Research note 043 — 2026-09-04
Awa-bancha, Goishicha, Ishizuchi-kurocha — Japan's Post-Fermented Teas
阿波晩茶 (Awa-bancha) of Tokushima Prefecture, 碁石茶 (Goishicha) of Kochi Prefecture, and 石鎚黒茶 (Ishizuchi-kurocha) of Ehime Prefecture are all post-fermented teas, finished after the tea leaves are fermented. The way each is fermented, however, is not the same across the three. Goishicha and Ishizuchi-kurocha both go through two stages, packing the leaves into a barrel for anaerobic fermentation by lactic acid bacteria after an aerobic fermentation by mold; Awa-bancha, after boiling the leaves to halt oxidative fermentation, brings about only lactic acid fermentation in a single stage. This difference in process also shows up as separate axes -- astringency and sourness -- in taste-sensor measurements of the infusion. This note lays the processes of the three teas side by side, reads the microbes involved and the taste-sensor results, and then compares them with the change pu-erh tea undergoes through pile fermentation.
What this page establishes
- Goishicha and Ishizuchi-kurocha are recorded as being made through a two-stage process, in which anaerobic fermentation by lactic acid bacteria follows an aerobic fermentation by mold.
- Awa-bancha is recorded as a process in which the tea leaves are heat-treated to halt oxidative fermentation, after which only lactic acid fermentation is brought about, in a single stage.
- In taste-sensor measurements, one report shows a result in which Goishicha has weaker astringency and umami and stronger sourness than other teas or coffee.
- For all three teas, no taste-sensor measurement or sensory evaluation targeting bitterness itself has yet been carried out.
Goishicha — Two-Stage Fermentation, and the Microbes Involved
Goishicha is a tea passed down in Otoyo, Kochi Prefecture, made by steaming the leaves and then putting them through two stages of fermentation.
Scope: Goishicha of Otoyo, Kochi Prefecture
Note: Process description by Ukeda (2015). Not a peer-reviewed original paper but a lecture record; included as an account compiled by a regional-collaboration researcher.
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process-goishi-cha-fermentation —is_prepared_by→ "The raw tea leaves are steamed for about 2 hours, then piled to a height of about 50-70cm on straw mats on an earthen floor for 7-10 days of aerobic fermentation (mold inoculation, pre-fermentation). The leaves are then packed into a barrel with a weight placed on top for 10-20 days of anaerobic fermentation (post-fermentation), after which they are cut and dried in the sun for 2-3 days to finish the product."The microbes involved in this fermentation are reported through isolation and identification by rDNA analysis. The source reports that the two fermentation stages -- mold inoculation and pickling -- each involve separate microbes, and that each is involved in producing separate aroma compounds.
Scope: Aroma-compound analysis of Goishicha (sample of unspecified origin) by GC-O/AEDA, and identification of isolated microbes.
Note: Only the abstract has been confirmed. Ukeda's (2015) lecture record names Aspergillus fumigatus as the main organism in pre-fermentation (mold inoculation), while Koyama et al.'s (2019) isolation and identification names Aspergillus niger — the reported species does not agree between the two sources. This entry adopts Koyama et al. (2019), who performed the isolation and identification, and records the discrepancy explicitly. Whether this is due to a difference in identification method or collection timing has not been confirmed.
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process-goishi-cha-fermentation —is_prepared_by→ "Isolation and identification by rDNA analysis reports 3 microbial species involved in the fermentation of Goishicha: Aspergillus niger, Pichia manshurica, and Lactobacillus plantarum. The source reports that A. niger is involved in producing ethyl furaneol and thiazoline compounds; P. manshurica in esters, alcohols, and phenols (including 4-ethylphenol and 4-ethyl-2-methoxyphenol); and L. plantarum in organic acids such as hexanoic acid and butanoic acid, and lactones."As for when Goishicha first began to be made, Edo-period records are cited.
