Sensory descriptor
Fermenting vat
The pungent, CO2-lifted smell of a ferment in full activity, met in very young cider straight from the vessel.
Also called Working ferment, Vat.
- Aroma family
- Fermentation-derived
- Does it indicate a fault?
- It depends on the style it is met in
What causes it
A vigorous fermentation produces carbon dioxide fast enough to strip volatiles from the liquid and carry them into the headspace, so the aroma above a working vat is a concentrated version of everything the yeast is making: acetaldehyde, ethyl acetate, higher alcohols, esters and sulphur compounds, all lifted by gas. Cider drawn from the vessel at this stage carries the same profile in solution together with dissolved CO2 that sharpens the perception. The character resolves over the weeks after fermentation ends as the most volatile components dissipate and the ester balance settles.
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.
Carbon dioxide
The other product of fermentation, which protects a cider from air while it is being made and, dissolved in the finished drink, changes both its texture and its perceived acidity.
Acetaldehyde
The compound sitting one step short of ethanol, which smells of bruised apple and sherry, binds most of the sulphite added to a cider, and is the chemical signature of oxidation.
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.
Hydrogen sulphide
The rotten-egg gas a nitrogen-starved yeast produces, detectable at concentrations too small to measure easily, and removable only if it is caught before it becomes something worse.
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.
Saccharomyces cerevisiae
The yeast that finishes essentially every cider, whether it arrives in a sachet or from the fruit, the press and the vessel.
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.
Metschnikowia pulcherrima
An early-succession yeast that suppresses competitors by locking up iron, and is used commercially as a controlled non-Saccharomyces partner rather than as a fermenter.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Fermentation monitoring
Watching a running ferment through gravity, temperature, smell and surface behaviour, and reading the rate of change rather than any single figure.
Gravity measurement
Measuring the density of juice or fermenting cider to follow sugar depletion and estimate alcohol, with the instrument limits and the perry complication that make the number less simple than it looks.
Oxygen management in fermentation
Giving the yeast the oxygen it needs early to build viable membranes, then excluding it once fermentation is under way and especially once it slows.
Racking
Moving cider off the sediment it has thrown, which both cleans the liquid and — by taking yeast and nitrogen away with the deposit — slows what is left of the ferment.
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 Fermenting vat
This descriptor names the reference state that cidermakers assess against during fermentation and that drinkers occasionally meet at a cellar door. It is not a characteristic of finished cider and its presence in a packaged product means the fermentation was not complete at bottling.
Its practical use is in fermentation monitoring, where a change in this composite — the arrival of sulphur, the loss of ester lift — is often noticed before any measurement shows it.
Others in the fermentation-derived family
Solvent, nail varnish, bread, yeast, cider-shop.
Nail varnish
The sharp solvent lift of ethyl acetate above threshold, the commonest volatile fault-adjacent note in cider.
Bread dough
A raw, yeasty, faintly sour note from live yeast in suspension, characteristic of unfiltered and bottle-conditioned cider.
Solvent
A general chemical, thinner-like impression from ethyl acetate and higher alcohols together.
Cider shop
The characteristic smell of a working cider house — ferment, wood, fruit and a trace of acetic lift together.
Fresh yeast
The clean, faintly sulphidic smell of an active yeast population, met in young cider and during fermentation.
Fusel
A hot, heavy, spirituous impression from elevated higher alcohols, felt as warmth as much as smelled.
Lees
A cloudy, faintly bitter, sedimentary character from yeast and fruit solids carried into the glass.
Yeast extract
A savoury, umami, meaty-broth note from yeast autolysis during extended lees 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 do i know when my cider has finished fermenting — Take two hydrometer readings several days apart: if the gravity has not moved, the ferment is over. Airlock activity is not a reliable test, because a slow ferment can produce gas too slowly to see.
- How long does cider take to ferment — A warm ferment with cultured yeast can finish in one to two weeks; a cool wild ferment in a cellar may take three months or more. Slow is not the same as stuck — the test is whether gravity is still falling.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- What is racking in cider making — Racking is siphoning cider off the sediment it has thrown into a clean vessel, leaving the lees behind. It clarifies the cider and, in traditional practice, is also used to slow a ferment by removing yeast with the lees.
- 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.
- Where does the fizz in cider come from — Either from fermentation trapped in a sealed container, or from carbon dioxide dissolved into the cider under pressure before filling. The French cider appellations permit only the first, and require at least 1.0 to 1.5 bar at 20 °C depending on the name.
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.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
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.