Stabilisation
Filtration
Passing cider through a porous medium to reach a stated visual brightness, at a real cost in colloidal material, body and aroma.
Also called Depth filtration, Sheet filtration, Pad filtration, Polishing filtration.
- Stage
- Stabilisation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Body down, phenolic character down
- Safety
- None recorded
What it is
Filtration drives cider through a porous barrier that holds back what is suspended in it, so the liquid leaving is brighter than the liquid entering. The word covers several formats at once: a slurry bed of diatomaceous earth or perlite dosed continuously onto a support, compressible pads of cellulose and filter aid held in a plate frame, and cartridge or lenticular modules that behave as a compact version of the same thing. All of them are described by what they are expected to retain rather than by any single hole size, because a deep bed catches particles by a winding path and by adsorption as much as by sieving.
Why it is used
- A cider that has been racked repeatedly and left to settle may still hold a fine suspension that will not drop under gravity in any useful time, and a filter removes it in one pass.
- Buyers who put cider into clear glass or into a glass on a bar top usually specify a brightness that natural settling cannot be relied on to deliver batch after batch.
- Taking out most of the yeast and fine solids slows the rate at which a packaged cider goes on changing, even at ratings far too coarse to make it microbiologically stable.
- Filtering ahead of a membrane or a bottling line protects both from blinding on material that a coarser medium could have taken out more cheaply.
How it works
- In a depth medium the liquid follows a tortuous route through a thick mat of fibres and mineral particles; solids are captured by interception along that route and by electrostatic attraction to the very large internal surface, so retention is statistical rather than absolute.
- Flow is driven by the pressure difference across the medium. As solids accumulate, that difference rises for the same flow — the medium is blinding — and the operator either accepts a falling rate or changes the medium.
- The adsorptive surfaces that hold fines also hold dissolved and colloidal macromolecules: pectin fragments, beta-glucans, protein–tannin complexes and a share of the higher-molecular-weight phenolics. That is the mechanism behind the loss of palate weight and colour, not an incidental side effect.
- Volatile aroma compounds are lost partly to adsorption and partly to the handling around the filter — pumping, level changes and headspace exchange all admit oxygen unless the line is run under inert gas.
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 |
|---|---|---|
| Body | Lowers | Colloidal macromolecules contribute viscosity and a coating quality on the palate; removing them by adsorption onto the filter medium takes that contribution with them. |
| Phenolic character | Lowers | Higher-molecular-weight procyanidins and protein-bound tannin are among the first things a depth medium adsorbs, so tannic structure softens along with the haze. |
| Oxidative character | Either way | The filter itself is neutral, but the pumping and headspace changes around it dissolve oxygen unless the whole operation is run under inert gas. |
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
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.
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Tannin–protein complexes
What astringency physically is: long tannin chains cross-linking salivary proteins and precipitating them, which is also the mechanism behind fining, protein haze and the classic cider-and-cheese pairing.
Total phenolics
The single number used to summarise everything phenolic in a juice, useful for comparing fruit and misleading whenever it is used to predict how a cider will taste.
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.
What it is done with
Filters: plate, sheet, cartridge and crossflow
Filtration ranges from coarse polishing that only brightens a cider to sterile membrane filtration that removes yeast and bacteria entirely; the equipment differs in whether it traps particles in a depth of material or on a surface, and in what it takes out of the cider along with the haze.
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.
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.
Colour loss
A cider left noticeably paler than it should be, usually because fining, filtration or sulphite has removed the phenolic material that gave it colour.
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.
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.
Gushing
Cider that erupts from the bottle on opening, either because it is over-pressurised or because something in it is nucleating the dissolved gas violently.
Pectin haze
A persistent, slightly viscous haze that will not settle, caused by pectin from the fruit remaining in solution as a colloid.
Protein haze
A fine haze that forms as protein and tannin combine into insoluble complexes, often appearing in a cider that had already been clear.
Ropiness
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
Starch haze
A persistent haze caused by starch carried in from under-ripe fruit, which has not yet been converted to sugar and stays suspended in the cider.
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.
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.
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.
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.
Still cider
Cider with no perceptible dissolved carbon dioxide, presented as a fermented fruit drink whose texture rests on body, acid and tannin alone.
Unfiltered cider
Cider packaged without filtration, retaining suspended yeast and fine solids and the body and aroma that come with them.
