Glossary · Chemistry
Polyphenol
Also written phenolics, phenolic compounds. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
The broad class of plant compounds carrying multiple phenol rings. In apples this includes procyanidins, hydroxycinnamic acids such as chlorogenic acid, flavonols, dihydrochalcones such as phloridzin, and anthocyanins in red-fleshed fruit.
- Subject
- Chemistry
- Also written
- phenolics, phenolic compounds
In more detail
Polyphenols do more than taste. They are the substrate for enzymatic browning, they bind proteins in fining and in the mouth, they scavenge oxygen and so protect a cider chemically, and they polymerise during ageing into larger, softer molecules — which is why a hard young tannic cider becomes rounder with time.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Chemistry
Total phenolics
The single number used to summarise everything phenolic in a juice, useful for comparing fruit and misleading whenever it is used to predict how a cider will taste.
Chemistry
Hydroxycinnamic acids
The family of small phenolic acids that browns a juice, and whose release from their esters supplies the raw material for every volatile phenol a cider can develop.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Chemistry
Tannin
In cider usage, the phenolic material responsible for bitterness and astringency, principally condensed tannins — procyanidins — built from catechin and epicatechin units.
Chemistry
Procyanidin
A chain of flavan-3-ol units — mainly epicatechin, with catechin as a terminal unit — and the principal tannin of cider apples. Chain length determines whether it tastes bitter or astringent.
Chemistry
Chlorogenic acid
The most abundant hydroxycinnamic acid in apple juice, and the principal substrate for enzymatic browning. It is also a precursor of the ethylphenols that *Brettanomyces* produces.
Chemistry
Polyphenol oxidase
The enzyme, released when fruit cells are broken, that oxidises phenolics to quinones in the presence of oxygen. It is the cause of the browning of cut apples and of milled pomace.
Sensory
Astringency
A tactile sensation of drying, roughening and puckering in the mouth, caused by tannins binding and precipitating the proteins that lubricate the oral surfaces. It is a feeling, not a taste.
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.
Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE)
INRAE · research institute · retrieved 2026-08-24
French national agricultural research. Its Angers programme produced much of the published work on apple procyanidin chain length and on the relationship between polymer size, bitterness and astringency.
Peer-reviewed literature on apple phenolics and cider sensory perception
Various journals · peer-reviewed literature · registered as competent for this subject
Registered as a class rather than as one paper, because the mechanisms CiderHQ describes — tannin chain length driving the split between bitterness and astringency, salivary protein precipitation, enzymatic browning — are established across many studies rather than resting on any single one. Individual papers are cited where a specific number is quoted.
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.