Material guide · 20
Material guide: isoamyl acetate — banana, banana oil, and the cheapest lesson in ester chemistry
· 13 min read
CAS 123-92-2, the body of the banana smell; the paint solvent Taiwanese hardware stores call banana water is named after it. A 1962 Nature paper identified it as an active component of the honeybee sting pheromone, and a 2003 brewing-yeast study proved the banana note in wheat beer comes from the yeast's ester synthases. High strength, evaluate at 1% or less, under 4 hours on the strip, flash point 25 °C. 93 suppliers; the first ester of the fruity starter kit.
Open a bottle of nail polish remover, then peel a ripe banana. The faint overlap between the two is this article's subject. In several countries the paint solvent is nicknamed "banana oil" after it, and our database's descriptors hold "banana" and "solvent" side by side.
What matters
- Isoamyl acetate is the body of the banana smell, and the cheapest lesson in ester chemistry: an alcohol plus an acid, minus water, gives an ester. The fruity alphabet starts here.
- High strength; the database says evaluate at 1% or less, the only material in this series so far marked down to 1%. Under 4 hours on the strip, a pure top note.
- It is also an active component of the honeybee sting alarm pheromone (identified in 1962), and the banana note in wheat beer is this molecule, brewed by yeast. One material, three worlds.
The record
| CAS | 123-92-2 |
| Formula | C₇H₁₄O₂ |
| MW | 130.18 |
| Odour | sweet, fruity, banana, solvent, ripe, estery |
| Odour family | fruity |
| Strength | high (evaluate at 1% or less) |
| Substantivity | < 4 h (neat, on a strip) |
| Specific gravity | 0.860–0.878 (25 °C) |
| Flash point | 25 °C |
| Shelf life | 24 months or longer (cool, dark, sealed) |
| Registers | GRAS, JECFA, CoE, FEMA GRAS, IFRA |
Plain reading: CAS is the material's ID number. Two numbers here are series firsts: the evaluation advice drops to 1% (that strong), and the flash point is 25 °C (that flammable — room temperature reaches it, so keep it away from ignition sources and out of a parked car in summer). The "<" in the substantivity row is rare too; the source data says outright that it doesn't even hold 4 hours.
The cheapest lesson in ester chemistry
Esters are the backbone of the fruity world, and the recipe fits on a sticky note: alcohol + acid → ester + water. Isoamyl acetate is isoamyl alcohol (in the catalogue at #1903) joined to acetic acid.
The fun is combinatorial. Keep the alcohol and swap the acid, and the fruit changes; keep the acid and swap the alcohol, and you get another shelf of fruit. Our catalogue carries a whole column of supplied items starting with "isoamyl" (see the family table below), all variations on this one alcohol. Buy two or three and smell them side by side; "same prefix, different fruit" teaches esters faster than any textbook.
Two lives outside perfumery
Isoamyl acetate is both an active component of the honeybee sting alarm and a yeast product behind wheat beer’s banana note. The biological context now lives in What plants, yeast and bees do with the same aroma molecules; this guide returns to ester chemistry and a top note lasting under four hours.
Smelling it
- Evaluate at 1% or less, per the database. I make a 0.5% and a 2% and compare: the low one is ripe banana, the high one starts showing solvent. Between "banana" and "banana oil" sits one dose.
- Under 4 hours on the strip, it lives only in the opening. For fruit that lasts, hand over to the lactones, gamma-decalactone and kin.
- The fruity opening kit: this one plays "ripe", cis-3-hexenol plays "green", the lactones play "flesh". Three bottles assemble a breathing fruit.
- Flash point 25 °C: keep it away from heat while working, and don't decant into static-prone containers.
The catalogue family
| Item | What it is |
|---|---|
| isoamyl acetate (93 suppliers) | the material itself: banana |
| isoamyl butyrate (87 suppliers) | swap in butyric acid, drifting to pear and ripe fruit |
| isoamyl alcohol (72 suppliers) | its parent alcohol; fusel, fermentation-scented |
| isoamyl isovalerate (67 suppliers) | the isovalerate, apple and dry hay |
| isoamyl propionate (54 suppliers) | the propionate, toward apricot and pineapple |
| isoamyl salicylate (49 suppliers) | the salicylate, farthest from fruit: floral green |
Six lives of one alcohol. The salicylate at the bottom is the reminder: swap in a big enough acid and even the "fruit" identity gets swapped away.
Regulatory
Listed on GRAS, JECFA, CoE, FEMA GRAS, IFRA. As always, registers carry no limit values. Esters are regulatorily uncomplicated; for skin formulae, consult the current IFRA Standards and the supplier's specification.
Buying it
- One small bottle is plenty; at tenths of a percent, 10 mL lasts a long time.
- Add isoamyl butyrate or ethyl butyrate to the order and run the "swap the acid, swap the fruit" comparison once.
- Check the flash point label on arrival and store away from heat; this is the most flammable material in the series.
→ Isoamyl acetate in the database: full properties, supplier list, suggested pairings. → Isoamyl butyrate | Ethyl butyrate | Search by odour: try "banana fruity" for its neighbours.
References
R. Boch, D. A. Shearer & B. C. Stone, Identification of isoamyl acetate as an active component in the sting pheromone of the honey bee, Nature, 195, 1018–1020 (1962). PMID 13870346
K. J. Verstrepen, S. D. M. Van Laere, B. M. P. Vanderhaegen, G. Derdelinckx, J.-P. Dufour, I. S. Pretorius, J. Winderickx, J. M. Thevelein & F. R. Delvaux, Expression levels of the yeast alcohol acetyltransferase genes ATF1, Lg-ATF1, and ATF2 control the formation of a broad range of volatile esters, Applied and Environmental Microbiology, 69(9), 5228–5237 (2003). PMID 12957907