Research note 052 — 2026-09-04
Citrus Peel — Bitterness Left in Chenpi, Yuzu, and Marmalade
When people talk about citrus bitterness, attention tends to go to the limonin and naringin in squeezed juice, but the bitterness that stays in the peel itself is recorded in a different way. Dried peel has its properties written up as a crude drug, and how peel sent for processing may be used is defined within a standard. Even for the same citrus fruit, the bitterness of the juice and the bitterness of the peel are written down in different sources, in different words. Here we look in turn at the Japanese Pharmacopoeia's description of chenpi (dried mandarin peel), the changes yuzu peel goes through in the marmalade process, and the international standard that accepts the peel. We also record, as it stands, that there are processed peel products where the name comes first but no claim backing it up could be reached.
What this page establishes
- The Japanese Pharmacopoeia states of chenpi 「味は苦くて、僅かに刺激性」 (in translation: "the taste is bitter, with slight pungency") in its crude-drug description, defines the mature peel of unshiu mikan and other species as its botanical origin, and sets a specification of hesperidin content of 4.0% or more on a dried basis.
- Chenpi's aging is a biotransformation process requiring 3 years or more, and analysis has confirmed that its flavonoid composition keeps changing as aging progresses.
- In marmalade made with yuzu peel, it has been measured in one study that soaking in water and heating reduces naringin by 63-76%, while the bitter compound nomilin instead increases.
- That perceived bitterness corresponds with the amount of nomilin has been confirmed in one study by a 13-member panel, but whether this extends to other citrus fruits and processes is not yet known.
How does the Japanese Pharmacopoeia describe chenpi?
Chenpi, as a crude drug, is dried citrus peel itself. Among its listed botanical origins is the mature peel of unshiu mikan.
Scope: The chenpi entries of the Japanese Pharmacopoeia
Note: Those entries record the mature peel of this species as one of the botanical origins of chenpi.
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organism-citrus-unshiu —provides_material_for→ ingredient-chenpi-jp-pharmacopoeiaThe Japanese Pharmacopoeia further lists the mature peel of Citrus reticulata Blanco as a botanical origin as well. The botanical origin is not confined to a single species. Under one and the same entry, 「陳皮」 (in translation: "chenpi"), the peels of multiple species are listed side by side as botanical origins.
Scope: The chenpi entries of the Japanese Pharmacopoeia
Note: This is a record of the crude drug's botanical origin under the Pharmacopoeia, not a classification covering dried mandarin peel used as food in general.
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ingredient-chenpi-jp-pharmacopoeia —is_mature_peel_of→ organism-citrus-unshiuAs a compositional specification, a quantitative standard of hesperidin content of 4.0% or more, on a dried basis, is set. This is a lower limit for measuring quality, not a number that measures bitterness strength. Since the botanical origin spans multiple species, binding the content to a single figure can also be read as a way of securing the crude drug's identity.
Scope: The chenpi specification in the Japanese Pharmacopoeia
Note: This is the lower limit of the specification, not the average content or the content distribution of commercial or home-made products.
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ingredient-chenpi-jp-pharmacopoeia —contains→ "A hesperidin content of 4.0% or more, calculated on a dried basis"The description of the crude drug's properties, on the other hand, is where bitterness itself appears in words. The Japanese Pharmacopoeia records the taste of chenpi as 「苦くて，僅かに刺激性」 (in translation: "bitter, with slight pungency"). This is a statement written in the section on properties confirmed by the senses, on a different axis from the compositional specification.
Scope: The crude-drug description in the Japanese Pharmacopoeia
Note: The original text states 「味は苦くて，僅かに刺激性」 (in translation: "the taste is bitter, with slight pungency"). This is not an intensity measurement by a food sensory panel.
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ingredient-chenpi-jp-pharmacopoeia —has_sensory_attribute→ sensation-bitterChenpi keeps being written about outside the Pharmacopoeia
Where the Japanese Pharmacopoeia writes only properties and a quantitative specification, sources in Chinese medicine place chenpi within a broader classification. In the taste-and-nature classification, chenpi is treated as having a warm nature together with a pungent and bitter taste, and is linked to the spleen and lung meridians.
Scope: Traditional classification in Chinese medicine
Note: This is a traditional classification, not a sensory measurement. It is retained in the bitterness database as a cultural positioning.
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ingredient-chenpi-cn-aged —is_classified_by→ "In traditional Chinese medicine's taste-and-nature classification, a warm nature and a pungent, bitter taste (targeting the spleen and lung meridians)"Chenpi also has a documented aging process. Aging is positioned as a complex biotransformation process, with a minimum period of 3 years cited, and is linked to a view in which phenolic acids accumulate progressively. Rather than ending once the peel is dried, the passage of time itself is written up as part of the process.
Scope: Chenpi (Citri Reticulatae Pericarpium)
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ingredient-chenpi-cn-aged —is_produced_through→ process-chenpi-agingThe total flavonoid content of chenpi that has gone through this aging is reported in a range of 36.24 to 88.64 mg/g, of which hesperidin accounts for 71-92%. Rather than a single value that flattens out differences in cultivar, growing region, and years of aging, it is recorded as a range.
Scope: Chenpi
Note: Hesperidin itself is not a bitter glycoside (the bitter compounds are of the naringin type). This claim does not assert an attribution of bitterness.
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ingredient-chenpi-cn-aged —contains→ "Total flavonoids of 36.24 to 88.64 mg/g. Hesperidin accounts for 71 to 92% of total flavonoids"Peel bitterness is not chenpi's alone
Bitter flavanone glycosides are not confined to chenpi. In bitter orange, it is documented that neohesperidin levels exceed naringin in every organ — leaf, flower bud, and fruit alike. Breaking the flower bud down further by organ, this ratio ranges as widely as 0.98 in the receptacle to 3.83 in the stigma, and while petals have a low ratio on their own, their contribution is not small, since they account for 42.34% of the flower's total weight.
