Organism
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.
Also called Kloeckera corticis.
- Kind
- Yeast
- Binomial
- Hanseniaspora osmophila
- Role
- Primary fermentation
What it does
- Ferments the opening days of a spontaneous ferment alongside H. valbyensis and H. uvarum, and in one Asturian survey accounted for 28 to 30 per cent of the isolates on the first sampling day.
- Tolerates more sugar and more ethanol than the other two apiculate species, which is where its name comes from and why it can persist a little further into a ferment than they do.
- Produces acetate esters, and is one of the several organisms behind the ethyl acetate a spontaneous ferment carries — welcome as fruit at low concentration and solvent above it.
- Declines sharply once Saccharomyces establishes; in the same survey it was down to 2 per cent or absent by the fourth day.
- Is not usually distinguished from its relatives without molecular identification, which is why older cider surveys report a single apiculate population where a modern one reports three species.
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 | Active across the cool cellar range, roughly 10–28 °C, and identified in Asturian ferments running at 12–15 °C. |
| pH | Comfortable at juice acidity, roughly pH 3.0–4.2. |
| Oxygen | Facultative; ferments without air but grows better with it, so it is most abundant before the ferment goes anaerobic. |
| Alcohol tolerance | Higher than the other apiculate species — generally reported to around 7–9% ABV against 4–6% — which is the property the species is named for. |
| Sulphite tolerance | Low. Juice sulphiting suppresses it along with the rest of the apiculate population. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
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.
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.
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.
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.
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.
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.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
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.
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.
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.
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.
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.
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.
Measured figures
Growth limits, tolerances and population counts, shown with the context each was taken in rather than averaged into a constant.
Fermentation temperature12.0–15.0 °C
Villaviciosa, Asturias, Spain, 2001–2002 · Cellar temperature of the spontaneous fermentations from which the species was isolated · Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31
The species was recovered from these ferments at 28 to 30 per cent of first-day isolates in 2001 and at 2 per cent or less in 2002. The temperature was the same in both years, which is a reminder that temperature is one variable among several and that the harvest was the larger one here.
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.
About Hanseniaspora osmophila
For most of the twentieth century the apiculate yeasts of cider were a single entity in the literature: lemon-shaped cells, present at the start, gone within a week, collectively called Kloeckera apiculata after the imperfect form. Molecular identification has since separated them, and Hanseniaspora osmophila is one of the species that emerged. It is a genuine cider organism rather than a curiosity — in the Asturian survey that identified its isolates by restriction analysis of the ribosomal spacer region it was between a quarter and a third of everything cultured from the must on the first day.
What distinguishes it from its relatives is tolerance. The epithet means sugar-loving, and the species handles both higher sugar and higher ethanol than H. valbyensis or H. uvarum. That does not make it a fermenting yeast in any useful sense: it still ferments inefficiently, still contributes a small share of the alcohol, and still gives way to Saccharomyces. It simply takes a little longer to be pushed out, and it is contributing esters and higher alcohols the whole time.
The practical significance is the same as for the rest of the apiculate group and is worth stating plainly rather than romantically. These organisms make a large part of what distinguishes a spontaneous cider from a pitched one, and they make it in the first days, and one of the things they make is ethyl acetate. A spontaneous ferment that smells of pear drops at day four is not failing; a spontaneous ferment that smells of nail varnish at day four has let the apiculate population run too long or too warm, and sulphiting the juice or pitching over it are both answers.
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.
- Why did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- 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.
- Why does my cider smell like nail varnish — That is ethyl acetate, formed when acetic acid combines with ethanol. In small amounts it reads as pear drops; above threshold it smells of solvent or nail varnish remover and usually accompanies rising volatile acidity.
- 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.
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.
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.