Glossary · Fermentation
Lees
Also written sediment, gross lees, fine lees. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
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.
- Subject
- Fermentation
- Also written
- sediment, gross lees, fine lees
In more detail
Gross lees are removed early because they are the fraction most likely to give reductive sulphur off-aromas and, in warm conditions, to autolyse unpleasantly. Fine lees are a resource: extended contact releases mannoproteins and amino acids that add body and a bready character, which is the basis of sur lie ageing.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Production
Lees ageing
Deliberately holding a cider or perry on its fine yeast deposit so that autolysing cells release material that changes texture and foam behaviour.
Fault
Reduction
A closed, stale, slightly sulphurous character in cider held under strongly oxygen-free conditions, sometimes clearing with air and sometimes not.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Fermentation
Racking
Transferring cider off its sediment into a clean vessel, leaving the lees behind. It is the basic maintenance operation of the cellar and the traditional method of slowing a fermentation.
Fermentation
Sur lie
Maturing cider in contact with its fine lees rather than racking clear, so that yeast autolysis contributes body, texture and savoury character. Literally "on the lees".
Microbiology
Autolysis
The self-digestion of dead yeast cells, which releases mannoproteins, amino acids and nucleotides into the cider. Controlled, it adds body and savoury complexity; uncontrolled, it gives meaty and sulphurous off-aromas.
Sensory
Reductive
Showing sulphurous, struck-match, rubbery or drain-like character arising from a lack of oxygen during fermentation or lees ageing. The opposite condition to oxidative.
Fermentation
Disgorging
Expelling the frozen plug of yeast sediment from the neck of a bottle-fermented cider, so that the finished drink is clear. The bottle is immediately topped up and closed.
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.
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.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.