Glossary · Faults
Ropiness
Also written oiliness, graisse, sliminess. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
A texture fault in which the cider becomes viscous and pours in an oily rope, caused by lactic acid bacteria producing extracellular glucan polysaccharide.
- Subject
- Faults
- Also written
- oiliness, graisse, sliminess
In more detail
Ropy cider looks normal in the glass until it is poured or stirred, when it moves as a continuous thread. Aroma and taste are often barely affected, which is why the fault is a texture problem first. Perry is more prone to it than cider.
Unusually among faults it is partially remediable: vigorous agitation or beating breaks the glucan chains, and the cider can then be sulphited and filtered. The organisms remain, so the underlying conditions — high pH, low sulphite, residual sugar — must be corrected or it returns.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
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.
Chemistry
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Microbiology
Lactic acid bacteria
The bacteria that convert malic acid to lactic acid and, in other conditions, produce the disorders of ropiness, mousiness and acrolein bitterness. *Oenococcus*, *Lactiplantibacillus* and *Lactobacillus* species dominate in cider.
Faults
Framboise
A spoilage disorder in which lactic acid bacteria acting on phenolic compounds produce a strong raspberry-like aroma alongside a characteristic haze and loss of colour.
Faults
Cider sickness
The historic name for a spoilage disorder of low-acid cider in which the drink turns turbid, loses colour, throws a deposit, produces gas and develops a milky, sometimes raspberry-like character.
Perry
Perry
A fermented alcoholic drink made from the juice of pears, and specifically from perry pears rather than dessert pears. It is not cider made with pears added: it is a separate drink with its own fruit, chemistry and problems.
Chemistry
pH
A logarithmic measure of hydrogen ion activity, and in cider the single most important number for microbial safety. Apple juice usually falls between pH 3.2 and 3.9.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
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.