Sensory descriptor
Ropy
An oily, viscous, pouring-in-a-thread texture from bacterial exopolysaccharide, with little aroma of its own.
Also called Ropiness, Oily, Graisse.
- Aroma family
- Volatile and fault-related
- Does it indicate a fault?
- Usually, yes
What causes it
Certain lactic acid bacteria — Pediococcus species, Lactobacillus collinoides and Leuconostoc mesenteroides among them — synthesise β-glucan exopolysaccharides that remain in solution and dramatically raise viscosity. The cider pours in a thread or an unbroken ribbon, hence the French name graisse, fatness. Aroma is often barely affected, which makes it one of the few faults diagnosed primarily by eye and by pouring behaviour. It develops in low-sulphite, low-acid cider left undisturbed, and it can appear in bottle after packaging.
No level is acceptable, though the fault is unusual in being largely reversible: vigorous agitation breaks the polysaccharide chains and restores normal viscosity, after which sulphiting and filtration prevent recurrence. The organisms remain, so treatment without stabilisation is temporary.
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.
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.
Glycerol
A syrupy three-carbon alcohol yeast produces as a side reaction of fermentation, which adds weight to a dry cider and is the raw material for one of its more obscure faults.
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.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Pediococcus species
Homofermentative lactic acid bacteria that grow in tetrads, associated in cider with ropiness, diacetyl and slow spoilage during maturation.
Leuconostoc mesenteroides
A heterofermentative lactic acid bacterium common on fruit and early in fermentation, and a classic producer of the dextran that causes ropiness.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Sulphite stabilisation
Managing free sulphur dioxide through maturation and at packaging so that a useful antimicrobial and antioxidant fraction survives into the bottle.
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.
Filtration
Passing cider through a porous medium to reach a stated visual brightness, at a real cost in colloidal material, body and aroma.
Acid adjustment
Correcting the acidity of low-acid juice before fermentation, usually with malic acid, and the difference between the pH question and the titratable acidity question.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
The fault it points at
Meeting this descriptor above a certain intensity is how the fault below is usually noticed first.
Fault
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
About Ropy
Ropiness is a historically important cider fault with a long literature and a memorable presentation, and it is one of the very few where a mechanical intervention genuinely works.
It is filed among the volatile and fault-related descriptors for consistency with the other spoilage records, though it is strictly a textural rather than an aromatic observation, and it should always be recorded alongside a check for the other lactic faults its organisms also cause.
Others in the volatile and fault-related family
Vinegar, glue, mousiness, sourness out of place.
Vinegar
Acetic acid from acetic acid bacteria oxidising ethanol in the presence of air — the classic cider spoilage.
Glue
Ethyl acetate at fault concentration, past the solvent stage and into adhesive.
Mousy
A retronasal-only taint of mouse cage and stale grain, from tetrahydropyridines produced by lactic bacteria and Brettanomyces.
Flat and lifeless
The absence of aroma and lift where both were intended — a fault defined by what is missing rather than present.
Metallic
A blood-and-tin taste from dissolved iron or copper, which also catalyses oxidation.
Peppery bitterness
A harsh, burning bitterness from acrolein formed when lactic bacteria degrade glycerol.
Acetone
A harsher, more chemical solvent note than ethyl acetate alone, from ketones alongside high volatile esters.
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 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 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.
- 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
- How do you adjust the acidity of cider
- What causes ropiness in cider — Ropiness is a polysaccharide produced by certain lactic acid bacteria, Lactobacillus collinoides among them, which makes the cider pour like oil. It can usually be broken up by agitation, but the organism is still there.
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.
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.