN 0902 (tea) classification |
| Amerika Serikat | GRAS by traditional tea use; FDA Prior Notice required |
| Tiongkok | GACC food facility registration |