Fault
Ethyl acetate taint
A solvent, nail-varnish or pear-drop aroma from ethyl acetate, the most abundant ester in cider and the one that turns from lift to fault over a narrow range.
Also called solvent character, nail varnish note.
- Severity
- Quality — the drink is worse for it
- Where it starts
- Fermentation, Maturation, Juice treatment
- Can it be fixed?
- Yes, if caught in time
- When you notice it
- Fermentation, Maturation, Storage
- Signs
- 5 recorded
What it is
Ethyl acetate is the ester of ethanol and acetic acid, and it is present in every cider ever made. At low concentration it reads as fruit and gives a general impression of lift and freshness. Above a fairly narrow band it stops smelling of fruit and starts smelling of solvent — nail varnish remover, model glue, or the sharper end of a pear drop — and it becomes the first thing the nose finds. It is closely tied to volatile acidity but is a distinct perception with its own causes.
What you notice
Grouped by sense, because that is how the fault presents itself rather than how it works.
On the nose
- A nail-varnish or glue note that hits the top of the nose before any apple does
- An exaggerated pear-drop or boiled-sweet character in a cider that should not have one
- A stinging, almost anaesthetic quality at the back of the nose in a strongly affected sample
On the palate
- A thin, hollow palate underneath an aggressive nose — Ethyl acetate is far more assertive in aroma than in flavour, so the cider smells stronger than it tastes.
How the batch behaves
- A cider that smells markedly worse after being left in the glass for a few minutes
The words for it: Nail varnish, Pear drop, Glue, Solvent, Acetone. Each links to what produces it.
When it appears. Can appear early, from apiculate yeasts in the first days of a spontaneous ferment, or slowly during maturation as acetic acid esterifies with ethanol. The early kind often fades; the slow kind does not.
The odour threshold is far below that of acetic acid, which is why a cider can smell strongly of solvent at an analytical volatile acidity that is not itself extreme. This is the main reason the two faults are reported together: the palate does not separate them, and the arithmetic does not predict which will dominate.
What it is mistaken for, and how to tell
One observation per rival, chosen because it separates them rather than because it describes either. Several of these are not faults at all — a style feature, a normal outcome, or the fruit behaving as it does.
- Volatile acidity — Solvent and nail varnish at the top of the nose is ethyl acetate; vinegar and a hot finish is acetic acid. Where both are present, warm the glass in the hand — the ester lifts first.
- Pear-drop character in a young perry — Concentration and context. Isoamyl acetate in a young perry is a pear-drop note that reads as fruit; ethyl acetate reads as a solvent and does not sit with the fruit at all.
- Acetification — Whether the vessel shows a film. Ethyl acetate from a stressed ferment leaves the surface clean.
What is actually happening
The chemistry or microbiology behind it. Understanding the mechanism is what makes the prevention make sense rather than being a list of rules.
Ethyl acetate is formed enzymatically by yeast, through alcohol acetyltransferase acting on acetyl-CoA and ethanol, and chemically over time by slow esterification of acetic acid with ethanol. The enzymatic route dominates during fermentation; the chemical route dominates in a cider that has been sitting with a raised acetic acid content for months.
The organisms matter. Apiculate yeasts — Hanseniaspora valbyensis, Hanseniaspora uvarum and Kloeckera apiculata — are prolific ethyl acetate producers and are exactly the yeasts that dominate the first days of a spontaneous ferment before ethanol accumulates and Saccharomyces cerevisiae takes over. Film-forming yeasts such as Pichia membranifaciens and Candida species produce large amounts of it at the surface of a standing vessel, which is why a film and a solvent nose so often appear together.
The perceptual problem is the ratio of threshold to typical concentration. Ethyl acetate is detectable at concentrations well below those of most other cider esters, so the gap between the amount that contributes fruitiness and the amount that reads unmistakably as solvent is narrow. Once the drink is over that line, no other aroma survives, because the nose fixes on the most volatile and most irritating component present.
It is also why acetified cider smells of pear drops as well as vinegar: the acetic acid produced by the bacteria is slowly converted into the ester that the nose finds far more readily than the acid itself.
How it happens
| Cause | Stage | How often |
|---|---|---|
| A long, cool, uninoculated start in which apiculate yeasts dominate for days before Saccharomyces takes over | Fermentation | common |
| A surface film of yeast on a standing vessel | Maturation | common |
| Raised acetic acid slowly esterifying during long storage | Maturation | common |
| Fermentation at an unusually high temperature, raising overall ester production | Fermentation | occasional |
| Juice standing warm and unprotected between pressing and the start of fermentation | Juice treatment | occasional |
Can it be put right?
Most cider faults cannot be reversed. Where that is the answer it is given plainly — an honest 'this batch is what it is' is more useful than a procedure that will not work.
| Option | Effectiveness | What it involves |
|---|---|---|
| Treat it as an early warning and secure the rest of the cellar | Reliable | A solvent nose usually means air, a film or an acetic population somewhere. Finding and correcting that protects the batches that are still sound. |
| Blend into a larger volume of clean cider | Partial | Because the fault is perceived against a threshold, dilution can genuinely put it back below the line. Bench trial first. |
| Let a lightly affected cider rest in a sealed vessel | Unlikely to work | Some volatile loss occurs slowly during racking and maturation, but it is small and unreliable, and the same period allows more ester to form from any acetic acid present. |
| Remove ethyl acetate from finished cider | Not possible | No practical domestic method exists. Do not attempt any heating, stripping or reduction process to drive it off; that is an operation with real burn and fire risk and it will strip everything else worth having. |
CiderHQ gives no additive dosage figures. An addition is a food-safety decision that depends on legal limits, on the juice in front of you and on what you are protecting against, and the right figure comes from your supplier’s or regulator’s own guidance rather than from a general reference.
