Fermentation
Fermentation temperature control
Managing the temperature at which a ferment runs, which sets not only how fast it goes but which aromatics survive it and what the finished cider tastes of.
Also called Temperature management, Cool fermentation.
- Stage
- Fermentation
- Traditional in
- Pays d’Auge, Asturias, Somerset, Herefordshire and 1 more
- What it most changes
- Fruit character up
- Safety
- None recorded
What it is
Fermentation temperature control covers everything from a jacketed stainless tank on a glycol loop to the choice of which corner of an unheated building a barrel is stood in. Fermentation is exothermic, so a vessel left to itself runs warmer than its surroundings, and the larger the vessel the greater the difference — a small tub in a cold shed tracks ambient temperature closely, while a large tank generates and holds enough heat to raise itself substantially. Control means either removing that heat, adding heat to keep a cold ferment moving, or knowingly accepting the temperature the building provides and choosing yeast and timing to suit it.
Why it is used
- Temperature sets fermentation rate, and rate determines whether a tank is ready in weeks or occupies the cellar until spring — a scheduling constraint as much as a quality one.
- Volatile aromatics are lost with the escaping carbon dioxide, and a warm, vigorous ferment strips far more of them than a slow cool one, so temperature is the main lever on how much fruit aroma survives.
- Warm ferments increase the formation of higher alcohols, which at elevated levels read as harsh and solvent-like rather than fruity.
- At the cold end, a ferment can slow below the point at which the yeast remains active and stop with sugar remaining, which is a fault if unintended and the basis of several traditional styles if intended.
How it works
- Yeast metabolic rate rises with temperature up to the strain’s optimum and then falls sharply as membranes and enzymes are compromised, so the relationship between temperature and rate is not linear and the upper limit is abrupt.
- Acetate esters such as isoamyl acetate are both formed and hydrolysed enzymatically, and their retention in the finished cider depends on temperature and on how much carbon dioxide has swept through the liquid carrying them out.
- Higher-alcohol formation is tied to amino acid catabolism, which accelerates disproportionately at warm temperatures, so a hot ferment tends towards fusel character even where nitrogen was adequate.
- Ethanol toxicity to yeast increases as temperature rises, so a warm ferment that starts fast is also the ferment most likely to stall late, when alcohol is high and the yeast is already stressed.
- At low temperature the yeast maintains membrane fluidity by altering its lipid composition; strains that cannot do this well simply cease to divide and flocculate out, leaving unfermented sugar.
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 |
|---|---|---|
| Fruit character | Raises | A slower, cooler ferment evolves carbon dioxide gently, so fewer of the volatile esters and aldehydes that carry apple aroma are swept out of the liquid with the escaping gas. |
| Fermentation character | Either way | Warm ferments push amino acid catabolism towards higher alcohols and give a heavier, more solvent-inflected fermentation signature, while cool ferments favour retention of the lighter acetate esters. |
| Sweetness | Either way | A ferment held cold enough to slow the yeast towards dormancy may finish with sugar unfermented, which is the intended outcome in some traditions and a stuck ferment in others. |
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
Ethanol
The alcohol yeast makes from fruit sugar, which converts a perishable juice into a keepable drink and carries most of its aroma to the nose.
Higher alcohols
The group of larger alcohols yeast makes from amino acids, welcome as background complexity in trace and harsh and solvent-like in quantity.
Isoamyl acetate
The banana and pear-drop ester, made by yeast from isoamyl alcohol, and one of the clearest chemical signatures of a warm fermentation.
Isoamyl alcohol
The most abundant fusel alcohol in cider, made from leucine, and the direct precursor of the banana ester that defines warm-fermented styles.
Ethyl hexanoate
One of the most powerfully aromatic esters in cider, perceptible at a few micrograms per litre, contributing green apple and aniseed to the fruit complex.
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.
Acetaldehyde
The compound sitting one step short of ethanol, which smells of bruised apple and sherry, binds most of the sulphite added to a cider, and is the chemical signature of oxidation.
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 uvarum
A cold-tolerant relative of S. cerevisiae recovered from spontaneous cider and wine ferments, associated with low-temperature fermentation and higher glycerol.
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.
