Pressing
Bladder pressing
Pressing by inflating a flexible membrane inside a drum so that the pomace is squeezed outwards against a drainage screen at low, evenly distributed pressure.
Also called Pneumatic press, Membrane press, Airbag press.
- Stage
- Pressing
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Oxidative character down, astringency down
- Safety
- None recorded
What it is
A pneumatic press is a horizontal cylinder containing a rubber or polymer membrane along one wall or down the axis. Pomace is loaded into the drum, the membrane is inflated with compressed air, and the pomace is pressed outward — or inward, in axial designs — against perforated drainage channels or a slotted screen that run juice to a tray beneath. Between inflations the drum rotates to break up the compacted cake and redistribute the pomace. The design came into cider from winemaking, where it displaced older basket and horizontal-screw machines for much the same reasons, and it is now common wherever juice character rather than throughput is the priority.
Described in full
- Shape
- A two-axis plot. The horizontal axis runs from little air contact on the left to a great deal on the right; the vertical axis runs from slow at the bottom to fast at the top. Five presses are plotted as marks: circles for batch presses, a circle in a different fill for the closed bladder press, and a diamond for the continuous belt press.
- Rack and cloth
- Low on both axes. The pomace is built into cloth-wrapped layers by hand and pressed slowly; the cheese is a largely sealed stack, so the juice inside meets little air. It gives clean juice and it is the slowest thing in the building.
- Basket and hydraulic
- Both batch methods, both slow, both with the pomace surface exposed while pressure is applied. The hydraulic press is the faster of the two because the pressure is applied mechanically rather than by a screw.
- Bladder
- The lowest air contact of all, because the press is a closed vessel and can be flushed or filled without the juice seeing much oxygen at all. Faster than the batch presses and slower than a belt.
- Belt
- The fastest and the most exposed. Pomace runs continuously between two moving belts through a series of rollers, in the open, in a thin layer with a large surface area. That is the trade: the juice is out quickly and it has met a great deal of air on the way.
- Why there are no numbers
- Throughput and yield figures for presses circulate widely and come almost entirely from manufacturers. CiderHQ has verified none of them and does not reproduce them. What can be defended without a number is the ordering, and the ordering is the useful part: the trade between speed and oxidation is the decision a maker is actually taking.
Why it is used
- A membrane applies its load over a very large surface at low pressure, so juice is released without the shearing and tissue maceration that a high-pressure ram produces.
- A closed drum can be flushed with inert gas or simply kept shut, which removes most of the air contact that an open rack-and-frame stack cannot avoid.
- The press cycle is programmable, so the same machine can run a gentle profile for an aromatic single varietal and a firmer one for tannic fruit.
- Loading, pressing and cake discharge are handled by the machine, which makes repeated small parcels practical without the labour of building and stripping cheeses.
How it works
- Air pressure behind a flexible membrane is transmitted as a nearly uniform normal load across the whole contact face, so no part of the pomace bed sees a stress concentration of the kind a rigid platen edge creates.
- The pressed layer is thin relative to the drum diameter, so juice has only a short path to the drainage screen and drains at modest pressure rather than needing force to push it through a deep bed.
- Rotation between inflations tumbles and re-forms the cake, opening new drainage paths through pomace that had consolidated into an impermeable layer.
- Because the peak pressure stays low, cell walls are drained rather than crushed, and much of the skin-bound phenolic material and insoluble pectin stays in the cake.
- Excluding air from the closed drum limits the substrate available to polyphenol oxidase, slowing the enzymatic oxidation of chlorogenic acid and flavanols that begins the moment milled fruit meets oxygen.
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 | Lowers | A closed or inert-gassed drum starves polyphenol oxidase of the oxygen it needs to convert phenolic substrates into the quinones that polymerise into brown pigments. |
| Fruit character | Preserves | Low shear and limited oxygen exposure leave the volatile esters and aldehydes of the fresh fruit largely intact rather than losing them to oxidation and heat of working. |
| Astringency | Lowers | Gentle distributed pressure drains cells rather than rupturing skin and cortical tissue, so much of the polymerised procyanidin load stays bound in the cake. |
| Freshness | Raises | Juice that has not browned retains its pale colour and unoxidised aroma compounds, which read on the palate as a brighter, more immediate fruit expression. |
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
Polyphenol oxidase
The copper enzyme that turns cut apple brown within seconds, and the reason a cidermaker has to decide, at the press, whether to let the juice oxidise or to stop it.
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.
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.
Procyanidins
The condensed tannins of cider fruit, whose chain length — not their quantity — decides whether the mouth registers bitterness or astringency.
Chlorogenic acid
The most abundant single phenolic in apple juice, the preferred substrate of the enzyme that browns it, and the precursor of one of the volatile phenols behind farmyard character.
