Fermentation
Microbial succession
The ordered handover of a spontaneous ferment from apiculate yeasts to Saccharomyces to lactic acid bacteria, and the spoilage organisms waiting at the end of it.
Also called Yeast succession, Population succession.
- Stage
- Fermentation
- Traditional in
- Asturias, Basque Country, Pays d’Auge, Somerset and 1 more
- What it most changes
- Fruit character up, acidity down
- Safety
- None recorded
What it is
A spontaneous cider ferment is not carried out by one organism but by a sequence of them, each dominant while conditions favour it and displaced as its own activity changes those conditions. The juice arrives carrying a mixed population from the fruit surface, the orchard, the mill and the press, in which Saccharomyces is usually a small minority. Over the following weeks and months the population turns over several times: fermentative yeasts of low ethanol tolerance first, then Saccharomyces as ethanol rises, then bacteria that work on the acids rather than the sugar, and finally, if conditions permit, organisms that live on what everything else has left.
Described in full
- Shape
- Two stacked bar charts one above the other, each with four bars. Bars are sampling days 1, 4, 16 and 28 after pressing. Each bar is divided into three segments summing to 100 per cent, and every segment carries its own percentage as a number so the reading does not depend on seeing the fill.
- What is counted
- The share of identified yeast isolates belonging to each group, not the number of cells. A group at 100 per cent was the only thing cultured from that sample; it does not mean nothing else was alive.
- The three groups
- Apiculate yeasts are Hanseniaspora valbyensis, H. uvarum and H. osmophila. Oxidative non-Saccharomyces are Metschnikowia pulcherrima and Pichia guillermondii. Saccharomyces is S. bayanus and S. cerevisiae together.
- Upper chart, pneumatic pressing
- Day 1: apiculate 84, oxidative 16, Saccharomyces 0. Day 4: apiculate 4, oxidative 10, Saccharomyces 86. Day 16: Saccharomyces 100. Day 28: apiculate 38, Saccharomyces 62. This is the textbook succession — non-Saccharomyces first, then a Saccharomyces takeover — except for the tail, where an apiculate yeast comes back at more than a third of isolates.
- Lower chart, traditional pressing
- Day 1: apiculate 66, oxidative 14, Saccharomyces 20. Day 4: apiculate 48, oxidative 4, Saccharomyces 48. Day 16: apiculate 90, Saccharomyces 10. Day 28: apiculate 94, Saccharomyces 6. Here the succession does not happen. Saccharomyces is present from the first day, never dominates, and the ferment finishes overwhelmingly apiculate.
- Why it matters
- Both ferments completed. Both gave dry cider of 6.4 to 6.5 per cent alcohol. The difference between them was how the fruit was pressed, and the account of cider fermentation as a fixed sequence of organisms does not survive it. Apiculate yeasts are usually described as dying out within days under rising alcohol; at 12 to 15 degrees Celsius, without sulphite, and on a must under 110 grams of sugar per litre, one of them ran the whole ferment.
- What this is not
- One cellar, one harvest, four ferments. It is evidence that the succession varies, not a measurement of how often it varies this way.
Why it is used
- The succession explains where much of the aromatic complexity of a spontaneously fermented cider comes from, and therefore what a heavy inoculation gives up.
- Knowing which organisms are dominant at which stage tells a maker when a particular fault becomes possible and when the window for it has closed.
- It accounts for the difference in character between ciders made in the same way in different cellars, since the resident populations of vessels and buildings differ.
- It is the framework within which sulphiting, inoculation and temperature can be understood as interventions in a sequence rather than as isolated treatments.
How it works
- The apiculate yeasts Hanseniaspora valbyensis, Hanseniaspora uvarum and Kloeckera apiculata, together with Metschnikowia pulcherrima and various Candida species, dominate the first days because they are numerous on the fruit and grow quickly in sugar-rich juice; they produce acetate esters, glycerol and some acetic acid and ethyl acetate, and they die back once ethanol reaches a level they cannot tolerate.
- Saccharomyces cerevisiae, often present initially in very small numbers, becomes dominant precisely because of its ethanol tolerance, and takes the ferment through to the end of the sugar; in cold ferments Saccharomyces uvarum may take this role instead.
- Once the sugar is gone and ethanol has stabilised the environment, lactic acid bacteria — Oenococcus oeni, Lactiplantibacillus plantarum, Lactobacillus collinoides and Leuconostoc mesenteroides — become active on malic acid and on residual sugars and glycerol, giving the malolactic conversion that characterises the maturation phase of many traditional ciders.
- The spoilage tail lives on what remains: Dekkera and Brettanomyces metabolise hydroxycinnamic acids to ethylphenols and can work on trace sugars long after everything else has stopped, Zygosaccharomyces bailii ferments residual fructose and tolerates sulphite, and acetic acid bacteria oxidise ethanol wherever oxygen reaches them.
