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.
Also called Strain choice, Yeast strain selection.
- Stage
- Fermentation
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Fermentation character and Body
- Safety
- None recorded
What it is
Yeast selection is the decision, made before the juice is pitched, about which of several hundred commercially available strains will carry out the fermentation. Nearly all of them are Saccharomyces cerevisiae, with a smaller number of Saccharomyces bayanus and Saccharomyces uvarum strains sold for cold or high-alcohol work. Strains differ in ways that matter operationally — the temperature band in which they will finish, how much nitrogen they demand, how much ethanol they survive, how readily they throw hydrogen sulphide, how tightly they settle — and in ways that matter sensorially, principally in the ester and higher-alcohol pattern they leave behind.
Why it is used
- A cellar that ferments cold, in an unheated building or under refrigeration, needs a strain that will actually finish at that temperature rather than stall part-way.
- Apple juice is often poorer in assimilable nitrogen than grape must, so a low-nitrogen-demand strain reduces both the nutrient bill and the risk of sulphide.
- A cider destined for bottle conditioning must be refermented by a strain that tolerates the ethanol already present and flocculates well enough to leave a compact, non-rousing deposit.
- Where a producer is aiming at a consistent house aroma across seasons, the strain is one of the few variables that can be held genuinely constant.
How it works
- Nitrogen demand reflects how efficiently a strain scavenges ammonium and alpha-amino acids; a high-demand strain in a low-nitrogen juice exhausts the supply mid-ferment and diverts to sulphur metabolism, releasing hydrogen sulphide.
- Ethanol tolerance is a membrane property — strains with more robust sterol and unsaturated fatty acid composition remain viable at higher alcohol, which is what makes them suitable for restarting a stuck ferment or for a second fermentation.
- Flocculation is governed by cell-surface proteins that cause cells to aggregate and sediment once sugar is exhausted; a highly flocculent strain clears well but can settle prematurely and leave sugar behind.
- Killer strains secrete a protein toxin that kills sensitive Saccharomyces cells, which helps a pitched strain dominate but can also cause a stuck ferment if a killer-sensitive strain is pitched into a cider already carrying a killer population.
- Ester production is strain-specific: the balance of acetate esters such as isoamyl acetate against ethyl esters of fatty acids is largely set by the strain’s acetyltransferase activity, and interacts with fermentation temperature.
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 | Strains differ in how much of the sugar carbon they route into acetate esters and higher alcohols rather than into ethanol and carbon dioxide, so the same juice can finish smelling of pear drop or of very little. |
| Body | Either way | Glycerol yield differs measurably between strains, and glycerol contributes to perceived weight, so strain choice moves texture slightly even at identical alcohol. |
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.
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.
Ethyl octanoate
A medium-chain ethyl ester contributing ripe pear and a waxy sweetness, and one of the compounds that makes an ester-forward cider feel rounder as well as fruitier.
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.
Torulaspora delbrueckii
A non-Saccharomyces yeast that ferments further than most of its early-succession neighbours while producing notably little acetic acid.
Lachancea thermotolerans
A non-Saccharomyces yeast that makes lactic acid out of sugar, and the one organism that can lower the pH of a cider juice without anything being added to it.
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.
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.
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.
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.
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.
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.
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.
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.
More on yeast selection
The awkward fact underlying strain choice in cider is that there are very few yeasts developed for cider. The commercial catalogue is dominated by wine strains selected on grape must and by champagne strains selected for second fermentation in bottle, with a handful of strains marketed specifically for cider and a smaller number of non-Saccharomyces cultures sold for co-inoculation. A cider maker is therefore usually choosing a yeast optimised for a different substrate, and the two substrates differ in the ways that matter most: apple juice generally carries less assimilable nitrogen, less potassium, a different acid profile dominated by malic acid, and a much smaller phenolic load in dessert-fruit juice than in red must. A strain’s published behaviour on grape must is a guide, not a specification.
The properties worth reading off a technical sheet are the ones that constrain the cellar rather than the ones that promise aroma. The usable temperature band determines whether a strain suits a cold farm building or a jacketed tank. Nitrogen demand sets the nutrient plan. Ethanol tolerance matters little for a typical cider strength but matters a great deal if the yeast is being asked to referment in bottle or to rescue a stuck batch. Flocculation determines both how well the cider clears and how compact the sediment is in a bottle-conditioned product. Killer factor is worth knowing because a killer-sensitive strain pitched after a resident killer population has established will simply be eliminated.
Aroma claims deserve more scepticism than the rest. Strain-derived esters are real and measurable, but their expression depends on temperature, nitrogen status and the sugar concentration of the juice, so a strain described as producing a fruity profile may do so only in the conditions in which it was trialled. The practical route is a bench comparison: split one juice across several strains under identical conditions and taste the results, which is what many producers do once and then hold to for years. Where a maker wants some of the aromatic breadth of a spontaneous ferment without abandoning control, sequential or co-inoculation with Torulaspora delbrueckii or a comparable non-Saccharomyces culture is the compromise, with Saccharomyces pitched afterwards to guarantee the ferment finishes.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
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.
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.
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.
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
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.
- 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.
- Can you make cider from shop bought apple juice — Yes, provided the juice contains no preservative — check for potassium sorbate or benzoate on the label. Pasteurised juice ferments perfectly well once yeast is added, because pasteurisation removes the organisms but not the sugar.
- 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 is sparkling cider made
- 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.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.