Compound
Ethyl octanoate
A medium-chain ethyl ester contributing ripe pear and a waxy sweetness, and one of the compounds that makes an ester-forward cider feel rounder as well as fruitier.
Also called Ethyl caprylate.
- Class
- Esters
- Formula
- C10H20O2
- How often it matters
- Occasional
What it does in cider
- Forms from octanoyl-CoA and ethanol during fermentation, alongside its shorter and longer relatives.
- Contributes ripe pear, apricot and a faintly waxy or soapy quality at higher concentration.
- Adds a perception of richness and roundness rather than pure aroma, particularly in ciders with little residual sugar.
- Accumulates with the medium-chain fatty acids that can themselves inhibit yeast late in a difficult fermentation.
How it is perceived
What the compound registers as, and at roughly what concentration. Perception is not a property of the molecule alone: sugar, tannin and carbonation all change where a threshold falls.
- ripe pear
- apricot
- waxy
- soap at high concentration
Perceptible in the low micrograms per litre; attractive as fruit at low levels and increasingly waxy and soapy as concentration rises.
Descriptors it is responsible for
Sensory records that name Ethyl octanoate as a cause. Each states the perception and the mechanism behind it.
- Peach — A soft, sweet stone-fruit aroma produced by γ- and δ-lactones formed during fermentation and maturation.
- Pineapple — Sharp, sweet tropical fruit from short-chain ethyl esters, chiefly ethyl butanoate and ethyl hexanoate.
- Quince — A dense, perfumed pome-fruit aroma sitting between apple and pear, driven by ethyl esters and terpene traces.
- Red fruit — A general soft red-berry impression from medium-chain ethyl esters, most often met in tannic ciders with some age.
- Cherry — Dark stone-and-berry character combining benzaldehyde with heavier ethyl esters, met in aged tannic cider.
- Plum — Dark, soft stone-fruit weight from heavier ethyl esters combined with polymerised phenolics in matured cider.
The structure it moves
| Dimension | What it is |
|---|---|
| Fruit character | How strongly the drink smells of apple or pear, and of fruit generally. |
| Body | How much weight and viscosity the drink has in the mouth. |
| Fermentation character | Aromas made by the ferment rather than carried in from the fruit. |
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
Wild fermentation
Letting the microflora already present on the fruit and in the press house carry the ferment, in a succession rather than as a single organism.
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
Faults it is implicated in
Being implicated is not the same as being a fault. Several of the compounds on this site are ordinary constituents of a sound cider and define a named fault only above a concentration.
Organisms that produce it
Which organism is responsible usually decides whether the compound is a feature or a symptom.
About Ethyl octanoate
Ethyl octanoate is the middle member of the medium-chain ethyl ester family and behaves as one would expect from its position: fruitier than the longer decanoate, less penetrating than the shorter hexanoate, and contributing a roundness that is felt as much as smelled.
Its parent acid has a second career worth knowing about. Octanoic and decanoic acids are themselves toxic to yeast at the concentrations a stressed ferment can reach, and they are among the compounds implicated in fermentations that slow towards the end for no obvious nutritional reason. Yeast hulls and some fining agents work partly by adsorbing them, which is why they appear in the standard advice for restarting a stuck ferment.
In a finished cider, the ester rather than the acid is what a drinker meets. At moderate concentration it is ripe pear and apricot; higher, it turns waxy and eventually soapy, which is one of the ways an over-estery cider tips from generous into cloying.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Esters
Ethyl hexanoate
One of the most powerfully aromatic esters in cider, perceptible at a few micrograms per litre, contributing green apple and aniseed to the fruit complex.
Esters
Ethyl decanoate
The longest of the common medium-chain esters, contributing waxy and faintly floral weight rather than obvious fruit, and prone to dropping out of solution in the cold.
Esters
Ethyl butanoate
A short-chain ethyl ester perceived at very low concentration, giving the sweet pineapple-and-apple lift that reads as ripe fruit in a young cider.
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- Why did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- How does cider ferment — Yeast consumes the sugar in apple juice and produces roughly equal masses of ethanol and carbon dioxide, along with the esters and higher alcohols that give cider much of its aroma. In a wild ferment several yeast species take turns before *Saccharomyces* finishes the job.
- Can you make cider from shop bought apple juice — Yes, provided the juice contains no preservative — check for potassium sorbate or benzoate on the label. Pasteurised juice ferments perfectly well once yeast is added, because pasteurisation removes the organisms but not the sugar.
Where to go next
- All compounds — Grouped by what the fruit brings and what the ferment makes of it.
- Sensory — Every descriptor, with the compound or process that causes it.
- Microbiology — The organisms whose metabolism most of this chemistry belongs to.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
The Science of Cidermaking and associated technical writing
Andrew Lea · reference work · passage verified 2026-08-24
Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.