Dry cider
Cider fermented out or finished so that little fermentable sugar remains, leaving acid, tannin and alcohol to carry the palate.
Australian cider
Cider from Australia, dominated by a large mainstream sector using dessert fruit and concentrate, with a smaller full-juice movement working from cool-climate orchards.
Cider vinegar
Not a cider but its next stage: cider whose ethanol has been oxidised to acetic acid by bacteria, made deliberately as a condiment and arrived at accidentally as a fault.
Eastern counties cider
Cider from eastern and south-eastern England made largely from dessert and culinary apples, giving a lighter, sharper and less tannic drink than the West Country tradition.
Hopped cider
Cider dry-hopped or hopped in process, borrowing aroma and bitterness from a brewing ingredient to supply what low-tannin apples cannot.
Irish cider
Cider from Ireland, dominated commercially by large-scale production from Armagh and imported fruit, with a smaller full-juice sector working from orchard-grown apples.
New Zealand cider
Cider from New Zealand, made in a country with a substantial export apple industry and a small but technically confident craft cider sector.
Sidra de nueva expresión
A modern Asturian category of filtered, clean, dry cider made with controlled fermentation and presented in a wine format rather than in the poured tradition.
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.
Spiced cider
Cider flavoured with spices, either fermented and packaged that way or mulled and served warm, with the two practices frequently confused.
Botanical cider
Cider infused with herbs, flowers, roots or bark, a small modern category with old antecedents in the practice of flavouring fermented drinks with what was to hand.
Polish cider
Cider from Poland, a recent sector built on Europe’s largest apple crop and on dessert and culinary fruit rather than on an inherited cider tradition.
South African cider
Cider from South Africa, where a very large mainstream category built on Western Cape dessert fruit dominates and a small craft sector works alongside it.
More on filtration
The useful way to think about a filter is as a device with two jobs that cannot be separated. It removes what makes the cider cloudy, and it removes a proportion of what makes the cider taste of something. Both happen on the same surfaces by the same mechanisms. A tight sheet will take out a yeast haze and will also strip protein–tannin complexes, pectin fragments and part of the phenolic fraction that carries astringency and mouthfeel. This is why a cider tasted before and after a hard filtration often reads as cleaner, brighter and noticeably thinner in the same breath. There is no filter medium that distinguishes between colloids the maker wants gone and colloids the maker wants kept.
Practice diverges sharply between traditions, and the divergence is about what clarity is taken to mean. Asturian sidra natural and Basque sagardoa are not filtered at all in their classic forms: they are drawn from the barrel or bottle with their own suspended matter and the pour is designed around it. English farmhouse cider has historically been sold as it fell bright or as it did not, and the persistence of scrumpy as a category is partly the persistence of that indifference. French cidre arrives at clarity by a different route entirely — a keeved juice ferments slowly from a nutrient-stripped must and clears itself as it goes, so filtration in a Norman cellar is often a light polish rather than the main clarifying step. German Apfelwein is conventionally bright, and modern mainstream cider in Britain, North America and Australasia is filtered as a matter of specification.
What the practitioner actually decides is the rating and the number of stages. Going straight to a tight medium blinds it on coarse material and costs far more in consumables and in product held up in the filter than a coarse pass followed by a fine one. Going too tight for the product is the commoner fault: a cider that was already lean loses its remaining structure and finishes short and hollow, and a deeply coloured cider fades. The other failure is filtering something that has not finished dropping its own solids, so the medium blinds within minutes and the batch stalls on the line. None of this makes an unfiltered cider a failed one. Cloudiness in a cider that was meant to be cloudy is a style decision, and the honest position is that the filter buys presentation and stability and pays for them in body.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
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.
Stabilisation
Fining
Adding a reactive agent that binds a target colloid and carries it to the bottom, chosen according to whether the problem is tannin, protein or a phenolic taste fault.
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.
Stabilisation
Cold stabilisation
Holding cider cold before packaging so that anything which would fall out of solution in a cold warehouse falls out in the tank instead.
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.
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.
- Is cider vegan — Cider itself is a plant product, but some producers clarify it with animal-derived finings such as gelatine, isinglass or chitosan. Vegan status therefore depends on the fining regime, which is why some ciders are certified and others are not.
- 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 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
- What kind of pump should be used for cider, and can a pump damage it
- What kinds of filter are used on cider and what does each remove
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 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.
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.