olive leaf
ingredient / ingredient-olive-leaf
オリーブ葉 / Olea europaea
Olive leaf is the silver-green leaves that support olive fruit can also be used for drinks infused in water and food extracts. Finer grinding may make compounds transfer into water more readily and bring both bitterness and astringency forward.
Photographs (captions in Japanese)
Branch, leaves, and fruit of the olive, Olea europaea. The leaves look green on one side and silvery white on the other.
Shown: Olea europaeaPart / state: Leaves and fruit on the branch
Photo: Prahlad balaji / CC BY-SA 4.0 / original image / ledger's original image
Scope and provenance of the photo
Identification: Identified as labelled in the source. The species name follows the source description on Commons.
Image shown: The 1920 px version from Wikimedia Commons. No cropping or color changes by NIGAMI LAB. 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
Olives may bring fruit or oil to mind, but this entry concerns the long, narrow, silver-green leaves covering the branches. Rather than being eaten directly, leaves can be dried, crushed, and steeped in water as a drink ingredient. The study compared infusions made from leaves ground to different degrees, not the taste of an intact fresh leaf. The leaf itself must be distinguished from the flavor transferred to water after processing.
Grinding fineness can substantially alter that flavor. In a study with 13 untrained panelists, finer grinding increased oleuropein in the infusion, and the most finely ground sample was rated very bitter and more astringent. Bitterness is a taste, whereas astringency is a tightening, drying sensation in the mouth; the experiment measured them as separate attributes.
When the extract is added to food, the surrounding flavors also matter. In a fruit-smoothie test by 11 trained panelists, olive-leaf extract produced strong bitterness even at a low addition level. At a higher addition level, sucrose and cyclamate reduced bitterness, while salt showed no comparable effect. These results concern a particular extract and beverage, not a universal mixing rule for home leaf teas.
Drying method also changes the taste of the infusion. Herbal tea brewed from microwave-dried leaves (400 W for 4 minutes) was rated 「より苦く、より渋い」 (in translation: "more bitter and more astringent") than tea from hot-air-dried leaves (50°C for 3 hours) in descriptive sensory analysis. On a consumer acceptability test using a 9-point hedonic scale, taste scores were about 5.8 for the hot-air-dried tea and about 2.5 for the microwave-dried tea; consumers clearly preferred the hot-air-dried herbal tea.
The study's discussion links stronger bitterness to total polyphenols being about 3 times higher after microwave drying than hot-air drying (approximately 3.0 mg/L GAE versus 1.0 mg/L GAE), along with an accompanying increase in oleuropein. The authors describe oleuropein as the most abundant phenolic compound in olive leaves and as a cause of their bitterness.
Sources for this overview
Checked for this overview: The study design comparing infusions from leaves ground to different degrees. / The separately assessed results for oleuropein, bitterness, and astringency.
Checked for this overview: The trained-panel study measuring bitterness of fruit smoothies containing the extract. / The comparison of bitterness-masking effects of sweeteners and salt.
Checked for this overview: The differences in bitterness, astringency, and liking scores by drying method. / The discussion attributing bitterness to total polyphenols and oleuropein.
Follow the connections
olive leaf →contains→ oleuropein →is a major cause of→ bitterness
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (1)
Scope: 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-oleuropeinHow processing and cooking change it (1)
Scope: Layer: food. Olive-leaf infusion (herbal tea); a trained descriptive sensory panel and consumer acceptability testing (9-point hedonic scale, 1 = dislike extremely through 9 = like extremely).
Show data
ingredient-olive-leaf —has_perceived_bitterness_affected_by→ (the claim sentence above)