Preventing it
- Get the primary ferment established quickly, so the apiculate phase is short rather than a fortnight long.
- Keep vessels full and sealed so no yeast film can establish at a surface.
- Control fermentation temperature; a cool, steady ferment produces a different and generally cleaner ester balance than a warm, fast one.
- Process juice promptly rather than letting it stand warm overnight in an open tub.
- Where a cultured yeast is used, rehydrate it as the supplier directs, so the intended population establishes before anything else does.
Ethyl acetate is a good example of a compound that is not a fault until it is. Every cider contains it, a fair amount of what people describe as fruitiness in a young cider is partly it, and the same molecule at a higher concentration is what people mean when they say a drink smells of nail varnish.
For anyone fermenting without an added yeast, the practical lever is time rather than technique. The apiculate yeasts that make the most of it are outcompeted once ethanol rises, so a ferment that starts promptly spends a short time in the phase that produces it and a long ferment that struggles to get going spends much longer.
The diagnostic value of the fault is high. Solvent on the nose of a maturing cider is a reliable signal that oxygen is reaching the liquid somewhere, and it is usually worth acting on before the vinegar note that follows becomes obvious.
It should not be confused with the genuine pear-drop character of some perries and of certain cider styles, where isoamyl acetate rather than ethyl acetate is doing the work. The distinction is in the edge: isoamyl acetate reads as banana and boiled sweet, ethyl acetate reads as sharp and chemical, and once noticed the difference is not subtle.
The compounds involved
Ethyl acetate
The most abundant ester in cider, giving lift and pear-drop at low concentration and nail varnish at high, and the earliest audible warning that acetic bacteria are at work.
Acetic acid
The vinegar acid, made by bacteria oxidising ethanol whenever air reaches a cider, and the one fault in cider that no later processing can undo.
Ethanol
The alcohol yeast makes from fruit sugar, which converts a perishable juice into a keepable drink and carries most of its aroma to the nose.
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.
The organisms involved
Hanseniaspora valbyensis
The apiculate yeast most consistently reported as dominating the first days of a spontaneous cider fermentation, and a major contributor to its aroma.
Hanseniaspora uvarum
The apiculate yeast most often reported from grapes and widely present on apples too, whose anamorph name *Kloeckera apiculata* still appears throughout older cider literature.
Kloeckera apiculata
The anamorph name for *Hanseniaspora uvarum*, still in wide use in cider writing, and often used loosely as a collective term for all apiculate yeasts.
Pichia membranifaciens
A film-forming yeast that grows as a skin on the surface of cider left in contact with air, consuming ethanol and acid and leaving the cider thin.
Candida species
A large, historically artificial grouping of yeasts that appears throughout cider microbiology, containing organisms with little in common beyond the absence of a sexual stage.
Acetobacter aceti
An acetic acid bacterium that oxidises ethanol to acetic acid wherever cider meets air, and the organism behind most volatile acidity in cider.
Where in the process it arises
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.
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
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.
Topping up
Refilling a maturing vessel as evaporation and racking losses lower the level, so that no significant surface of cider is ever left in contact with air.
Juice storage
Holding unfermented juice sound between pressing and fermentation, by chilling, sulphiting, gas blanketing, freezing or aseptic filling.
Faults it is confused with
These present similarly. What separates them is set out on each page.
Volatile acidity
The measurable fraction of acidity that can be steam-distilled off, dominated by acetic acid and read as vinegar sharpness in the nose and a hard, hot finish.
Acetification
The active conversion of a cider’s ethanol into acetic acid by acetic acid bacteria at an air interface — the process, running in the vessel, that produces volatile acidity.
Film yeast growth
A pale, powdery or wrinkled film of aerobic yeast growing on the surface of a standing cider, consuming alcohol and acid and producing acetaldehyde.
Where this comes up in a guide
The link lands on the step where the fault arises rather than at the top of the pathway, because that is where the decision that causes it is taken.
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 does my cider taste like vinegar — Acetic acid bacteria have reached the cider and, given air, are converting its alcohol into acetic acid. The cause is almost always oxygen — an unfilled vessel, a leaking bung, or a slow transfer.
- 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.
- 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.
- Can you fix a cider that has gone vinegary — Not really. Volatile acidity cannot be removed at small scale, and blending it away only dilutes it. The realistic options are to accept it, to blend a lightly affected batch into a much larger sound one, or to let it finish becoming vinegar.
- How many calories are in cider — Roughly 40 to 60 kcal per 100 ml for most ciders, so a UK pint falls somewhere around 200 to 250 kcal. Alcohol contributes about 7 kcal per gram and residual sugar about 4, so both strength and sweetness matter.
- Can you make cider from shop bought apple juice — Yes, provided the juice contains no preservative — check for potassium sorbate or benzoate on the label. Pasteurised juice ferments perfectly well once yeast is added, because pasteurisation removes the organisms but not the sugar.
Where to go next
- The fault finder — Describe what you can smell and see, and narrow it down from the signs.
- All faults — Grouped by where they come from and how serious they are.
- Cider science — The chemistry and microbiology these faults come out of.
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.
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.
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.