Fault
Metallic taint
A metallic, inky or blood-like taste from dissolved iron, copper or zinc picked up from equipment, usually accompanied by accelerated oxidation.
Also called metallic character, inky taste.
- Severity
- Quality — the drink is worse for it
- Where it starts
- Pressing, Maturation, Juice treatment, Stabilisation, Harvest, Storage
- Can it be fixed?
- Yes, if caught in time
- When you notice it
- Pressing, Maturation, Packaging
- Signs
- 5 recorded
What it is
Metallic taint is the taste of dissolved metal in cider — most often iron, sometimes copper or zinc. It presents as an inky, coin-like or faintly blood-like sensation, more felt than smelled, sitting across the middle of the palate and lingering. Where it appears, it usually indicates something in the cider path that should not be there, and the same metal is catalysing oxidation while it is tasted.
What you notice
Grouped by sense, because that is how the fault presents itself rather than how it works.
On the palate
- An inky, coin-like taste across the tongue
- A blood-like or ferrous impression in the finish
In the mouth
- A hard, drying quality that is not the drying of tannin
How the batch behaves
- The cider oxidising unusually fast for the way it has been handled
To look at
- A grey, bluish or inky haze developing alongside the taste — Where haze and metallic taste appear together, see the metal haze record.
The words for it: Metallic. Each links to what produces it.
When it appears. After contact with an unsuitable metal, which may be a single fitting rather than a vessel. It does not develop on its own.
The diagnosis usually comes from the equipment audit rather than from the glass, because the causes are specific and traceable: a taint that appeared after a change of press, tap, hose fitting or vessel names its own source.
Peter Mitchell / Cider and Perry Academy
What it is mistaken for, and how to tell
One observation per rival, chosen because it separates them rather than because it describes either. Several of these are not faults at all — a style feature, a normal outcome, or the fruit behaving as it does.
- Metal haze — The same contamination shows in two places. The haze is visible and the taint is on the palate, and a cider can have either without the other.
- Excessive astringency — A metallic finish and a tannic one both read as hard. Metallic character sits on the tongue as a coin-like impression rather than as a drying.
- A cider tasted from a metal vessel or cup — Pour into glass. The commonest false positive on this fault is the container it was tasted from.
What is actually happening
The chemistry or microbiology behind it. Understanding the mechanism is what makes the prevention make sense rather than being a list of rules.
Iron and copper in cider are perceived directly at low concentrations, and the perception is partly a taste and partly a consequence of the metal catalysing lipid oxidation on the tongue and in the mouth, producing carbonyl compounds that are themselves perceived. This is why the sensation feels physical and lingers rather than behaving like an ordinary flavour.
The metals arrive from equipment. Bare or rusted iron, mild steel, brass fittings containing copper and zinc, galvanised containers, and unplated or worn press components all release ions into an acidic liquid. Cider at its ordinary pH is an effective solvent for these metals, and contact time need not be long.
The same ions are potent oxidation catalysts, cycling between oxidation states and enabling the reduction of oxygen to hydrogen peroxide, which then oxidises ethanol to acetaldehyde and drives phenolic oxidation. So a metallic cider is also an ageing cider, and the two faults are usually found together.
Above certain concentrations the metals also form insoluble complexes with phosphate and with phenolics, giving the haze covered separately. The taste generally appears at lower concentrations than the haze, so a metallic-tasting but bright cider is entirely possible.
How it happens
| Cause | Stage | How often |
|---|---|---|
| Bare iron or rusted steel in the press, mill or fittings | Pressing | occasional |
| Brass taps and connectors on vessels | Maturation | occasional |
| Galvanised or unsuitable containers used for juice or cider | Juice treatment | occasional |
| Copper treatment for sulphur compounds leaving residual copper | Stabilisation | rare |
| Soil and grit on unwashed windfall fruit | Harvest | rare |
| Damaged or poorly lined tanks and kegs | Storage | rare |
Can it be put right?
