limonin
compound / compound-limonin
リモニン
Limonin is a citrus limonoid associated with delayed bitterness in citrus products.
Photographs (captions in Japanese)
グレープフルーツ（Citrus paradisi）の果実。limonin は柑橘製品の遅発性苦味に関連するリモノイドであり、化合物そのものではなく代表的な給源果実の写真である。
原料写っているもの: Citrus paradisi（グレープフルーツ）部位・状態: 果実(外観)
写真: א (Aleph)／ CC BY-SA 2.5／ 原画像／ 台帳の原画像
写真の範囲と来歴
被写体の確認: 原典の記載による同定。ingredient-grapefruit-juice・compound-naringin で使用した写真とは別ファイル（重複回避）。
掲載画像: Wikimedia Commons の原寸ファイル。苦味研究所では切り抜き・色調変更なし。 表示用には幅1200px上限のWebPを配信し、台帳の原画像は上のリンクから確認できます。
On this page (10 sections)
Reading the bitterness
Limonin is a compound involved in delayed bitterness (「遅発性苦味」, in translation: "delayed bitterness") in citrus juice that intensifies gradually after expression. Before expression, the fruit contains not limonin itself but its tasteless precursor (limonoate A-ring lactone, LARL), which converts to bitter limonin under acidic conditions when tissue ruptures during expression. The recognition threshold for limonin bitterness in distilled water is approximately 1 mg/L, and this threshold rises several-fold when sugar or citric acid is present. Thus, at the same limonin concentration, palatability varies depending on the surrounding sugar and acid levels.
In orange juice, the discrimination threshold for limonin is highest at pH 3.8 (6.5 mg/kg), making bitterness least perceptible. As pH deviates from this value, the threshold decreases and bitterness becomes more prominent. Research using Navel orange juice has confirmed that limonin concentration increases during storage and stabilizes at a certain level; heating and acidification accelerate this increase but do not change the final concentration; and filtration or expressing juice after prolonged fruit storage lowers the final concentration.
Regarding the mechanism of conversion from precursor to limonin, research perspectives diverge. Studies using seedless Navel orange juice treat this conversion as an acid- and heat-driven reaction, largely excluding enzyme involvement. Conversely, research using enzyme purified from citrus seeds positions the conversion as enzyme-catalyzed. The presence or absence of seeds in fruit may explain this difference, but the sources reviewed do not explicitly address this point.
Sources for this overview
Citrus Taste Modification Potentials by Genetic Engineering
Checked for this overview: Confirmed the conversion process of delayed bitterness from precursor to limonin.
Effect of some citrus juice constituents on taste thresholds for limonin and naringin bitterness
Checked for this overview: Confirmed recognition threshold of 1 mg/L in distilled water and effects of sugar and acid.
Checked for this overview: Confirmed threshold of 6.5 mg/kg at pH 3.8 in orange juice.
Checked for this overview: Confirmed concentration increase during storage and effects of heating and filtration. / Confirmed the perspective of acid-promoted reaction in seedless juice.
Checked for this overview: Confirmed the opposing view of enzyme-mediated conversion from seed sources.
Follow the connections
limonin →is associated with→ bitterness →can be measured separately …→ astringency
Hassaku →contains→ limonin
amanatsu (Citrus natsudaidai) →contains→ limonin
Measured values (3)
| Kind | Compound | Target | Value | Conditions | Source |
|---|---|---|---|---|---|
| human recognition threshold | limonin | — | 1 mg/L | Distilled water (threshold rises several-fold when sugar and acid are present) | Guadagni DG, 1973 |
| concentration | limonin | pomelo pith | 0.2907 mg/g DW | Untreated Kao Nampung pomelo albedo (Table 3。) | Jaroennon Pattamaporn, 2025 |
| concentration | limonin | pomelo pith | 0.0776 mg/g DW | 0.7% β-CD plus ultrasonic treatment (Table 3。) | Jaroennon Pattamaporn, 2025 |
Values are the reported values of each source (with units and conditions). Thresholds and EC50 depend on the panel and method; they are not single true values.
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (8)
Scope: Hassaku fruit (juice, inner peel, outer peel); analysis by TLC and HPLC
Note: Note that these are not the bitter limonin (aglycone) itself, but glycosides whose bitterness has been weakened through glucose conjugation. This connects, as data on debittering through sugar conjugation during ripening, separately from the existing claim (compound-limonin's delayed bitterness).
Show data
ingredient-hassaku —contains→ compound-limoninScope: Kumamoto Prefectural Industrial Technology Center research, 2005-2007 fiscal years, 8-variety comparison
Note: The summary and detailed sections of the source material do not match in their enumeration of varieties; both are recorded as stated.