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.
What it is done with
The bladder or pneumatic press
A press in which a rubber membrane is inflated with compressed air inside a perforated or channelled drum, squeezing pomace outward against the drainage surface with a low, even, gentle pressure.
Press types compared
A side-by-side account of how the common press types differ in yield, in oxygen exposure, in the phenolic load they put into the juice, in labour and in what they demand of the mill.
Inert gas: carbon dioxide, nitrogen and argon
Gas is used to push air out of tanks, bottles, kegs and lines, and the three common gases are not interchangeable: carbon dioxide dissolves readily and will carbonate a cider, nitrogen barely dissolves at all, and argon is heavy enough to lie on a surface.
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.
Enzymatic browning
The rapid darkening of milled fruit and fresh juice as polyphenol oxidase converts phenolics to quinones, taking colour and some tannin structure with it.
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.
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.
Single-varietal cider
Cider made wholly or overwhelmingly from one apple cultivar, presented so that the fruit’s own character is the subject of the drink.
Apfelwein
The dry, sharp, still apple wine of Hesse, fermented out from culinary and local fruit and served in ridged glasses from a stoneware jug.
More on bladder pressing
The argument for a pneumatic press is not yield and it is not speed. It is that pressure applied gently, evenly and repeatedly extracts free juice while leaving the tissue that carries harsh phenolics and pectin comparatively intact. Juice off a well-run membrane cycle is typically paler, lower in suspended solids and lower in extracted phenolics than the same fruit through a hard pack-press cycle, and it settles more readily. For an aromatic dessert or sharp cultivar pressed as a single varietal, that is the whole point: the volatile esters and fresh fruit character that define such a juice are easily buried under oxidative colour and extracted tannin.
Closed-chamber operation is the second reason, and it is the one that changes chemistry rather than texture. Milled apple is a suspension of substrate and enzyme in contact with air, and enzymatic browning starts immediately; an open press stack has no defence against it. A drum that can be closed, and in some installations purged with carbon dioxide or nitrogen, keeps dissolved oxygen low from crush to tank. Whether that is desirable is a genuine divide in practice: much German Apfelwein and modern aromatic cider work protects juice throughout, while a good deal of English and Normandy farmhouse tradition lets juice brown deliberately, on the reasoning that phenolics oxidised and dropped before fermentation cannot cause haze or harshness later.
What the practitioner decides is the cycle programme — how many inflations, to what pressure, how long each is held, and how many rotations between them. A long sequence of low-pressure inflations with frequent cake breaking will recover most of what a harder cycle would, but takes considerably longer per load; a short, firm cycle turns the machine round faster and starts to bring the phenolic and solids profile back towards pack-press juice. Run badly, the failure modes are a cake that has consolidated into a sealed layer and stopped draining, or a membrane damaged by stalks, stones or over-inflation, which takes the press out of service in the middle of a harvest.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Pressing
Rack-and-cloth pressing
Building pomace into thin cloth-wrapped layers separated by racks, so that juice has a short path out and the stack can carry the pressure needed to force it.
Pressing
Hydraulic pressing
Pressing in which a pump drives fluid against a ram, so that a small pumped pressure becomes a large, controllable and repeatable load on the pomace.
Juice treatment
Juice oxidation
The enzymic browning that begins the moment apple juice meets air, which some traditions deliberately allow and others suppress.
Juice treatment
Sulphiting
Adding sulphur dioxide to juice to suppress spoilage organisms and oxidative browning, at a level that only means anything once the juice pH is known.
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.
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 are apples pressed for cider — The fruit is first milled to a pulp, then that pulp is squeezed — traditionally in cloth-wrapped layers under a screw or hydraulic ram, and industrially in a belt or bladder press. Whole apples cannot be pressed usefully; they must be broken first.
- Why is sulphite added to cider — Sulphur dioxide suppresses spoilage bacteria and wild yeast before fermentation and protects the finished cider from oxidation. How much of it is active depends strongly on pH, which is why low-acid juice is harder to protect.
- What are carbon dioxide, nitrogen and argon used for in cider making, and how dangerous are they — Air is what damages finished cider, and the cheapest way to remove air is to displace it with a gas that will not react with the cider. That is the whole purpose of inert gas in a cider house.
- Which type of cider press should i use — No press is best. Each one sits at a different point on four trade-offs: how much juice it recovers, how much air the juice meets, how hard it works the solids, and how much labour and capital it needs.
- What are procyanidins in cider — They are the condensed tannins of apples: chains of catechin-type units whose length decides how much of the phenolic load reads as bitterness and how much as astringency. Two ciders with identical total tannin can taste nothing alike.
- 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.
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.
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.
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.