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 oldest known surviving record is a description found in the 1745 (Enkyo 2) work of Anyoji Kamaro: 『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 area: Goishicha, together with Rokuzo tea, 3,154 balls in cases of 30 kin"), and a description in 『南路志』 (in translation: "Nanroshi") (compiled around 1815): 『茶 韭生郷 大抜茶 本川郷 碁石茶』 (in translation: "Tea: Nirao area, Otsunuki tea; Honkawa area, Goishicha"). From these, Goishicha is inferred to have already been in production before 1745."Ishizuchi Kurocha — Following the Same Two Stages, Now a Designated Technique
Ishizuchi-kurocha, passed down in the Ishizuchi district of Saijo, Ehime Prefecture, also goes through the same two-stage fermentation as Goishicha.
Scope: the Ishizuchi district of Komatsu, Saijo, Ehime Prefecture
Note: As recorded on Saijo City's official website.
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process-ishizuchi-kurocha-fermentation —is_prepared_by→ "Made through the processes of plucking, kill-green (fixation), mold inoculation (aerobic fermentation by filamentous fungi, about 1 week), rolling, pickling (anaerobic fermentation by lactic acid bacteria, about 2 weeks), sun-drying, and sorting. Mainly produced in July and August."This manufacturing technique is designated as an Important Intangible Folk Cultural Property.
Scope: Saijo, Ehime Prefecture
Note: Included after directly checking the original record in the Agency for Cultural Affairs' 「文化遺産オンライン」 (in translation: "Cultural Heritage Online") (heritage id 589236).
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process-ishizuchi-kurocha-fermentation —is_registered_as→ "Designated as an Important Intangible Folk Cultural Property under the name 『石鎚黒茶の製造技術』 (in translation: "Manufacturing technique of Ishizuchi-kurocha") on March 22, 2023. The area of transmission is the Ishizuchi district of Komatsu, Saijo, Ehime Prefecture. The preserving body is the Ishizuchi Kurocha Manufacturing Technique Preservation Society."Awa Bancha — Halted by Boiling, Then Only Lactic Acid Fermentation Through Pickling
Awa-bancha, passed down in Kamikatsu, Naka, and Minami, Tokushima Prefecture, combines fermentation differently from Goishicha and Ishizuchi-kurocha. The tea leaves are heat-treated in advance so that oxidative fermentation does not occur, and only lactic acid fermentation through pickling is brought about.
Scope: Kamikatsu, Naka, and Minami, Tokushima Prefecture
Note: Included after directly checking the original record in the Agency for Cultural Affairs' 「文化遺産オンライン」 (in translation: "Cultural Heritage Online") (heritage id 541631).
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process-awa-bancha-fermentation —is_prepared_by→ "Hard tea leaves picked in the late part of summer are given heat treatment, such as boiling in a large kettle, to prevent oxidative fermentation from occurring, after which they are packed into barrels or vats to promote a new lactic acid fermentation. The process goes through tea picking, tea boiling, tea rubbing, pickling, tea drying, and sorting."Awa-bancha's manufacturing technique is likewise designated as an Important Intangible Folk Cultural Property.
Scope: Kamikatsu, Naka, and Minami, Tokushima Prefecture
Note: Included after directly checking the original record in the Agency for Cultural Affairs' 「文化遺産オンライン」 (in translation: "Cultural Heritage Online") (heritage id 541631).
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process-awa-bancha-fermentation —is_registered_as→ "Designated as an Important Intangible Folk Cultural Property under the name 『阿波晩茶の製造技術』 (in translation: "Manufacturing technique of Awa-bancha") on March 11, 2021. The area of transmission is Kamikatsu (Katsuura District), Naka (Naka District), and Minami (Kaifu District), Tokushima Prefecture. The preserving body is the Awa Bancha Manufacturing Technique Preservation Society (the preservation societies of each town)."What the Taste Sensor Shows — Weak Astringency and Strong Sourness
There is a report that measured the infusion of Goishicha with a taste sensor and compared it with green tea, black tea, hojicha, coffee, and red wine. The result showed weaker astringency and umami and stronger sourness than the other teas or coffee, and the source states that this pattern closely resembled red wine.
