Cider science

The aroma families and where each comes from

What are the standard aroma categories for cider?

In short

CiderHQ groups cider and perry aroma into twenty families, from fresh apple through to the volatile fault characters. Each family carries a stated origin — the class of compound or the process that produces it — and a note on whether encountering it usually indicates a problem.

Most families are style-dependent rather than good or bad. Phenolic, earthy, lactic and oxidative characters are traditional signatures in some categories and faults in others, and the molecule is identical in both cases.

Two families are usually a fault wherever they appear: the sulphur group and the volatile fault group. Everything else is judged against what the style was meant to be.

Every aroma family CiderHQ classifies descriptors into, in the order the sensory model lists them. Representative descriptors for each are given below.

Described in full

Shape: Twenty equal sectors round a hub, read clockwise from the top. Sectors alternate in tone so the divisions are visible, and the two families that usually indicate a fault carry a filled marker at the rim as well as their own tone.
Apple and pear, sectors one to four: Fresh apple, for crisp just-cut apple and apple skin; ripe apple, for full orchard fruit; cooked and baked apple, for apple pie, stewed fruit and caramelised apple; and pear, for fresh pear, pear drop and pear skin.
Other fruit, sectors five to eight: Citrus, for lemon, grapefruit peel and lime zest; stone fruit, for peach, apricot and nectarine; tropical fruit, for pineapple, mango, banana and passion fruit; and berry, for strawberry, raspberry and red-fruit notes.
Floral and sweet, sectors nine and ten: Floral covers blossom, rose, elderflower and hawthorn — the rose note is 2-phenylethanol, a yeast product. Honeyed covers honey, beeswax and nectar, and rises with age and mild oxidation.
Spice, herbal and earthy, sectors eleven to thirteen: Spice: clove, cinnamon, nutmeg, pepper. Herbal and vegetal: hay, grass, hedgerow, green leaf. Earthy: farmyard, wet stone, damp cellar, mushroom — welcome in traditional farmhouse cider and out of place in a clean modern one.
Wood and phenolic, sectors fourteen and fifteen: Woody covers oak, vanilla, toast, cedar and smoke, all from barrel contact. Phenolic covers leather, smoke, sticking plaster, horse and medicinal notes from ethylphenols — a traditional signature at low levels and a fault above them.
Ferment-derived, sectors sixteen to eighteen: Fermentation-derived: solvent, nail varnish, bread, yeast. Dairy and lactic: butter, butterscotch, yoghurt, cream, from diacetyl. Oxidative: sherry, walnut, bruised apple, cardboard.
The two fault families, sectors nineteen and twenty: Sulphur covers rotten egg, struck match, drains, rubber and cooked cabbage. Volatile and fault-related covers vinegar, glue and mousiness. Both are marked because encountering them usually indicates a problem rather than a style.
Why the families are not simply good or bad: Most sit in the middle: the same molecule is traditional in one style and a fault in another. Only the last two families are classed as usually a fault, and even they have thresholds below which nobody notices.

The twenty families

The CiderHQ aroma families, their origin and whether they usually indicate a problem.
Family	Covers	Where it comes from	Valence
Fresh apple	Crisp, green, just-cut apple and apple skin	Six-carbon aldehydes and alcohols from broken fruit tissue, plus light esters surviving a cool ferment	Typical
Ripe apple	Full, sweet-smelling orchard apple	Esters accumulated during ripening, chiefly hexyl and butyl, carried through fermentation	Typical
Cooked and baked apple	Apple pie, stewed fruit, caramelised apple	Gentle oxidation and heat, including pasteurisation; characteristic of ice cider	Style-dependent
Pear	Fresh pear, pear drop, pear skin	Perry pear esters, including the pear-specific decadienoates; pear drop is isoamyl acetate	Typical
Citrus	Lemon, grapefruit peel, lime zest	High malic acid read alongside terpene and ester traces; associated with sharp cultivars	Typical
Stone fruit	Peach, apricot, nectarine	Lactones and certain esters, more common in warmer ferments	Typical
Tropical fruit	Pineapple, mango, banana, passion fruit	Esters formed at higher fermentation temperatures or by particular yeasts; banana is isoamyl acetate	Style-dependent
Berry	Strawberry, raspberry, red fruit	Occasionally fermentation-derived; more often from added fruit	Style-dependent
Floral	Blossom, rose, elderflower, hawthorn	Terpenes and 2-phenylethanol, which is the rose note and a yeast product	Typical
Honeyed	Honey, beeswax, nectar	Phenylacetaldehyde and related compounds, rising with age and mild oxidation	Typical
Spice	Clove, cinnamon, nutmeg, pepper	Volatile phenols such as 4-vinylguaiacol, wood contact, or added spice	Style-dependent
Herbal and vegetal	Hay, grass, hedgerow, green leaf	Fruit-derived green-leaf volatiles and wild-fermentation character	Style-dependent
Earthy	Farmyard, wet stone, damp cellar, mushroom	Wild yeast and bacterial activity	Style-dependent
Woody	Oak, vanilla, toast, cedar, smoke	Barrel contact: oak lactones, vanillin, furfural	Style-dependent
Phenolic	Leather, smoke, sticking plaster, horse, medicinal	Ethylphenols from Brettanomyces or lactic bacteria acting on hydroxycinnamic acids	Style-dependent
Fermentation-derived	Solvent, nail varnish, bread, yeast	Higher alcohols, ethyl acetate, autolysing yeast	Style-dependent
Dairy and lactic	Butter, butterscotch, yoghurt, cream	Diacetyl from malolactic fermentation	Style-dependent
Oxidative	Sherry, walnut, bruised apple, cardboard	Acetaldehyde and phenolic oxidation products	Style-dependent
Sulphur	Rotten egg, struck match, drains, rubber, cabbage	Hydrogen sulphide and mercaptans from nitrogen-stressed yeast; struck match from excess sulphite	Usually a fault
Volatile and fault-related	Vinegar, glue, mousiness	Acetic acid bacteria, high ethyl acetate, or the tetrahydropyridines behind mousiness	Usually a fault

