Fermentation
Fermentation vessels
The container a cider ferments in — wood, stainless, plastic, glass or concrete — and how its permeability, thermal mass and resident microflora shape the result.
Also called Fermenters, Fermentation containers.
- Stage
- Fermentation
- Traditional in
- Asturias, Basque Country, Somerset, Herefordshire and 2 more
- What it most changes
- Oxidative character and Phenolic character
- Safety
- None recorded
What it is
The fermentation vessel is not a neutral container. Its material determines whether oxygen reaches the cider through the walls, how quickly the ferment heats up and cools down, whether the surface can be cleaned to a microbiological standard or harbours an established population, and what the vessel contributes in the way of flavour. Cider is fermented in oak vats and casks, in chestnut toneles and Basque kupela, in stainless tanks of every size, in plastic drums and intermediate bulk containers, in glass carboys and demijohns, and in concrete. Each of these is a coherent choice with an internal logic; none is simply an inferior version of another.
Why it is used
- Vessel volume and material together determine the thermal behaviour of the ferment, which for a producer without refrigeration is the main means of controlling temperature at all.
- Whether the vessel admits oxygen through its walls decides how much slow oxidative development occurs alongside and after fermentation.
- A cleanable, non-porous vessel makes a batch microbiologically independent of the ones before it; a wooden one does not, which is a liability in one tradition and the point in another.
- Headspace geometry and the ratio of surface to volume govern how exposed the cider is once fermentation stops producing protective carbon dioxide.
How it works
- Oak and chestnut staves are slightly permeable to oxygen, admitting it at the staves and joints at a rate that depends on the wood, the size of the vessel and the humidity of the cellar — a large vat has far less surface per unit volume than a cask, so the same wood gives a very different oxygen exposure at different scales.
- Thermal mass rises with volume while heat loss rises with surface area, so a large vessel warms during a vigorous ferment and holds that heat, while a small one tracks the temperature of the room.
- Stainless is impermeable, non-reactive and can be cleaned and sanitised to a repeatable standard, and its thin walls conduct heat readily — which is what makes jacketed temperature control possible and also what makes an unjacketed stainless tank follow the cellar closely.
- Wood that has held cider before carries yeasts and bacteria in the pores and behind the staves, so a working vat inoculates each new fill from its own resident population; this cannot be sanitised away without destroying the property, and it works in both directions.
- Concrete has very high thermal mass and holds a stable temperature through a ferment, but requires an inert lining because untreated concrete reacts with acid and can leach calcium into the cider.
What it changes
The direction this step pushes the finished drink in, dimension by dimension. A direction, not a measurement: how far it moves depends on the juice, the temperature and how the step is carried out.
| Dimension | Direction | Why |
|---|---|---|
| Oxidative character | Either way | Permeable wood admits a slow trickle of oxygen that develops aldehydic and nutty notes over months, where stainless and glass admit none at all and any oxidation must come from handling. |
| Phenolic character | Either way | A vat carrying resident Dekkera and Brettanomyces converts hydroxycinnamic acids to ethylphenols, which is a defining note in some traditional ciders and a fault in others. |
| Body | Either way | Slow oxygen ingress through wood promotes gradual polymerisation of tannins, which shifts the texture from grippy towards rounder over a long maturation in a way an impermeable vessel cannot. |
The chemistry and the organisms
What is actually being changed, and by what. Each entry says what that compound or organism does in cider generally; this page is one place it does it.
Compounds involved
Dissolved oxygen
Essential to a healthy yeast population at the start of fermentation and the principal enemy of a cider from the moment fermentation ends.
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.
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.
Oak lactones
The coconut-and-wood compounds of oak, whose concentration depends more on which species of oak the barrel was made from than on anything a cidermaker does.
Vanillin
The vanilla compound released from oak lignin, and a good illustration of why fermenting in a barrel gives less wood character than maturing in one.
Organisms involved
Saccharomyces cerevisiae
The yeast that finishes essentially every cider, whether it arrives in a sachet or from the fruit, the press and the vessel.
Brettanomyces anomalus
The second Brettanomyces species regularly recovered from cider and beer, less studied than B. bruxellensis but capable of the same phenolic chemistry.
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.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
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.
Oenococcus oeni
The acid-tolerant lactic acid bacterium that carries out most deliberate malolactic fermentation, converting malic acid to lactic acid after the yeast has finished.
Where it is traditional
The places this step belongs to as a matter of practice. It is not a claim of exclusivity — a method can be traditional in one region and perfectly ordinary in another.
What it is done with
Oak vats and wooden tuns
Large upright vats of oak or chestnut were the standard fermentation vessel of the farm cider house for centuries; they breathe, they hold a resident microflora, and they are almost impossible to sterilise.
Stainless steel tanks
Stainless steel is inert, effectively impermeable to oxygen, and the only common vessel material that can genuinely be cleaned and sanitised — which is why it displaced wood almost completely in commercial cider making.
Plastic vessels and what "food-grade" actually means
High-density polyethylene and polypropylene vessels made and certified for food contact are entirely suitable for fermenting cider; the question is never "is it plastic" but "was this container made and used for food".
