Compound
Beta-glucan
The bacterial exopolysaccharide behind ropiness, which turns a cider oily and thread-like without changing how it smells or tastes.
Also called Exopolysaccharide, Ropiness polymer.
- Class
- Polysaccharides
- Formula
- Not a single molecule — see below
- How often it matters
- Occasional
What it does in cider
- Is secreted by certain lactic acid bacteria as a protective capsule, chiefly a β-1,3-linked glucan with side branches.
- Raises viscosity dramatically at very low concentration, so a cider pours in threads or ropes.
- Leaves aroma and flavour largely unaffected, which is why the fault is diagnosed by eye rather than by nose.
- Can be broken up mechanically by vigorous stirring, though the organism that produced it remains unless it is dealt with separately.
How it is perceived
What the compound registers as, and at roughly what concentration. Perception is not a property of the molecule alone: sugar, tannin and carbonation all change where a threshold falls.
- oily texture
- slimy
- thick
- thread-forming
A textural fault rather than a flavour one. Very small quantities of polymer produce a large change in viscosity, and a cider can be visibly ropy while tasting essentially normal.
Descriptors it is responsible for
Sensory records that name Beta-glucan as a cause. Each states the perception and the mechanism behind it.
- Beeswax — A dry, waxy, faintly sweet note from long-chain fatty acids and their esters, associated with lees contact.
- Lees — A cloudy, faintly bitter, sedimentary character from yeast and fruit solids carried into the glass.
- Ropy — An oily, viscous, pouring-in-a-thread texture from bacterial exopolysaccharide, with little aroma of its own.
- Yeast extract — A savoury, umami, meaty-broth note from yeast autolysis during extended lees contact.
The structure it moves
| Dimension | What it is |
|---|---|
| Body | How much weight and viscosity the drink has in the mouth. |
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
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.
Lees ageing
Deliberately holding a cider or perry on its fine yeast deposit so that autolysing cells release material that changes texture and foam behaviour.
Cellar storage
Holding packaged cider in conditions that let it change slowly and predictably, where stability of temperature matters more than the temperature itself.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
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.
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.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Faults it is implicated in
Being implicated is not the same as being a fault. Several of the compounds on this site are ordinary constituents of a sound cider and define a named fault only above a concentration.
Ropiness
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
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.
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.
Gushing
Cider that erupts from the bottle on opening, either because it is over-pressurised or because something in it is nucleating the dissolved gas violently.
Excessive sediment
More deposit in the bottle or vessel than the presentation intends, ranging from a normal conditioning yeast layer to a loose sludge that clouds every pour.
Thin body
A cider with no weight or texture in the mouth, most often from over-watered pomace, low-gravity juice or a blend with nothing to give it substance.
Yeast haze
Cloudiness from yeast cells that have not settled out, usually because the strain flocculates poorly or the cider has not been left alone long enough.
Organisms that produce it
Which organism is responsible usually decides whether the compound is a feature or a symptom.
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.
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.
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.
About Beta-glucan
Ropiness — graisse in French cellar language, oiliness in English — is one of the oldest recorded cider faults and one of the least understood by the people who meet it, because it does not smell of anything. Certain lactic acid bacteria, notably Pediococcus species and some Lactobacillus, secrete a β-glucan capsule around themselves, and the polymer dissolves into the cider. A very small mass of it raises viscosity enormously, so the cider pours in a continuous thread and looks like thin oil.
The polymer can be broken by shear: stirring a ropy cider vigorously, or pumping it hard, reduces the viscosity noticeably. That is a cosmetic fix, since the organism responsible is still present and will make more, and it needs to be followed by sulphiting, racking and, where appropriate, filtration.
The conditions that permit it are the standard high-risk set — high pH, low free sulphur dioxide, extended lees contact, warm cellar — which is why ropiness so often appears in the same batches that show other lactic problems. A cider that is ropy is telling its maker something about the whole cellar rather than about one vessel.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Acids
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.
Polysaccharides
Pectin
The structural polysaccharide of fruit cell walls, which decides how much juice a press releases, whether a cider ever clears, and whether keeving is possible at all.
Polysaccharides
Arabinan
The branched neutral sugar side chains of pectin, which can be liberated intact by pectinase treatment and then form a haze that appears weeks after the juice looked perfectly clear.
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 does pectin do in cider — Pectin is the structural polysaccharide that holds fruit cells together. In juice it holds haze in suspension, and it is the molecule keeving depends on: strip its methyl groups and it will gel with calcium and float the nutrients out of the juice.
- 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.
- 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.
- 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.
- How should i store cider — Cool, dark and at a steady temperature. Light causes light-strike in clear glass, warmth accelerates oxidation, and temperature swings push cider past the closure of a bottle that is not tightly sealed.
- 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.
Where to go next
- All compounds — Grouped by what the fruit brings and what the ferment makes of it.
- Sensory — Every descriptor, with the compound or process that causes it.
- Microbiology — The organisms whose metabolism most of this chemistry belongs to.
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.
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.