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kaki astringency recurrence

process / process-kaki-astringency-recurrence

渋戻り

Kaki astringency recurrence is a phenomenon in which persimmon tannins insolubilized by de-astringing treatment become soluble again under conditions such as heating or storage, making astringency perceptible again. It is a problem when making heated Japanese sweets, pastes, jams, and similar products.

On this page (7 sections)
  1. Overview
  2. Sources for this overview (5)
  3. Topic hubs
  4. Follow the connections
  5. Related entries (10)
  6. Mechanism and receptors (3)
  7. How processing and cooking change it (3)
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Reading the bitterness

Astringency recurrence is the renewed perception of astringency when persimmon tannins insolubilized by de-astringing treatment become soluble again during heating or storage. In one of the earliest direct experimental studies of its mechanism, 「北川」 (Kitagawa; 1969, Faculty of Agriculture, Kagawa University) confirmed that boiling immature 「'平核無'」 (Hiratanenashi) persimmons de-astringed in warm water (42°C) restored astringency. Microscopy showed a gel-like mass of protoplasm in tannin cells. This gel did not dissolve in cold water or alcohols but did in hot water or dilute hydrochloric acid. Kitagawa concluded that recurrence results from heating dissolving the gelled mass of tannin-cell contents and tannins, allowing soluble tannins to seep out again, rather than reversal of chemical condensation or polymerization of tannins themselves.

In contrast, a 2008 fiscal-year report from the Gifu Prefectural Food Science Research Institute explains recurrence as 「縮重合し不溶化した不溶性タンニンが、加熱により重合が解して可溶性タンニンになることにより生じる現象」 (in translation: "a phenomenon in which condensed and insolubilized tannins become soluble when heating reverses polymerization"). This wording differs from Kitagawa's (1969) gel-dissolution mechanism and, as an applied food-processing report, does not include independent structural analysis. The accounts are presented side by side as differing levels of description rather than necessarily contradictory hypotheses.

How readily insoluble tannins resolubilize differs by de-astringing method. 「平」 (Taira), 「松本」 (Matsumoto), and 「小野」 (Ono) (1999, Yamagata University), comparing multiple de-astringing treatments using 「'平核無'」 (Hiratanenashi), found resolubilization most difficult after acetaldehyde treatment, followed by peeled-fruit drying, carbon dioxide, ethanol on the tree, and ethanol after harvest; freezing and thawing made it easiest. Difficulty correlated significantly (5% level) with acetaldehyde accumulation in flesh; greater accumulation was inferred to bind insoluble tannins more strongly. Resolubilization also tended to grow harder with longer time since de-astringing was completed, especially after on-tree ethanol treatment.

Heating method also matters. In experiments with 「'西条'」 (Saijo) persimmon paste, Tsurunaga, Onda, and Takahashi (2021, Shimane University) observed no recurrence under any tested dry stir-frying condition with moisture evaporation (100–150°C, 1–10 minutes), but recurrence under every boiling (80–100°C, 40–60 minutes) and pressurized-heating condition (121°C, 4–20 minutes). A Gifu Prefecture report (fiscal 2008) states that, as another countermeasure, adding 1% collagen peptide, which readily binds tannins, on a solids basis prevented recurrence in both warm-water- and alcohol-de-astringed paste. In both cases, this addition was accompanied by fading on heating, and adding trehalose or ascorbic acid did not prevent it.

In experiments on the 'Triumph' cultivar by Ben-Arie and Sonego (1993; abstract checked only), warm-water treatment at 60°C for more than 2 hours was reported to cause recurrence, which subsequent carbon dioxide treatment did not resolve. Recurrence was also described in non-astringent fruit de-astringed by carbon dioxide after high-temperature exposure, suggesting temperature control after de-astringing matters. Detailed conditions have been checked only in the abstract, not the full text.

Sources for this overview

  1. カキの脱渋および貯蔵に関する研究(第6報) 温湯脱渋果における渋味の再現について

    北川博敏 / 1969 / journal article / full text checked

    Checked for this overview: Used Kitagawa's 1969 microscopy results to support this paragraph.

