Glossary · Fermentation
Keeving
Also written défécation, defecation. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
A pre-fermentation clarification in which pectin in the juice is gelled into a floating brown cap, taking nutrients and yeast with it, so that the clear juice drawn from beneath ferments slowly and stops with sugar remaining.
- Subject
- Fermentation
- Also written
- défécation, defecation
In more detail
The chemistry is specific. Native pectin methylesterase strips methyl groups from the juice’s pectin, exposing carboxyl groups that bind calcium into an insoluble calcium pectate gel. Gas from the beginning of fermentation lifts that gel as a cap — the chapeau brun — while heavier solids settle as a sédiment. Drawing off the clear middle layer removes much of the nitrogen and much of the yeast at once.
The result is a nutrient-starved ferment that runs for months and dies naturally before the sugar is gone. That is how traditional French cider is sweet and lightly sparkling without pasteurisation, sweetener or added gas. It requires low-nitrogen juice, cold conditions and patience, and it fails in nitrogen-rich juice or if temperatures rise.
Calcium salts and exogenous enzyme are sometimes added to make the cap form reliably. That is a modern intervention on a traditional mechanism, not a different process.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Production
Keeving
Forming a floating pectin gel that lifts nutrients and solids out of the juice, so that the ferment starves before it finishes and leaves natural sweetness behind.
Style
Keeved cider
Cider clarified before fermentation by a pectin gel that strips nutrients from the juice, producing a slow ferment that stops naturally with sugar still in solution.
Chemistry
Pectin methylesterase
The enzyme that strips methyl groups from pectin, exposing the charged sites that calcium bridges — which is the reaction the whole of keeving is built on.
Chemistry
Calcium pectate
The gel formed when calcium bridges de-esterified pectin chains, which floats to the surface as the brown cap of a keeve and carries the juice’s nutrients out with it.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Fermentation
Chapeau brun
The brown gelatinous cap of pectate, solids and yeast that floats to the surface during keeving. Its formation is the visible test that keeving has worked.
Fermentation
Défécation
The French name for keeving, from the Latin for removing the dregs. It describes the same pectate-gel clarification and the same nutrient stripping that keeving does.
Equipment
Keeve
The open vessel in which juice is held while it forms its brown cap. The word is also used as a verb for the process itself, which took its name from the vessel.
Chemistry
Pectin
A structural polysaccharide of fruit cell walls, released into juice during milling and pressing. It thickens juice, holds haze in suspension and is the raw material of the keeving cap.
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.
Cider
Cidre bouché
French cider sold in a heavy bottle closed with a mushroom cork and wire cage, sparkling from fermentation continuing in the bottle. Literally "corked cider".
Perry
Poiré
French perry: pear juice fermented, in the Domfrontais made largely from local perry pears, keeved and bottled to finish sparkling and off-dry.
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.
Institut Français des Productions Cidricoles (IFPC)
IFPC · research institute · retrieved 2026-08-24
The French technical institute for cider production. The authority for the French cultivar classification families, for keeving as an industrial process, and for the pectin and nitrogen chemistry that keeving depends on.
Long Ashton Research Station cider fruit analyses
National Fruit and Cider Institute / University of Bristol · research institute · registered as competent for this subject · covers 1903–2003
The foundational body of cider-fruit science in English. Long Ashton produced the acid-and-tannin classification that divides cider apples into sweet, sharp, bittersweet and bittersharp, and analysed hundreds of cultivars grown at its Somerset site. Its figures are historic measurements of specific fruit at a specific place, not universal constants — a distinction CiderHQ preserves in every measurement record that cites it.