Sensory descriptor
Sticking plaster
The sharp antiseptic-and-adhesive note of 4-ethylphenol, the principal volatile phenol of Brettanomyces activity in cider.
Also called Band-aid, Elastoplast, Antiseptic.
- Aroma family
- Phenolic
- Does it indicate a fault?
- It depends on the style it is met in
What causes it
Apples carry p-coumaric acid, largely esterified as p-coumaroylquinic acid, as part of their hydroxycinnamic acid fraction. Dekkera bruxellensis and Brettanomyces anomalus possess both a cinnamate decarboxylase, which converts it to 4-vinylphenol, and a vinylphenol reductase, which reduces that to 4-ethylphenol. In cider — and this is a real difference from wine — Lactobacillus collinoides can perform the same conversion, so the fault has a bacterial route as well as a yeast one. 4-ethylphenol has a threshold in cider of a few hundred micrograms per litre and an odour that most tasters describe as sticking plaster or antiseptic.
Below threshold 4-ethylphenol contributes to the general savoury depth of traditional cider without being identifiable. Just above it, it reads as farmyard or leather within a broader picture. Well above it, it is unmistakably sticking plaster and displaces everything else, and at that point every style framework records it as a fault.
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.
4-Ethylphenol
The horse-and-sticking-plaster compound, made by *Dekkera* from a phenolic acid the fruit supplied, and the clearest case in cider of one molecule being a tradition in one glass and a fault in another.
p-Coumaroylquinic acid
The second most abundant hydroxycinnamic ester in apple, and the reservoir from which the p-coumaric acid behind 4-ethylphenol is slowly released.
Hydroxycinnamic acids
The family of small phenolic acids that browns a juice, and whose release from their esters supplies the raw material for every volatile phenol a cider can develop.
The organisms that make it
Where a specific organism is implicated rather than the fruit. Naming one answers a different question from naming a molecule: what is in the cellar, rather than what is in the glass.
Dekkera bruxellensis
The yeast behind 4-ethylphenol, and the organism that a cider tradition may regard as its signature or its ruin depending on where and how it is made.
Brettanomyces anomalus
The second Brettanomyces species regularly recovered from cider and beer, less studied than *B. bruxellensis* but capable of the same phenolic chemistry.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
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.
Barrel ageing
Holding cider in wood — which may mean an old neutral vat used simply as a vessel, or fresh or spirit-seasoned oak used as a source of flavour, and the two are not the same operation.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Sulphite stabilisation
Managing free sulphur dioxide through maturation and at packaging so that a useful antimicrobial and antioxidant fraction survives into the bottle.
Sterile filtration
Membrane filtration at a rating that retains viable yeast and bacteria, which is what allows a sweet cider to be shelf-stable without heat or preservative — provided the filling that follows is aseptic.
The fault it points at
Meeting this descriptor above a certain intensity is how the fault below is usually noticed first.
Fault
Farmyard, horse-blanket, smoky and sticking-plaster aromas from Brettanomyces yeast converting hydroxycinnamic acids into volatile phenols.
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 Sticking plaster
This is the descriptor around which the entire phenolic argument in cider turns. West Country farmhouse cider, Asturian sidra natural and Norman cidre fermier all carry measurable 4-ethylphenol as part of their traditional character, and a modern clean cider carrying the same level would be rejected. Neither judgement is wrong; they are assessments against different specifications.
The practical significance is that the compound is progressive. A cider with an active Brettanomyces population does not sit at a stable level: the population continues working on a large reservoir of precursor, and a cider that shows an acceptable level at bottling may not at twelve months. Sterile filtration or adequate free sulphur dioxide are the controls, and old wood is the classic reservoir.
Others in the phenolic family
Leather, smoke, sticking plaster, horse, medicinal.
Horse blanket
An animal, stable-like note from 4-ethylphenol combined with branched short-chain fatty acids.
Medicinal
A hospital-antiseptic note from volatile phenols, or from chlorophenols formed by chlorine contacting phenolic material.
Smoky
A wood-smoke note from 4-ethylguaiacol, the guaiacyl counterpart of the ethylphenol pathway.
Leather
A dry, tanned-hide note from low levels of volatile phenols over well-polymerised tannin.
Acrid smoke
Harsh, ashy smoke from atmospheric smoke absorbed by the fruit, chemically distinct from microbial smokiness.
Bacon
A savoury smoked-meat note from 4-ethylguaiacol with residual sweetness, met in tannic ciders with Brett character.
Plastic
A synthetic, hot-plastic or crayon note from packaging materials, hose or liner contact.
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.
- 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.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- What is brettanomyces — *Brettanomyces*, correctly *Dekkera* in its spore-forming form, is a slow yeast that ferments sugars other strains leave behind and produces volatile phenols smelling of farmyard, leather or sticking plaster. In cider it is common and not always unwanted.
- What is scrumpy — Scrumpy is an informal West Country word for strong, still, usually cloudy farmhouse cider. It has no legal definition, so it describes a style expectation rather than a guaranteed method.
- What is sidra natural — Sidra natural is the still, dry, unfiltered cider of Asturias and the Basque Country, bottled without added carbonation and poured from a height to rouse it. It is tart, funky and made to be drunk in small measures poured one at a time.
- Should i ferment cider in an oak barrel — A sound, full barrel is a fine maturation vessel; a leaky, half-empty or previously spoiled one is the fastest route to vinegar. Wood cannot be sterilised, so a barrel carries whatever lived in it before.
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.
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.
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.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.