Glass demijohns and carboys
Glass is inert, impermeable, transparent and cleanable, which is why it performs so well as a small-scale fermenter — offset by weight, fragility and a batch size that stops being convenient somewhere around twenty-five litres.
Concrete and stone vats
Concrete tanks give a wooden vat’s thermal steadiness and a steel tank’s indifference to flavour, provided the interior is lined or well passivated — and they are effectively permanent, for better and worse.
Choosing a fermentation vessel: material and shape
Vessel material decides oxygen ingress, flavour contribution and how well the thing can be cleaned; vessel shape decides temperature behaviour, lees depth and how much surface the cider presents to whatever is above it.
What can go wrong
Faults that begin at this step, or that this step makes more likely. Each one is set out with its causes and whether it can be put right.
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.
Brettanomyces character
Farmyard, horse-blanket, smoky and sticking-plaster aromas from Brettanomyces yeast converting hydroxycinnamic acids into volatile phenols.
Oxidation
The cumulative effect of oxygen on finished cider: fruit aroma flattens, colour deepens towards amber, and a bruised-apple or sherry-like character replaces the fresh one.
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.
Vinegar fly contamination
Small flies carrying acetic acid bacteria and spoilage yeasts directly into juice and cider, and depositing them wherever they land.
Plastic and packaging taint
Plastic, rubber, adhesive or chemical notes picked up from unsuitable containers, liners, hoses, gaskets or cleaning residues.
Metal haze
A haze or dark cast caused by dissolved iron or copper picked up from equipment, forming insoluble complexes with phosphate or with the cider’s phenolics.
Metallic taint
A metallic, inky or blood-like taste from dissolved iron, copper or zinc picked up from equipment, usually accompanied by accelerated oxidation.
Styles it produces
Categories in which this step is characteristic or required. Some name it in their definition; for others it is simply how they have always been made.
Sidra natural
The still, dry, unfiltered cider of Asturias and the Basque Country, wild-fermented from local high-acid fruit and poured from a height to raise a momentary sparkle.
Euskal Sagardoa
Basque cider under its own protected designation, made from Basque-grown apples in the sagardotegi tradition of barrel service and dry, high-acid, still cider.
West Country farmhouse cider
Cider made on the farm from tannic bittersweet fruit, wild-fermented in wood and sold still and unfiltered, in a tradition whose variability is one of its defining features.
Barrel-aged cider
Cider matured in wood, where slow oxygen ingress, extraction from the staves and the barrel’s resident microflora all change the finished drink.
More on fermentation vessels
The Asturian llagar and the Basque sagardotegi represent a tradition of very large wooden vessels that is genuinely distinct from the English and Norman use of wood. The Asturian tonel and the Basque kupela are typically chestnut rather than oak, are large enough that surface-to-volume ratio makes oxygen ingress modest, and are used year after year with an established resident microflora that is understood as part of the identity of sidra natural rather than as contamination to be managed away. English West Country practice historically used oak vats and, at smaller scale, oak casks, where the higher surface-to-volume ratio gives markedly more oxygen exposure. Norman foudres sit somewhere between. The choice of wood species, the size and the reuse pattern are not incidental details but the substance of the difference.
Modern vessels solve different problems. Stainless is impermeable, cleanable, inspectable, available in any size and can be jacketed for temperature control, which together account for its dominance in commercial production; what it does not do is contribute anything, which is either its virtue or its limitation depending on the drink. Food-grade plastic intermediate bulk containers are cheap, stackable and adequate for a single ferment, but they are slightly oxygen-permeable, they scratch, and scratches harbour organisms that survive cleaning — they serve as fermenters rather than as maturation vessels. Glass carboys are inert and let the maker see what is happening, which makes them ideal at small scale and impractical above it. Lined concrete offers the thermal stability of a wooden vat without the oxygen ingress or the microflora.
What a practitioner actually decides usually comes down to what the vessel will be asked to do after the ferment, because that is where the differences bite. During active fermentation, carbon dioxide protects the cider whatever the vessel; the vulnerability begins when gas evolution stops. A wooden vat that is not kept full will oxidise and can grow film yeast or acetic acid bacteria in its headspace, which is why topping up is a discipline rather than an option in wooden-vessel traditions. Poor practice in wood shows as volatile acidity and a vinegary lift; poor practice in scratched plastic shows as a batch that tastes of the batch before it; poor practice in stainless usually shows as nothing at all, which is precisely why it is the default for anyone whose priority is a predictable result.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Fermentation
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.
Fermentation
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.
Maturation
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.
Juice treatment
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Maturation
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.
Fermentation
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.
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.
- 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.
- 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.
- 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.
- 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.
- Can i ferment cider in a plastic barrel, and how do i know it is safe — Plastic fermenters are usually high-density polyethylene, polypropylene or, for carboys, polyethylene terephthalate. All three are used throughout the food industry and none of them are a problem in themselves.
Where to go next
- How cider is made — The whole sequence, stage by stage, with the choices open at each one.
- Cider science — The chemistry and microbiology the methods on this page rest on.
- Troubleshooting — What goes wrong, how to recognise it, and whether it can be reversed.
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.
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.
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.
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.