Sensory descriptor
Drains
A heavy, stagnant, sewer-like note from mercaptans formed when hydrogen sulphide is left to react.
Also called Sewage, Stagnant.
- Aroma family
- Sulphur
- Does it indicate a fault?
- Usually, yes
What causes it
Hydrogen sulphide left in contact with the cider reacts with ethanol, with acetaldehyde and with other components to form thiols and mercaptans — ethanethiol, methanethiol and their relatives — which have thresholds as low as their parent compound and odours described as drains, sewage or rotting vegetation. These are chemically far more stable than hydrogen sulphide, so aeration no longer removes them; copper treatment can bind some of them, and even that is partial and reversible on later storage.
There is no acceptable level and, unlike hydrogen sulphide, no simple remedy. The descriptor marks the point at which a correctable fermentation problem has become a permanent one.
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.
Hydrogen sulphide
The rotten-egg gas a nitrogen-starved yeast produces, detectable at concentrations too small to measure easily, and removable only if it is caught before it becomes something worse.
Ethanol
The alcohol yeast makes from fruit sugar, which converts a perishable juice into a keepable drink and carries most of its aroma to the nose.
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.
The organisms that make it
Where a specific organism is implicated rather than the fruit. Naming one answers a different question from naming a molecule: what is in the cellar, rather than what is in the glass.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Racking
Moving cider off the sediment it has thrown, which both cleans the liquid and — by taking yeast and nitrogen away with the deposit — slows what is left of the ferment.
Oxygen management in fermentation
Giving the yeast the oxygen it needs early to build viable membranes, then excluding it once fermentation is under way and especially once it slows.
Fining
Adding a reactive agent that binds a target colloid and carries it to the bottom, chosen according to whether the problem is tannin, protein or a phenolic taste fault.
Yeast nutrition
What a fermenting yeast population actually needs from apple juice — assimilable nitrogen, vitamins and membrane lipids — and what goes wrong when the juice cannot supply it.
The fault it points at
Meeting this descriptor above a certain intensity is how the fault below is usually noticed first.
Fault
Onion, garlic, burnt rubber and cooked-cabbage aromas from thiols and disulphides formed when hydrogen sulphide is left in cider long enough to react onwards.
About Drains
Drains is the second stage of the hydrogen sulphide fault and the reason producers are urged to act on sulphide the day they smell it. The compounds involved are stable, low-threshold and largely irreversible.
It is not the same as reduction, which is a milder and often reversible state, and it should be recorded as a distinct and more serious observation.
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.
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.
Lightstruck
A skunky, sulphidic note produced when light degrades riboflavin in clear or green glass.
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.
- Is cider vegan — Cider itself is a plant product, but some producers clarify it with animal-derived finings such as gelatine, isinglass or chitosan. Vegan status therefore depends on the fining regime, which is why some ciders are certified and others are not.
- How many calories are in cider — Roughly 40 to 60 kcal per 100 ml for most ciders, so a UK pint falls somewhere around 200 to 250 kcal. Alcohol contributes about 7 kcal per gram and residual sugar about 4, so both strength and sweetness matter.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- What is racking in cider making — Racking is siphoning cider off the sediment it has thrown into a clean vessel, leaving the lees behind. It clarifies the cider and, in traditional practice, is also used to slow a ferment by removing yeast with the lees.
- Does cider need oxygen to ferment — Yeast needs a little oxygen early on to build the sterols it uses to stay healthy, but the ferment itself is anaerobic. After the first days oxygen is a liability, because it feeds acetic acid bacteria and oxidises the cider.
- What is yeast nutrition in cider making
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.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.