Sensory descriptor
Lightstruck
A skunky, sulphidic note produced when light degrades riboflavin in clear or green glass.
Also called Skunky, Light-struck.
- Aroma family
- Sulphur
- Does it indicate a fault?
- Usually, yes
What causes it
Riboflavin absorbs light in the blue and near-ultraviolet range and, once excited, drives the photodegradation of sulphur-containing amino acids in the drink to produce volatile thiols — most notably 3-methylbut-2-ene-1-thiol, which is the compound behind skunked beer and has an odour threshold in the nanograms per litre. Clear glass offers essentially no protection, green glass a little, brown glass a great deal. The reaction is fast: minutes of direct sunlight or hours under retail fluorescent lighting are sufficient.
There is no acceptable level. Because the reaction happens after packaging, a cider can be faultless at dispatch and faulty on a shop shelf, and the producer’s only control is the choice of bottle.
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.
Mercaptans
What hydrogen sulphide becomes if it is left alone: onion, garlic and rubber notes that are far harder to remove than the gas they came from.
Amino acids
The largest usable nitrogen fraction in apple juice, and the raw material from which yeast builds both its own protein and most of the aroma compounds a cider carries.
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.
Canning
Filling cider into lined aluminium, a format that blocks light completely, seals tightly and depends entirely on an intact polymer coating between an acidic drink and the metal.
Shelf-life management
Establishing how long a cider stays acceptable in its package and setting a durability date that reflects evidence rather than convention.
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
A skunky, cooked-cabbage or drain-like aroma produced when light acting on riboflavin generates sulphur compounds in a bottle.
About Lightstruck
Lightstrike is a packaging decision expressed as a fault, and it puts an unavoidable tension in front of producers: clear glass shows the colour of the cider and offers no protection, brown glass protects and hides it.
It is less discussed in cider than in beer, partly because cider’s riboflavin content is generally lower, but the mechanism is the same and clear-bottled cider on a sunlit shelf is exposed to it.
Others in the sulphur family
Rotten egg, struck match, drains, rubber, cooked cabbage.
Rotten egg
Hydrogen sulphide from yeast under nitrogen stress — the commonest sulphur fault and the most correctable.
Drains
A heavy, stagnant, sewer-like note from mercaptans formed when hydrogen sulphide is left to react.
Struck match
The sharp, mineral, matchhead note of free sulphur dioxide above its perception threshold.
Cooked cabbage
A vegetal sulphur note from dimethyl sulphide, rising slowly during storage rather than during fermentation.
Flinty
A sub-threshold reductive note read as struck flint rather than as sulphur, the mildest state of reduction.
Rubber
A burnt-rubber note from disulphides and higher mercaptans, generally a late stage of reductive fault.
Garlic
A pungent allium note from specific thiols and disulphides, occasionally from orchard spray residues.
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.
- 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
- How is cider canned
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.
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.
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.
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.