Scope: Quantification of C. aurantium by organ and developmental stage (fruit including the peel)
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ingredient-bitter-orange-peel —contains→ compound-neohesperidinThe marmalade standard accepts the peel, bitterness and all
Even under an international standard, citrus marmalade is defined on the premise that it uses materials including the peel. Codex defines citrus marmalade as a product that may use whole fruit, pulp, purée, juice, water extract, peel, and the like. It is not a standard that excludes bitter peel; it is a standard built around using it.
Scope: Codex CXS 296-2009 (revised 2025)
Note: A product definition under the standard. It does not indicate the presence or desirability of bitterness.
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seasoning-citrus-marmalade —is_defined_in_codex_as→ "A product that brings citrus fruit to a suitable viscosity and that may use whole fruit, pulp, purée, juice, water extract, peel, and the like"How much peel is blended, however, falls outside the standard, and becomes something confirmed through sensory evaluation. In a trial comparing 0, 2, 4, and 6% blends of a certain citrus's treated peel, the 2% blend was rated highest. The range the standard sets as 「使ってよい」 (in translation: "may be used") and the range that is felt to taste good are decided by different sources, using different methods.
Scope: This marmalade trial under TCVN 3215-79
Note: This is a comparison within this formulation and process; the best ratio is not generalized to other fruits or production methods.
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seasoning-sanh-orange-marmalade —has_sensory_acceptability_increased_by→ "Among the 0, 2, 4, and 6% levels tested, a 2% treated-peel formulation"Yuzu peel shifts toward nomilin during processing
Yuzu peel is also a place where multiple compounds move within the same processed product, marmalade. In a sensory evaluation of single-fruit and blended marmalades of yuzu, konatsu, kumquat, and navel orange, the perceived strength of bitterness corresponded with the amount of nomilin.
Scope: Single-fruit and blended marmalades of yuzu, konatsu, kumquat, and navel orange; sensory evaluation by 13 panelists
Note: Bitterness and nomilin were correlated in this sample set. This is not asserted as the sole cause of bitterness in marmalade in general.
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seasoning-yuzu-peel-marmalade —has_perceived_bitterness_associated_with→ compound-nomilinHow that compound moves can also be traced within the process. In a process of soaking yuzu peel in water and heating it, naringin decreased while nomilin increased. Peel bitterness is not a simple process that only decreases in one direction; it moves in a way where one bitter compound decreases while another bitter compound increases.
Scope: A 1994 marmalade process using yuzu peel
Note: The candidate bitter compounds do not move in the same direction. Naringin was reported to be below threshold in this sample.
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seasoning-yuzu-peel-marmalade —was_observed_with→ "A decrease in naringin and an increase in nomilin after water soaking and heating"What is not known
- Chinotto marmalade appears by name as an entry, but no claim backing up its bitterness could be found within this ledger. Rather than putting the name forward first, this is left blank until the next source is found.
- For bergamot peel, too, this ledger has no corresponding claim. Within the line of describing citrus peel bitterness, there is a place that remains unfilled.
- Hesperidin's quantitative specification is an indicator of quality, not a value that measures the strength of bitterness itself. While the Japanese Pharmacopoeia's description of properties records bitterness in words, the quantitative specification measures a different axis.
Frequently asked
Why is chenpi bitter?
The Japanese Pharmacopoeia states of chenpi's properties 「味は苦くて、僅かに刺激性」 (in translation: "the taste is bitter, with slight pungency"), and this is a statement in an official standard based on the mature peel of botanical-origin plants such as unshiu mikan. The main flavonoid contained in chenpi is hesperidin, and the Japanese Pharmacopoeia specifies a content of 4.0% or more on a dried basis, but this is not a number that measures the strength of bitterness itself. In the traditional classification of Chinese medicine as well, chenpi is classified as having a warm nature and a pungent, bitter taste, but this too is a framework separate from bitterness measurement by sensory testing. In other words, the statement that chenpi is bitter is common to multiple sources, but sensory data that measured that bitterness quantitatively is not found in this material.
Why do marmalade and yuzu jam sometimes turn out bitter?
In a study that examined the production process of marmalade made with yuzu peel, it has been measured that soaking in water and heating reduces naringin by 63-76%, while nomilin, whose bitterness is strong, instead increases. The same study also confirmed, with a 13-member panel, that the strength of bitterness evaluated by the senses corresponds with the amount of nomilin. In a sensory trial of marmalade made with Vietnamese citrus peel, among the 0, 2, 4, and 6% treated-peel blends tested, the 2% blend was rated best, showing that how bitterness is perceived changes with the amount of peel blended in. However, these are all results from a single small-scale preparation condition and panel, and have not been confirmed to apply directly to other citrus fruits or processes.
Related items:chinpi (Japanese Pharmacopoeia chenpi) / Chenpi (aged) / chenpi aging / bitter orange peel / bitter orange marmalade / yuzu peel marmalade / citrus marmalade / chinotto marmalade
Related research notes: Citrus Bitterness Arrives Late / What Changes When Bitterness Is Preserved / Standards Certify Bitterness, and the Shelf Chooses It
Source ledger: Source list
How to cite this page
Aoki, M. (NIGAMI LAB) (2026). Citrus Peel Bitterness: Chenpi, Yuzu, Marmalade. https://nigamilab.com/en/notes/citrus-peel-bitterness/
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