Most cider faults cannot be reversed. Where that is the answer it is given plainly — an honest 'this batch is what it is' is more useful than a procedure that will not work.
| Option | Effectiveness | What it involves |
|---|---|---|
| Remove the source | Reliable | Solves the problem for future batches, which is the only place it can be solved. |
| Blend into a larger clean volume | Partial | Lowers the concentration below the taste threshold if a suitable batch is available. The metal is still present and still catalysing oxidation. |
| Add citric acid to chelate the metal | Partial | Binds the ions and reduces both the taste and the hazing tendency. It adds acidity and does not remove the metal, so trial on a sample first. |
| Drink the batch young | Partial | A metallic cider will oxidise faster than a clean one, so keeping it makes it worse. Where it is still acceptable, using it sooner is sensible. |
| Treat with a metal-removing preparation | Unlikely to work | Regulated, requires an analytical measurement of the metal concentration, and is not a home procedure. CiderHQ publishes no dose. |
CiderHQ gives no additive dosage figures. An addition is a food-safety decision that depends on legal limits, on the juice in front of you and on what you are protecting against, and the right figure comes from your supplier’s or regulator’s own guidance rather than from a general reference.
Preventing it
- Keep the whole cider path in stainless steel, food-grade plastic, glass or wood.
- Replace brass fittings and taps, which are a common survival in otherwise modern cellars.
- Inspect old presses and mills each season for rust, worn plating and exposed metal.
- Wash fruit, particularly windfalls, before milling.
- Avoid copper treatments unless working from a laboratory result and a specification.
Metallic taint has become uncommon because the equipment that caused it has largely been replaced, but it survives in exactly the places a small producer is likely to be working: old presses bought second-hand, brass taps on barrels, and equipment inherited rather than specified.
Its practical importance is less the taste than what accompanies it. Iron and copper are among the most effective oxidation catalysts available to a cider, and a batch that tastes metallic is a batch that will brown, flatten and develop bruised-apple character faster than it should.
It should not be confused with the flinty, mineral character some tasters find in a low-sulphide cider, which is an aromatic impression and not a metallic taste. Metallic taint sits on the tongue and in the finish, and it does not lift out of the glass.
It is worth being clear that this is a quality fault rather than a safety one at the concentrations involved in an ordinary cellar. The reason to eliminate it is that it spoils the drink and accelerates its decline, not that a cider with a metallic edge presents a hazard.
The compounds involved
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.
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.
Citric acid
A minor acid in apples and a much more significant one in pears, whose metabolism by lactic bacteria is the reason perry gains more butter and more vinegar from malolactic fermentation than cider does.
Where in the process it arises
Traditional screw pressing
The wooden farm press in which one or two hand-turned screws drive a follower down onto a built cheese of pomace, tightened by degrees over hours.
Fermentation vessels
The container a cider ferments in — wood, stainless, plastic, glass or concrete — and how its permeability, thermal mass and resident microflora shape the result.
Fruit washing
Removing soil, grass, stones and surface contamination from gathered fruit, usually in a water flume, before it reaches the mill.
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.
Kegging
Filling cider into a sealed keg for gas dispense or into a vented cask for gravity and handpump service — two formats whose difference is not the container but whether the cider ever meets air.
Faults it is confused with
These present similarly. What separates them is set out on each page.
Metal haze
A haze or dark cast caused by dissolved iron or copper picked up from equipment, forming insoluble complexes with phosphate or with the cider’s phenolics.
Oxidation
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.
Acetaldehyde excess
A bruised-apple, green-nut or sherry aroma from acetaldehyde, produced by oxidation, by film yeast, or left behind by a ferment that was interrupted.
Where this comes up in a guide
The link lands on the step where the fault arises rather than at the top of the pathway, because that is where the decision that causes it is taken.
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.
- What is oxidation in cider
- 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.
- What should i ferment cider in — Anything inert, cleanable and closable: glass demijohns, food-grade plastic, stainless steel, or a wooden cask if you can keep it sound. Vessel shape and material change how much oxygen the cider sees and how fast it clears.
- Why does my cider taste like sherry — Acetaldehyde, the compound that sits between alcohol and acetic acid, gives a bruised-apple and sherry-like character. It rises when cider is exposed to air or when a ferment is interrupted.
- How do i carbonate cider in a keg
- What is a traditional screw press
Where to go next
- The fault finder — Describe what you can smell and see, and narrow it down from the signs.
- All faults — Grouped by where they come from and how serious they are.
- Cider science — The chemistry and microbiology these faults come out of.
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.