Fermentation
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
Also called Pitched fermentation, Cultured yeast fermentation.
- Stage
- Fermentation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Fruit character down, oxidative character down
- Safety
- None recorded
What it is
Inoculated fermentation means adding a deliberately chosen yeast — almost always a strain of Saccharomyces cerevisiae, supplied as active dried yeast or as a liquid culture — to juice in sufficient numbers that it dominates from the outset. The juice may or may not have been sulphited first; sulphiting knocks back the resident population and makes domination easier, but a heavy pitch into untreated juice will usually win on numbers alone. The point is not sterility. It is that the maker knows which organism is doing the fermenting, and therefore has some claim to knowing in advance how the ferment will behave and roughly what it will taste of.
Why it is used
- It makes fermentation kinetics broadly predictable, so a producer filling tanks week after week can plan racking, vessel turnaround and packaging rather than waiting on a ferment that may or may not start.
- A characterised strain has a documented ester and sulphur profile, which lets a maker aim at a house style instead of accepting whatever the season’s microflora delivers.
- A rapid, dominant Saccharomyces population shortens the window during which spoilage organisms have sugar and low alcohol to exploit, reducing the risk of volatile acidity and ethyl acetate.
- For a second fermentation in bottle or tank, a known strain that tolerates ethanol and flocculates tightly is a practical requirement, not a preference.
How it works
- Pitching at a high enough cell count means the added strain reaches the exponential phase before the resident yeasts and bacteria do, and its ethanol output then suppresses them.
- Dried yeast is rehydrated before pitching so that the cells repair their membranes in water rather than in sugar-rich juice; pitched dry into juice, a large fraction of the population is lost to osmotic shock.
- Because a pure, fast ferment consumes assimilable nitrogen quickly and steadily, nutrient status becomes the limiting variable rather than yeast count — nitrogen exhaustion mid-ferment is the usual cause of hydrogen sulphide in an inoculated cider.
- Suppressing the early non-Saccharomyces population removes the acetate esters and the glycerol contribution those yeasts make, which is why an inoculated ferment of the same juice smells narrower than a spontaneous one.
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 |
|---|---|---|
| Fermentation character | Either way | A single strain expresses its own ester and higher-alcohol pattern consistently, so the fermentation signature becomes a chosen one rather than an emergent one; whether that reads as more or less fermentative depends entirely on the strain. |
| Fruit character | Lowers | The early apiculate yeasts that contribute much of the acetate-ester fruitiness in a spontaneous ferment never reach a meaningful population when a heavy Saccharomyces pitch dominates from hour one. |
| Oxidative character | Lowers | A vigorous ferment reaching full speed quickly blankets the juice in carbon dioxide and shortens the period during which dissolved oxygen and acetic acid bacteria can act. |
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Choosing a fermentation vessel: material and shape
Vessel material decides oxygen ingress, flavour contribution and how well the thing can be cleaned; vessel shape decides temperature behaviour, lees depth and how much surface the cider presents to whatever is above it.
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.
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.
Nitrogen deficiency character
The set of characters a nitrogen-starved fermentation produces together — sulphide, a stalled or dragging ferment, harsh higher alcohols and a thin, hard cider.
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.
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.
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.
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.
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.
Sparkling cider
Cider carrying enough dissolved carbon dioxide to produce a persistent bubble, by bottle fermentation, tank fermentation or injection.
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.
Herefordshire cider
Cider from the county with England’s largest cider orchard area, protected as a geographical indication and spanning farmhouse practice, bottle-fermented cider and industrial-scale production.
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.
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.
Graff
A hybrid of cider and beer, fermented from apple juice with malt and usually hops, originating in North American homebrewing rather than in any orchard tradition.
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.
More on inoculated fermentation
The honest case for inoculation is a case about risk and repeatability, not about quality. A pitched ferment removes one large unknown from a process that still contains many. The maker knows the organism, knows its temperature range and ethanol tolerance, and can therefore reason about what a slowing ferment means. The honest case against it is that the resident microflora of a good orchard is not merely a hazard to be eliminated: the Hanseniaspora, Metschnikowia and Torulaspora species that dominate the first days of a spontaneous ferment produce acetate esters, glycerol and a broadening of aroma that a pure culture does not reproduce. Inoculation buys predictability by spending complexity, and a maker should know which of the two they are short of.
Practice diverges sharply and along lines that are cultural as much as technical. In Asturias, sidra natural is overwhelmingly a spontaneous ferment in the llagar, and inoculation is not part of the tradition; in Normandy, the AOC specifications for cidre restrict what may be added and the keeving-based sweet ciders of the Pays d’Auge depend on a slow, nutrient-starved ferment that a vigorous pitched yeast would simply drive to dryness. English West Country farmhouse practice has historically been spontaneous, though many mid-sized English producers now inoculate. Most large-volume production worldwide inoculates as a matter of course, and most modern North American cideries do too, often with wine or champagne strains chosen from a catalogue rather than isolated from fruit.
What a practitioner actually decides is threefold: whether to sulphite before pitching, which strain to use, and how to feed it. The first two get most of the attention and the third causes most of the failures. A pure culture driving hard through a low-nitrogen apple juice — and apple juice is frequently low in assimilable nitrogen compared with grape must — will strip the available nitrogen well before the sugar is gone, and a yeast in that position breaks down sulphur-bearing amino acids for what nitrogen they hold, liberating hydrogen sulphide as a by-product. The characteristic failure of an inoculated ferment is not a stuck one but a reduced, sulphurous one, produced by exactly the vigour that made inoculation attractive. Staged nutrient additions and early oxygen are the mitigations; simply pitching more yeast is not.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Fermentation
Wild fermentation
Letting the microflora already present on the fruit and in the press house carry the ferment, in a succession rather than as a single organism.
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
Yeast rehydration
Reviving active dried yeast in warm water before pitching, so the cells restore their membranes without being ruptured by the sugar concentration of juice.
Fermentation
Yeast nutrition
What a fermenting yeast population actually needs from apple juice — assimilable nitrogen, vitamins and membrane lipids — and what goes wrong when the juice cannot supply it.
Juice treatment
Sulphiting
Adding sulphur dioxide to juice to suppress spoilage organisms and oxidative browning, at a level that only means anything once the juice pH is known.
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.
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 does cider ferment — Yeast consumes the sugar in apple juice and produces roughly equal masses of ethanol and carbon dioxide, along with the esters and higher alcohols that give cider much of its aroma. In a wild ferment several yeast species take turns before *Saccharomyces* finishes the job.
- 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.
- Why is sulphite added to cider — Sulphur dioxide suppresses spoilage bacteria and wild yeast before fermentation and protects the finished cider from oxidation. How much of it is active depends strongly on pH, which is why low-acid juice is harder to protect.
- 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.
- 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.
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.
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.
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.
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.