Organism
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.
Also called Candida pulcherrima.
- Kind
- Yeast
- Binomial
- Metschnikowia pulcherrima
- Role
- Primary fermentation
What it does
- Secretes pulcherriminic acid, which chelates ferric iron out of the medium as the red pigment pulcherrimin; iron-dependent competitors are inhibited, which is a genuine antimicrobial mechanism rather than simple competition for sugar.
- Ferments weakly, contributing little ethanol, so its effect on a cider is aromatic and microbiological rather than a share of the alcohol.
- Expresses a broad set of extracellular enzymes — β-glucosidase, protease, pectinase — which can release bound aroma compounds and assist clarification.
- Declines early, giving way to Saccharomyces well before the ferment is finished, which is what makes it usable as a deliberate first stage in a sequential inoculation.
- Is a real and substantial part of a spontaneous cider population, not only a laboratory partner: it made up 10 to 32 per cent of first-day isolates across four Asturian ferments and had largely gone by the fourth day.
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 5–30 °C and remains active at the low end, which suits cold-settled juice. |
| pH | Tolerates fruit-juice acidity, roughly pH 3.0–4.0. |
| Oxygen | Largely oxidative; most active in the aerobic conditions of fresh juice and declines as the ferment goes anaerobic. |
| Alcohol tolerance | Low, generally around 4–5% ABV. |
| Sulphite tolerance | Moderate to low; suppressed by juice sulphiting, though somewhat less readily than the apiculate yeasts. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
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.
2-Phenylethanol
The yeast-made alcohol responsible for the rose and honey note in cider, produced from phenylalanine and one of the few floral aromas that is not carried in from the fruit.
Terpenes
The floral and citrus aroma compounds that apples carry only in traces and that hops, spices and botanicals bring in quantity, which is why a hopped cider smells so different from an unhopped one.
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.
Where in the process it appears
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.
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.
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.
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.
Juice clarification
The deliberate use of enzyme, fining agents or mechanical separation to produce a bright juice before fermentation, and what that costs the ferment.
Keeving
Forming a floating pectin gel that lifts nutrients and solids out of the juice, so that the ferment starves before it finishes and leaves natural sweetness behind.
Maceration
Holding milled pomace before pressing so that phenolics, aroma precursors and pectin have time to move out of the solid tissue and into the juice.
Juice pasteurisation
Heat treatment of juice before fermentation, which inactivates enzymes and microorganisms, and in doing so removes the wild flora that would otherwise ferment it.
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.
About Metschnikowia pulcherrima
Metschnikowia pulcherrima is the early-succession yeast with the most interesting mechanism. It secretes pulcherriminic acid, which binds ferric iron and precipitates as pulcherrimin — the rust-red pigment that gives colonies of the species their appearance on plate. Iron is not optional for most microorganisms, so removing it from solution inhibits a range of competitors, including moulds and some bacteria. This is a defined antimicrobial mode of action, not a vague notion of one organism “outcompeting” another.
That property has made it one of the few non-Saccharomyces yeasts with a real commercial presence. It is sold for sequential inoculation, where it is given the first day or two of a ferment before Saccharomyces is added, on the reasoning that it will suppress spoilage organisms and add aromatic and enzymatic contributions while contributing almost no alcohol. In a spontaneous cider it plays the same part without being asked to.
The limits are as important as the mechanism. It ferments feebly and stops early, so it cannot displace Saccharomyces from the main ferment and is not intended to. Claims about how much aroma a given preparation adds to a given juice are strain- and substrate-specific and are not made here.
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.
- 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.
- 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 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 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.
- How is apple juice clarified before fermentation
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.
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.