  2. 柿の新規加工技術に関する研究(加熱時に渋戻りを起こす脱渋渋柿への防止加工技術に関する研究)

    神山真一; 加島隆洋 / 2008 / government document / full text checked

    Checked for this overview: Used verbatim confirmation of the Gifu Prefecture report's explanation to support this paragraph. / Used the effect of adding collagen peptide to support this paragraph.

  3. 数種の脱渋処理によって不溶化した渋ガキタンニンの可溶化の難易

    平智; 松本尚子; 小野未来 / 1999 / journal article / full text checked

    Checked for this overview: Used differences in resolubilization difficulty across de-astringing treatments to support this paragraph.

  4. Effect of heating methods on astringency recurrence, syneresis, and physical properties of persimmon paste

    Tsurunaga Yoko; Onda Misaki; Takahashi Tetsuya / 2021 / journal article / full text checked

    Checked for this overview: Used the presence or absence of recurrence by heating method to support this paragraph.

  5. Temperature Affects Astringency Removal and Recurrence in Persimmon

    Ben-Arie R; Sonego L / 1993 / journal article / abstract checked

    Checked for this overview: Used the temperature-threshold condition in the abstract to support this paragraph.

Follow the connections

hot-water kaki de-astringing →can generate→ kaki astringency recurrence

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

Mechanism and receptors (3)

kaki astringency recurrence — currently proposed mechanisms: Across 6 de-astringing treatments (acetaldehyde, carbon dioxide, on-tree ethanol, postharvest ethanol, peeled-fruit drying, and freezing/thawing), insoluble tannins were hardest to resolubilize (which approximately corresponds to recurrence) in this order: acetaldehyde, peeled-fruit drying, carbon dioxide, on-tree ethanol, postharvest ethanol, and freezing/thawing. Difficulty correlated with acetaldehyde accumulation in flesh (correlation with 0.1% HCl-MeOH extraction at treatment completion: -0.683; with 1% HCl-MeOH room-temperature extraction 3 days later: -0.737; both significant at the 5% level). Greater accumulation was inferred to bind insoluble tannins more strongly. Under every treatment, longer time after completion made them harder to resolubilize, especially after on-tree ethanol treatment.supported

Scope: 「'平核無'」 (Hiratanenashi), compared under uniform staged extraction conditions (0.02%–1% HCl-MeOH, room temperature to 80°C).

Note: Taira, Matsumoto, and Ono (1999). They did not measure recurrence itself directly; ease of dissolution in extraction solvent was used as a proxy for propensity to recur.

