Compound
Hexyl acetate
The apple-skin and pear ester that is genuinely carried in from the fruit rather than made by the yeast, and one of the few fresh-fruit aromas that survives fermentation.
- Class
- Esters
- Formula
- C8H16O2
- How often it matters
- Occasional
What it does in cider
- Is formed in the ripening fruit from hexanol, so its concentration in a juice reflects cultivar and ripeness rather than fermentation practice.
- Contributes a fresh apple-skin and pear character distinct from the yeast-derived banana and pear-drop notes.
- Is partly retained through fermentation and partly stripped by escaping carbon dioxide, so a vigorous warm ferment keeps less of it than a cool slow one.
- Declines with storage, making it a marker of a young, fruit-forward cider.
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.
- apple skin
- pear
- fresh fruit
- sweet green
Reported thresholds sit in the low hundreds of micrograms per litre — higher than the ethyl esters of medium-chain fatty acids, so it contributes as part of a fruit complex rather than dominating on its own.
Descriptors it is responsible for
Sensory records that name Hexyl acetate as a cause. Each states the perception and the mechanism behind it.
- Bittersweet apple — The soft, low-acid, faintly earthy ripe-fruit character of traditional West Country cider fruit, inseparable from its phenolic weight.
- Ripe apple — Full orchard-apple aroma from the acetate esters an apple accumulates through ripening and carries into the finished drink.
- Apple skin — The dry, faintly waxy and slightly bitter aroma of the fruit’s surface rather than its flesh, carried by cuticular waxes, hexyl esters and skin-concentrated phenolics.
- Dessert apple — The bright, aromatic, low-tannin fruit character of eating apples, dominant in eastern counties and most modern mainstream cider.
- Pressed apple juice — The full, sweet, unfermented smell of fresh juice, met in cider where residual sugar and surviving fruit esters combine.
- Ripe pear — Full, soft, honeyed pear character from fruit at or just past maturity, heavier than fresh pear and lower in green notes.
- Sweet apple — An impression of sweet fruit produced by aroma rather than by sugar, common in dry ciders with a high ester load and low acidity.
- Bubblegum — A confected tropical note from acetate esters at high concentration with 2-phenylethanol behind them.
- Fruit store — The close, sweet, faintly fermenting smell of a loft of apples held before milling, met in ciders made from sweated fruit.
- Melon — A soft, watery, faintly green tropical note from hexyl esters and residual nine-carbon aldehydes.
The structure it moves
| Dimension | What it is |
|---|---|
| Fruit character | How strongly the drink smells of apple or pear, and of fruit generally. |
| Freshness | Whether the drink smells and tastes of live fruit or of time and air. |
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
Ripeness assessment
Judging when cider fruit has converted enough starch, loosened enough on the spur and hardened enough for the store to be worth gathering.
Fermentation temperature control
Managing the temperature at which a ferment runs, which sets not only how fast it goes but which aromatics survive it and what the finished cider tastes of.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
Tank maturation
Resting cider in stainless steel or a lined vessel, where the point of the container is that it contributes nothing and admits almost no oxygen.
Bottle maturation
What happens to a cider after it is sealed in glass — which for most ciders is slow decline rather than improvement, and saying so is more useful than implying otherwise.
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.
Cooked character
A stewed-apple, caramel or jam-like character from heat applied to juice or cider, most often through pasteurisation or hot storage.
Flat and lifeless
A cider with nothing obviously wrong and nothing to say: aroma faded, acidity dulled, finish short — usually the cumulative result of over-processing or slow oxidation.
About Hexyl acetate
Most of what a cider smells of is made by the yeast. Hexyl acetate is one of the exceptions: the ripening apple makes it from its own hexanol, and it arrives in the fermenter already present. That gives it a different significance from the fermentation esters, because its concentration is a property of the fruit and of when the fruit was picked rather than of how the cider was made.
Its aroma is the fresh apple-skin and pear note that trained cider panels distinguish from the confected pear-drop of ethyl and isoamyl acetate. Where the confected note says warm ferment, this one says ripe fruit, and a cider carrying both smells more complexly of apple than one carrying either.
Keeping it is largely a matter of not blowing it away. Carbon dioxide leaving a vigorous fermentation carries volatiles with it, so a hot, fast ferment strips fruit-derived aroma at the same time as it builds fermentation aroma. Cool, slow fermentation retains more of what the fruit brought, which is one of the reasons the practice is associated with fruit-driven ciders.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Aldehydes
Hexanal
The green-apple aldehyde generated within seconds of breaking fruit tissue, which gives fresh juice its cut-grass smell and is largely converted away by the yeast.
Aldehydes
trans-2-Hexenal
The sharper, more penetrating green aldehyde of the same pathway as hexanal, made from linolenic rather than linoleic acid, and a marker of underripe fruit.
Esters
Isoamyl acetate
The banana and pear-drop ester, made by yeast from isoamyl alcohol, and one of the clearest chemical signatures of a warm fermentation.
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.
- What temperature should cider ferment at — Most cider is fermented cool, commonly between about 12 and 18 °C. Cooler ferments keep more fruit aroma and run slower; above the low twenties the cider tends towards hot, solvent-like higher alcohols.
- Does cider get better with age — Some does. Tannic, dry, bottle-conditioned ciders and ice ciders can gain for several years. Light, fruit-driven and commercially filtered ciders lose their aroma and do not gain anything in exchange.
- When are cider apples harvested — In the northern hemisphere the cider harvest runs from about September to November, with late bittersweets such as Dabinett and Vilberie coming in last. Cider fruit is generally picked riper than dessert fruit, and often gathered from the ground.
- What are esters in cider — Esters are compounds formed when an acid and an alcohol combine, and they carry most of the fruity aroma in cider — banana, pear drop, apple, pineapple. Yeast makes them during fermentation, and warm ferments make more.
- How is cider matured
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.
Washington State University cider research programme
Washington State University Northwestern Washington Research and Extension Center · university · passage verified 2026-08-24
The single most useful open cider dataset CiderHQ has found. The programme’s cultivar performance database gives juice chemistry, orchard behaviour, bloom and harvest timing and cider-maker tasting notes for 73 cultivars grown at one maritime site over fifteen years, and — unusually — publishes its classification thresholds alongside its figures, so the classification can be checked rather than taken on trust. It also states outright that its results diverge from the English ones. Read in full on 2026-08-24 and transcribed into `data/trials/wsu-mount-vernon.ts`; four published figures were found to be impossible and are withheld there with their reasons.
Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE)
INRAE · research institute · retrieved 2026-08-24
French national agricultural research. Its Angers programme produced much of the published work on apple procyanidin chain length and on the relationship between polymer size, bitterness and astringency.