Glossary · Chemistry
Pectin
Definition
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.
- Subject
- Chemistry
In more detail
Pectin is why freshly pressed juice is slow to clear and why an unfermented juice can carry a permanent haze. In fermentation it is largely broken down, but a cider that retains pectin will not clarify by settling and gives a pectin haze that fining cannot fix — the answer is an enzyme, not a finings.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Chemistry
Pectin
The structural polysaccharide of fruit cell walls, which decides how much juice a press releases, whether a cider ever clears, and whether keeving is possible at all.
Fault
Pectin haze
A persistent, slightly viscous haze that will not settle, caused by pectin from the fruit remaining in solution as a colloid.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Chemistry
Pectic enzyme
A commercial enzyme preparation, usually fungal, that depolymerises pectin so that juice clarifies, presses more freely and yields more.
Chemistry
Pectin methylesterase
The native fruit enzyme that removes methyl groups from pectin, exposing the carboxyl groups that then bind calcium. It is the enzyme on which keeving depends.
Chemistry
Calcium pectate
The insoluble gel formed when calcium ions cross-link de-methylated pectin. It is the substance of the keeving cap, and the reason calcium salts are sometimes added to encourage one.
Fermentation
Keeving
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.
Faults
Pectin haze
A persistent, fine haze caused by pectin remaining in suspension. It does not settle, does not respond to fining and is cleared only by pectolytic enzyme.
Perry
Stone cells
Clusters of thick-walled lignified cells in pear flesh that give it its gritty texture. They blunt mills, complicate pressing and contribute to the sediment a perry throws.
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.
Hochschule Geisenheim University — beverage technology
Hochschule Geisenheim · university · retrieved 2026-08-24
German beverage-technology research covering apple wine and fruit juice processing, including the enzymology of clarification.