Glossary · Fermentation
Stuck fermentation
Also written stuck ferment. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
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.
- Subject
- Fermentation
- Also written
- stuck ferment
In more detail
The commonest causes in cider are a shortage of assimilable nitrogen, a temperature that is too low or that dropped sharply, an excessive sulphite dose, and yeast stressed by very high starting gravity. A stuck ferment is a real hazard as well as a nuisance: sugar plus a depleted yeast population is exactly the condition in which spoilage organisms flourish and in which an unwanted refermentation later occurs in bottle.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Fault
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.
Production
Restarting a stuck fermentation
Diagnosing why a ferment has stopped with sugar remaining, then building an acclimatised starter and stepping the cider into it rather than pitching yeast into the problem.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Fermentation
Attenuation
The proportion of the original sugar that fermentation has consumed, calculated from the fall in gravity from the starting to the current reading and expressed as a percentage.
Chemistry
YAN
The nitrogen a yeast can actually use — free amino nitrogen plus ammonium — expressed in milligrams of nitrogen per litre. Apple juice is frequently short of it.
Fermentation
Arrested fermentation
Deliberately stopping a fermentation before the sugar is exhausted, in order to retain natural sweetness. Achieved by repeated racking, chilling, filtration, sulphite, or a combination.
Faults
Unwanted refermentation
Fermentation restarting in a sealed container that was not intended to be conditioned, producing gas, haze, sediment and, in bottles, dangerous pressure.
Fermentation
Yeast nutrient
Nitrogen and micronutrients added to a must that cannot supply the yeast’s needs. Diammonium phosphate provides inorganic nitrogen; complex nutrients also supply amino acids, vitamins and sterols.
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.
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.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.
The Science of Cidermaking and associated technical writing
Andrew Lea · reference work · passage verified 2026-08-24
Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.