Maturation
Lees ageing
Deliberately holding a cider or perry on its fine yeast deposit so that autolysing cells release material that changes texture and foam behaviour.
Known as sur lie where it originates. Also called Sur lie maturation, Lees contact.
- Stage
- Maturation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Body up, astringency down
- Safety
- None recorded
What it is
Lees ageing is the choice not to rack. Once the coarse deposit is gone and the cider is sitting on a fine, light layer of spent yeast, the maker leaves it there for months rather than weeks, occasionally stirring the deposit back into suspension to speed the exchange. The cells are dead or dying, and as their walls break down they give up polysaccharides, peptides and amino acids into the cider. It is a texture technique rather than a flavour-addition technique: what changes most is the way the drink feels and how its bubbles behave, not what it smells of.
Why it is used
- The polysaccharide material released by autolysing yeast, mannoproteins in particular, gives a rounder and less angular impression in the mouth in a drink that has little residual sugar to do that job.
- In sparkling cider and perry made by a bottle-fermented method, the same material stabilises foam, so bubbles persist as a fine, durable mousse rather than collapsing quickly.
- Mannoproteins bind to condensed tannins and to protein, which softens the perception of astringency and reduces the tendency of a cider to throw a haze later.
- For a producer working without additives, extended lees contact is one of the few ways of building perceived weight into a dry cider without back-sweetening it.
How it works
- Yeast autolysis is enzymatic self-digestion: once the cell dies its own proteases and glucanases break down the cell contents and then the cell wall, releasing mannoproteins, beta-glucan fragments, peptides and free amino acids into the surrounding liquid.
- The released mannoproteins are surface-active, so they concentrate at the gas-liquid interface of a rising bubble and slow the drainage of liquid from the bubble film, which is what makes a mousse persist.
- The same colloids form complexes with condensed tannin, removing some of the tannin fraction that would otherwise bind salivary proteins and register as astringency.
- A deep, undisturbed bed of lees becomes strongly reducing, and yeast under that stress liberates hydrogen sulphide; periodically rousing the deposit keeps the layer shallow and the exchange even.
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 | Raises | Yeast-derived polysaccharides remain dissolved in the finished cider and raise its colloidal load, which reads as weight and viscosity even at low residual sugar. |
| Astringency | Lowers | Mannoproteins complex with condensed tannins and take part of the tannin fraction out of contention for binding salivary proteins. |
| Carbonation | Preserves | The gas volume is unchanged, but surface-active yeast material slows film drainage in the bubble wall so the same carbonation is expressed as a longer-lasting mousse. |
| Fermentation character | Raises | Autolysis releases the peptides and nitrogen compounds behind bready and yeasty aromas, which build steadily as long as contact continues. |
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
Amino acids
The largest usable nitrogen fraction in apple juice, and the raw material from which yeast builds both its own protein and most of the aroma compounds a cider carries.
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Glycerol
A syrupy three-carbon alcohol yeast produces as a side reaction of fermentation, which adds weight to a dry cider and is the raw material for one of its more obscure faults.
Hydrogen sulphide
The rotten-egg gas a nitrogen-starved yeast produces, detectable at concentrations too small to measure easily, and removable only if it is caught before it becomes something worse.
Mercaptans
What hydrogen sulphide becomes if it is left alone: onion, garlic and rubber notes that are far harder to remove than the gas they came from.
Carbon dioxide
The other product of fermentation, which protects a cider from air while it is being made and, dissolved in the finished drink, changes both its texture and its perceived acidity.
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.
Saccharomyces bayanus
A name applied both to a hybrid Saccharomyces lineage and, loosely, to a whole class of commercial high-alcohol yeasts, and one of the least stable names in fermentation microbiology.
Brettanomyces anomalus
The second Brettanomyces species regularly recovered from cider and beer, less studied than B. bruxellensis but capable of the same phenolic chemistry.
What it is done with
Stainless steel tanks
Stainless steel is inert, effectively impermeable to oxygen, and the only common vessel material that can genuinely be cleaned and sanitised — which is why it displaced wood almost completely in commercial cider making.
Drawing a sample without spoiling the batch
Every sample is a small hole made in the protection around a batch: something goes in, air goes in with it, and cider comes out — so the technique is about drawing a representative sample while putting nothing back and letting in as little air as possible.
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.
Reduction
A closed, stale, slightly sulphurous character in cider held under strongly oxygen-free conditions, sometimes clearing with air and sometimes not.
Hydrogen sulphide
A rotten-egg or drain smell from hydrogen sulphide produced by stressed yeast, usually the first visible consequence of a nitrogen-short juice.
Mercaptan taint
Onion, garlic, burnt rubber and cooked-cabbage aromas from thiols and disulphides formed when hydrogen sulphide is left in cider long enough to react onwards.
Excessive sediment
More deposit in the bottle or vessel than the presentation intends, ranging from a normal conditioning yeast layer to a loose sludge that clouds every pour.
Brettanomyces character
Farmyard, horse-blanket, smoky and sticking-plaster aromas from Brettanomyces yeast converting hydroxycinnamic acids into volatile phenols.
Excess diacetyl
A butter, butterscotch or popcorn character from diacetyl, produced by lactic acid bacteria metabolising citric acid, and by yeast under stress.
Excessive astringency
A drying, roughening, mouth-puckering sensation that outstays its welcome, produced by larger phenolic polymers precipitating salivary proteins.
