日本語版

chestnut pellicle

ingredient / ingredient-chestnut-inner-skin

渋皮 / Castanea crenata

Chestnut pellicle is the thin inner skin (shibukawa, seed coat) inside the hard outer chestnut shell (onigawa, the pericarp). It is rich in tannins (proanthocyanidins) and is left in place when making dishes such as chestnuts simmered in their inner skins. Cooking sources describe "slight bitterness" added by leaving the skin on, while the peer-reviewed papers checked by NIGAMI LAB describe its properties in terms of astringency, tannins, and ease of peeling without using the word bitterness.

On this page (5 sections)
  1. Overview
  2. Sources for this overview (3)
  3. Topic hubs
  4. Related entries (10)
  5. Sensory (2)
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Reading the bitterness

The chestnut's inner skin is a thin skin (the seed coat) on the inside of the hard outer skin (the pericarp) and is rich in tannins. For chestnuts simmered in their inner skins, the skin is left on rather than peeled, and a cooking article writes that leaving the skin on adds a distinctive 「ほろ苦さ」 (in translation: "slight bitterness") and toasted aroma. The same article explains that baking-soda treatment softens the inner skin and makes fibers and fuzz easier to remove, while at the same time removing tannins, the astringent component, to leave a taste without 「えぐみ」 (in translation: "harshness"), and it uses the three terms 「ほろ苦さ」 (in translation: "slight bitterness"), 「渋み」 (in translation: "astringency"), and 「えぐみ」 (in translation: "harshness") distinctly.

A peer-reviewed paper that examined the composition of the inner skin reports that the inner-skin extract is rich in tannins, but the terms bitterness or bitter are never used in the body text. Another peer-reviewed paper that examined the ease of peeling the skin is similar: it reports that, in a panel evaluation by 11 female students, frying treatment shortened peeling time to 60% of the untreated value, while not using the terms bitterness or astringency and not describing the taste of the inner skin. Both papers describe the inner skin in terms of the amounts of tannins and other compounds, or its ease of peeling, and the term 「ほろ苦さ」 (in translation: "slight bitterness") appears only in cooking articles. Among the sources NIGAMI LAB has gathered, none has measured whether the 「ほろ苦さ」 of the inner skin refers to bitterness or to astringency.

Sources for this overview

  1. 栗の渋皮煮レシピ｜失敗しない下処理と重曹の使い方・保存方法

    やまだまゆみ（和ごころごはん帖） / 2025 / other / full text checked

    Checked for this overview: The part explaining the slight bitterness added by leaving the skin on and the baking-soda treatment.

  2. Phenolic Compositions and Antioxidant Properties in Bark, Flower, Inner Skin, Kernel and Leaf Extracts of Castanea crenata Sieb. et Zucc

    Phung Thi Tuyen; Tran Dang Xuan; Do Tan Khang; Ateeque Ahmad; Nguyen Van Quan; Truong Thi Tu Anh; La Hoang Anh; Truong Ngoc Minh / 2017 / journal article / full text checked

    Checked for this overview: The part showing the tannin content and the fact that the term bitterness is not used.

  3. 官能評価によるクリ皮のむきやすさの検討

    畑江敬子; 嶋田淑子; 戸田貞子; 壽和夫; 香西みどり / 2002 / journal article / full text checked

    Checked for this overview: The part showing the shortened peeling time and the fact that taste terms are not used.

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

Sensory (2)

chestnut pellicle — sensory attribute: A distinctive 「ほろ苦さ」 (in translation: "slight bitterness") and toasted aroma added by leaving the inner skin on rather than peeling it.contextual

Scope: A recipe article on chestnuts simmered in their inner skins 「和ごころごはん帖」 (Wagokoro Gohanchō).

Note: A description in a cooking web publication, not a sensory panel or chemical analysis. The same article separately says that boiling and discarding water with baking soda removes 「えぐみ」 (in translation: "harshness") and distinguishes this from the skin's astringent component (tannin). The only explicit wording corresponding to 「苦味」 (in translation: "bitterness") is 「ほろ苦さ」 (in translation: "slight bitterness").

