Carbonation
Tank conditioning
Running a second fermentation in a sealed pressure tank so the gas is generated by yeast but the sediment never reaches the bottle.
Known as Cuve close where it originates. Also called Charmat method, Tank method, Sealed-tank secondary fermentation.
- Stage
- Carbonation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Carbonation up, fermentation character up
- Safety
- Carries a safety consideration — see below
A tank in which a fermentation is deliberately sealed is a pressure vessel and must be rated, certified and maintained as one, fitted with a pressure relief device sized for the vessel and a gauge that is actually read. A fermentation that runs further than intended will keep generating gas, so the relief path must never be isolated by a closed valve, and the tank must not be topped up or transferred into without confirming its pressure first.
What it is
Tank conditioning ferments a measured quantity of sugar in a finished cider inside a pressure-rated, sealed tank. The carbon dioxide produced has nowhere to go, so it dissolves into the cider and the tank pressure climbs as the fermentation proceeds. When the target is reached the cider is chilled, the yeast removed by filtration or centrifugation, and the clear cider filled under counter-pressure so the dissolved gas is retained. The approach is the cuve close of French practice, known in sparkling wine as the Charmat method, and it produces a fermentation-carbonated drink with no deposit in the package.
Why it is used
- It gives a cider carbonated by fermentation rather than by injection, while presenting completely clear and sediment-free in the bottle.
- It handles a batch as a single unit rather than as thousands of individual fermentations, so the carbonation level is uniform across the run and can be measured directly as tank pressure.
- It avoids the labour of riddling and disgorging altogether, which is what makes fermentation-carbonated cider viable at commercial volume.
- It allows the sweetness to be set after the second fermentation, since the cider is handled in bulk before filling rather than sealed away in its final bottle.
How it works
- Yeast ferments the added sugar to ethanol and carbon dioxide. In a sealed vessel the gas cannot escape, so it partitions into the liquid according to Henry’s law, and the pressure the tank reaches is a direct reading of how far the fermentation has gone.
- Because the tank is a single large volume with a small surface-to-volume ratio compared with a bottle, the lees settle to one place and the cider’s contact with them is limited and brief — quite unlike the intimate, whole-bottle contact of a conditioned bottle.
- The fermentation is stopped where the maker wants it, by chilling the tank to drop the yeast out and then separating it, rather than by waiting for the sugar to be exhausted.
- Every transfer after that point — filter, buffer tank, filler — is held under counter-pressure above the equilibrium pressure of the cider, or the dissolved gas breaks out and the carbonation is lost before the closure goes on.
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 |
|---|---|---|
| Carbonation | Raises | Gas evolved by the second fermentation is trapped by the sealed vessel and dissolves into the cider instead of escaping. |
| Fermentation character | Raises | A live fermentation in the finished cider adds esters and higher alcohols that injection cannot, though the short and limited lees contact keeps the effect well short of a bottle-conditioned cider. |
| Alcohol | Raises | The sugar fermented for gas also yields ethanol, so the finished strength rises slightly above that of the base cider. |
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
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.
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.
Sucrose
The disaccharide of apple juice and the sugar most often added to it, split into glucose and fructose by the yeast’s own invertase before any of it is fermented.
Glucose
The sugar yeast takes first and the smallest of the three in apple juice, which is why the last sugar left in a slow ferment is almost never glucose.
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.
Saccharomyces bayanus
A name applied both to a hybrid Saccharomyces lineage and, loosely, to a whole class of commercial high-alcohol yeasts, and one of the least stable names in fermentation microbiology.
What it is done with
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.
Counter-pressure filling
Carbon dioxide stays dissolved only under pressure, so carbonated cider poured into an open bottle foams, loses its gas and takes on air; a counter-pressure filler removes the pressure difference by purging and pressurising the bottle first, and vents it under control at the end.
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.
Under-carbonation
A cider intended to sparkle that has little or no dissolved gas, usually because the bottle conditioning never started or the closure did not hold.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
Flat and lifeless
A cider with nothing obviously wrong and nothing to say: aroma faded, acidity dulled, finish short — usually the cumulative result of over-processing or slow oxidation.
Yeast haze
Cloudiness from yeast cells that have not settled out, usually because the strain flocculates poorly or the cider has not been left alone long enough.
