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.
Known as Cuvage where it originates. Also called Cuvage, Pulp maceration, Skin contact.
- Stage
- Fruit preparation
- Traditional in
- Normandy, Pays d’Auge, Cotentin, Domfrontais and 1 more
- What it most changes
- Tannin up, astringency up
- Safety
- None recorded
What it is
Maceration is the deliberate holding of milled pomace, usually for some hours and occasionally overnight, between the mill and the press. In French practice it is cuvage, and it is a standard step rather than an option. During that hold the liquid phase sits in contact with ruptured cell walls, skin and seed-adjacent tissue, and compounds that were bound in the solid fraction diffuse into it: procyanidins and other phenolics, aroma precursors, potassium, and pectin. The juice that comes off a macerated pomace is measurably different in composition from juice pressed immediately, and the difference is large enough to change the style of the finished cider.
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
- Phenolics are concentrated in and just beneath the skin, and a short press run leaves much of them in the pomace; time in contact moves them into the juice.
- Softened, partly enzymatically broken-down pomace releases juice more readily, so maceration raises press yield as well as extraction.
- It liberates pectin and the fruit’s native pectin methylesterase into the juice, which is a precondition for keeving.
- It gives the maker a lever on tannin intensity that does not involve changing the blend of fruit.
How it works
- Diffusion drives the process: once cells are ruptured, soluble compounds move down a concentration gradient from the solid tissue into the surrounding liquid until the two phases approach equilibrium.
- Endogenous enzymes continue working during the hold — pectic enzymes loosen the middle lamella so cell walls collapse further, and polyphenol oxidase converts phenolics to quinones wherever oxygen reaches them.
- Procyanidins of different chain length extract at different rates: the smaller, more bitter fractions move quickly, the larger, more astringent polymers more slowly, so contact time changes the balance between bitterness and astringency rather than simply raising both.
- Temperature accelerates all of it, which is why a cool cellar maceration and a warm press-house maceration of identical length give different juice.
- Wild yeast and bacteria on the fruit are also being incubated in a warm sugar-rich medium, so the same hold that extracts phenolics is a microbial opportunity.
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 |
|---|---|---|
| Tannin | Raises | Extended contact moves procyanidin from the solid tissue, where most of it sits, into the liquid phase that becomes juice. |
| Astringency | Raises | The larger procyanidin polymers extract more slowly than the small ones, so a long maceration shifts the phenolic profile towards the fractions that bind salivary protein. |
| Bitterness | Raises | Lower-molecular-weight procyanidins and phloridzin move into the juice early in the hold and are the fraction perceived as bitter rather than drying. |
| Body | Raises | Pectin and other colloidal material released from the cell walls raise the viscosity and the mid-palate weight of the juice. |
| Fruit character | Either way | Aroma precursors are extracted, but where oxygen reaches the pomace the same hold destroys fresh volatile esters, so the direction depends on how the maceration is protected. |
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
Procyanidins
The condensed tannins of cider fruit, whose chain length — not their quantity — decides whether the mouth registers bitterness or astringency.
Epicatechin
The flavan-3-ol that apple procyanidins are almost entirely built from, and the most bitter of the phenolic monomers a cider contains.
Catechin
The minor flavan-3-ol of apple, present largely as the terminal unit of procyanidin chains, and consequently a useful analytical handle on chain length.
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.
Hydroxycinnamic acids
The family of small phenolic acids that browns a juice, and whose release from their esters supplies the raw material for every volatile phenol a cider can develop.
Phloridzin
A dihydrochalcone found in apple and essentially nowhere else, which makes it both a contributor to bitterness and the standard chemical proof that a juice is apple juice.
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.
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.
Terpenes
The floral and citrus aroma compounds that apples carry only in traces and that hops, spices and botanicals bring in quantity, which is why a hopped cider smells so different from an unhopped one.
Organisms involved
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.
Kloeckera apiculata
The anamorph name for Hanseniaspora uvarum, still in wide use in cider writing, and often used loosely as a collective term for all apiculate yeasts.
Metschnikowia pulcherrima
An early-succession yeast that suppresses competitors by locking up iron, and is used commercially as a controlled non-Saccharomyces partner rather than as a fermenter.
Acetobacter aceti
An acetic acid bacterium that oxidises ethanol to acetic acid wherever cider meets air, and the organism behind most volatile acidity in cider.
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
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.
The pomace belt, and what becomes of pomace
Pressed cake leaves a modern press on a belt or an auger and goes to stock feed, to land, to anaerobic digestion or to pectin extraction; on a farm it usually goes to cattle or back on the orchard, and neither is as simple as it is usually described.
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.
Excessive astringency
A drying, roughening, mouth-puckering sensation that outstays its welcome, produced by larger phenolic polymers precipitating salivary proteins.
Excessive bitterness
Bitterness that dominates the palate rather than supporting it, usually from a blend weighted too heavily towards high-tannin fruit or extracted too hard.
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.
Acetification
The active conversion of a cider’s ethanol into acetic acid by acetic acid bacteria at an air interface — the process, running in the vessel, that produces volatile acidity.
Ethyl acetate taint
A solvent, nail-varnish or pear-drop aroma from ethyl acetate, the most abundant ester in cider and the one that turns from lift to fault over a narrow range.
Vinegar fly contamination
Small flies carrying acetic acid bacteria and spoilage yeasts directly into juice and cider, and depositing them wherever they land.
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.