The article says 「渋皮を残すことで独特のほろ苦さと香ばしさが加わり」 (in translation: "leaving the inner skin adds a distinctive slight bitterness and toasted aroma") and that a final boil to remove the baking soda gives 「すっきりと上品な渋皮煮に仕上がります」 (in translation: "the result is a clean-tasting, refined simmered chestnut dish"). It explains that baking soda works 「アルカリ性の力で渋皮をやわらかくし、筋や毛羽立ちを取りやすくするため」 (in translation: "through its alkalinity, it softens the inner skin and makes fibers and fuzz easier to remove") and 「同時に渋み成分（タンニン）を抜いて、仕上がりをえぐみのない味に整えてくれる役割も」 (in translation: "also removes astringent components (tannins) and leaves the finished dish without harshness").
Limitations: One web-media article without sensory-panel or chemical-analysis corroboration. It distinguishes 3 different terms—「ほろ苦さ」 (in translation: "slight bitterness"), 「渋み」 (in translation: "astringency"), and 「えぐみ」 (in translation: "harshness")—and the article alone does not establish how far they refer to the same phenomenon.
Source: 栗の渋皮煮レシピ｜失敗しない下処理と重曹の使い方・保存方法 (やまだまゆみ（和ごころごはん帖）, 2025) · full text checked
Show dataingredient-chestnut-inner-skin —has_sensory_attribute→ "A distinctive 「ほろ苦さ」 (in translation: "slight bitterness") and toasted aroma added by leaving the inner skin on rather than peeling it."
claim: clm-aprep-chestnut-skin-horonigai / type: sensory / updated: 2026-09-13
chestnut pellicleA description using the terms bitterness or bitter. has insufficient evidence for: observation

Scope: A peer-reviewed paper on phenolic composition of the inner skin (Phung et al. 2017) and a sensory-evaluation paper on peelability of the inner skin (Hatae et al. 2002).

Note: Neither paper uses the terms "bitter""bitterness" or 「苦味」 (in translation: "bitterness") anywhere in its body (both full texts were checked directly). They describe the skin chiefly in terms of 「渋味」 (in translation: "astringency"), 「タンニン」 (in translation: "tannins"), 「収斂性」 (in translation: "astringency"), and 「剥皮のしやすさ」 (in translation: "ease of peeling"). This does not establish that bitterness is absent in reality; it records only the absence of mention, an honest negative finding under this institute's collection rule of using only sources that explicitly mention bitterness for bitterness claims.

The full text reporting phenolic compounds and antioxidant properties of Castanea crenata bark, flowers, inner skin, kernel, and leaves was checked; the words "bitter""bitterness" do not appear even once. It reports 1034±7.21 mg GAE/g total phenols and 253.89±5.59 mg CE/g tannins in inner-skin extract.
Limitations: A peer-reviewed paper on composition and antioxidant properties; it did not conduct sensory evaluation of taste (bitterness or astringency).
Source: Phenolic Compositions and Antioxidant Properties in Bark, Flower, Inner Skin, Kernel and Leaf Extracts of Castanea crenata Sieb. et Zucc (Phung Thi Tuyen; Tran Dang Xuan; Do Tan Khang; Ateeque Ahmad; Nguyen Van Quan; Truong Thi Tu Anh; La Hoang Anh; Truong Ngoc Minh, 2017) · full text checked
The full text was checked for a panel of 11 female students evaluating reduced peeling times for outer and inner skins after 3 treatments—immersion in boiling water, steaming, and frying—but it never used the terms 「苦味」 (in translation: "bitterness") or 「渋味」 (in translation: "astringency") and did not describe the taste of the inner skin (the introduction does use 「甘味」 (in translation: "sweetness") and 「風味」 (in translation: "flavor") for chestnuts). It reported that 「揚げる」 (in translation: "frying") reduced inner-skin peeling time to 60% of the untreated value (a physical ease-of-peeling measure, not a taste measure).
Limitations: A sensory evaluation limited to the physical difficulty of peeling; it did not assess taste.
Source: 官能評価によるクリ皮のむきやすさの検討 (畑江敬子; 嶋田淑子; 戸田貞子; 壽和夫; 香西みどり, 2002) · full text checked
Show dataingredient-chestnut-inner-skin —has_insufficient_evidence_for→ "A description using the terms bitterness or bitter."
claim: clm-aprep-chestnut-skin-no-bitterness-in-peer-reviewed / type: sensory / updated: 2026-09-13

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