Difficulty of resolubilizing insoluble tannins differed substantially by treatment: greatest after acetaldehyde, intermediate after postharvest ethanol, and least after freezing and thawing. It was associated with acetaldehyde accumulation in flesh, with greater accumulation tending toward harder resolubilization. The order of inferred strength of tannin binding through polymerization was acetaldehyde, peeled-fruit drying, carbon dioxide, on-tree ethanol, postharvest ethanol, then freezing and thawing.
Limitations: Because the full text was extracted by OCR, some numbers may contain recognition errors. The abstract and conclusion were checked against multiple passages.
Source: 数種の脱渋処理によって不溶化した渋ガキタンニンの可溶化の難易 (平智; 松本尚子; 小野未来, 1999) · full text checked
Show dataprocess-kaki-astringency-recurrence —has_currently_proposed_mechanisms→ "Across 6 de-astringing treatments (acetaldehyde, carbon dioxide, on-tree ethanol, postharvest ethanol, peeled-fruit drying, and freezing/thawing), insoluble tannins were hardest to resolubilize (which approximately corresponds to recurrence) in this order: acetaldehyde, peeled-fruit drying, carbon dioxide, on-tree ethanol, postharvest ethanol, and freezing/thawing. Difficulty correlated with acetaldehyde accumulation in flesh (correlation with 0.1% HCl-MeOH extraction at treatment completion: -0.683; with 1% HCl-MeOH room-temperature extraction 3 days later: -0.737; both significant at the 5% level). Greater accumulation was inferred to bind insoluble tannins more strongly. Under every treatment, longer time after completion made them harder to resolubilize, especially after on-tree ethanol treatment."
claim: clm-w40c-resolubilization-difficulty-ranking / type: mechanism / updated: 2026-09-02
kaki astringency recurrence — currently proposed mechanisms: When astringent persimmon de-astringed by warm-water treatment (immersion at 42°C) is boiled, astringency recurs. Microscopic observation showed that in the tannin cells of the de-astringed fruit, the protoplasm had set into a gel, and this coagulated substance was insoluble in cold water, methanol, ethanol, ether, acetone, and formamide, but soluble in hot water, 1% hydrochloric acid, 1% methanolic hydrochloric acid, and 1% ethanolic hydrochloric acid. From this it was concluded that astringency recurrence is not due to chemical condensation or polymerization of the tannin substance (and its reversible dissociation), but rather that the contents of the tannin cell gel together with the tannin substance so that the whole cell coagulates, and this dissolves under heating and is re-released as soluble tannin. Boiling untreated astringent persimmon dissolved about 55% of the soluble tannin substance present before de-astringing after 150 minutes, and in 100°C water, more than about 90% of the amount dissolved in 1% methanolic hydrochloric acid was dissolved. When the tannin-cell gel was broken by ultrasound, about 56% was dissolved after 60 minutes.supported

Scope: Immature 'Hiratanenashi' de-astringed with warm water (42°C); an experiment at the Faculty of Agriculture, Kagawa University.

Note: Kitagawa (1969). One of the oldest primary sources to directly address the mechanism of astringency recurrence.

Astringency appeared again after boiling the fruits which had apparently lost their astringency with the warm water treatment. The protoplast in the tannin cells had jelled; this substance was insoluble in cold water, methyl/ethyl alcohol, ether, acetone and formamide, but soluble in hot water and dilute acids. Astringency reappeared when the protoplast gel in the tannin cells was dissolved in hot water; more than 90% of the tannin substances were dissolved in 100°C water. The text includes the discussion 「タンニン物質は縮合,重合したポリフェノールが煮沸や薄いメチルアルコール性塩酸に溶解することによって再びもとの物質に戻るのではなく...タンニン細胞の内容物質がタンニン物質とともにゲル化して全体が凝固する」 (in translation: “it is not that the tannin substance, a condensed and polymerized polyphenol, reverts to its original substance by dissolving in boiling water or dilute methanolic hydrochloric acid... rather, the contents of the tannin cell gel together with the tannin substance so that the whole coagulates”). After 150 minutes of boiling, about 55% of the soluble tannin substance present before de-astringing was dissolved, and with ultrasonic treatment, about 56% was dissolved after 60 minutes.
Source: カキの脱渋および貯蔵に関する研究(第6報) 温湯脱渋果における渋味の再現について (北川博敏, 1969) · full text checked
Show dataprocess-kaki-astringency-recurrence —has_currently_proposed_mechanisms→ "When astringent persimmon de-astringed by warm-water treatment (immersion at 42°C) is boiled, astringency recurs. Microscopic observation showed that in the tannin cells of the de-astringed fruit, the protoplasm had set into a gel, and this coagulated substance was insoluble in cold water, methanol, ethanol, ether, acetone, and formamide, but soluble in hot water, 1% hydrochloric acid, 1% methanolic hydrochloric acid, and 1% ethanolic hydrochloric acid. From this it was concluded that astringency recurrence is not due to chemical condensation or polymerization of the tannin substance (and its reversible dissociation), but rather that the contents of the tannin cell gel together with the tannin substance so that the whole cell coagulates, and this dissolves under heating and is re-released as soluble tannin. Boiling untreated astringent persimmon dissolved about 55% of the soluble tannin substance present before de-astringing after 150 minutes, and in 100°C water, more than about 90% of the amount dissolved in 1% methanolic hydrochloric acid was dissolved. When the tannin-cell gel was broken by ultrasound, about 56% was dissolved after 60 minutes."
claim: clm-w40c-recurrence-gel-mechanism-kitagawa / type: mechanism / updated: 2026-09-02
kaki astringency recurrence — currently proposed mechanisms: A report by the Gifu Prefectural Food Science Research Institute (fiscal year 2008) explains astringency recurrence as 「縮重合し不溶化した不溶性タンニンが、加熱により重合が解して可溶性タンニンになることにより生じる現象」 (in translation: “a phenomenon that arises when insoluble tannin, which has become insoluble through condensation and polymerization, has its polymerization undone by heating and becomes soluble tannin”).contextual