- Each stage alters the environment for the next — the early yeasts remove sugar and add ethanol, Saccharomyces removes the rest and consumes the nitrogen, the bacteria remove malic acid and raise the pH, and a higher pH makes the cider more hospitable to the organisms that follow.
- The sequence is a tendency and not a law, and the clearest demonstration is two ferments in one cellar from one crop. In an Asturian survey, must pressed pneumatically ran the textbook succession — apiculate yeasts at 84 per cent of first-day isolates, Saccharomyces at 100 per cent by day sixteen — while must from the same harvest pressed traditionally never made the handover, finishing at 94 per cent Hanseniaspora valbyensis on day twenty-eight. Both ferments completed and both gave dry cider at around 6.5 per cent.
- Two Saccharomyces species share the middle of the ferment rather than one. S. bayanus predominated through the opening and middle stages at 33 to 41 per cent of isolates, and S. cerevisiae took over only at the end — a division the older literature, which identified yeasts by colony appearance rather than by their ribosomal spacer regions, could not see.
- The bacterial stage ends in a monoculture rather than a community. Oenococcus oeni proliferates past roughly a million cells per millilitre and at that point becomes the only bacterial species that can be cultured from the cider at all.
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 | The apiculate yeasts of the early phase are strong producers of acetate esters, so a ferment allowed to pass through that phase carries an ester profile a pure Saccharomyces pitch never generates. |
| Acidity | Lowers | The lactic phase converts dicarboxylic malic acid to monocarboxylic lactic acid, removing one acid function per molecule and raising the pH along with it. |
| Phenolic character | Either way | Dekkera and Brettanomyces at the tail of the succession decarboxylate and reduce hydroxycinnamic acids to 4-ethylphenol and 4-ethylguaiacol, which read as barnyard or medicinal depending on concentration and on what else is present. |
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.
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.
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 acetate
The most abundant ester in cider, giving lift and pear-drop at low concentration and nail varnish at high, and the earliest audible warning that acetic bacteria are at work.
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.
Lactic acid
The softer acid that replaces malic when malolactic fermentation runs, halving the acid a cider carries and changing its texture as much as its sharpness.
Acetic acid
The vinegar acid, made by bacteria oxidising ethanol whenever air reaches a cider, and the one fault in cider that no later processing can undo.
4-Ethylphenol
The horse-and-sticking-plaster compound, made by Dekkera from a phenolic acid the fruit supplied, and the clearest case in cider of one molecule being a tradition in one glass and a fault in another.
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
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.
Hanseniaspora uvarum
The apiculate yeast most often reported from grapes and widely present on apples too, whose anamorph name Kloeckera apiculata still appears throughout older cider literature.
Kloeckera apiculata
The anamorph name for Hanseniaspora uvarum, still in wide use in cider writing, and often used loosely as a collective term for all apiculate yeasts.
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.
Candida species
A large, historically artificial grouping of yeasts that appears throughout cider microbiology, containing organisms with little in common beyond the absence of a sexual stage.
Torulaspora delbrueckii
A non-Saccharomyces yeast that ferments further than most of its early-succession neighbours while producing notably little acetic acid.
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.
Oenococcus oeni
The acid-tolerant lactic acid bacterium that carries out most deliberate malolactic fermentation, converting malic acid to lactic acid after the yeast has finished.
Lactiplantibacillus plantarum
A versatile lactic acid bacterium, renamed out of Lactobacillus in 2020, capable of malolactic conversion and of a range of faults depending on conditions.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Leuconostoc mesenteroides
A heterofermentative lactic acid bacterium common on fruit and early in fermentation, and a classic producer of the dextran that causes ropiness.
Dekkera bruxellensis
The yeast behind 4-ethylphenol, and the organism that a cider tradition may regard as its signature or its ruin depending on where and how it is made.
Brettanomyces anomalus
The second Brettanomyces species regularly recovered from cider and beer, less studied than B. bruxellensis but capable of the same phenolic chemistry.
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.
Acetobacter aceti
An acetic acid bacterium that oxidises ethanol to acetic acid wherever cider meets air, and the organism behind most volatile acidity in cider.
Hanseniaspora osmophila
The sugar-tolerant apiculate yeast, more ethanol-tolerant than its relatives and a substantial part of the early population in some spontaneous cider ferments.
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 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.
Volatile acidity
The measurable fraction of acidity that can be steam-distilled off, dominated by acetic acid and read as vinegar sharpness in the nose and a hard, hot finish.
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.
Brettanomyces character
Farmyard, horse-blanket, smoky and sticking-plaster aromas from Brettanomyces yeast converting hydroxycinnamic acids into volatile phenols.
Mousiness
A retronasal taint of mouse cage, stale popcorn or crackers that appears only after swallowing — and that a substantial fraction of people cannot detect at all.
