Organism
Torulaspora delbrueckii
A non-Saccharomyces yeast that ferments further than most of its early-succession neighbours while producing notably little acetic acid.
Also called Candida colliculosa.
- Kind
- Yeast
- Binomial
- Torulaspora delbrueckii
- Role
- Primary fermentation
What it does
- Ferments sugar to ethanol with a low yield of acetic acid and acetaldehyde relative to other non-Saccharomyces yeasts, which is the trait it is selected for.
- Persists further into the ferment than Hanseniaspora or Metschnikowia, tolerating ethanol into the region where those species have already stopped.
- Produces glycerol and contributes to mouthfeel, and generates a different ester balance from Saccharomyces, weighted towards compounds other than ethyl acetate.
- Withstands osmotic stress well, so it remains active in high-gravity juice where other early-succession species struggle.
- Is used sequentially rather than alone: given the juice first and then followed by Saccharomyces, which is the arrangement most of the published work on it in cider actually tests.
- Raised the ester fraction significantly in a controlled apple cider comparison against single-strain Saccharomyces fermentation, along with total polyphenols and flavonoids — the aroma effect being the one the authors put first.
- Shifted the organic acid balance in the same experiment, giving a more even distribution of malic, succinic and citric acid while holding titratable acidity lower than the single-strain control.
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 | Ferments across roughly 10–30 °C and is used at the cooler end in commercial practice. |
| pH | Tolerates the cider range, roughly pH 3.0–4.0. |
| Oxygen | Facultative; ferments anaerobically once established. |
| Alcohol tolerance | Moderate for a non-Saccharomyces yeast, commonly reported in the region of 7–9% ABV. |
| Sulphite tolerance | Moderate; less sensitive than apiculate yeasts but not equal to *Saccharomyces*. |
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.
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.
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.
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.
Yeast haze
Cloudiness from yeast cells that have not settled out, usually because the strain flocculates poorly or the cider has not been left alone long enough.
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.
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.
About Torulaspora delbrueckii
Torulaspora delbrueckii occupies the middle of the succession. It is not an apiculate yeast dying at 4% ABV, and it is not Saccharomyces; it ferments a meaningful share of the sugar before its own alcohol tolerance stops it, usually somewhere between 7% and 9% ABV. In a cider ferment that means it can still be present and active when the apiculates have gone, overlapping with Saccharomyces rather than simply preceding it.
Its commercial interest rests on a negative rather than a positive: it produces conspicuously little acetic acid. Most non-Saccharomyces yeasts raise volatile acidity, which is the standing objection to using them deliberately. A yeast that adds non-Saccharomyces aromatic complexity without adding volatile acidity is worth having, and T. delbrueckii is now widely sold for co-inoculation and sequential inoculation in wine, with growing use in cider.
Its osmotolerance gives it a second niche in concentrated juices — ice cider and other high-gravity ferments — where sugar concentration alone inhibits many yeasts. As with every organism in this file, the claims here are species-level. How a particular preparation behaves in a particular juice at a particular temperature is not something CiderHQ asserts.
The evidence base deserves a caveat that applies to almost all the non-Saccharomyces literature. The controlled cider work on this species is small, recent, and largely done on dessert-apple juice in laboratory ferments — the study CiderHQ cites used a Chinese cultivar, Huaniu, and compared single, co- and sequential inoculation of two named strains. Its findings on ester production and acid balance are real results about those strains on that juice. What they do not establish is how a commercial preparation behaves on a tannic bittersweet must at cellar temperature, which is the question a West Country or Norman maker would be asking, and nothing published answers it yet.
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.
- 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.
Zeng, Mu, Yuan, Zhang, Song and Kang, Molecules 29(8):1750 · peer-reviewed literature · passage verified 2026-08-24 · covers 2024
Open access; read in full on 2026-08-24. Cited for a threshold rather than for its main result: β-damascenone, which smells of baked apple, flowers and honey, is stated at 0.05 micrograms per litre. That is two orders of magnitude below hydrogen sulphide and it explains why a compound nobody would find on a routine analysis can be among the first things a taster names. The paper’s co-fermentation findings are on a Chinese dessert cultivar in a laboratory ferment and are not generalised here.