Why the families are organised by origin

A tasting vocabulary organised only by resemblance produces long lists of adjectives that cannot be checked against anything. Organising by origin makes each family a claim about mechanism: if a cider smells of banana, the family says isoamyl acetate, which says fermentation, which says temperature and yeast rather than apple variety.

That makes the vocabulary diagnostically useful. A rubber note points at mercaptans and therefore at nitrogen deficiency and lees contact; a butter note points at diacetyl and therefore at malolactic conversion; a sherry note points at acetaldehyde and therefore at oxygen exposure. In each case the descriptor tells a producer where to look.

It also disciplines the writing. A descriptor that cannot name a plausible origin is either a genuine gap in knowledge, which should be said, or an adjective that has been carried along by convention.

The same molecule, judged differently

Four families are routinely both signature and fault. Volatile phenols at trace level give the leathery complexity of some traditional farmhouse and Spanish ciders and at higher levels give sticking plaster and horse. Acetaldehyde gives the depth of an oxidatively matured cider and, in excess, a flat and papery drink. Diacetyl gives roundness in a traditional cider and reads as artificial butter in a fresh, fruit-driven one. Ethyl acetate contributes lift at low levels and smells of nail varnish above them.

The determinant is concentration and expectation together. A concentration well below the point where a compound dominates, in a style whose drinkers expect it, is character; the same compound above threshold, or in a style built on freshness, is a fault. This is treated at length on its own page, because it is the single most misunderstood thing about cider assessment.

The two families that are not treated this way are sulphur and the volatile fault group. Hydrogen sulphide, mercaptans and mousiness have no recognised traditional role in cider at any level, and volatile acidity has one only in a narrow band within specific Spanish and English traditions.

Descriptors, families and thresholds

Individual descriptors — fresh-cut apple, bruised apple, pear drop, wet stone, farmyard, sticking plaster, struck match — sit inside these families and are recorded separately, each with the compound or process most responsible for it.

Detection thresholds vary across an enormous range. Some esters are detectable at a few parts per billion, while ethanol is not perceived as a distinct aroma until percentage concentrations. This is why a compound present in trace can dominate a cider’s nose while a major component contributes nothing recognisable.

Individual sensitivity varies too, and for some compounds it varies by orders of magnitude between people for partly genetic reasons. Two experienced tasters can disagree about whether a phenolic note is present and both be reporting accurately, which is one of the reasons panels use several assessors and treat individual disagreement as data rather than as error.

Also answered on this page

Questions this page covers, so you can tell at a glance whether it is the one you want.

Why does cider smell of farmyard?
What causes the pear drop smell?
What is Brett character?
Why do some people not smell what others do?
What is a detection threshold?

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.

Does cider taste of the apples it was made from — Partly, and less than most people assume. The fruit contributes the acid, nearly all the tannin, the sugar and a set of aroma compounds, but a large part of the fruit’s own volatile aroma is lost during fermentation, stripped out by escaping carbon dioxide or metabolised by yeast.
Is a farmyard character in cider a fault — The composite animal-and-straw note of volatile phenols with short-chain fatty acids, central to traditional farmhouse character.
My cider tastes of sticking plaster — what went wrong — The sharp antiseptic-and-adhesive note of 4-ethylphenol, the principal volatile phenol of *Brettanomyces* activity in cider.
What does pear drop mean in a cider tasting note — The sweet-shop confectionery note of isoamyl acetate with ethyl acetate behind it — a fermentation product, not a pear one.
How does ciderhq describe what a cider tastes like
Is that a fault or is it meant to taste like that

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.

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.
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.
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.
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.
Peer-reviewed literature on apple phenolics and cider sensory perception
Various journals · peer-reviewed literature · registered as competent for this subject
Registered as a class rather than as one paper, because the mechanisms CiderHQ describes — tannin chain length driving the split between bitterness and astringency, salivary protein precipitation, enzymatic browning — are established across many studies rather than resting on any single one. Individual papers are cited where a specific number is quoted.