Organism
Saccharomyces uvarum
A cold-tolerant relative of S. cerevisiae recovered from spontaneous cider and wine ferments, associated with low-temperature fermentation and higher glycerol.
Also called Saccharomyces bayanus var. uvarum.
- Kind
- Yeast
- Binomial
- Saccharomyces uvarum
- Role
- Primary fermentation
What it does
- Ferments sugar to ethanol like its close relative S. cerevisiae, but retains activity at temperatures where S. cerevisiae slows markedly, so it can be recovered as a significant part of the population in cold cellars and winter ferments.
- Produces comparatively more glycerol and 2-phenylethanol and less acetic acid than typical S. cerevisiae populations, which is the basis of its interest to fermentation researchers.
- Consumes fructose relatively efficiently, a trait that matters in apple juice, where fructose is the dominant sugar rather than a minor one.
- Reaches a lower final ethanol concentration than S. cerevisiae, so a ferment it dominates can stop short of dryness at temperatures that suit it.
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 | Cryotolerant: grows well from roughly 6 °C to 20 °C and is outcompeted above roughly 25 °C, the reverse of the pattern in *S. cerevisiae*. |
| pH | Tolerates the normal cider range, roughly pH 3.0–4.0. |
| Oxygen | Facultative, with the same early sterol requirement as other *Saccharomyces* species. |
| Alcohol tolerance | Lower than *S. cerevisiae*, generally reported in the region of 10–12% ABV, which is still above the alcohol a cider ferment produces. |
| Sulphite tolerance | Broadly comparable to *S. cerevisiae*; normal juice sulphiting does not eliminate 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.
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.
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.
Succinic acid
An acid made by the yeast rather than the fruit, which adds a salty-bitter edge to a dry cider and, unlike malic acid, cannot be removed by malolactic fermentation.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Sluggish fermentation
A fermentation that is still moving but far more slowly than it should, extending the period during which the cider is weak, sweet and exposed.
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.
Fermentation temperature control
Managing the temperature at which a ferment runs, which sets not only how fast it goes but which aromatics survive it and what the finished cider tastes of.
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.
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.
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.
Bottle conditioning
Carbonating cider by letting a second fermentation finish inside the sealed bottle, so the gas is generated where it is going to stay.
Ice concentration
Freezing pressed juice and drawing off the unfrozen fraction, so that water is removed as ice and everything else in the juice is left behind more concentrated.
Natural carbonation
Bottling before the primary fermentation has finished, so the sugar still in the cider produces the carbonation with nothing added and nothing restarted.
Described in full
- Axes
- Days after pressing run left to right, from nought to thirty. Population on a logarithmic scale runs up the vertical axis. Each group is drawn with its own dash pattern and named in the key below the chart.
- Apiculate yeasts
- Rise fastest, peaking around day three at a level below the Saccharomyces peak, then collapse. They are killed by the alcohol the next group makes, which is why their curve falls while the ferment is still vigorous.
- *Saccharomyces*
- Starts as a small fraction of the population and becomes almost the entire population by the end of the first week. Holds a plateau through the main ferment and declines slowly as sugar runs out and it settles to the lees.
- Lactic acid bacteria
- Flat and low for the first two weeks, then rising. They need the sugar gone and the yeast quiescent before they establish, which is why malolactic fermentation is a late event or a spring one.
- What the crossings mean
- The point where the apiculate and Saccharomyces curves cross is the handover. Before it, aroma is being set by wild yeasts; after it, by the fermenting strain.
- Why sulphite changes the picture
- Sulphiting the juice suppresses the apiculate peak almost entirely and lets an inoculated Saccharomyces start from a high population. The same chart for a sulphited, inoculated ferment has one curve, not three.
- The vertical scale
- Logarithmic, because the populations differ by orders of magnitude rather than by percentages. A group at one hundredth of the peak is still millions of cells per millilitre.
About Saccharomyces uvarum
For most of the twentieth century Saccharomyces uvarum was treated as a variety of S. bayanus rather than a species, and a good deal of older cider and wine literature refers to it that way. Modern genome work separates it: S. uvarum is a distinct species, and much of what was sold and studied as S. bayanus turns out to be a hybrid carrying S. uvarum ancestry. The record for `saccharomyces-bayanus` deals with that tangle directly.
What makes the species interesting in cider is temperature. Cider is often fermented cold, in unheated stone or timber buildings, through a northern-hemisphere winter, and a yeast that is still dividing at 8 °C occupies a niche S. cerevisiae handles poorly. Where spontaneous ferments have been surveyed at low temperature, cryotolerant Saccharomyces have been recovered as a real component of the population rather than a curiosity.
Its metabolic signature — more glycerol, more 2-phenylethanol, less acetic acid — is consistently reported at species level and is the reason it appears in research on low-temperature fermentation. CiderHQ states that at species level only. Whether a particular commercial preparation delivers those differences in a particular juice is a strain question and is not asserted 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 temperature should cider ferment at — Most cider is fermented cool, commonly between about 12 and 18 °C. Cooler ferments keep more fruit aroma and run slower; above the low twenties the cider tends towards hot, solvent-like higher alcohols.
- 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.
- Why is my cider fermenting so slowly
- 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.
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.
Hochschule Geisenheim University — beverage technology
Hochschule Geisenheim · university · retrieved 2026-08-24
German beverage-technology research covering apple wine and fruit juice processing, including the enzymology of clarification.
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.