oleuropein
compound / compound-oleuropein
オレウロペイン
Phenolic secoiridoid abundant in olive, associated with bitterness.
Photographs (captions in Japanese)
A branch of olive (Olea europaea) with fruit. Oleuropein is a phenolic secoiridoid abundant in olive, and this is a photograph of the source fruit, not of the compound itself.
Raw materialShown: Olea europaea (olive)Part / state: Branch with fruit
Photo: Emőke Dénes / CC BY-SA 4.0 / original image / ledger's original image
Scope and provenance of the photo
Identification: Identified as labelled in the source. A different file from the photograph used for ingredient-table-olives (to avoid duplication).
Image shown: The full-size file from Wikimedia Commons, reduced to 2400 px on the long side with sips. No cropping or color changes by NIGAMI LAB (resizing only). For display, a WebP capped at 1200 px wide is served; the ledger's original image can be checked from the link above.
On this page (7 sections)
Reading the bitterness
Oleuropein is a phenolic secoiridoid abundant in olives. In research on naturally processed green olives, the bitterness of olives is described as arising primarily from this oleuropein, and a review also describes the drupe as 「果実が熟すにつれて弱まる、苦いオレウロペインを特徴とする」 (in translation: "bitter oleuropein that diminishes as the fruit matures"). However, this characterization pertains to naturally processed green olives and should not be generalized wholesale to all olive oils or all processing methods.
In table-olive processing, the breakdown of oleuropein through enzymatic and chemical reactions has been tracked across the process. The final product's oleuropein content varies considerably with processing method: for example, dry-salt-cured Thassos-style olives show high oleuropein levels even in the finished product, whereas Spanish alkaline treatment is described as able to remove oleuropein completely. In short, whether oleuropein remains in the final product depends strongly on which processing method is chosen.
Conversely, a high phenolic content including oleuropein does not necessarily translate into strong bitterness as perceived. A study comparing 5 varieties of naturally fermented olives found that although the final product's phenolic composition differed by variety, an 8-member panel showed no significant difference in perceived bitterness ratings. This is a small-scale panel comparison at a single harvest point and does not rule out relationships between individual phenolics and individual scores.
Sources for this overview
Oleuropein hydrolysis in natural green olives: Importance of the endogenous enzymes
Checked for this overview: Statement that the bitterness of naturally processed green olives arises primarily from oleuropein / Statement on tracking enzymatic and chemical breakdown across processing
Table Olives: An Overview on Effects of Processing on Nutritional and Sensory Quality
Checked for this overview: Verbatim expression from a review: bitter oleuropein that weakens with maturation / Verification of processing differences: high content in dry-salt-cured products and complete removal in Spanish alkaline treatment
Checked for this overview: Result from 5 varieties: phenolic differences across varieties but no significant difference in 8-member panel bitterness ratings
Follow the connections
oleuropein →is a major cause of→ bitterness →can be measured separately …→ astringency
table olives →contains, before and during…→ oleuropein
olive leaf →contains→ oleuropein
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (6)
Scope: Natural green olives, in the cited processing studies
Note: The content changes through enzymatic and chemical hydrolysis.
Show data
ingredient-table-olives —contains_before_and_during_processing→ compound-oleuropeinScope: Review integrating multiple primary studies (Olea europaea fruit, multiple varieties)
Note: A ripening-dependent pattern distinct from bitter orange (Castillo 1992): in olive, 「生育初期に高濃度→成熟に向け一貫して減少」 (in translation: "early growth shows high concentration → consistent decline toward maturity"), contrasting with bitter orange's nonmonotonic fluctuation within flower buds. In olive, young fruit and growth phase peak, then decline monotonically—differing from bitter orange's pattern. The "14%" and "3-4.5 g/kg" are representative values from separate primary studies cited in the review, not time-series data from a single study.
Show data
compound-oleuropein —has_content_change_with_fruit_maturation→ (the claim sentence above)Scope: A review's generalization about olive fruit and leaves
Note: This passage of the review does not present quantitative comparison data by tissue (skin/around the seed versus the flesh as a whole). It remains a qualitative description of localization.
Show data
compound-oleuropein —occurs_in→ (the claim sentence above)Scope: 2 primary studies cited in a review (variety and region within each primary study)
Show data
compound-oleuropein —shows_developmental_concentration_decline_due_to→ (the claim sentence above)Scope: Layer: food. A comparison of salt and fermentation conditions in the same Gaeta PDO olives, with oleuropein quantified by chemical analysis.
Note: A counterexample showing that increasing salt does not chemically remove the principal bitter compound.
Show data
ingredient-table-olives —does_not_significantly_influence→ compound-oleuropeinScope: Layer: food. A discussion passage that links measurement of total polyphenol content in olive-leaf herbal tea (infusion) with sensory analysis.
Note: With microwave drying, total polyphenol content (TPC) increased to about 3 times that of hot-air drying (MWD approx. 3.0 mg/L GAE vs. AD approx. 1.0 mg/L GAE), corresponding to a sensory increase in bitterness. Beyond the existing compound-oleuropein claim (declining content with plant age), this adds oleuropein's positioning as the bitter principle itself.
Show data
ingredient-olive-leaf —contains→ compound-oleuropeinSensory (2)
Scope: Naturally processed green olives investigated during processing
Note: Other phenolic compounds and processing conditions also contribute to final sensory quality.
Show data
compound-oleuropein —is_a_major_cause_of→ sensation-bitterScope: The final product of naturally fermented olives across 5 cultivars
Note: The amount of bitterness-related phenolics differed among cultivars, but there was no significant difference in the final perceived bitterness rated by an 8-member panel. This does not mean chemical quantity in general is irrelevant.
Show data
compound-oleuropein —does_not_reliably_track→ sensation-bitter