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→ "Comparing Goishicha with green tea, black tea, hojicha, coffee, and red wine using a taste sensor (a radar chart made up of astringency, bitterness, umami, sourness, bitterness aftertaste, astringency aftertaste, and umami aftertaste) brought out the characteristic that Goishicha has weaker astringency and umami and stronger sourness than the other teas and coffee. Among the palatable beverages compared, this pattern was extremely similar to that of red wine."In a report comparing the four teas -- Ishizuchi-kurocha, Awa-bancha, sencha, and black tea -- with the same taste sensor, the sourness output value was highest for Ishizuchi-kurocha, followed by Awa-bancha. The report discusses this sourness as resulting from the anaerobic fermentation becoming more vigorous on the nutrient source generated by microbes during aerobic fermentation, increasing metabolites such as lactic acid.
Scope: Comparison of infusions of Ishizuchi-kurocha, Awa-bancha, sencha, and black tea (Tokushima Prefectural Industrial Technology Center, taste sensor SA402B)
Note: A comparison between single samples, with no mention of replicate count or statistical testing. The description that sourness comes to the fore is included as stated, without bending it toward a bitterness axis.
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ingredient-ishizuchi-kurocha —has_sensory_attribute→ "In a taste-sensor (SA402B) measurement of the infusion, the sourness output value was highest for Ishizuchi-kurocha among the 4 teas — Awa-bancha, Ishizuchi-kurocha, sencha, and black tea — followed by Awa-bancha. The report discusses this as resulting from the tea leaves being enzymatically broken down by the aerobic mold fermentation that precedes anaerobic fermentation, generating a nutrient source for microbes, which made the anaerobic fermentation more vigorous and increased metabolites such as lactic acid."In the same comparison of the four teas, Awa-bancha had lower output values for astringency stimulus and umami than sencha or black tea, and its sourness output value was the second highest, after Ishizuchi-kurocha.
Scope: A comparison of infusions of awa-bancha, Ishizuchi-kurocha, sencha, and black tea (Tokushima Prefectural Industrial Technology Center, taste sensor SA402B)
Note: A comparison between single samples; the number of replicates and statistical testing are not stated.
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ingredient-awa-bancha —has_sensory_attribute→ "Measuring infusions with a taste sensor (SA402B), awa-bancha showed lower output values for astringency stimulus and umami than sencha and black tea. Its sourness output value was the second highest, after Ishizuchi-kurocha. These results are reported to show that awa-bancha has a sour, clean-tasting profile."There is also an analysis that tracked the main chemical components involved in astringency numerically. Analyzing the leaves of Awa-bancha, Ishizuchi-kurocha, sencha, and black tea, tannin content was highest in sencha, lower in Awa-bancha and Ishizuchi-kurocha, and lower still in black tea. Caffeine content was highest in black tea, followed by sencha, and low in Awa-bancha and Ishizuchi-kurocha.
Scope: Leaf analysis of awa-bancha and Ishizuchi-kurocha (both post-fermented teas), sencha (an unfermented tea), and black tea (a fermented tea)
Note: Included after checking the full text (Table 2) from the Tokushima Prefectural Industrial Technology Center. Details of sample size and origin/lot are not given.
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ingredient-awa-bancha —has_composition→ "In an analysis conducted under the Food Labeling Standards (Cabinet Office Ordinance No. 10 of Heisei 27), tannin content was 8.1 g/100g for awa-bancha, 7.5 g/100g for Ishizuchi-kurocha, 11.4 g/100g for sencha, and 6.5 g/100g for black tea; caffeine content was 1.5 g/100g for awa-bancha, 1.4 g/100g for Ishizuchi-kurocha, 2.1 g/100g for sencha, and 3.0 g/100g for black tea. Awa-bancha had less protein, caffeine, and tannin than sencha, and less protein and caffeine than black tea."For Goishicha, there is an analysis comparing the total amount of catechins and gallic acid in a hot-water extract against other teas, with a result far lower than green tea, oolong tea, or black tea.
