Organism
Pichia membranifaciens
A film-forming yeast that grows as a skin on the surface of cider left in contact with air, consuming ethanol and acid and leaving the cider thin.
- Kind
- Yeast
- Binomial
- Pichia membranifaciens
- Role
- Surface film, Spoilage
What it does
- Grows oxidatively at the liquid surface, forming a dry, wrinkled or powdery pellicle that spreads across any headspace left open to air.
- Oxidises ethanol and organic acids to carbon dioxide and water rather than fermenting sugar, so it removes alcohol and acidity from the cider instead of adding anything.
- Produces acetaldehyde and a range of oxidised volatiles as intermediates, giving the flat, stale, faintly bruised character that accompanies film growth.
- Requires a free liquid surface and an oxygen supply, so it appears in ullaged vessels, part-emptied barrels and containers that are not topped up — and disappears when those conditions are removed.
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 | Grows across roughly 10–30 °C, faster in a warm cellar. |
| pH | Tolerates the whole cider range and grows readily below pH 3.5. |
| Oxygen | Obligately dependent on air at the surface; it cannot establish in a full, sealed vessel. |
| Alcohol tolerance | Grows on cider at normal strength, generally reported to around 10–12% ABV. |
| Sulphite tolerance | More tolerant than most spoilage yeasts, and film growth is regularly seen on sulphited cider — sulphite alone is not a reliable control. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
Acetaldehyde
The compound sitting one step short of ethanol, which smells of bruised apple and sherry, binds most of the sulphite added to a cider, and is the chemical signature of oxidation.
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.
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.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Film yeast growth
A pale, powdery or wrinkled film of aerobic yeast growing on the surface of a standing cider, consuming alcohol and acid and producing acetaldehyde.
Oxidation
The cumulative effect of oxygen on finished cider: fruit aroma flattens, colour deepens towards amber, and a bruised-apple or sherry-like character replaces the fresh one.
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.
Flat and lifeless
A cider with nothing obviously wrong and nothing to say: aroma faded, acidity dulled, finish short — usually the cumulative result of over-processing or slow oxidation.
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.
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.
Vinegar fly contamination
Small flies carrying acetic acid bacteria and spoilage yeasts directly into juice and cider, and depositing them wherever they land.
Where in the process it appears
Topping up
Refilling a maturing vessel as evaporation and racking losses lower the level, so that no significant surface of cider is ever left in contact with air.
Racking
Moving cider off the sediment it has thrown, which both cleans the liquid and — by taking yeast and nitrogen away with the deposit — slows what is left of the ferment.
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.
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.
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.
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.
Oxygen management in fermentation
Giving the yeast the oxygen it needs early to build viable membranes, then excluding it once fermentation is under way and especially once it slows.
About Pichia membranifaciens
Pichia membranifaciens is the organism behind the white or grey skin that appears on cider in a partly empty barrel. It is not fermenting anything. It respires, using dissolved oxygen at the surface to oxidise ethanol and organic acids, and what it takes out of a cider — alcohol, malic acid, aroma — it does not replace. A cider that has carried a film for a season tastes hollowed out.
The condition it needs is simple and so is the control: a free surface in contact with air. Topping up, keeping vessels full, minimising headspace, using a blanket gas where that is available, and racking cleanly are all the same intervention, and all of them work better than sulphite, which this species tolerates comparatively well.
Film growth also matters because of what follows it. A pellicle is a sign that oxygen is reaching the liquid, and the same oxygen supports acetic acid bacteria. Finding a film yeast on a cider is a reason to check for volatile acidity as well as to top up the vessel, because the two problems have one cause.
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 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.
- What is oxidation in cider
- What is racking in cider making — Racking is siphoning cider off the sediment it has thrown into a clean vessel, leaving the lees behind. It clarifies the cider and, in traditional practice, is also used to slow a ferment by removing yeast with the lees.
- 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.
- Where does the fizz in cider come from — Either from fermentation trapped in a sealed container, or from carbon dioxide dissolved into the cider under pressure before filling. The French cider appellations permit only the first, and require at least 1.0 to 1.5 bar at 20 °C depending on the name.
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.
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.
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.