Compound
Decadienoate esters
The esters that smell specifically of pear rather than generically of fruit, carried in from the fruit itself, and perceptible at concentrations that barely register on any instrument.
Also called Pear esters, Ethyl (2E,4Z)-decadienoate.
- Class
- Esters
- Formula
- Not a single molecule — see below
- How often it matters
- Occasional
What it does in cider
- Provides the aroma most people identify unmistakably as pear, distinct from the pear-drop note of the acetate esters.
- Originates in the ripening pear rather than in fermentation, so it depends on cultivar and ripeness.
- Is perceptible at extremely low concentration, making it a defining aroma of perry even where analysis finds almost nothing.
- Declines with heat and with time, so it is a marker of fresh, carefully handled perry.
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.
- pear
- pear flesh
- ripe orchard pear
Reported among the lowest thresholds of any fruit volatile, which is why a perry can smell distinctly of pear when instrumental analysis shows only traces.
Descriptors it is responsible for
Sensory records that name Decadienoate esters as a cause. Each states the perception and the mechanism behind it.
- Fresh pear — Clean, watery, faintly green pear aroma, the base fruit note of perry and of pear-fruited cider.
- Ripe pear — Full, soft, honeyed pear character from fruit at or just past maturity, heavier than fresh pear and lower in green notes.
- Tinned pear — The syrupy, slightly flat pear character of canned fruit, from heat-degraded pear esters over residual sweetness.
- Williams pear — The intense, perfumed pear character of Williams and Bartlett fruit, driven by decadienoate esters at high concentration.
- Cooked pear — Soft, sweet, heat-treated pear character, with the decadienoate top note stripped and a lactone-like weight left behind.
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.
Pasteurisation
Heating cider enough to inactivate the organisms that would spoil it, either in the sealed package or in-line before filling, at a measurable cost in fresh aroma.
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.
About Decadienoate esters
There is a difference between smelling of fruit and smelling of pear, and the decadienoate esters are what makes the second possible. Where acetate esters give a generic confected sweetness that people label pear drop, these give the specific aroma of the fruit itself, and they are made by the ripening pear rather than by anything in the fermenter.
They are extraordinarily potent. Their thresholds are among the lowest recorded for any fruit volatile, which produces the mismatch familiar to anyone who has analysed a perry: the chromatogram is dominated by yeast products, and the nose is dominated by a compound present in traces.
They are also fragile. Heat degrades them, which is part of why a pasteurised perry loses its varietal pear character and gains a cooked note, and time reduces them, so the aroma is at its clearest in a young perry. Perry pears vary enormously in how much they carry, and the cultivars with a reputation for aromatic perry are largely the ones that carry more.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Esters
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.
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.
Sugar alcohols
Sorbitol
The unfermentable sugar alcohol that pears carry in quantity and apples carry only in trace, and the single reason a fully fermented perry keeps a sweetness a fully fermented cider cannot.
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 is sorbitol important in perry — Sorbitol is a sugar alcohol that pears carry in quantity and that Saccharomyces cannot ferment. It passes through the whole fermentation untouched, so a perry can taste sweet while being dry by measurement.
- 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 pasteurised
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.
Research on pear juice composition and sorbitol in perry
Various journals and institute reports · peer-reviewed literature · registered as competent for this subject
The evidence base for the single most important chemical difference between cider and perry: pears carry substantial sorbitol, which yeast does not ferment, so a fully fermented perry retains sweetness a fully fermented cider cannot.
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.
Perry Pears
L. C. Luckwill and A. Pollard (eds), published for the National Fruit and Cider Institute by the University of Bristol, 1963 · reference work · bibliographic record verified, not opened 2026-08-25 · covers 1963
Bibliographic record verified on 2026-08-25 against Open Library, which records the work as Luckwill, 1963, published for the National Fruit and Cider Institute by the University of Bristol. The catalogue entry names Luckwill alone where the standard citation names Luckwill and Pollard as joint editors; CiderHQ keeps both names and records the discrepancy rather than silently following one catalogue. This is the foundational descriptive work on English perry pears and the ancestor of most later variety lists. No copy was opened: it is sixty years old, out of print, and held in research libraries rather than in open digital collections.