Sensory descriptor
Williams pear
The intense, perfumed pear character of Williams and Bartlett fruit, driven by decadienoate esters at high concentration.
Also called Bartlett pear.
- Aroma family
- Pear
- Does it indicate a fault?
- No — a normal part of cider and perry aroma
What causes it
Williams, known as Bartlett in North America, produces ethyl (2E,4Z)-2,4-decadienoate at concentrations far above those of most other pears, and it is the reference fruit for the compound. Because the ester’s odour threshold is in the low parts per billion, the fruit reads as almost synthetically pear-like, and it is the aroma most people carry as a mental template for pear even when they have never eaten the cultivar. In perry it appears where dessert pears form part of the blend, which is common outside the traditional perry pear regions and rare within them.
The compounds responsible
Where the molecule is established. Some descriptors in this lexicon name a compound the compound register does not yet hold a record for; those are named in the cause above instead.
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.
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.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Juice blending
Combining juices from different cultivars before fermentation so that the blend ferments as a single batch, as against fermenting separately and blending later.
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.
Cold maturation
Holding cider at low temperature so that it settles bright, sheds colloidal material and stops changing microbially, without any additive or treatment being applied.
Where it is usually met
Fruit and styles this character is recorded in. A record here is where the descriptor is commonly found, not a claim that every example shows it.
About Williams pear
Naming this separately from fresh pear is useful because it distinguishes perry made from traditional perry pears — which are small, hard, tannic and generally low in decadienoates — from perry made from dessert pears, which is a different drink. Traditional Three Counties and Normandy perry rarely smells like this, and a perry that does has usually had dessert fruit in the press.
It sits at the boundary with pear drop and is often mistaken for it, though the two are chemically unrelated. Williams character is fruit-derived and persists as a rounded aroma; pear drop is ferment-derived and carries a solvent lift behind it.
Others in the pear family
Fresh pear, pear drop and pear skin.
Fresh pear
Clean, watery, faintly green pear aroma, the base fruit note of perry and of pear-fruited cider.
Pear drop
The sweet-shop confectionery note of isoamyl acetate with ethyl acetate behind it — a fermentation product, not a pear one.
Ripe pear
Full, soft, honeyed pear character from fruit at or just past maturity, heavier than fresh pear and lower in green notes.
Pear skin
A dry, gritty, faintly tannic pear note from the fruit’s skin and stone cells, prominent in traditional perry pears.
Tinned pear
The syrupy, slightly flat pear character of canned fruit, from heat-degraded pear esters over residual sweetness.
Unripe pear
Hard, green, markedly astringent pear character from fruit pressed before it softened.
Bletted pear
Deep, faintly winey overripe pear character from fruit softened past ripeness, met in traditional perry and in medlar-like notes.
Cooked pear
Soft, sweet, heat-treated pear character, with the decadienoate top note stripped and a lactone-like weight left behind.
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.
- What is perry — Perry is an alcoholic drink made by fermenting the juice of pears, traditionally of specific perry pear cultivars rather than eating pears. It is to pears what cider is to apples, and has its own history in the three counties of England and in Normandy.
- What is juice blending
- What is sparkling perry
- What is new zealand cider
Where to go next
- The sensory model — The thirteen structural dimensions and the twenty aroma families, in full.
- Compounds — The chemistry behind the words.
- Troubleshooting — When a perception turns out to be a problem, this is where it is diagnosed.
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.
GRIN-Global germplasm database — Malus and Pyrus
United States Department of Agriculture, Agricultural Research Service · research institute · retrieved 2026-08-24
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.