Glossary · Microbiology
Yeast
Definition
A single-celled fungus that ferments sugar to ethanol and carbon dioxide. Cider is fermented by a succession of yeast species, of which Saccharomyces cerevisiae usually finishes the job.
- Subject
- Microbiology
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Microbiology
Saccharomyces cerevisiae
The yeast that finishes essentially every cider, whether it arrives in a sachet or from the fruit, the press and the vessel.
Production
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.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Microbiology
Saccharomyces cerevisiae
The principal fermenting yeast of cider, beer and wine, tolerant of alcohol and of sulphite and capable of taking a cider to dryness. Most commercial cider yeasts are strains of it.
Microbiology
Wild yeast
Yeast arriving with the fruit and resident in the press house and its equipment, as opposed to a pitched commercial culture. The term covers both useful and spoilage species.
Microbiology
Apiculate yeast
Lemon-shaped, weakly fermenting yeasts — *Hanseniaspora* and its anamorph *Kloeckera* — that dominate the first days of a wild cider fermentation before alcohol suppresses them.
Fermentation
Inoculation
Adding a selected yeast culture to the juice to conduct the fermentation, usually after rehydrating dried yeast or building a starter.
Microbiology
Flocculation
The clumping together of yeast cells into aggregates that settle out of suspension. Highly flocculent strains drop bright quickly; powdery strains stay suspended and are harder to clear.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
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.