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What keeving is

What is keeving and why does it make cider sweet?

In short

Keeving is a way of deliberately starving a fermentation. The juice is treated so that a thick brown gel forms and floats to the top, taking most of the nutrients — nitrogen in particular — with it. The clear juice underneath is drawn off and fermented.

Because that juice is so poor in nitrogen, the yeast works slowly and eventually stops while sugar is still present. The cider is therefore sweet and low in alcohol without anything having been added or removed afterwards.

It is the traditional route to cidre doux and cidre demi-sec in Normandy and Brittany, it is used by a small number of producers elsewhere, and it is difficult: it depends on pectin chemistry that can simply fail to work.

How pectin chemistry lifts a brown cap, strips the juice of nitrogen and leaves a fermentation that stops while sugar remains.

Described in full

Step one: the enzyme: Pectin methylesterase, present naturally in apple tissue and sometimes added, acts on the pectin released by milling. Cool temperatures and a slow start are what allow it time to work before yeast takes over.
Step two: de-esterification: The enzyme strips methyl groups from the pectin chains. What was a soluble, methylated pectin becomes a bare polygalacturonic acid backbone carrying free carboxyl groups.
Step three: calcium bridges the chains: Calcium ions — from the fruit, or added as calcium chloride or carbonate — bind between adjacent bare chains. The chains cross-link into a network instead of staying dissolved.
Step four: the gel forms and rises: The cross-linked network becomes calcium pectate, a gel. It traps yeast cells, solids and the fine bubbles of the earliest fermentation, and the trapped gas floats the whole mass to the surface.
The *chapeau brun*: The floating gel is the brown cap. Below it the juice runs clear, and a layer of heavier solids falls to the bottom as lees. The vessel separates into three layers without filtration.
The nitrogen-stripped middle: The clear middle layer is the point of the whole operation. Rising and falling solids carry most of the assimilable nitrogen out of it, so what is racked off is juice that yeast cannot ferment quickly.
Arrested fermentation: Starved of nitrogen, the ferment runs slowly and stops of its own accord with fermentable sugar still present. That is how a cidre doux reaches natural sweetness and low alcohol without back-sweetening or sterile filtration.
Why it fails: Too warm, too much nitrogen, or fruit low in pectin and the gel never forms — the juice simply ferments out dry. Keeving is not a step that can be added to an ordinary ferment part way through.

The gel, in plain language

Apple flesh contains pectin, a structural carbohydrate, and an enzyme called pectin methylesterase that modifies it. Under the right conditions the enzyme strips methyl groups from the pectin, exposing sites that bind calcium ions. The pectin then cross-links into a gel.

That gel is not neutral. As it forms it traps suspended solids, yeast cells and — critically — a large part of the juice’s nitrogen and other nutrients. Carbon dioxide from the very earliest fermentation activity lifts it, and it rises as a thick brown cap. The French name for that cap, chapeau brun, is the whole point of the exercise: it is the visible sign that the process has worked.

The clear, nutrient-stripped juice between the cap and the sediment is then racked off carefully into a clean vessel, leaving the gel and the lees behind. That juice is what becomes the cider.

Why nutrient-poor juice makes sweet cider

Yeast needs nitrogen to build the proteins it uses to metabolise sugar. Deprive it of nitrogen and it can only build a small population and can only work slowly. The ferment proceeds gently over months, and at some point the yeast simply cannot continue while sugar remains.

The result is a cider that is sweet because fermentation stopped, not because sugar was added. It is also low in alcohol for the same reason — often under 4% and in the doux category sometimes under 3% — and it retains fruit character that a full, fast ferment would have stripped out.

This is why the French sweetness categories are cut on alcoholic strength rather than on residual sugar. In a keeved cider, the two are directly linked: the further the ferment ran, the more alcohol and the less sugar. Defining the bands on strength is a sensible way to describe a tradition where sweetness comes from arrested fermentation.

What makes it difficult

The juice must contain enough pectin and enough active pectin methylesterase, which depends on the fruit and on how it was handled.
Enough calcium must be available for the cross-linking; in soft-water areas a calcium salt is added, and getting the dose wrong prevents the gel or makes it too solid to rise.
The temperature has to be low enough that fermentation does not run away before the gel has formed and risen — traditionally a cold cellar, in practice a narrow window.
The juice must not be sulphited heavily, which would suppress the very early fermentation that lifts the cap.
The racking has to be clean. Disturb the cap or draw up lees and the nutrients go back into the juice.
It can simply fail, producing a normal ferment on a slightly clearer juice.

What keeved cider tastes like, and what it is not

A well-keeved cider is sweet, low in alcohol, gently sparkling in the bouché bottled form, and marked by fruit and floral character rather than by fermentation esters. Because so little of the juice was fermented, a lot of what was in the apple is still there.

It is not the same as a cider fermented dry and sweetened, even where the residual sugar figures match. A back-sweetened cider has been through a complete fermentation, so it carries the alcohol, the ester profile and the stripped-out aroma of a finished ferment, with sugar returned on top. The two are different drinks that a sweetness figure describes identically.

It is also not the same as a cider whose fermentation was stopped by filtration, chilling or pasteurisation, though those routes also leave sugar. Keeving stops the ferment by starvation from the beginning; the others intervene at the end.

Keeving and *défécation*The French technical term for the clarification step is défécation, which in this context means the removal of sediment rather than anything else. English writing uses keeving, from an older English word for the vat.

Also answered on this page

Questions this page covers, so you can tell at a glance whether it is the one you want.

How does keeving work?
Why is French cider naturally sweet?
Can keeving fail?
Is keeved cider the same as back-sweetened cider?

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 keeving, and how does it differ from an ordinary fermentation — Keeving deliberately strips nitrogen out of the juice before fermentation so the yeast runs out of nutrient and stops with sugar still present. The result is naturally sweet without anything being added, where an ordinary fermentation runs to dryness and any sweetness has to be put back.
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 keeved cider — A cider made naturally sweet by starving the yeast rather than by adding sugar. Keeving strips nutrients out of the juice before fermentation, so the ferment slows and stops with fruit sugar still in it, and nothing has been put back.
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.
Why does cider need yeast nutrient
Why is one cider 4% and another 8%

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.
Long Ashton Research Station cider fruit analyses
National Fruit and Cider Institute / University of Bristol · research institute · registered as competent for this subject · covers 1903–2003
The foundational body of cider-fruit science in English. Long Ashton produced the acid-and-tannin classification that divides cider apples into sweet, sharp, bittersweet and bittersharp, and analysed hundreds of cultivars grown at its Somerset site. Its figures are historic measurements of specific fruit at a specific place, not universal constants — a distinction CiderHQ preserves in every measurement record that cites it.
Institut national de l’origine et de la qualité (INAO)
INAO · regulator · passage verified 2026-08-24
The Cidre Pays d’Auge cahier des charges was read in full on 2026-08-24, in the version homologated by arrêté of 17 January 2026 and published in the Journal officiel on 21 January. That qualification is not decoration. A revision adopted by the Comité national on 10 September 2025 is currently under the procédure nationale d’opposition, is clearly marked as not prejudging the final text, and specifies carbonation differently from the text in force — as grams of CO2 per litre rather than as a minimum pressure in bar. A summary citing the draft would have put a figure on the page that no producer is held to. CiderHQ records the operative text and says which one it is.

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