Glossary · Sensory
Reductive
Definition
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.
- Subject
- Sensory
In more detail
Mild reduction often blows off with aeration or a splash racking; established mercaptans do not. A tightly sealed vessel, a nitrogen-starved ferment and prolonged lees contact are the usual combination behind it.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Chemistry
Hydrogen sulphide
A volatile sulphur compound produced by stressed yeast, smelling of rotten eggs at very low concentrations. In cider it is usually a symptom of nitrogen deficiency during fermentation.
Faults
Mercaptan
A sulphur compound formed when hydrogen sulphide reacts with ethanol and other constituents, smelling of onion, rubber, garlic or drains. Far harder to remove than the hydrogen sulphide it comes from.
Sensory
Oxidative
Showing the character that oxygen exposure brings — bruised apple, nuts, dried fruit, sherry and toffee — with fresh fruit aromas diminished. It may be a fault or a deliberate style.
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.
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.
Sensory
Struck match
A descriptor for the sharp sulphurous note of sulphur dioxide or of reductive sulphur compounds, resembling a freshly struck match.
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.
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.