Fault
Ropiness
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
Also called oiliness, graisse, sickness.
- Severity
- Quality — the drink is worse for it
- Where it starts
- Maturation, Blending, Storage
- Can it be fixed?
- Partly — it can be reduced, not removed
- When you notice it
- Maturation, Storage
- Signs
- 5 recorded
What it is
Ropiness is a texture fault: the cider becomes viscous and, when poured, forms a continuous oily rope or thread rather than breaking into droplets. It is caused by lactic acid bacteria producing extracellular polysaccharide — chiefly beta-glucan — which builds a polymer network in the liquid. The flavour is often barely affected, which is what makes it so disconcerting. Historically known in French cider as graisse and in English farmhouse usage as the cider being sick.
What you notice
Grouped by sense, because that is how the fault presents itself rather than how it works.
In the mouth
- Cider that pours as a thread or rope instead of breaking up — The classic demonstration: tip the vessel slightly and watch the last of the stream.
- A slippery, oily, almost egg-white mouthfeel
To look at
- Liquid that looks slightly viscous when swirled, clinging to the glass
On the palate
- Flavour that is largely unchanged, or only slightly duller — A fault you can see and feel but often cannot taste.
How the batch behaves
- Cider that has been sitting undisturbed in a warm cellar for months
The words for it: Ropy. Each links to what produces it.
When it appears. In a finished, low-acid, low-alcohol cider or perry that has been standing. It develops over weeks and is often first noticed when the liquid is poured.
It is one of the few faults on this list that is diagnosed by pouring rather than by smelling or tasting, and it is more common in perry than in cider because the conditions that favour it — low acid, low alcohol, residual sugar — are perry’s ordinary finishing state.
Various journals, Cider and Perry Academy (Peter Mitchell)
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.
- Pectin haze — Pour it. A pectin haze is cloudy and pours normally; ropiness pours in a thread or an oily stream and the liquid is often still clear.
- Microbial haze — Ropiness is a texture, not a turbidity. A ropy cider can be perfectly bright.
- A perry that is simply viscous — Whether the thread persists. A high-sorbitol perry has body; a ropy one forms a visible strand.
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.
Certain strains of lactic acid bacteria synthesise exopolysaccharides and secrete them into the surrounding liquid. In cider the important polymer is a beta-1,3-glucan with beta-1,2-glucosyl side chains, produced by a small number of strains carrying the relevant glycosyltransferase gene. The polymer is long, highly hydrated and forms a network that raises the viscosity of the whole liquid at very low concentration.
The organisms involved are Pediococcus species, Lactobacillus collinoides, Oenococcus oeni and Leuconostoc mesenteroides, though only particular strains within these species have the capability. This is why an entirely normal malolactic fermentation in one cellar is harmless and in another produces ropiness: the species is not the determinant, the strain is.
Conditions favouring it are those favouring lactic acid bacteria generally — high pH, low or absent free sulphur dioxide, residual sugar, warmth and stillness — with the addition that the polymer accumulates over months rather than appearing suddenly. Low-acid ciders from bittersweet fruit are the classic victims.
The polymer is a physical structure rather than a chemical modification of the cider, which is the reason for the fault’s one redeeming feature: the network can be broken. Vigorous agitation shears the chains, and the viscosity drops immediately. The polymer is still present, and the bacteria are still there to make more.
How it happens
| Cause | Stage | How often |
|---|---|---|
| Lactic acid bacteria active in a high-pH, low-acid cider | Maturation | common |
| Residual sugar available to spoilage lactic bacteria | Maturation | common |
| No free sulphur dioxide during a long, still maturation | Maturation | common |
| A blend made entirely from low-acid fruit | Blending | occasional |
| Warm storage in an undisturbed vessel over many months | Storage | occasional |
| Equipment carrying a resident population between batches | Maturation | occasional |
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 |
|---|---|---|
| Break the polymer by vigorous stirring or beating | Partial | The traditional response and it genuinely works on the texture, immediately. It does not kill the bacteria and does not stop the polymer being made again, so it must be combined with stabilisation to be worth anything. |
| Stabilise after breaking the rope | Partial | Filtration, pasteurisation or an appropriate sulphite addition after agitation prevents recurrence. This combination is the only route that actually resolves the fault, and it is more work than most home producers expect. |
| Fine or filter the polymer out without agitation | Unlikely to work | A viscous cider blinds filter media almost immediately. Breaking the network first is a prerequisite rather than an option. |
| Wait for it to clear on its own | Unlikely to work | It does sometimes resolve as the bacteria die back and the polymer settles, over a long period, but a cider left to it is a cider left exposed to everything else the same organisms do. |
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
- Blend for a pH low enough to restrain lactic acid bacteria, rather than relying on taste to judge acidity.
- Ferment to genuine dryness where the style allows, so no sugar remains for spoilage organisms.