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
Temperature control: glycol, coils and a cold room
Cooling can be applied to the vessel — a glycol jacket or a coil in the liquid — or to the air around it, and for most small producers a cold room, an insulated container or simply a cold building is the cheaper and more reliable answer.
Heat exchangers and chilling the juice
A heat exchanger puts two liquids either side of a thin wall so heat crosses and the liquids do not mix; in a cider house the same machine chills warm press juice, holds a tank at temperature, and carries out flash pasteurisation.
Thermometers and temperature measurement
Temperature drives fermentation rate, yeast stress and the aromatic compounds that result, and the only reading that means anything is one taken in the liquid — not on the outside of the vessel and not in the room.
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.
Stuck fermentation
A fermentation that has stopped before the sugar is gone and will not restart, leaving a sweet, low-alcohol cider that is vulnerable to everything.
Sluggish fermentation
A fermentation that is still moving but far more slowly than it should, extending the period during which the cider is weak, sweet and exposed.
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.
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.
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.
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 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.
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.
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.
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.
Ice cider
Cider made from apple juice concentrated by freezing, fermented slowly and stopped while a large residual sugar remains, giving a dessert-strength drink of high acid and high sweetness.
Modern American cider
The dominant contemporary American category: cider from culinary and dessert apples, fermented clean, often carbonated and frequently flavoured, defined against the heritage sector rather than by any tradition.
Quebec ice cider
Ice cider made under Quebec’s reserved designation, which sets out how the juice may be concentrated, what may be added and what the finished product must contain.
Apple wine
A fermented apple drink made to wine strength, usually by raising the starting gravity, and presented and taxed as a wine rather than as a cider.
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.
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.
Ice perry
Perry made from pear juice concentrated by freezing, in which the fruit’s unfermentable sorbitol adds to the residual sweetness the arrested ferment leaves behind.
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.
Tasmanian cider
Cider from Tasmania, whose cool maritime climate and long apple-growing history give fruit with the acid that most Australian districts cannot hold.
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.
Scottish cider
Cider from Scotland, made in a cool maritime climate from dessert, culinary and cold-tolerant fruit, in a small sector built largely within recent decades.
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.
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.
2 separate analyses of fermentation temperature. They are shown as they were measured, in their own contexts, and are not averaged — the same fruit grown somewhere else can genuinely give a different number.
Fermentation temperature12.0–15.0 °C
Villaviciosa, Asturias, Spain, 2001–2002 · Unheated Asturian cellar, spontaneous fermentation · Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31
The cold end of the range cider is actually fermented at, and not a controlled temperature at all — it is whatever the building was. Recorded here so the deliberate 20 °C below has something to sit against.
Fermentation temperature20.0 °C
Ithaca, New York, United States, 2016 · Temperature-controlled room, held constant across every treatment in the experiment · Song, Gibney, Cheng, Liu and Peck, Frontiers in Microbiology 11:1264
A laboratory holding temperature, chosen so that nitrogen was the only variable. It is roughly the warm end of ordinary cider practice: fast, clean, and with more of the volatile aroma carried out of the vessel with the gas than a cellar ferment would lose.
The temperature a ferment was actually run at, which governs how much aroma is made and how much is blown off with the gas. Measured in degrees celsius.
More on fermentation temperature control
The most useful thing to understand about fermentation temperature is that a slow cool ferment is not a warm ferment played back at half speed. The two produce chemically different drinks. Carbon dioxide leaving the liquid carries volatile compounds with it, and the volume of gas is the same either way — but a ferment that releases it over four months loses far less aroma to stripping than one that releases it over ten days. Cool conditions also shift the balance of nitrogen metabolism away from higher alcohols and towards ester retention. Against that, cool ferments spend longer with sugar present and alcohol low, so the microbiological risk window is longer, and a strain unsuited to the temperature will simply stop.
The international divergence here is genuine and not merely a matter of scale. In Normandy and the English West Country the traditional ferment is a cool cellar ferment running over months through the winter, and the cidre of the Pays d’Auge in particular depends on a slow, nutrient-poor ferment that will not run to dryness. In Asturias the ferment takes place in large chestnut toneles in an unheated llagar, where the mass of the vessel and the building temperature between autumn and spring, rather than any equipment, set the profile of sidra natural. Modern plants in North America, Britain and elsewhere run temperature-controlled stainless with glycol jackets, holding a target band deliberately and finishing in weeks. None of these is a degraded version of another; each produces a recognisably different drink.
