Fruit preparation
Milling
Reducing whole fruit to a pulp so that the press has cell walls it can drain, rather than intact apples it can only bruise.
Known as Broyage where it originates. Also called Scratting, Grinding.
- Stage
- Fruit preparation
- Traditional in
- Somerset, Herefordshire, Normandy, Asturias and 1 more
- What it most changes
- Oxidative character up
- Safety
- None recorded
What it is
Milling is the reduction of whole fruit to a coarse wet pulp — pomace in English, marc in France, magaya in Asturias, Trester in German-speaking practice — before anything reaches the press. An apple is mostly water held inside cells that are themselves held together by pectin, and a whole apple under pressure simply deforms and springs back rather than giving up its juice. Milling ruptures those cells and creates a granular mass with drainage paths through it. Every later decision — press type, extraction rate, how much phenolic material ends up in the juice, whether a keeve is possible — is constrained by what the mill did first.
Described in full
- The section
- A cut across the fruit: a thin skin, a broad band of flesh, and a small core holding the seeds. The drawing is schematic and the layers are not to scale.
- Skin
- Tannin and aroma concentrate here and immediately beneath. The polyphenol content of the outer few millimetres is several times that of the middle of the flesh, which is why milling fineness and skin contact change tannin more than cultivar choice alone does.
- Flesh
- Sugar and acid live in the flesh, held in the vacuoles of its cells. Fructose is the largest single sugar in apple juice, and malic acid is almost the entire acid content.
- Cell walls
- Pectin is structural: it is the cement between cells, not something dissolved in the juice. Milling releases it, which is why fresh juice is cloudy and why pectinase, or keeving, is a treatment applied to juice rather than to fruit.
- Core
- Seeds and the tough carpel walls. The core yields little juice, and the seeds carry amygdalin, which is a reason milled fruit is pressed rather than left standing indefinitely.
- Why this governs practice
- Every extraction decision is a decision about which zone is being worked. A fine mill and a long maceration take more from the skin; a coarse mill and a fast press take proportionally more from the flesh.
Why it is used
- Whole fruit under press pressure deforms rather than draining; only a ruptured, granular mass gives up juice at a workable rate.
- The size and uniformity of the particles set how fast juice can escape, which is the practical limit on press yield.
- Milling is the point at which flesh, skin and the phenolic material concentrated near the skin are brought into contact with the juice, and so where extraction begins.
- It exposes the fruit to air and to the enzymes released from broken cells, which is either a problem to be suppressed or an effect to be used.
How it works
- A mill breaks the fruit by impact, shear or crushing — a knife or hammer rotor, a grating drum, a pair of rollers, or in the oldest form a stone runner turning in a circular trough.
- Cell rupture releases juice, and with it the cytoplasmic contents: sugars, malic acid, and polyphenol oxidase which immediately begins to act on chlorogenic acid and the catechins in the presence of air.
- Particle size governs drainage. Too coarse and juice is still locked inside intact tissue; too fine and the pomace becomes a slurry that blinds the press cloth or the drainage channels and holds juice by capillarity rather than releasing it.
- Milling also begins to liberate pectin from the middle lamella, along with the fruit’s native pectin methylesterase — the enzyme on which keeving depends.
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 |
|---|---|---|
| Phenolic character | Either way | Finer milling exposes more skin and sub-skin tissue to the juice, and phenolics are concentrated there, so mill setting changes how much procyanidin the press has the opportunity to extract. |
| Oxidative character | Raises | Rupturing cells brings polyphenol oxidase, its phenolic substrates and atmospheric oxygen together for the first time, so browning begins at the mill rather than at the press. |
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.
Pectin methylesterase
The enzyme that strips methyl groups from pectin, exposing the charged sites that calcium bridges — which is the reaction the whole of keeving is built on.
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.
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.
Procyanidins
The condensed tannins of cider fruit, whose chain length — not their quantity — decides whether the mouth registers bitterness or astringency.
Malic acid
The acid of apples, which supplies almost all the sharpness a cider has and, through pH, decides how vulnerable that cider is to everything that could spoil it.
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.
Fructose
The dominant sugar of apple juice and the sweetest of the common sugars, which is why apple juice tastes sweeter than its total sugar figure implies and why a stuck ferment leaves sweetness behind.
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.
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
The scratter
A roller mill that tears apples into coarse pomace between toothed or spiked rollers, the machine that replaced the stone mill on most farms and still the commonest mill at small and medium scale.
The hammer mill
A high-speed mill in which swinging hammers on a rotor smash fruit against a breaker plate and force it through a screen, producing a fine, uniform pomace suited to belt and continuous pressing.
The centrifugal mill
A mill in which fruit is thrown outwards by a rotating disc or drum against a serrated ring or grating surface, cutting rather than smashing it and giving an unusually even particle size.
Hand mills and small-scale milling
Hand-cranked roller mills, drill-driven grating mills, and the improvised methods — freezing, chopping, a clean baulk of timber in a tub — that people use for the first few batches, with an honest account of how much work each is.
The stone circular mill and horse gin
A circular stone trough in which a heavy edge-runner stone, dragged round by a horse, crushed apples slowly over an hour or more — the standard English farm mill from the seventeenth century until the scratter displaced it.
Particle size, yield and phenolic extraction
Milling finer raises the juice that can theoretically be extracted and the phenolic load carried into it, but past a point the pomace stops draining and yield collapses — so the right particle size is set by the press, not by the mill.
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.
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.
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.
Pectin haze
A persistent, slightly viscous haze that will not settle, caused by pectin from the fruit remaining in solution as a colloid.
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.