- Maintain free sulphur dioxide at a level chosen for the measured pH, from the supplier’s guidance and within the applicable limit.
- Clean and sanitise vessels, hoses and taps between fills.
- Check maturing vessels periodically by pouring a little rather than only by tasting; ropiness is visible before it is obvious in any other way.
Ropiness is the most physically startling of cider faults and one of the least damaging to flavour, a combination that makes it memorable. A cider that pours like thin oil and forms a thread from the tap looks ruined and often tastes almost normal, and the traditional English name for the condition — the cider being sick — captures the impression rather well.
Its association with low-acid West Country cider is not accidental. Everything that makes a bittersweet blend what it is also makes it hospitable to lactic acid bacteria: high pH, low malic acid, long slow maturation in wood at cellar temperature. The sharp fruit in a traditional blend is not there only for the palate.
The traditional remedy of beating the cider with a stick or a whisk is real and it works, because the fault is a physical network rather than a chemical change. What the tradition did not have was any way of stopping the bacteria afterwards, which is why the sickness so often came back. A modern maker who breaks the rope and then does nothing else has reproduced exactly the historical outcome.
The most useful takeaway is diagnostic. A cider going ropey is direct evidence of an unrestrained lactic population, and the same population produces faults that are far harder to live with, mousiness among them. Ropiness is worth treating as a warning about the cellar rather than as an isolated curiosity.
The compounds involved
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Lactic acid
The softer acid that replaces malic when malolactic fermentation runs, halving the acid a cider carries and changing its texture as much as its sharpness.
Glucose
The sugar yeast takes first and the smallest of the three in apple juice, which is why the last sugar left in a slow ferment is almost never glucose.
The organisms involved
Pediococcus species
Homofermentative lactic acid bacteria that grow in tetrads, associated in cider with ropiness, diacetyl and slow spoilage during maturation.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Oenococcus oeni
The acid-tolerant lactic acid bacterium that carries out most deliberate malolactic fermentation, converting malic acid to lactic acid after the yeast has finished.
Leuconostoc mesenteroides
A heterofermentative lactic acid bacterium common on fruit and early in fermentation, and a classic producer of the dextran that causes ropiness.
Lactobacillus brevis
An obligately heterofermentative lactic acid bacterium, renamed *Levilactobacillus* in 2020, associated with volatile acidity, biogenic amines and mousiness rather than with clean malolactic conversion.
Where in the process it arises
Malolactic fermentation
A bacterial conversion of sharp malic acid into softer lactic acid, which lowers acidity, changes aroma, and in most traditional cider happens whether it was planned or not.
Sulphite stabilisation
Managing free sulphur dioxide through maturation and at packaging so that a useful antimicrobial and antioxidant fraction survives into the bottle.
Filtration
Passing cider through a porous medium to reach a stated visual brightness, at a real cost in colloidal material, body and aroma.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Tank maturation
Resting cider in stainless steel or a lined vessel, where the point of the container is that it contributes nothing and admits almost no oxygen.
Faults it is confused with
These present similarly. What separates them is set out on each page.
Lactic off-flavours
Sauerkraut, sour milk, silage or cheesy notes from lactic acid bacteria working on sugars and other substrates rather than on malic acid alone.
Mousiness
A retronasal taint of mouse cage, stale popcorn or crackers that appears only after swallowing — and that a substantial fraction of people cannot detect at all.
Microbial haze
Cloudiness caused by a growing population of spoilage organisms, and therefore a symptom of something worse rather than a clarity problem in itself.
Low acidity
A cider without enough acid to give it definition, tasting soft, heavy and dull — and sitting at a pH that leaves it exposed to spoilage organisms.
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 mousiness in cider — Mousiness is a fault caused by tetrahydropyridines produced by *Brettanomyces* and some lactic acid bacteria. It tastes of stale grain or a mouse cage and appears in the aftertaste rather than in the aroma.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- What is malolactic fermentation — Malolactic fermentation is a bacterial conversion of sharp malic acid into softer lactic acid, releasing carbon dioxide. It lowers total acidity and raises pH, and in cider it is often the source of a farmyard or buttery note as well.
- Which bacterium carries out malolactic fermentation in cider — Oenococcus oeni, in cider as in wine. Genome studies find that the cider strains are genetically distinguishable from the wine ones and that the strain most basal to the whole species was isolated from cider.
- Why does cider contain lactic acid — Because malolactic bacteria converted the malic acid into it. Malic acid has two acid groups and lactic acid has one, so roughly half the titratable acidity disappears and the cider tastes softer.
- Do i need a filter to make cider
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.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.
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.
Institut Français des Productions Cidricoles (IFPC)
IFPC · research institute · retrieved 2026-08-24
The French technical institute for cider production. The authority for the French cultivar classification families, for keeving as an industrial process, and for the pectin and nitrogen chemistry that keeving depends on.