Ropiness
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
Framboise
A raspberry-and-rotten-fruit character with sulphurous overtones, produced by Zymomonas mobilis in sweet ciders that still contain sugar.
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.
Acetification
The active conversion of a cider’s ethanol into acetic acid by acetic acid bacteria at an air interface — the process, running in the vessel, that produces volatile acidity.
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.
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.
Wild-fermented cider
Cider fermented by the yeast population already present on the fruit and in the cellar, without an added cultured strain.
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.
Euskal Sagardoa
Basque cider under its own protected designation, made from Basque-grown apples in the sagardotegi tradition of barrel service and dry, high-acid, still cider.
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.
Fermentation temperature12.0–15.0 °C
Villaviciosa, Asturias, Spain, 2001–2002 · Cellar temperature during the two spontaneous fermentations the succession below was sampled from · Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31
The succession described on this page was observed at cellar temperature in an unheated Asturian llagar. Temperature is one of the strongest levers on which organism wins a stage, so a succession sampled at 20 °C in a controlled room looks different and is a different observation.
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.
Microbial population6.0 log CFU/mL
context not recorded · Population Oenococcus oeni exceeds once it dominates the post-alcoholic stage, reported as “above 10⁶ cells/ml” · Campbell-Sills, El Khoury, Favier and others, Genome Biology and Evolution 7(6):1506–1518
The last act of the succession, and the only stage for which CiderHQ has a sourced population figure rather than a sequence of species. At this density the source records that it becomes the only detectable bacterial species — the succession does not end in a community, it ends in a monoculture.
Viable cells per millilitre, on the log scale. What separates an organism that is present from one that is running the ferment. Measured in log colony-forming units per millilitre.
More on microbial succession
Succession is the concept that makes spontaneous fermentation intelligible as something other than luck. The organisms do not compete on equal terms throughout; each is favoured by a set of conditions that its own metabolism then destroys. The apiculate yeasts are abundant on the fruit and grow fast in sugar-rich, low-alcohol juice, which describes the first days exactly — and their production of ethanol, modest though it is, together with what Saccharomyces produces once it starts, brings that period to an end. Saccharomyces wins not by outnumbering anything at the start but by being the organism still alive when the ethanol has risen. The lactic acid bacteria then find an environment their competitors have left: no sugar to speak of, malic acid abundant, and the yeast settling out of suspension.
The early phase is where much of the argument about wild fermentation actually lies. Hanseniaspora and Metschnikowia contribute acetate esters, glycerol and enzymatic activity that a pure Saccharomyces culture does not, and their brief dominance leaves a permanent mark on the finished cider. They also produce acetic acid and ethyl acetate, which is why an uncontrolled early phase in warm or dirty conditions gives a volatile, solvent-inflected cider rather than a complex one. Sulphiting is most usefully understood as an intervention that shortens or removes this phase, since the non-Saccharomyces yeasts are generally more sulphite-sensitive than Saccharomyces; a heavy inoculation without sulphite achieves something similar by numbers alone.
The tail of the succession is where the character of long-matured traditional ciders is made and, when it goes too far, unmade. Dekkera bruxellensis and Brettanomyces anomalus work slowly on trace sugars and on hydroxycinnamic acids, producing 4-ethylphenol and 4-ethylguaiacol; in Asturian and West Country ciders a degree of this is part of the expected profile, and in a clean modern cider the same compounds are a fault. Lactic acid bacteria in the wrong conditions produce mousiness, ropiness or the framboise character rather than a clean malolactic conversion. Acetic acid bacteria are limited only by oxygen. The practical implication is that a traditional cider is never microbiologically finished — it is at a point in a sequence, and the maker’s job is to bottle, stabilise or sell it while that point is the one they want.
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
Malolactic fermentation
A bacterial conversion of sharp malic acid into softer lactic acid, which lowers acidity, changes aroma, and in most traditional cider happens whether it was planned or not.
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.
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 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.
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.
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.
- 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.
- What is malolactic fermentation — Malolactic fermentation is a bacterial conversion of sharp malic acid into softer lactic acid, releasing carbon dioxide. It lowers total acidity and raises pH, and in cider it is often the source of a farmyard or buttery note as well.
- 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.
- 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.
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.
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 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.
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.
Campbell-Sills, El Khoury, Favier and others, Genome Biology and Evolution 7(6):1506–1518 · peer-reviewed literature · passage verified 2026-08-24
Open access; read in full on 2026-08-24. Fifty genomes of the bacterium that performs malolactic fermentation, and the finding that the cider strains are not simply wine strains that happened to land in cider. The strain basal to the whole species came out of cider, and the authors read the pattern as separate domestication of one ancestral low-alcohol fruit organism into two drinks. It is also the source CiderHQ uses for what a malolactic population actually reaches, which is the difference between an organism being present and an organism running the process.