Scope: A report on applied processing technology using astringent persimmons grown in Gifu Prefecture ('Ijira Oomi' and 'Tone Wase').

Note: This is a different way of describing the mechanism from the one Kitagawa (1969) showed for warm-water de-astringed fruit — 「化学的な縮合・重合の可逆的解離ではなくタンニン細胞内容物のゲル溶解」 (in translation: “not the reversible dissociation of chemical condensation and polymerization, but the dissolving of a gel formed from the tannin cell's contents”). This is an explanation from a prefectural research report oriented toward applied development, and may not have been verified by the report's own structural analysis, so it is placed alongside the academic finding of Kitagawa (1969) and treated as a difference in descriptive granularity.

「渋戻りは縮重合し不溶化した不溶性タンニンが、加熱により重合が解して可溶性タンニンになることにより生じる現象である」 (in translation: “astringency recurrence is a phenomenon that arises when insoluble tannin, which has become insoluble through condensation and polymerization, has its polymerization undone by heating and becomes soluble tannin.”)
Limitations: This is an introductory explanation without an accompanying citation or empirical data, and the prefectural report itself provides no direct evidence, such as structural analysis.
Source: 柿の新規加工技術に関する研究(加熱時に渋戻りを起こす脱渋渋柿への防止加工技術に関する研究) (神山真一; 加島隆洋, 2008) · full text checked
Show dataprocess-kaki-astringency-recurrence —has_currently_proposed_mechanisms→ "A report by the Gifu Prefectural Food Science Research Institute (fiscal year 2008) explains astringency recurrence as 「縮重合し不溶化した不溶性タンニンが、加熱により重合が解して可溶性タンニンになることにより生じる現象」 (in translation: “a phenomenon that arises when insoluble tannin, which has become insoluble through condensation and polymerization, has its polymerization undone by heating and becomes soluble tannin”)."
claim: clm-w40c-recurrence-condensation-framing-gifu / type: mechanism / updated: 2026-09-02

How processing and cooking change it (3)

kaki astringency recurrence is reduced by In a test adding protein-like tannin-binding compounds (collagen peptide, various gelatins, defatted soy protein, wheat protein) at 0.5–3% of solids and boiling for 40 minutes, collagen peptide gave the greatest suppression at 1%, preventing recurrence in both warm-water-de-astringed 「'伊自良大実'」 (Ijira Omi) and alcohol-de-astringed 「'刀根早生'」 (Tone Wase) persimmon paste. Confectionery gelatin worked at 1% under some conditions; at 3%, it and defatted soy protein were effective. Wheat protein required at least 3%. Every additive caused fading on heating, which trehalose or ascorbic acid did not prevent.supported

Scope: Frozen paste from Gifu-grown 「'伊自良大実'」 (Ijira Omi; warm-water de-astringing) and 「'刀根早生'」 (Tone Wase; alcohol de-astringing).

Note: Kamiyama and Kashima (Gifu Prefectural Food Science Research Institute report, fiscal 2008).