Excessive astringency
A drying, roughening, mouth-puckering sensation that outstays its welcome, produced by larger phenolic polymers precipitating salivary proteins.
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.
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.
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.
Cidre de Normandie
Protected Normandy cider made from the region’s bitter and bittersweet fruit, characteristically low in alcohol, sweet-edged and lightly sparkling.
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.
Perry
The fermented drink of pears, a tradition parallel to cider rather than derived from it, in which unfermentable sorbitol leaves a sweetness the maker never chose.
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.
Most
The farmhouse fermented fruit drink of Austria and southern Germany, made from apples, pears or both, and belonging to a meadow-orchard landscape as much as to a recipe.
Mostviertel Birnenmost
Austrian pear Most from the Mostviertel, made from the region’s tannic standard-tree perry pears, in which sorbitol leaves a soft sweetness no fermentation removes.
Suure Most
The Swiss farmhouse cider of the plateau, typically dry and still, drawn from meadow-orchard fruit and distinguished in local usage from the unfermented sweet juice of the same name.
Recorded figures
Shown with the place, period and method each was taken under, and never averaged: the same step run in another cellar genuinely gives a different number.
Juice yield63–825 L/t
WSU Mount Vernon NWREC, Skagit Valley, Washington, USA, 2015–2017 · Juice pressed from 25 fruit per cultivar under a common milling and pressing protocol, across 44 cultivars. · Washington State University Northwestern Washington Research and Extension Center
Recorded on this page because the mill sets the ceiling: juice sits inside cell walls and no pressure releases it until those walls are broken. A thirteenfold spread across cultivars under one milling protocol is a statement about the fruit, and it is also the reason a yield figure without its milling conditions means very little.
How much juice a tonne of fruit gives up, which depends on the fruit and on the press. Measured in litres per tonne.
More on milling
The oldest surviving cider mills are stone: a circular trough of dressed stone with an upright runner wheel dragged round it by a horse, crushing fruit slowly and heavily. Museum collections in Hereford and Somerset hold examples, and the design persisted for centuries because it does something a modern mill does not — it works slowly, at low speed, tearing rather than chopping, and it produces a pomace with a wide range of particle sizes that drains well in a straw or hair cheese. The scratter mill that replaced it, a toothed roller in a hopper, was the nineteenth-century farm answer, and the hammer or knife mill driven off a motor is the twentieth-century one. Each produces a measurably different pomace from the same fruit.
What a maker is choosing between is extraction and drainage, and the two pull in opposite directions. A fine grind ruptures more cells and puts more sugar, acid and phenolic material into contact with the liquid phase, which raises both potential yield and phenolic intensity. But fine pomace packs. Under pressure it forms an impermeable layer and the juice cannot get out; on a rack-and-cloth press the cheese slumps and bursts, and on a belt press the bed blinds. Coarse pomace drains freely and presses cleanly but leaves juice behind in unbroken tissue. The right setting depends on the fruit — soft, sweated, late bittersweet fruit mills much finer than firm early sharps — and on which press is waiting.
The mill is also where oxidation is decided, and traditions genuinely diverge here. West Country and Norman practice historically allowed milled pomace to stand and brown, because the quinones formed from chlorogenic acid and the catechins polymerise and take some of the harsher phenolic material out of solution with them; the juice runs a deep russet and the finished cider is softer than the fruit analysis alone would predict. Modern aromatic practice — much Pacific Northwest, New Zealand and single-varietal work — treats the same reaction as the loss of the varietal aroma it is trying to bottle, and mills into sulphited or inert-gassed pomace to stop it. Neither is a mistake; they are different objectives applied to the same chemistry.
Done badly, milling shows up two stages later. Over-milled pomace produces a press run that stalls at low yield and a juice loaded with fine solids that will not settle, carrying starch and pectin into the ferment and reappearing later as haze. Under-milled pomace wastes fruit. Milling fruit that includes rotted material distributes the rot, and its patulin, through the entire batch rather than confining it to one apple — which is why sorting belongs before the mill and not after it. And a mill run hot and fast, with the pomace held warm in a hopper, will begin fermenting on the press floor, which is how acetic acid bacteria and vinegar flies get their start.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Fruit preparation
Maceration
Holding milled pomace before pressing so that phenolics, aroma precursors and pectin have time to move out of the solid tissue and into the juice.
Fruit preparation
Pomace conditioning
Letting milled pomace stand before it goes to the press so that it drains better, presses faster and gives more juice.
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.
Fruit preparation
Enzyme addition to pomace
Dosing pectin-degrading enzyme into milled pomace rather than into juice, to raise press yield and change how the cake drains.
Fermentation
Keeving
Forming a floating pectin gel that lifts nutrients and solids out of the juice, so that the ferment starves before it finishes and leaves natural sweetness behind.
Pressing
Pressing yield
The proportion of a fruit charge recovered as juice, and why a single headline figure for it is not a meaningful number.
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.
- What is keeving — Keeving is a technique for starving a ferment of nitrogen so that it stops before all the sugar is gone, leaving a naturally sweet cider. Pectin is made to gel and float as a brown cap, carrying nutrients and yeast out of the juice with it.
- What is pressing yield — Pressing yield is the proportion of fruit weight recovered as juice. It varies from under half on a poorly loaded basket press to around seventy per cent on a well-run rack-and-cloth or belt press.
- What is malic acid and why does it matter in cider — Malic acid is the acid of apples and supplies almost all the sharpness a cider has. It also sets pH, which decides how well sulphite works and how exposed the cider is to spoilage, so it does far more work than its taste suggests.
- How do i clear a cloudy cider
- 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.
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.
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.
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.
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.