Glossary · Microbiology
Flocculation
Definition
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.
- Subject
- Microbiology
In more detail
Flocculation timing matters as much as degree: a strain that flocculates early can drop out before the sugar is finished and leave a stuck ferment, while one that stays in suspension gives more lees contact and a hazier cider.
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.
Fermentation
Lees
The deposit that settles under a fermenting or maturing cider: dead and living yeast, fruit solids, pectin, tartrate and protein. Gross lees are the coarse first deposit; fine lees are the finer yeast layer that forms afterwards.
Fermentation
Stuck fermentation
A fermentation that has halted before the sugar is used up and will not restart on its own. It is distinct from a deliberately arrested ferment and from a merely sluggish one.
Fermentation
Filtration
Passing cider through a porous medium to remove suspended solids, yeast and haze. Coarse filtration polishes appearance; fine filtration approaches microbiological stability.
Fermentation
Unfiltered
Packaged without filtration, so the cider retains yeast and colloidal material and is usually hazy. It is a process statement rather than a quality claim, and unfiltered ciders throw a sediment.
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.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.