Concentration and speciality
Ice concentration
Freezing pressed juice and drawing off the unfrozen fraction, so that water is removed as ice and everything else in the juice is left behind more concentrated.
Known as Cryoconcentration where it originates. Also called Cryoconcentration, Freeze concentration.
- Stage
- Concentration and speciality
- Traditional in
- Quebec, Vermont, New England, New York State
- What it most changes
- Sweetness up, acidity up
- Safety
- Carries a safety consideration — see below
A must this rich in sugar can leave a very large fermentable residue in the finished drink, so a bottled ice cider that has not been stabilised or sterile-filtered is capable of restarting in the bottle and generating pressure a still-wine bottle is not built to hold. Producers verify microbial stability before packaging rather than relying on the ferment having stopped once.
What it is
Ice concentration removes water from apple or pear juice by freezing it out rather than by boiling it off. When a sugar solution is cooled below its freezing point, the crystals that form are close to pure ice; the sugars, acids, phenolics and aroma compounds are excluded from the crystal lattice and remain in the shrinking volume of unfrozen liquid. Separating that liquid from the ice gives a juice of much higher sugar concentration than the fruit ever produced. It is the defining step of ice cider as practised in Quebec, and of ice perry, and it is the reason those drinks can carry both high residual sugar and substantial alcohol without anything being added to them.
Described in full
- Shape
- A chain of eight stages top to bottom — perry pears, sweating, milling, pressing, juice, fermentation, maturation, bottling — with a separate branch leaving the juice stage to the right and rejoining at bottling.
- Sweating
- A stage cider does not always need. Perry pears are commonly held after picking until the flesh softens, because most are unpressable when picked hard and lose acid and gain sugar as they sit.
- The sorbitol branch
- Pear juice carries sorbitol, a sugar alcohol. It is sweet on the tongue and Saccharomyces cannot ferment it, so it passes through the whole ferment untouched and arrives in the bottle intact.
- What that means for the finish
- A perry can therefore taste distinctly sweet while being fully fermented and carrying no fermentable sugar at all. The same drink is dry by measurement and sweet by taste.
- Pressing
- Pear pomace is more slippery than apple pomace and can slump in a press, which is one reason rack-and-cloth and bladder presses are favoured for perry.
- Bottling
- Because the residual sweetness is unfermentable, a bottled perry is more stable against refermentation than a back-sweetened cider carrying the same perceived sweetness.
Why it is used
- It raises the sugar concentration of the juice far above what apples achieve on the tree, which is what makes a naturally sweet, comparatively strong drink possible without added sugar.
- It concentrates acid and phenolics along with the sugar, so the resulting drink retains the acid structure needed to carry that sweetness rather than tasting merely syrupy.
- Unlike thermal concentration it involves no heat, so no cooked or caramelised character is introduced and the volatile aroma fraction survives.
- In cold-winter regions it can be done with ambient cold, which is how the practice began and why it is regionally specific rather than universal.
How it works
- Freezing a solution is a fractional crystallisation: the solid phase forms almost pure, and solutes are rejected into the remaining liquid, so the unfrozen fraction becomes progressively more concentrated as more ice forms.
- The concentrated liquid is separated from the ice by draining, by centrifugal separation, or in the traditional outdoor method simply by collecting what has not frozen at the bottom of the vessel.
- Freezing-point depression works against the process: the more concentrated the residual liquid becomes, the lower the temperature required to freeze any more water out of it, which sets a practical ceiling on the concentration achievable.
- The resulting must exerts high osmotic pressure on yeast. Fermentation is slow and stressed, glycerol production rises, and the ferment characteristically stops of its own accord with a large amount of sugar unfermented — which is where the sweetness of the finished drink comes from.
- Because acid concentrates in step with sugar, the balance of the finished drink is largely set by the acid of the starting fruit rather than by anything done later.
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 |
|---|---|---|
| Sweetness | Raises | Concentration puts far more sugar into the must than yeast can ferment before osmotic and ethanol stress halt them, so a large residual fraction survives into the finished drink. |
| Acidity | Raises | Malic acid is excluded from the ice lattice along with the sugar, so it concentrates in the same proportion and the finished drink is markedly more acidic than ordinary cider. |
| Body | Raises | High residual sugar together with the elevated glycerol produced by osmotically stressed yeast gives a viscosity and mid-palate weight ordinary cider does not have. |
| Alcohol | Raises | Even a ferment that stops early converts far more sugar than a normal juice contains, so the finished drink sits well above the strength of table cider. |
| Fruit character | Raises | No heat is applied, so aroma compounds concentrate alongside the sugar instead of being driven off as they would be in thermal concentration. |
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
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.
Sucrose
The disaccharide of apple juice and the sugar most often added to it, split into glucose and fructose by the yeast’s own invertase before any of it is fermented.
Sorbitol
The unfermentable sugar alcohol that pears carry in quantity and apples carry only in trace, and the single reason a fully fermented perry keeps a sweetness a fully fermented cider cannot.
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.
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.
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.
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.