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→ "HPLC analysis of hot-water extracts found the total amount of the main catechins and gallic acid in goishicha to be extremely low compared with other teas -- about 1/7 that of green tea and about half that of oolong and black tea, the source reports. Because catechins are the components involved in tea astringency, the source describes goishicha, whose catechins decrease during fermentation, as having mild astringency."The Aromas Overlap, but Bitterness and Astringency Go Unmentioned
An analysis comparing the aroma compounds of hot-water extracts of Goishicha and Awa-bancha confirms an aroma pattern common to both. However, this analysis deals only with aroma compounds, and no mention of bitterness or astringency is found.
Compared with Pu-erh Tea's Pile Fermentation
Pu-erh tea from China is also a tea that undergoes fermentation by piling, and there is a study that tracked its fermentation time series. The source reports that at the endpoint of fermentation, both bitterness and astringency were lower than in the raw material.
Scope: A 36-day fermentation time series of one sun-dried green maocha from old-tree tea
Note: A comparison between RM and F4. This is a time series from a single fermentation batch, not the causal effect or effect size of fermentation in general.
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process-tea-pile-fermentation —was_observed_with→ "Lower bitterness and astringency than the raw material at the 36-day endpoint"At the same endpoint, the source reports that sweetness rose, the color changed from yellow-green to reddish-brown, and the aroma changed in the direction the source text recorded as from "fresh" to "stale."
Scope: The same 36-day fermentation, evaluated by a trained panel of 9
Note: Multiple attributes were observed at the same time. Do not convert the correlation of sugars, pigments, and microorganisms into the sole cause of each individual change.
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process-tea-pile-fermentation —was_observed_with→ "A rise in sweetness, a shift to a reddish-brown color, and a change in aroma to what the source called "stale aroma""There is also a report that tracked this change in terms of components. In the same fermentation time series, the content of tea polyphenols and catechins is reported to have decreased significantly as fermentation progressed.
Scope: One shou (ripe) pu-erh fermentation made from sun-dried green maocha from old-tree tea (the same time series as the existing claim on pu-erh fermentation and bitterness)
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process-tea-pile-fermentation —was_observed_with→ "In the same 36-day fermentation time series, tea polyphenol content decreased significantly (p<0.05) from 21.59% in the raw material (RM) to 10.58% at the fermentation endpoint (F4). The 5 catechins — epicatechin gallate, epigallocatechin gallate (EGCG), gallocatechin gallate, catechin, and catechin gallate — also decreased significantly (p<0.05). The source reports that theaflavin and thearubigin content also decreased during fermentation."Another report tracking the pile fermentation of a different shou (ripe) pu-erh tea likewise states that tea polyphenol content decreased greatly as fermentation progressed.
Scope: Shou (ripe) pu-erh tea from the small-leaf cultivar grown in Yunnan Province, the middle layer of a single pile-fermentation batch
Note: An additional connection to the existing entry for tea pile fermentation (no duplicate entry created). This is a time series from a single batch and a single layer, so the causal effect or effect size cannot be separated out. Whether the source's 107.22 mg/g refers to the amount of decrease or the endpoint value has not been determined this time. This report itself makes no mention of astringency or bitterness.
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process-tea-pile-fermentation —was_observed_with→ "In one pile-fermentation batch of shou (ripe) pu-erh tea made from the small-leaf cultivar grown in Yunnan Province (fermentation days 0-30, 15 time points, with samples taken in 6 groups from the middle layer of the tea pile at each time point), tea polyphenol content is reported to have shown "marked reductions, by 56.8% (107.22 mg/g)" (the source's own wording) as fermentation progressed."Among the words used to talk about pu-erh tea is huigan (回甘). Tea-trade articles explain this word with pu-erh tea as their main subject. Where the sources on Awa-bancha, Goishicha, and Ishizuchi-kurocha talk about astringency and sourness in taste-sensor output values, the sources on pu-erh tea talk about taste through huigan, a word that carries the passage of time -- even for the same 「発酵した茶」 (in translation: "fermented tea"), where the telling is placed differs.