Show data
ingredient-amanatsu —contains→ compound-limoninScope: Kumamoto Prefectural Industrial Technology Center research, 2005-2007 fiscal years, 8-variety comparison
Show data
ingredient-banpeiyu —contains→ compound-limoninScope: Kumamoto Prefectural Industrial Technology Center research, 2005-2007 fiscal years, 8-variety comparison
Note: The summary and detailed sections of the source material do not match in their enumeration of varieties; both are recorded as stated.
Show data
ingredient-kawachi-bankan —contains→ compound-limoninScope: Part-by-part analysis of 1 sample of natsumikan (from Ehime). The division of parts is the same as in Morohoshi and Sugawara (1971). Quantified by a color development method as total limonoids in limonin equivalents.
Note: This is the amount of limonoids (bitter substances mainly limonin), not a sensory evaluation of bitterness. The content is total limonoids, not limonin alone. Unlike the distribution of naringin (higher in the albedo and segment membrane than in the flavedo), limonoids are higher in the flavedo than in the albedo and segment membrane, and highest in the seeds. The color development is unstable, measurement was made within 3 minutes after color development, and the recovery of added amounts is stated as ±10%.
Show data
ingredient-natsumikan —contains→ compound-limoninScope: Limonin and nomilin by part (flesh, segment membrane, seeds, peel) of hassaku fruit (Ehime Prefecture), quantified with a dual-wavelength thin-layer chromatography scanner. Harvested on November 16, January 18, March 23 and May 17.
Show data
ingredient-hassaku —contains→ compound-limoninScope: Fruit collected at about 1-month intervals from July 28 to January 17 from 2 hassaku trees aged 12 years at the attached farm of the Faculty of Agriculture, Kagoshima University (10 M-grade fruits, in 2 replicates of 5 fruits each). 40 g of flesh, 10 g of segment membrane and other parts were extracted with methylene chloride and quantified by thin-layer chromatography.
Note: This is the amount of limonoids as bitter substances, not a sensory evaluation. The author states that part of the bitterness of hassaku may depend on limonoids, and that the bitterness of nomilin is stronger than that of limonin (citing earlier studies). The limonoids in the segment membrane of natsumikan follow the same pattern of change as in hassaku, with the content said by the author to be about 2 times higher in hassaku.
Show data
ingredient-hassaku —contains→ compound-limoninScope: Natsumikan grown on the grounds of the Faculty of Agriculture, Yamaguchi University. The peel, segment membrane and seeds were dried and ground, extracted with benzene, and the weight of the precipitate separated with ether was taken as limonoids (from September 1962 to April 1963).
Note: This is a research note; limonoids were measured by the weight of the precipitate, and the composition is unconfirmed (mainly limonin). The result that limonoids in the segment membrane increase with ripening runs opposite to later reports by thin-layer chromatography and HPLC (Hashinaga and Ito 1983, Fukutani and Miyamoto 1983: limonoids in each part decrease as the fruit ripens), and this may be due to the difference in measurement method (precipitate weight method). The author states that values were disturbed from January 1963 onward by frost damage.
Show data
ingredient-natsumikan —contains→ compound-limoninSensory (5)
Scope: In many of the citrus products where it occurs, a delayed bitterness contribution
Note: Matrix and precursor conversion affect how it is perceived over time.
Show data
compound-limonin —is_associated_with→ sensation-bitterScope: A panel of 20-27 screened judges. Distilled water, sucrose, and citric acid model systems, and orange juice
Note: Sucrose and citric acid raise the threshold. In both the model systems and the juice, the pH optimum for suppression is 3.8. Later debittering literature cites the 6.5 ppm juice value from this same lineage.
Show data
compound-limonin —has_bitter_recognition_threshold→ "1 mg/L in distilled water. Maximum recognition threshold of 6.5 mg/kg in orange juice at pH 3.8"Scope: Layer: food. A threshold and intensity panel using natural orange juice (Dea et al. 2013).
Show data
compound-limonin —has_perceived_bitterness_unchanged_by→ "Addition of citric acid (did not lower the perceived bitterness from limonin and nomilin in orange juice)"Scope: Layer: food. A recognition-threshold panel using natural orange juice (Dea et al. 2013). For comparison, the same threshold measurement was also carried out in a simple matrix containing sucrose and citric acid.
Show data
compound-limonin —has_recognition_thresholds_of→ "Recognition thresholds in natural orange juice were 4.7 mg/L for limonin and 2.6 mg/L for nomilin. In a simple matrix for comparison (sucrose, citric acid), they were 4.0 mg/L for limonin and 5.4 mg/L for nomilin. When the two were mixed 1:1, they acted synergistically and both thresholds decreased."Scope: A panel of 10 laboratory researchers, repeated 2 times, ascending series of the method of limits. Limonin and nomilin were extracted and purified from natsumikan seeds and adjusted to 1 to 12 ppm.