Yeast-assimilable nitrogen
The nitrogen a yeast can actually use, which apple juice is chronically short of — the shortage behind both stuck fermentations and rotten-egg aromas, and the shortage keeving deliberately makes worse.
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.
Saccharomyces uvarum
A cold-tolerant relative of S. cerevisiae recovered from spontaneous cider and wine ferments, associated with low-temperature fermentation and higher glycerol.
Zygosaccharomyces bailii
A preservative-resistant spoilage yeast that refements sweetened cider and juice, and one of very few organisms able to grow through sorbate and benzoate at cider strength.
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 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.
Excessive acidity
Acidity high enough to dominate everything else, leaving a cider that is thin, hard and sour rather than fresh.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
Acetaldehyde excess
A bruised-apple, green-nut or sherry aroma from acetaldehyde, produced by oxidation, by film yeast, or left behind by a ferment that was interrupted.
Cooked character
A stewed-apple, caramel or jam-like character from heat applied to juice or cider, most often through pasteurisation or hot storage.
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.
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.
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.
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.
Sweet cider
Cider in which sugar is the leading sensation, whether retained from an arrested fermentation, added after it, or produced by keeving.
More on ice concentration
Ice cider is a young category with an old physical principle behind it. Freeze concentration is fractional crystallisation: as a sugar solution is cooled below its freezing point, water molecules assemble into a crystal lattice that will not accommodate sugars, acids or phenolics, and everything the ice will not take is pushed into the diminishing volume of liquid that remains. Drain that liquid off and you have removed water without removing anything else and without applying any heat. Quebec producers formalised the technique into a commercial category from the late twentieth century onwards, and the province’s regulatory framework distinguishes it from concentration by evaporation or by added concentrate — the concentration must come from cold.
Two distinct routes reach the same place, and conflating them is the commonest error in writing about the category. In cryoconcentration, which is this process, sound fruit is pressed in autumn and the juice is then frozen — outdoors in the traditional method, in a chamber in the industrial one — and the unfrozen concentrated fraction collected. In cryoextraction, the fruit itself is left to freeze on the tree or in the orchard and is pressed frozen or part-thawed, so the concentration happens inside the apple and the press does the separating. Cryoextraction gives lower yields and demands robust equipment; cryoconcentration is more controllable and is the more common commercial route. Quebec’s standard recognises both, and some producers use each for different lots.
The fermentation that follows is unlike any other in cider. A must at this sugar concentration exerts osmotic pressure that dehydrates yeast cells, and the yeast responds by accumulating glycerol as a compatible solute — one reason the finished drink is viscous. Fermentation is slow, often taking months at low temperature, and it characteristically stops while a great deal of sugar remains, held up by the combination of osmotic stress, accumulating ethanol and exhausted nitrogen. That arrest is not a failure; it is the mechanism by which the drink acquires its sweetness. The maker’s real decision is where to let it stop, because every additional gram of sugar fermented is both a gain in alcohol and a loss of the sweetness that balances the concentrated acid.
What can go wrong is mostly a matter of balance and of stability. Fruit chosen for sugar alone gives a concentrate that is cloying, because acid was the component that was going to make the sweetness legible; producers accordingly select for high-acid fruit, and the classic Quebec practice of blending in sharp cultivars exists for exactly this reason. Concentrating juice from fruit that was not sound concentrates its faults just as efficiently as its sugar. And the finished drink is a metastable object: a large fermentable reserve sitting with a viable, if exhausted, yeast population. Bottled without stabilisation it can restart, which is a pressure problem as well as a quality one. Ice perry raises an additional wrinkle, since much of the sweetness a pear carries is sorbitol, which yeast largely cannot ferment — the drink is sweet for two reasons at once, and only one of them is under the maker’s control.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Concentration and speciality
Cryoextraction
Milling and pressing fruit that has frozen on the tree or in store, so the ice stays behind in the pomace and only concentrated juice runs from the press.
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.
Blending
Back-sweetening
Adding sugar, juice or concentrate to a cider that has fermented dry — a straightforward adjustment that leaves the drink microbiologically unstable until something is done about it.
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.
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.
Packaging
Bottling
Transferring finished cider into glass, where the dominant variable is how much oxygen the liquid picks up in the few seconds it takes to fill and close each bottle.
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.
- What temperature should cider ferment at — Most cider is fermented cool, commonly between about 12 and 18 °C. Cooler ferments keep more fruit aroma and run slower; above the low twenties the cider tends towards hot, solvent-like higher alcohols.
- How do i make my cider sweeter
- 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.
- How many calories are in cider — Roughly 40 to 60 kcal per 100 ml for most ciders, so a UK pint falls somewhere around 200 to 250 kcal. Alcohol contributes about 7 kcal per gram and residual sugar about 4, so both strength and sweetness matter.
- 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.
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.
University of Vermont cider research
University of Vermont Extension · university · retrieved 2026-08-24
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 alcoholic beverage labelling requirements
Canadian Food Inspection Agency · regulator · retrieved 2026-08-24