Sensory descriptor
Wet cardboard
The flat, papery note of (E)-2-nonenal and related aldehydes, the sensory signature of oxidative staling.
Also called Papery, Cardboard, Stale.
- Aroma family
- Oxidative
- Does it indicate a fault?
- It depends on the style it is met in
What causes it
Oxidation of unsaturated lipids in the drink produces a series of carbonyl compounds, of which (E)-2-nonenal is the most odour-active, with a threshold in the low nanograms per litre and a distinctly papery, cardboard odour. The reaction is driven by dissolved oxygen and catalysed by trace iron and copper, and it accelerates sharply with storage temperature. Unlike the acetaldehyde and phenolic oxidation that give sherry and walnut, this pathway contributes nothing that any tradition seeks; it is staling rather than maturation.
There is no level at which this contributes. It is the descriptor that separates oxidative maturation, which traditional styles pursue, from oxidative staling, which nobody does.
The compounds responsible
Where the molecule is established. Some descriptors in this lexicon name a compound the compound register does not yet hold a record for; those are named in the cause above instead.
Dissolved oxygen
Essential to a healthy yeast population at the start of fermentation and the principal enemy of a cider from the moment fermentation ends.
Acetaldehyde
The compound sitting one step short of ethanol, which smells of bruised apple and sherry, binds most of the sulphite added to a cider, and is the chemical signature of oxidation.
Ascorbic acid
An oxygen scavenger that protects colour and aroma while it lasts and can promote browning once it is exhausted, which is why it is never used without sulphur dioxide.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Bottling
Transferring finished cider into glass, where the dominant variable is how much oxygen the liquid picks up in the few seconds it takes to fill and close each bottle.
Closure selection
Choosing between cork, crown, screwcap, cage and swing-top, a decision that fixes how much oxygen reaches the cider, whether it can hold pressure, and which faults it is exposed to.
Shelf-life management
Establishing how long a cider stays acceptable in its package and setting a durability date that reflects evidence rather than convention.
Cold chain
Keeping an unpasteurised, unfiltered or back-sweetened cider refrigerated from the packaging hall to the point of sale, because refrigeration is the only thing holding it stable.
Cellar storage
Holding packaged cider in conditions that let it change slowly and predictably, where stability of temperature matters more than the temperature itself.
The fault it points at
Meeting this descriptor above a certain intensity is how the fault below is usually noticed first.
Fault
The cumulative effect of oxygen on finished cider: fruit aroma flattens, colour deepens towards amber, and a bruised-apple or sherry-like character replaces the fresh one.
About Wet cardboard
Wet cardboard is the most useful single fault descriptor for packaged cider because it reports on oxygen pickup at bottling and on storage conditions afterwards — the two variables a producer loses control of soonest.
It is frequently confused with cork taint, which produces a similar damp-paper impression through a completely different compound. The distinguishing feature is that oxidation affects a whole batch consistently and worsens with time, while cork taint affects individual bottles.
Others in the oxidative family
Sherry, walnut, bruised apple, cardboard.
Bruised apple
The brown, soft, faintly sweet note of enzymatic browning, met wherever apple tissue or juice has met air.
Sherry
A nutty, oxidised, faintly volatile character from acetaldehyde and sotolon in long-air-exposed cider.
Walnut
A dry, slightly bitter nut note from advanced phenolic oxidation, characteristic of long-matured tannic cider.
Dried apple
Concentrated, leathery apple character from moderate oxidation, sitting between fresh fruit and full oxidative development.
Dried fruit
Raisin and sultana character from long oxidative ageing, most often met in concentrated and fortified styles.
Hazelnut
A lighter, sweeter nut note from early oxidative development and from lees contact.
Maderised
Heat-and-air damage together: cooked, browned, flat character from cider stored warm in the presence of oxygen.
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- How long does cider last — An unopened commercial cider is usually at its finest within a year of packaging, and filtered, pasteurised products carry a stated date. Strong, tannic, bottle-conditioned ciders can improve for several years.
- Does cider need to be refrigerated — Unopened, no — cool and dark is enough for most cider. Unpasteurised, unfiltered cider keeps far better cold, and anything opened should go in the fridge.
- How should i store cider — Cool, dark and at a steady temperature. Light causes light-strike in clear glass, warmth accelerates oxidation, and temperature swings push cider past the closure of a bottle that is not tightly sealed.
- Can i use screw top bottles for cider — For still cider, yes. For anything carbonated, a reused screw-top wine or juice bottle is not designed to hold pressure and should not be used.
- How is cider bottled
- What is acetaldehyde
Where to go next
- The sensory model — The thirteen structural dimensions and the twenty aroma families, in full.
- Compounds — The chemistry behind the words.
- Troubleshooting — When a perception turns out to be a problem, this is where it is diagnosed.
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.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.
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.