Stabilisation
Centrifugation
Separating solids from cider by density in a rapidly spinning bowl, continuously and without a filter medium, at the price of shear and oxygen pick-up.
Also called Centrifugal clarification, Disc-stack separation.
- Stage
- Stabilisation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Fermentation character down
- Safety
- None recorded
What it is
A centrifuge clarifies by making gravity effectively much stronger. Cider is fed into a bowl spinning fast enough to generate an acceleration thousands of times that of gravity; anything denser than the liquid — yeast, fruit solids, precipitated colloids — is driven to the bowl wall and removed, while clarified liquid leaves from the centre. In the disc-stack design used for beverages a nest of closely spaced conical discs shortens the distance a particle must travel before it is captured, so the machine can be small and still fast. It runs continuously, with no consumable medium at all.
Why it is used
- It handles a heavy solids load continuously, where a filter would blind within minutes, so it is the sensible first stage on cloudy juice or on cider straight off gross lees.
- It removes the great majority of the yeast before filtration, which cuts consumable cost and extends the life of the filter medium substantially.
- It strips a fermenting cider of yeast quickly and thoroughly, which is one of the practical ways of arresting a fermentation at a chosen sweetness rather than letting it run dry.
- It recovers liquid from lees that would otherwise be discarded, since the machine can be fed a slurry no filter would accept.
How it works
- Settling velocity depends on the density difference between particle and liquid, on particle size and on the acceleration acting on it. A centrifuge cannot change the first two, so it changes the third, replacing gravity with a field large enough to make sedimentation happen in seconds.
- The disc stack divides the flow into many thin layers. A particle in a thin layer reaches a collecting surface after a very short journey, so the effective settling area of a compact bowl is enormous compared with its physical size.
- Because separation is by density and not by size exclusion, dissolved and neutrally buoyant material passes straight through. A centrifuge will not remove what a filter removes by adsorption, and it will not sterilise.
- The liquid experiences high shear at the inlet and around the discs, and any air drawn in at the feed or the discharge dissolves readily under those conditions, which is why beverage centrifuges are run with an inert gas blanket and a flooded, sealed feed.
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 | High shear and any entrained air dissolve oxygen efficiently, so an unblanketed machine oxidises cider quickly while a properly inerted one need not. |
| Sweetness | Either way | Where the machine is used to strip yeast from an active ferment, the fermentation stops where it stood and whatever sugar remained stays in the cider. |
| Fermentation character | Lowers | Removing suspended yeast removes the source of the yeasty, autolytic character that lees contact would otherwise develop. |
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.
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Pectin
The structural polysaccharide of fruit cell walls, which decides how much juice a press releases, whether a cider ever clears, and whether keeving is possible at all.
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.
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.
What it is done with
The centrifuge
A centrifuge separates solids from liquid by spinning them at high speed, clarifying juice or cider in a single continuous pass without filter aid — fast, effective, expensive, and capable of doing real damage if it draws air.
Pumps, and what a rough pump does to cider
A pump that shears, cavitates or draws air changes the cider it moves — stripping carbon dioxide, dissolving oxygen and breaking up lees — so the choice between centrifugal and positive-displacement types is a quality decision, not only an engineering one.
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.
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.
Thin body
A cider with no weight or texture in the mouth, most often from over-watered pomace, low-gravity juice or a blend with nothing to give it substance.
Stuck fermentation
A fermentation that has stopped before the sugar is gone and will not restart, leaving a sweet, low-alcohol cider that is vulnerable to everything.
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.
Modern mainstream cider
The industrially produced, consistent, carbonated cider that accounts for most of what is sold worldwide, generally made partly from concentrate and finished to a fixed specification.
Sweet cider
Cider in which sugar is the leading sensation, whether retained from an arrested fermentation, added after it, or produced by keeving.
Still cider
Cider with no perceptible dissolved carbon dioxide, presented as a fermented fruit drink whose texture rests on body, acid and tannin alone.
More on centrifugation
A centrifuge occupies a distinct place in the clarification sequence, and it is not a substitute for a filter so much as a different kind of tool used before one. Its strength is bulk: it will take a slurry with a solids load that would blind a sheet filter almost instantly and deliver a clear stream continuously, with nothing to change and nothing to dispose of except the solids themselves. Its limitation follows directly from its mechanism. Separation by density does nothing to material of the same density as the cider, so dissolved colloids, fine phenolic material and anything neutrally buoyant pass through untouched. A centrifuged cider is bright to the eye but not polished and certainly not stable.
The counterpart to that continuous throughput is what the machine does to the liquid on the way through. Feed and discharge are points where air can be entrained, and the shear field inside the bowl mixes any entrained air into solution with unusual efficiency, so a centrifuge run casually is one of the fastest ways to oxidise a cider in the whole cellar. Beverage practice therefore runs the feed flooded, the discharge sealed and the whole machine under an inert blanket, and treats a positive check on that blanket as part of the start-up routine. The shear itself is also not neutral: it breaks up flocs and can disperse material that would otherwise have settled, so a cider that has been over-sheared can be harder to clarify afterwards, not easier.
The use that most changes the finished drink is stripping yeast from a fermenting cider. Because the machine removes cells rather than inhibiting them, a single pass can take a ferment from active to effectively stopped, leaving whatever sugar was present at that moment in the cider — a physical route to a sweet cider without back-sweetening, and one that leaves no additive to declare. It is not by itself a stabilisation: enough cells survive to restart a fermentation given time and warmth, so the pass is normally followed by filtration, sulphite, heat or cold. Small producers rarely have access to a centrifuge at all; it is a capital item with a demanding cleaning regime, and for most cellars settling, fining and filtration remain the practical route.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Stabilisation
Filtration
Passing cider through a porous medium to reach a stated visual brightness, at a real cost in colloidal material, body and aroma.
Juice treatment
Juice clarification
The deliberate use of enzyme, fining agents or mechanical separation to produce a bright juice before fermentation, and what that costs the ferment.
Fermentation
Arrested fermentation
Deliberately halting a ferment while sugar remains, to obtain natural sweetness from the fruit rather than from an addition — and accepting the instability that follows.
Maturation
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.
Juice treatment
Juice settling
Letting freshly pressed juice stand cold and undisturbed so that gross solids fall, then racking the cleaner juice off the deposit before pitching.
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.
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 you stop cider from fermenting — By removing the yeast, by chilling, by filtering it out, by pasteurising, or by a combination — and in practice a home maker cannot reliably stop a ferment mid-way with chemicals alone. Sorbate prevents yeast multiplying but will not stop an active ferment.
- 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.
- 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 did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- What does pectin do in cider — Pectin is the structural polysaccharide that holds fruit cells together. In juice it holds haze in suspension, and it is the molecule keeving depends on: strip its methyl groups and it will gel with calcium and float the nutrients out of the juice.
- What is oxidation in cider
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.
Hochschule Geisenheim University — beverage technology
Hochschule Geisenheim · university · retrieved 2026-08-24
German beverage-technology research covering apple wine and fruit juice processing, including the enzymology of clarification.