Show data
compound-limonin —has_bitter_recognition_threshold→ "In the same model solution (sugar content 12°Bx, acid 0.45 g/100 g, pH 3.5), more than half of the panel perceived bitterness for limonin at 4 ppm (55% in the table) and 100% at 12 ppm, and for nomilin 50% at 3 ppm and 100% at 8 ppm. The bitterness of limonin and nomilin tended to linger somewhat longer in the mouth after being perceived."Mechanism and receptors (3)
Scope: Citrus juice that develops delayed bitterness during storage after pressing
Show data
compound-limonin —is_produced_through→ "In citrus juice after pressing, the conversion of the non-bitter precursor limonoate A-ring lactone (LARL) into bitter limonin"Scope: Post-pressing limonin formation in citrus juice. Kinetic evidence from seedless Newhall navel orange juice versus an enzyme purified from seeded sweet-orange seeds
Note: Zhang 2018 concludes the reaction is acid-promoted and likely excludes enzyme involvement in seedless juice. Zhang 2024 places LDLH catalysis as the source of delayed bitterness formation. Whether seeds are present could reconcile the two, but no source read here states this explicitly.
Show data
compound-limonin —has_currently_proposed_mechanisms→ "Acid-promoted lactonization of LARL versus conversion catalyzed by limonin D-ring lactone hydrolase (LDLH)"Scope: Review of bitter taste components in food (Kiyokazu Hagihara, Cooking Science vol. 13, no. 1)
Note: This is a review account of the general mechanism of limonoid bitterness development in citrus and other Rutaceae, not a direct measurement targeting yuzu peel.
Show data
compound-limonin —has_perceived_bitterness_affected_by→ "Cyclization and bitterness development from tasteless precursor by heating or storage (12-24 hours)"How processing and cooking change it (4)
Scope: Newhall navel orange juice stored after pressing. 3 harvest batches
Note: Heat processing and acidification only sped up limonin formation; they did not change the maximum steady-state value itself. Filtration and longer fruit storage lowered the maximum value.
Show data
compound-limonin —has_juice_content_affected_by→ "Post-harvest fruit storage time (the juice maximum fell from about 24.24 to 1.04 mg/L over 0-45 days), heat processing, pH, and filtration"Scope: Same as above (grapefruit juice, naringinase immobilized on an agarose carrier)
Note: The same treatment is reported to have reduced limonin concentration by 76%, bringing both naringin and limonin below their detection thresholds.
Show data
process-citrus-enzymatic-naringinase-debittering —reduces→ compound-limoninScope: Layer: Food. Grapefruit juice treated with enzyme immobilized on butyl-glyoxyl agarose (BGA) support.
Show data
process-citrus-enzymatic-naringinase-debittering —reduces→ compound-limoninScope: One lot of juice pressed from 20 commercial grapefruits. The composition just after pressing, according to the original's abstract and Table 1, was naringin 47.5 mg%, limonin 10.0 ppm, nomilin 6.0 ppm, organic acids 1.44% and sugar content 9.2% (however, the starting point for limonin in Figure 1 is about 0.5 ppm, and the 10.0 ppm in Table 1 matches the value for limonate A-ring lactone). Quantified by HPLC. A measurement of components, not a sensory evaluation
Note: The abstract and Table 1 of the text give limonin in fresh juice as 10.0 ppm, but in Figure 1 limonin increases from almost 0 ppm while limonate A-ring lactone decreases from 10 ppm, so the value in Table 1 may have been mixed up with the figure for limonate A-ring lactone. Because of this change in components, the study warmed the juice for sensory evaluation to 60°C once and then froze it to standardize conditions. The numbers are read from the figure; the only figure stated in the text is "an increase of about 38%". This concerns warming juice; changes in components during jam or marmalade making, where peel and flesh are cooked, were not measured. The authors speculate that naringin increases because naringin present in an insoluble form in the flesh dissolves on heating (speculation).
Show data
compound-limonin —has_juice_content_affected_by→ "Warming juice. When fresh commercial grapefruit juice was warmed to 60°C over 15 minutes, limonin, a bitter component, increased as the temperature rose (read from Figure 1, from almost 0 ppm near 20°C to about 8 ppm near 50°C) and decreased slightly at 60°C. Naringin, another bitter component, also increased slightly with temperature and was about 38% higher at 60°C than at 20°C. Even when the juice was left to cool after warming, limonin, nomilin and naringin tended to increase gradually. Limonate A-ring lactone, the precursor of limonin, decreased gradually from around 10 ppm."