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.
Sparkling cider
Cider carrying enough dissolved carbon dioxide to produce a persistent bubble, by bottle fermentation, tank fermentation or injection.
Sidra espumosa
Sparkling Asturian cider made by a second fermentation under pressure or in bottle, presented as a fine sparkling drink rather than in the still poured tradition.
Cidre doux
The sweet tier of the French cider scale, defined since 2025 by a density at or above 1.024 together with an acquired strength no greater than 3% vol, so that the sweetness is demonstrably unfermented juice sugar.
Medium cider
Cider carrying enough residual or added sugar to be perceptible without dominating, the commonest sweetness level in British retail.
Sparkling perry
Perry carrying a persistent bubble, a presentation that suits pear’s aromatics and residual sorbitol and has a documented history going back to the seventeenth century.
Pétillant cider
Lightly carbonated cider in which the gas is felt as a prickle rather than a stream of bubbles, the level most traditional bottle fermentation reaches on its own.
More on tank conditioning
Tank conditioning is most usefully understood as an attempt to keep the compositional benefit of a second fermentation while discarding its logistical cost. The gas comes from yeast, so the cider is genuinely fermented in its finished state and picks up the esters and the slight alcohol increment that go with that. But it happens in one vessel that can be sampled, gauged, chilled and clarified as a unit, instead of in thousands of sealed bottles that must each be turned, frozen and opened. For a producer making sparkling cider at any scale, that difference is decisive; the cuve close exists because riddling and disgorging tens of thousands of bottles is an expense the finished price often cannot carry.
The mouthfeel difference from a bottle-conditioned cider is real, and it comes down to lees contact rather than to the gas. In a bottle, the entire volume is in contact with its own yeast deposit across a large surface relative to the liquid, often for months or years, and yeast autolysis releases mannoproteins and other cell-wall material that build a soft, slightly creamy texture and a bready aroma. In a tank the lees fall to a small area at the bottom, contact is brief because the cider is clarified as soon as pressure is reached, and the cider is then filtered — which takes out more colloidal material again. The result is cleaner, more direct and more obviously fruit-driven, and thinner in the middle of the palate.
The decisions are the target pressure, the point at which the fermentation is arrested, and whether sweetness is set before or after. Because the cider is in bulk right up to filling, a producer can carbonate dry and sweeten afterwards, which is how much commercial sparkling cider reaches a doux or demi-sec balance — but that sweetened, gas-charged cider is then microbiologically vulnerable and normally goes through a sterile filtration or a heat step on the way to the pack. The characteristic failures are a fermentation that stalls short of the target pressure, leaving a flat product with unfermented sugar; a transfer train that loses gas because some part of it was not counter-pressured; and a cider filled with viable yeast and residual sugar, which refermenting in bottle undoes the entire point of the method.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Carbonation
Bottle conditioning
Carbonating cider by letting a second fermentation finish inside the sealed bottle, so the gas is generated where it is going to stay.
Carbonation
Transfer method
Fermenting in bottle for the character, then emptying the bottles under counter-pressure into a tank, filtering and refilling to remove the deposit without riddling.
Carbonation
Forced carbonation
Dissolving carbon dioxide into cider under pressure to a chosen level, giving complete control of the sparkle and none of the flavour a second fermentation would contribute.
Fermentation
Secondary fermentation
Any fermentative event that follows the primary ferment — residual sugar refermenting, a deliberate second alcoholic fermentation, or the malolactic conversion of the maturation phase.
Stabilisation
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.
Packaging
Bottling
Transferring finished cider into glass, where the dominant variable is how much oxygen the liquid picks up in the few seconds it takes to fill and close each bottle.
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 is cider carbonated — Either by dissolving carbon dioxide into finished cider under pressure, or by letting a small second fermentation produce the gas inside a sealed bottle or tank. The first is faster and more repeatable; the second leaves sediment and a finer bead.
- How is sparkling cider made
- 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.
- 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 should i know about stainless steel fermentation tanks — A stainless tank is a welded vessel, usually cylindrical, in an austenitic stainless grade chosen for corrosion resistance in acidic, chloride-containing conditions. It contributes nothing to the cider and lets no oxygen in.
- 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
- 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.