Glossary · Chemistry
Citric acid
Definition
A minor acid in apples but a significant one in pears, where it makes up a larger share of total acidity and behaves differently from malic acid under bacterial attack.
- Subject
- Chemistry
In more detail
Lactic acid bacteria metabolise citric acid to acetic acid and diacetyl, so a perry undergoing malolactic conversion can gain volatile acidity and buttery character from the citrate that a cider would not. This is one of several reasons perry is less forgiving than cider.
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
Malic acid
The dominant acid of apples and pears, giving the sharp, clean acidity of fresh juice. Its name comes from *malum*, the Latin for apple.
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.
Faults
Diacetyl
A compound produced by lactic acid bacteria from citrate and by yeast as a fermentation intermediate, smelling of butter, butterscotch or hot popcorn.
Fermentation
Malolactic fermentation
The bacterial conversion of malic acid into lactic acid and carbon dioxide, which lowers total acidity, raises pH slightly and softens the drink. It is a bacterial process, not a yeast fermentation.
Perry
Pear must
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.
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.
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.