Organism
Brettanomyces anomalus
The second Brettanomyces species regularly recovered from cider and beer, less studied than B. bruxellensis but capable of the same phenolic chemistry.
Also called Dekkera anomala.
- Kind
- Yeast
- Binomial
- Brettanomyces anomalus
- Role
- Secondary fermentation, Spoilage
What it does
- Converts hydroxycinnamic acids to ethylphenols by the same decarboxylation-and-reduction route as B. bruxellensis, though the reported yields differ between species and between isolates.
- Ferments slowly on residual sugar during maturation and packaging, producing carbon dioxide in sealed containers long after a cider was assumed finished.
- Produces acetic acid in the presence of oxygen, contributing to volatile acidity in barrels and ullaged vessels.
- Persists in wood, in cellar surfaces and in bottling equipment, since it grows slowly enough to be missed by short-cycle quality checks.
Conditions it works in
What the organism tolerates and what suppresses it. These are the levers a maker actually has: temperature, acidity, air, alcohol and sulphite.
| Condition | What is recorded |
|---|---|
| Temperature | Roughly 10–32 °C, with slow growth continuing at cellar temperature. |
| pH | Tolerates the whole cider range. |
| Oxygen | Facultative; favoured by low-level oxygen ingress. |
| Alcohol tolerance | High, comparable with *B. bruxellensis* and above cider strength. |
| Sulphite tolerance | Suppressed by molecular SO2 in the same pH-dependent way as *B. bruxellensis*; not reliably eliminated by it. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
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.
4-Ethylguaiacol
The smoky, clove-like partner of 4-ethylphenol, made by the same organisms from ferulic acid, and the compound that pushes phenolic character from medicinal towards spicy.
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.
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.
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.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Brettanomyces character
Farmyard, horse-blanket, smoky and sticking-plaster aromas from *Brettanomyces* yeast converting hydroxycinnamic acids into volatile phenols.
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.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
Microbial haze
Cloudiness caused by a growing population of spoilage organisms, and therefore a symptom of something worse rather than a clarity problem in itself.
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.
Where in the process it appears
Barrel ageing
Holding cider in wood — which may mean an old neutral vat used simply as a vessel, or fresh or spirit-seasoned oak used as a source of flavour, and the two are not the same operation.
Bottle maturation
What happens to a cider after it is sealed in glass — which for most ciders is slow decline rather than improvement, and saying so is more useful than implying otherwise.
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.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
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.
Sterile filtration
Membrane filtration at a rating that retains viable yeast and bacteria, which is what allows a sweet cider to be shelf-stable without heat or preservative — provided the filling that follows is aseptic.
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.
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.
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 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.
Secondary fermentation
Any fermentative event that follows the primary ferment — residual sugar refermenting, a deliberate second alcoholic fermentation, or the malolactic conversion of the maturation phase.
Cold maturation
Holding cider at low temperature so that it settles bright, sheds colloidal material and stops changing microbially, without any additive or treatment being applied.
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.
About Brettanomyces anomalus
Brettanomyces anomalus — also written Dekkera anomala, the same teleomorph-anamorph pairing described in the bruxellensis record — is the less-studied of the two Brettanomyces species that turn up in fermented drinks. It has been isolated from beer, wine and cider, and it shares the phenolic metabolism that makes the genus notorious, but the quantitative work behind statements about ethylphenol yield has overwhelmingly been done on B. bruxellensis.
That imbalance in the literature is a reason for caution rather than for silence. It is fair to say that B. anomalus can produce ethylphenols, that it grows slowly in maturing and packaged cider, and that it is controlled by the same measures. It is not fair to transfer bruxellensis numbers to it, and this record does not.
In practice a cider maker will rarely distinguish the two without sequencing, and rarely needs to: the corrective actions are identical. Wood hygiene, minimised oxygen ingress, attention to molecular SO2 rather than to total sulphite, and — where a cider is intended to be free of the character — removal of the organism before packaging.
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.
- Can you fix a cider that has gone vinegary — Not really. Volatile acidity cannot be removed at small scale, and blending it away only dilutes it. The realistic options are to accept it, to blend a lightly affected batch into a much larger sound one, or to let it finish becoming vinegar.
- Does cider get better with age — Some does. Tannic, dry, bottle-conditioned ciders and ice ciders can gain for several years. Light, fruit-driven and commercially filtered ciders lose their aroma and do not gain anything in exchange.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- Why did my sweetened cider start fermenting again — Live yeast met the sugar that was added back. Sweetening is only stable if the yeast has been removed by sterile filtration, killed by pasteurisation, or held in check by sorbate together with sufficient sulphite.
- 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
- All organisms — Grouped by what each does in the ferment, and by what kind of organism it is.
- Compounds — The chemistry this microbiology produces.
- Troubleshooting — Work from the symptom in the glass back to the organism.
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.
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.