Glossary · Perry
Pear must
Definition
Freshly pressed, unfermented pear juice destined for perry. It differs from apple must in its sorbitol content, its citric acid fraction and its lower assimilable nitrogen.
- Subject
- Perry
In more detail
Low nitrogen is the practical consequence that most affects the cellar: pear must ferments slowly and stalls readily, which is a problem when a dry perry is wanted and an asset when keeving is. The same shortage is part of why Domfrontais perry keeves so reliably.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Chemistry
Yeast-assimilable nitrogen
The nitrogen a yeast can actually use, which apple juice is chronically short of — the shortage behind both stuck fermentations and rotten-egg aromas, and the shortage keeving deliberately makes worse.
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.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Milling and pressing
Must
Freshly pressed, unfermented juice, from the moment it leaves the press until fermentation begins. The word is borrowed from wine-making and shares a root with German *Most*.
Perry
Perry
A fermented alcoholic drink made from the juice of pears, and specifically from perry pears rather than dessert pears. It is not cider made with pears added: it is a separate drink with its own fruit, chemistry and problems.
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.
Chemistry
Sorbitol
A sugar alcohol present in substantial quantity in pears and in smaller amounts in apples. Yeast does not ferment it, so it survives fermentation and leaves a fully dry perry tasting faintly sweet.
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.
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.
Research on pear juice composition and sorbitol in perry
Various journals and institute reports · peer-reviewed literature · registered as competent for this subject
The evidence base for the single most important chemical difference between cider and perry: pears carry substantial sorbitol, which yeast does not ferment, so a fully fermented perry retains sweetness a fully fermented cider cannot.
Perry Pears
L. C. Luckwill and A. Pollard (eds), published for the National Fruit and Cider Institute by the University of Bristol, 1963 · reference work · bibliographic record verified, not opened 2026-08-25 · covers 1963
Bibliographic record verified on 2026-08-25 against Open Library, which records the work as Luckwill, 1963, published for the National Fruit and Cider Institute by the University of Bristol. The catalogue entry names Luckwill alone where the standard citation names Luckwill and Pollard as joint editors; CiderHQ keeps both names and records the discrepancy rather than silently following one catalogue. This is the foundational descriptive work on English perry pears and the ancestor of most later variety lists. No copy was opened: it is sixty years old, out of print, and held in research libraries rather than in open digital collections.