Glossary · Microbiology
Killer yeast
Definition
A yeast strain that secretes a protein toxin lethal to sensitive strains of the same or related species, giving it a competitive advantage in a mixed fermentation.
- Subject
- Microbiology
In more detail
The killer factor is one reason a pitched strain can dominate a wild population that outnumbers it at the start, and one reason two cultured strains should not be co-pitched without checking their compatibility.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Microbiology
Yeast
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.
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.
Fermentation
Inoculation
Adding a selected yeast culture to the juice to conduct the fermentation, usually after rehydrating dried yeast or building a starter.
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.
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.