「コラーゲンペプチドが最も効果を示し、1%の添加で渋戻りが防げることが分かった。ゼラチンは菓子用が1%で効果を示す条件もあったが、3%添加で脱脂大豆同様に効果が確認出来た。一方、小麦タンパクは3%以上の添加が必要であった。なお、いずれの場も加熱により退色が生じた」 (in translation: "Collagen peptide was most effective, and 1% prevented recurrence. Confectionery gelatin worked at 1% under some conditions, while at 3% it and defatted soy were effective. Wheat protein required at least 3%. All treatments faded on heating.")
Source: 柿の新規加工技術に関する研究(加熱時に渋戻りを起こす脱渋渋柿への防止加工技術に関する研究) (神山真一; 加島隆洋, 2008) · full text checked
Show dataprocess-kaki-astringency-recurrence —is_reduced_by→ "In a test adding protein-like tannin-binding compounds (collagen peptide, various gelatins, defatted soy protein, wheat protein) at 0.5–3% of solids and boiling for 40 minutes, collagen peptide gave the greatest suppression at 1%, preventing recurrence in both warm-water-de-astringed 「'伊自良大実'」 (Ijira Omi) and alcohol-de-astringed 「'刀根早生'」 (Tone Wase) persimmon paste. Confectionery gelatin worked at 1% under some conditions; at 3%, it and defatted soy protein were effective. Wheat protein required at least 3%. Every additive caused fading on heating, which trehalose or ascorbic acid did not prevent."
claim: clm-w40c-collagen-peptide-prevention / type: processing / updated: 2026-09-02
kaki astringency recurrence is reduced by No recurrence was observed at any tested dry stir-frying condition with moisture evaporation (100–150°C for 1–10 minutes). By contrast, recurrence was observed under all boiling (80–100°C, 40–60 minutes) and pressurized-heating (121°C, 4–20 minutes) conditions.supported

Scope: 「'西条'」 (Saijo) persimmon paste; Shimane University experiment (2021).

Note: Tsurunaga, Onda, and Takahashi (2021). The paper suggests that moisture evaporation may explain the difference between heating methods.

Stir frying at 100°C and 150°C for 1-10 min showed no recurrence of persimmon astringency at any temperature or time, in contrast to boiling and pressurization, which both showed recurrence.
Source: Effect of heating methods on astringency recurrence, syneresis, and physical properties of persimmon paste (Tsurunaga Yoko; Onda Misaki; Takahashi Tetsuya, 2021) · full text checked
Show dataprocess-kaki-astringency-recurrence —is_reduced_by→ "No recurrence was observed at any tested dry stir-frying condition with moisture evaporation (100–150°C for 1–10 minutes). By contrast, recurrence was observed under all boiling (80–100°C, 40–60 minutes) and pressurized-heating (121°C, 4–20 minutes) conditions."
claim: clm-w40c-stirfry-no-recurrence / type: processing / updated: 2026-09-02
hot-water kaki de-astringing can generate kaki astringency recurrencesupported

Scope: The 'Triumph' cultivar, an experiment by Ben-Arie & Sonego (1993).

Note: Extending the 60°C treatment beyond 2 hours caused astringency recurrence, which was not resolved by subsequent CO2 treatment. Astringency recurrence also occurred, when exposed to high temperature, even in non-astringent fruit that had been de-astringed by CO2 treatment. Only the abstract was checked; the details of the experimental conditions in the full text were not confirmed.

Astringency was removed from 'Triumph' persimmons by immersion in water at 40°C for 5h or 60°C for 1h; treatments at 20°C and 80°C had no effect. Extending the 60°C treatment beyond 2h resulted in recurrence of astringency that was not reduced by subsequent CO2 treatment. Astringency also recurred in CO2-treated non-astringent fruit when exposed to high temperatures.
Limitations: Only the abstract was checked. The full table of temperature and time conditions, and the details of statistical testing, in the full text were not confirmed.
Source: Temperature Affects Astringency Removal and Recurrence in Persimmon (Ben-Arie R; Sonego L, 1993) · abstract checked
Show dataprocess-kaki-hot-water-deastringing —can_generate→ process-kaki-astringency-recurrence
claim: clm-w40c-benarie-recurrence-temperature / type: processing / updated: 2026-09-02

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