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.
Lactic off-flavours
Sauerkraut, sour milk, silage or cheesy notes from lactic acid bacteria working on sugars and other substrates rather than on malic acid alone.
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.
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.
Sparkling cider
Cider carrying enough dissolved carbon dioxide to produce a persistent bubble, by bottle fermentation, tank fermentation or injection.
Bottle-conditioned cider
Cider that completes a fermentation inside its sealed bottle, generating its own carbonation and, in most cases, leaving a yeast deposit behind.
Sparkling perry
Perry carrying a persistent bubble, a presentation that suits pear’s aromatics and residual sorbitol and has a documented history going back to the seventeenth century.
Bottle-conditioned perry
Perry that completes its fermentation in the sealed bottle, generating carbonation and lees character while the fruit’s sorbitol keeps a sweetness the yeast cannot remove.
Dry cider
Cider fermented out or finished so that little fermentable sugar remains, leaving acid, tannin and alcohol to carry the palate.
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.
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.
Wild-fermented cider
Cider fermented by the yeast population already present on the fruit and in the cellar, without an added cultured strain.
Barrel-aged cider
Cider matured in wood, where slow oxygen ingress, extraction from the staves and the barrel’s resident microflora all change the finished drink.
Cidre brut
The dry tier of the French cider scale, defined since 2025 by a density no greater than 1.016 with an acquired strength of at least 3.5% vol — correspondingly more of the juice’s sugar converted to alcohol.
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.
Unfiltered cider
Cider packaged without filtration, retaining suspended yeast and fine solids and the body and aroma that come with them.
Vintage cider
Cider from the fruit of a single named harvest, made and sold as an expression of that season rather than of a house style.
More on lees ageing
The chemistry is borrowed wholesale from sparkling wine, and it transfers well because the organism is the same. When a Saccharomyces cell dies its own hydrolytic enzymes dismantle it from the inside, a process that takes months rather than days at cellar temperature. The cell wall is the last thing to go and it is the interesting part: it is largely mannoprotein, a mannose polysaccharide with a protein backbone, and once liberated it stays in solution and behaves as a protective colloid. That is the whole mechanism behind the three benefits usually claimed — a fuller mouthfeel, a more persistent bead, and a less astringent finish — and it is also why the effect builds slowly and cannot be rushed by any means other than raising the surface area of yeast in contact with the liquid.
Practice divides fairly sharply along the line between sparkling and still. In traditional-method sparkling cider and perry, lees ageing is not an optional refinement but the default: the second fermentation happens in the sealed bottle, the yeast has nowhere to go, and the maker is choosing how many months or years to leave it there before disgorging. In still farmhouse cider it is much less usual. West Country and Norman practice has historically leaned the other way, racking off the deposit to keep the ferment slow and the cider clean, and a farmhouse maker who leaves cider sitting on lees for a year is more often doing so because the cask has not been touched than as a designed intervention. Some modern producers, particularly in North America and among those making dry, low-tannin ciders from dessert and culinary fruit, have adopted deliberate sur lie handling precisely because their base material lacks the tannin and body that a bittersweet blend would supply.
What goes wrong is reduction. Yeast buried in a thick, anaerobic bed falls back on sulphur-bearing amino acids and gives off hydrogen sulphide, and a cider that smelt clean at racking can turn eggy over a few weeks under a deposit that was left too deep. Caught early, a splash racking usually clears it. Left, the sulphide reacts with ethanol and with other cider components to form mercaptans and disulphides, which smell of drains and burnt rubber, do not blow off, and are not fixable in any way available to a small producer. The judgement calls are how thick the deposit is, how often to rouse it, and — for a cider with any Brettanomyces present — whether extended lees contact in a warm cellar is simply an invitation to a slow spoilage ferment on the sugars that autolysis makes available.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
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.
Carbonation
Traditional method
A second fermentation in the bottle the cider will be sold in, followed by riddling the deposit into the neck and expelling it, so the drink is both bottle-fermented and clear.
Carbonation
Bottle conditioning
Carbonating cider by letting a second fermentation finish inside the sealed bottle, so the gas is generated where it is going to stay.
Fermentation
Secondary fermentation
Any fermentative event that follows the primary ferment — residual sugar refermenting, a deliberate second alcoholic fermentation, or the malolactic conversion of the maturation phase.
Carbonation
Transfer method
Fermenting in bottle for the character, then emptying the bottles under counter-pressure into a tank, filtering and refilling to remove the deposit without riddling.
Maturation
Tank maturation
Resting cider in stainless steel or a lined vessel, where the point of the container is that it contributes nothing and admits almost no oxygen.
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 is sparkling cider made
- 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.
- What should i know about stainless steel fermentation tanks — A stainless tank is a welded vessel, usually cylindrical, in an austenitic stainless grade chosen for corrosion resistance in acidic, chloride-containing conditions. It contributes nothing to the cider and lets no oxygen in.
- How do i get rid of the sulphur smell in my cider — Racking with a little splashing usually blows off free hydrogen sulphide while it is still fresh. Once it has reacted into mercaptans the smell becomes rubbery and no longer responds to aeration.
- How do you pour bottle conditioned cider — Stand the bottle upright for a day, chill it, and pour in one continuous movement, stopping when the sediment reaches the shoulder. Some traditions deliberately rouse the sediment instead, and both are defensible.
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.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.
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.