What a practitioner decides is really what they are willing to give up. Refrigerated control costs capital and energy and buys repeatability plus aromatic retention. An unheated building costs nothing and gives a ferment whose speed varies with the weather, which is fine if the yeast tolerates the low end and the schedule can absorb a slow spring. Done badly at the warm end, the cider arrives fusel-heavy, thin and stripped of fruit, and may still stall late from combined heat and ethanol stress. Done badly at the cold end, the yeast flocculates out with sugar remaining, and the maker then has a metastable cider that will restart when the cellar warms — which is dangerous if it has already been bottled.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Fermentation
Yeast selection
Choosing which cultured strain to pitch, on the basis of the temperature, nitrogen, alcohol and aroma behaviour that separates one commercial yeast from another.
Fermentation
Fermentation monitoring
Watching a running ferment through gravity, temperature, smell and surface behaviour, and reading the rate of change rather than any single figure.
Fermentation
Fermentation vessels
The container a cider ferments in — wood, stainless, plastic, glass or concrete — and how its permeability, thermal mass and resident microflora shape the result.
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.
Fermentation
Arrested fermentation
Deliberately halting a ferment while sugar remains, to obtain natural sweetness from the fruit rather than from an addition — and accepting the instability that follows.
Fermentation
Restarting a stuck fermentation
Diagnosing why a ferment has stopped with sugar remaining, then building an acclimatised starter and stepping the cider into it rather than pitching yeast into the problem.
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 long does cider take to ferment — A warm ferment with cultured yeast can finish in one to two weeks; a cool wild ferment in a cellar may take three months or more. Slow is not the same as stuck — the test is whether gravity is still falling.
- What yeast should i use for cider — CiderHQ does not recommend brands. The choice is between a neutral, reliable strain that lets the fruit show, an aromatic wine strain that adds its own esters, and no addition at all. Alcohol tolerance, cold tolerance and nitrogen demand are the properties worth comparing.
- How do i restart a stuck cider fermentation — Warm the batch gently, then build an active starter and acclimatise it to the cider in stages rather than pitching dry yeast straight in. Yeast dropped into a cold, alcoholic, nutrient-poor liquid usually dies without restarting anything.
- How do you stop cider from fermenting — By removing the yeast, by chilling, by filtering it out, by pasteurising, or by a combination — and in practice a home maker cannot reliably stop a ferment mid-way with chemicals alone. Sorbate prevents yeast multiplying but will not stop an active ferment.
- 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 should i ferment cider in — Anything inert, cleanable and closable: glass demijohns, food-grade plastic, stainless steel, or a wooden cask if you can keep it sound. Vessel shape and material change how much oxygen the cider sees and how fast it clears.
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.
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 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.
Yeast species associated with the spontaneous fermentation of cider
Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31 · peer-reviewed literature · passage verified 2026-08-24 · covers 2001–2002
SERIDA’s survey of what is actually growing in an Asturian cellar during a spontaneous ferment, across two harvests and two pressing technologies. Read in full from the author institution’s open repository (ria.asturias.es, handle 123456789/925) on 2026-08-24. Two things make it worth citing rather than summarising: it identifies its isolates molecularly rather than by colony appearance, and it publishes the analytical composition of the finished ciders alongside the microbiology, so a reader can see the organisms and the numbers they produced in the same paper. It also contradicts the textbook account of apiculate yeasts dying out early, which is why CiderHQ cites it on that point specifically.
Song, Gibney, Cheng, Liu and Peck, Frontiers in Microbiology 11:1264 · peer-reviewed literature · passage verified 2026-08-24 · covers 2016
Open access; read in full on 2026-08-24. This is the paper CiderHQ cites against the folk rule that low nitrogen causes sulphide and adding nutrient cures it. Two Saccharomyces strains fermented the same Cornell juice at three nitrogen levels: one strain produced no detectable hydrogen sulphide at any level, and in the strain that did, the middle nitrogen treatment produced the most — twice the low treatment and six times the high. A rule that is true on average is being applied to individual batches where it can be exactly backwards, and the correction is worth a page of its own.