Cidre de Normandie
Protected Normandy cider made from the region’s bitter and bittersweet fruit, characteristically low in alcohol, sweet-edged and lightly sparkling.
Cidre Pays d’Auge
The controlled appellation cider of the Pays d’Auge in Calvados, made by keeving from bitter Norman fruit and bottle-conditioned to a low alcohol and a high residual sugar.
Keeved cider
Cider clarified before fermentation by a pectin gel that strips nutrients from the juice, producing a slow ferment that stops naturally with sugar still in solution.
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.
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.
Poiré
French perry, made chiefly in southern Normandy and Maine from local perry pears, characteristically sweet, low in alcohol and firmly sparkling.
Poiré Domfront
The controlled appellation perry of the Domfrontais in southern Normandy, made predominantly from the Plant de Blanc pear on high-standard trees and finished sweet, low in alcohol and bottle-conditioned.
Cidre de Bretagne
Protected Breton cider, built on a distinct western fruit inventory and generally drier, lighter and more acid-led than its Norman counterpart.
Cidre fermier
Farm-made French cider, pressed and fermented on the holding that grew the fruit, sold as an agricultural product of that farm rather than as a regional or industrial one.
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.
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.
Total phenolics460.0–3490.0 mg/L
Gloucestershire, Herefordshire, Worcestershire and neighbouring counties, England, 2022–2024 · Sum of the true tannin and phenolic acid fractions across 34 single-variety perry pear juices, measured as separate fractions rather than as one permanganate total. · Cider and Perry Academy (Peter Mitchell)
Recorded on this page as the size of the prize and of the risk. Maceration extracts more of this material into the juice, and oxidation consumes it — the same phenolic pool, moved in opposite directions by two processes that begin at the same moment the mill breaks the cells.
All phenolic compounds together, usually reported as gallic acid equivalents. Measured in milligrams per litre.
More on maceration
Maceration is the clearest example of a step that English-language cider writing tends to treat as optional and French practice treats as structural. In Normandy and the Domfrontais the milled marc is normally held before pressing, and the hold is understood as part of how the juice is made rather than as a delay before the real work. The reason is the fruit. French bittersweet and bitter varieties carry their value in the phenolic fraction, and that fraction is not evenly distributed through the apple: it is concentrated in the skin and the tissue immediately below it. Press immediately and a large part of what those cultivars were grown for stays in the pomace and goes to the stock heap.
The chemistry is a diffusion problem complicated by enzymes. Once milling has ruptured the cells, soluble phenolics move into the liquid phase down a concentration gradient, and they do not all move at the same speed. Monomeric and short-chain procyanidins — the fraction the palate reads as bitter — extract quickly. The longer polymers, which bind salivary proteins and are read as drying astringency, come out more slowly and continue to do so for hours. This is why maceration length is a genuine sensory lever rather than a simple volume control: a short hold shifts the juice towards bitterness, a long one towards astringency and weight. At the same time pectic enzymes are loosening the cell wall matrix, which is why macerated pomace also presses more freely and yields more.
The same hold is a precondition for keeving, and this is not incidental. Keeving depends on the fruit’s own pectin methylesterase acting on pectin that has been liberated from the cell wall into the juice. A pomace pressed immediately gives a juice comparatively poor in both, and the chapeau brun either fails to form or forms too thinly to lift the solids. Conversely, a commercial pectinase preparation added to the pomace does the opposite of what a keeve needs — it depolymerises the pectin backbone rather than de-esterifying it — which is why enzyme addition and keeving are mutually exclusive routes from the same mill.
What goes wrong is oxidation and microbiology, and the two arrive together. Milled pomace held open to air is a very large surface area of sugar-rich, enzyme-rich tissue at ambient temperature. Polyphenol oxidase browns it; acetic acid bacteria and Hanseniaspora find it immediately; vinegar flies find it shortly afterwards; and a hold that was intended to last a few hours in a cool cellar becomes, in a warm press house, the start of an uncontrolled ferment with ethyl acetate already forming. Long macerations also over-extract: a juice can be pushed past the point at which any amount of residual sugar or maturation will balance it, and there is no way back from a cider that is simply too astringent to drink. Practitioners who macerate seriously do it cold, keep the pomace covered or gassed, and stop on taste rather than on the clock.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
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.
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.
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.
Juice treatment
Juice oxidation
The enzymic browning that begins the moment apple juice meets air, which some traditions deliberately allow and others suppress.
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.
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.
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.
- How are apples milled for cider
- 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.
- Why does my cider taste like vinegar — Acetic acid bacteria have reached the cider and, given air, are converting its alcohol into acetic acid. The cause is almost always oxygen — an unfilled vessel, a leaking bung, or a slow transfer.
- 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.
Institut Français des Productions Cidricoles (IFPC)
IFPC · research institute · retrieved 2026-08-24
The French technical institute for cider production. The authority for the French cultivar classification families, for keeving as an industrial process, and for the pectin and nitrogen chemistry that keeving depends on.
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.
Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE)
INRAE · research institute · retrieved 2026-08-24
French national agricultural research. Its Angers programme produced much of the published work on apple procyanidin chain length and on the relationship between polymer size, bitterness and astringency.
Peer-reviewed literature on apple phenolics and cider sensory perception
Various journals · peer-reviewed literature · registered as competent for this subject
Registered as a class rather than as one paper, because the mechanisms CiderHQ describes — tannin chain length driving the split between bitterness and astringency, salivary protein precipitation, enzymatic browning — are established across many studies rather than resting on any single one. Individual papers are cited where a specific number is quoted.