Note: The group of tea-trade articles explaining pu-erh tea's tasting vocabulary (huigan, shengjin, houyun, and huitian) all explain huigan with pu-erh tea as their main subject.
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ingredient-puer-tea —has_defining_sensory_theme→ concept-huiganWhat is not known
- For none of Goishicha, Awa-bancha, or Ishizuchi-kurocha is a report of taste-sensor measurement or sensory evaluation targeting bitterness itself to be found. Astringency, sourness, and umami output values have been measured, but there is no material comparing bitterness output values across the three teas.
- The analysis comparing the aroma compounds of Goishicha and Awa-bancha does not touch on bitterness or astringency, and whether the overlap in aroma and the overlap in taste come from the same cause cannot be told from this material alone.
- The taste-sensor measurements of Ishizuchi-kurocha and Awa-bancha are treated as reference values by the report itself, after positioning the sourness and saltiness output as below the no-taste point, and there is no mention of sample number, replicates, or statistical testing either.
- Goishicha's fermentation microbes and their involvement in aroma production are based on a sample from a single origin, and it has not been confirmed whether the same microbes and the same aroma pattern occur when the origin or lot changes.
- The study of pu-erh tea's pile fermentation is a time-series observation without a control fermentation vessel, and the drop in bitterness and astringency cannot be separated out as an effect of the process of pile fermentation itself.
Frequently asked
How do Awa-bancha and Goishicha differ?
Goishicha is recorded as being made by steaming the raw material and then, after about 2 hours of heat treatment, layering two fermentations -- about 7-10 days of aerobic fermentation by mold and about 10-20 days of anaerobic fermentation by lactic acid bacteria. Ishizuchi-kurocha is likewise recorded as following the same two-stage fermentation, while Awa-bancha differs in that heat treatment stops oxidative fermentation beforehand, and only lactic acid fermentation through pickling is brought about, in a single stage. In reports that measured the infusion with a taste sensor, Ishizuchi-kurocha and Awa-bancha each have a higher sourness output value than sencha or black tea, while Goishicha shows weaker astringency and umami and stronger sourness -- different results for each. However, these measurements have no mention of sample number or replicates, and remain reports at the level of reference values.
Does fermentation lower the bitterness of Goishicha or pu-erh tea?
In one time-series study tracking pu-erh tea's pile fermentation, both bitterness and astringency are reported to have become significantly lower than in the raw material at the endpoint of fermentation, with sweetness rising at the same time. For Goishicha, Awa-bancha, and Ishizuchi-kurocha, on the other hand, while there are taste-sensor reports measuring astringency, sourness, and umami, no measurement targeting bitterness itself is found. For Goishicha, there is an analysis showing the total amount of catechins and gallic acid to be considerably lower than green tea, and a description stating that its astringency is mild, but this too is not a direct measurement of bitterness.
Related entries:Goishi tea / Ishizuchi kurocha / Awa bancha / ripe Pu-erh tea / goishi-cha two-stage fermentation / ishizuchi kurocha two-stage fermentation / awa bancha boil-then-lactic fermentation / tea pile fermentation / sweet aftertaste
Related topic hub: Bitterness, Astringency, and Egumi
Related research notes: Bitterness Has a Clock / How Bitterness, Astringency, and Egumi Differ / Cooking Does Not Erase Bitterness — It Edits It / What Changes When Bitterness Is Preserved
Source ledger: Source list
How to cite this page
Aoki, M. (NIGAMI LAB) (2026). Awa-bancha, Goishicha, Ishizuchi-kurocha. https://nigamilab.com/en/notes/japanese-post-fermented-teas/
Each claim card has a stable anchor (#clm-…). The dataset is CC BY 4.0; see the data page. Dataset DOI: 10.5281/zenodo.22739101