Compound
Calcium pectate
The gel formed when calcium bridges de-esterified pectin chains, which floats to the surface as the brown cap of a keeve and carries the juice’s nutrients out with it.
- Class
- Polysaccharides
- Formula
- Not a single molecule — see below
- How often it matters
- Regularly encountered
What it does in cider
- Forms when calcium ions cross-link the free carboxyl groups exposed by pectin methylesterase, converting soluble pectin into an insoluble network.
- Traps suspended solids, yeast cells and much of the juice’s assimilable nitrogen within the network as it forms.
- Floats when carbon dioxide from a slow incipient fermentation lodges in the gel, producing the chapeau brun that gives keeving its visible sign.
- Leaves behind a clear, nutrient-poor juice that ferments slowly and stops with sugar remaining.
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
Keeving
Forming a floating pectin gel that lifts nutrients and solids out of the juice, so that the ferment starves before it finishes and leaves natural sweetness behind.
Juice settling
Letting freshly pressed juice stand cold and undisturbed so that gross solids fall, then racking the cleaner juice off the deposit before pitching.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
Pectinase treatment
Adding pectin-degrading enzyme preparations to juice so that haze-forming and viscosity-forming pectin is broken down before fermentation.
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.
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.
Pectin haze
A persistent, slightly viscous haze that will not settle, caused by pectin from the fruit remaining in solution as a colloid.
Stuck fermentation
A fermentation that has stopped before the sugar is gone and will not restart, leaving a sweet, low-alcohol cider that is vulnerable to everything.
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.
Organisms that produce it
Which organism is responsible usually decides whether the compound is a feature or a symptom.
Saccharomyces cerevisiae
The yeast that finishes essentially every cider, whether it arrives in a sachet or from the fruit, the press and the vessel.
Hanseniaspora valbyensis
The apiculate yeast most consistently reported as dominating the first days of a spontaneous cider fermentation, and a major contributor to its aroma.
About Calcium pectate
A keeve is a controlled gelation. Pectin methylesterase strips the methyl esters from pectin, exposing carboxyl groups; calcium, present naturally in the juice or added as a salt, bridges those groups between adjacent chains; and the dissolved polymer becomes a continuous three-dimensional network. What is remarkable is not that a gel forms but that it rises. Slow fermentation at low temperature generates just enough carbon dioxide for bubbles to lodge in the network and lift the whole mass, and it collects at the surface as the brown cap.
The cap is not merely a way of separating solids. As the network forms it entrains the suspended material of the juice — fine pomace particles, the wild yeast population, and, crucially, a large fraction of the assimilable nitrogen. What is racked out from underneath is therefore not just clearer juice but nutritionally poorer juice, and that is the point of the exercise. A ferment on nutrient-poor juice proceeds slowly, produces restrained aroma, and stops before the sugar is gone.
Everything about keeving is a set of conditions arranged to allow this and nothing else. The juice must be cold enough for enzyme action to outpace fermentation, must not have been treated with a pectinase that would have cut the chains, must have calcium available, and must be left alone for days. If the fermentation starts too vigorously the cap breaks up and the juice remains cloudy; if nothing happens at all, the enzyme activity was inadequate. It is the most demanding traditional technique in cidermaking and the only one that produces natural sweetness without addition, filtration or heat.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
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.
Enzymes
Pectin methylesterase
The enzyme that strips methyl groups from pectin, exposing the charged sites that calcium bridges — which is the reaction the whole of keeving is built on.
Acids
Galacturonic acid
The sugar acid that pectin chains are built from, released as they break down, and a significant part of why juice from rotten fruit binds so much of the sulphite added to it.
Nitrogen compounds
Yeast-assimilable nitrogen
The nitrogen a yeast can actually use, which apple juice is chronically short of — the shortage behind both stuck fermentations and rotten-egg aromas, and the shortage keeving deliberately makes worse.
Alcohols
Methanol
A small alcohol released not by fermentation but by enzymes stripping methyl groups off pectin, which is why juice handling rather than yeast choice governs how much a cider contains.
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.
- Why did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- How do i clear a cloudy cider
- 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.
- What is yan and why does cider juice run short of it — Yeast assimilable nitrogen is the nitrogen yeast can actually use. Apple juice is usually short of it — in one Virginia survey of 108 samples, 94 per cent fell below the level wine practice treats as a minimum — which is why cider ferments stall more readily than wine ferments.
- What is keeving — Keeving is a technique for starving a ferment of nitrogen so that it stops before all the sugar is gone, leaving a naturally sweet cider. Pectin is made to gel and float as a brown cap, carrying nutrients and yeast out of the juice with it.
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.
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.
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.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.