Glossary · Sensory
Bitterness
Definition
One of the basic tastes, detected by receptors chiefly on the posterior tongue. In cider it comes principally from short-chain procyanidins and from certain phenolic acids.
- Subject
- Sensory
In more detail
Individual sensitivity to bitterness varies genetically by a wide margin, so panellists disagree about the same cider more here than on almost any other attribute. Bitterness is also slow to register and slow to fade compared with acidity, which is why judgements about balance should be made across the whole tasting rather than at first sip.
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.
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.
Chemistry
Tannin
In cider usage, the phenolic material responsible for bitterness and astringency, principally condensed tannins — procyanidins — built from catechin and epicatechin units.
Chemistry
Oligomer
A molecule built from a small number of repeating units. Oligomeric procyanidins — roughly two to about ten flavan-3-ol units — are the fraction of cider tannin perceived mainly as bitterness.
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.
Sensory
Balance
The relationship between a cider’s sweetness, acidity, tannin, alcohol and carbonation, judged by whether any one of them dominates unintentionally.
Chemistry
Acrolein
A pungent compound formed when certain lactic acid bacteria metabolise glycerol. Reacting with phenolics, it produces an intense and persistent bitterness known historically as *amertume*.
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.
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.
Washington State University cider research programme
Washington State University Northwestern Washington Research and Extension Center · university · passage verified 2026-08-24
The single most useful open cider dataset CiderHQ has found. The programme’s cultivar performance database gives juice chemistry, orchard behaviour, bloom and harvest timing and cider-maker tasting notes for 73 cultivars grown at one maritime site over fifteen years, and — unusually — publishes its classification thresholds alongside its figures, so the classification can be checked rather than taken on trust. It also states outright that its results diverge from the English ones. Read in full on 2026-08-24 and transcribed into `data/trials/wsu-mount-vernon.ts`; four published figures were found to be impossible and are withheld there with their reasons.