Harvest
Sweating the fruit
Deliberately heaping or storing gathered fruit so that it softens, loses water and finishes converting starch before it goes to the mill.
Known as maturation en cave where it originates. Also called Sweating, Maturing the fruit, Ripening in store, Conditioning the fruit.
- Stage
- Harvest
- Traditional in
- Pays d’Auge, Normandy, Somerset, Devon and 1 more
- What it most changes
- Alcohol up, body up
- Safety
- Carries a safety consideration — see below
Sweating gives any established rot weeks in which to grow. Fruit carrying soft brown lesions must be removed before the heap is made and again before milling, because Penicillium expansum growing in a warm heap produces patulin that spreads into flesh that still looks sound and is not removed by pressing, fining or pasteurisation. See the patulin control and fruit sorting records.
What it is
A holding period imposed on purpose, in which fruit that could physically be milled is instead left in heaps on a barn floor, in bins, or in a cool building until it reaches a condition the maker considers better than the one it arrived in. The fruit softens, the skin loses its gloss and takes on the slightly greasy, wrinkling look that gives the practice its English name, and the mass of the crop falls as water is transpired away. It is one of the oldest deliberate interventions in cider making and one of the few that happens entirely before any equipment touches the fruit.
Described in full
- Shape
- Four labelled curves on a common horizontal axis running from earlier to later on the tree. There is no numeric scale on either axis. Starch begins near the top and falls to almost nothing. Sugar begins low and rises, flattening towards the end. Acid begins high and falls steadily. Firmness begins high and falls, more steeply late.
- Starch
- Falls to zero as the fruit converts stored starch to sugar. This is what the starch–iodine test reads, and it is the most used field indicator of harvest maturity because the change is large, ordered and visible with a cut fruit and a bottle of iodine.
- Sugar
- Rises as starch converts and as the fruit continues to import sugar from the leaves, then flattens. Sugar sets potential alcohol, so a maker pressing early accepts a weaker cider.
- Acid
- Falls throughout, because malic acid is respired by the fruit itself. Waiting for more sugar therefore costs acid, and in low-acid bittersweet fruit that is a microbiological cost as well as a sensory one.
- Firmness
- Falls as the cell walls break down, slowly at first and faster late. It governs how the fruit mills: firm fruit grates cleanly, soft fruit smears and presses badly.
- Why there is no scale
- The directions here are general across cider fruit. The rates are not — they belong to a cultivar, a season and a site, and an axis with numbers on it would invite a reader to read a picking date off a drawing. What the figure shows is the shape of the trade-off, not its timing.
- The point of the figure
- The four curves do not cross a useful threshold at the same moment. Pressing when the starch has gone means pressing before the sugar has finished rising; waiting for maximum sugar means accepting lower acid and softer fruit. There is no moment at which all four are optimal, so harvest maturity is a choice about which curve the maker is prioritising.
Why it is used
- Hard, unripe-textured fruit mills into a coarse, springy pomace that holds its juice; softened fruit mills finer and releases juice more freely, so press yield improves without any change to the press.
- Water lost by transpiration concentrates the sugar that remains, so the juice comes off at a higher gravity than the same crop would have given at harvest.
- Late bittersweets and late French amères are routinely gathered before their starch is fully converted, and the hold finishes that conversion in the barn instead of on the tree.
- It smooths the harvest peak, letting a crop that arrives over three weeks be pressed over three months without the fruit simply sitting idle.
How it works
- Respiration continues after harvest, and the fruit’s own amylases go on hydrolysing stored starch to glucose, fructose and sucrose, so the fermentable sugar available at pressing rises even as respiration consumes a little of it.
- Water leaves through the cuticle and lenticels far faster than solids are consumed, so the soluble solids concentration climbs and the pressed juice reads several points of gravity higher than it would have at gathering.
- Endogenous pectin methylesterase and polygalacturonase de-esterify and then depolymerise the pectin of the middle lamella, weakening the cement between cells so the flesh yields — the same softening that makes the fruit easier to mill also makes it easier for a fungus to colonise.
- The green C6 aldehydes that dominate fresh-cut apple aroma decline while esters continue to form, so the aromatic register of the fruit shifts from sharp and fresh towards ripe and mellow before it ever reaches a fermenter.
- All of these run faster with warmth, and so does Penicillium expansum, which is why the practice has no fixed duration and must be judged by looking at the heap.
What it changes
The direction this step pushes the finished drink in, dimension by dimension. A direction, not a measurement: how far it moves depends on the juice, the temperature and how the step is carried out.
| Dimension | Direction | Why |
|---|---|---|
| Alcohol | Raises | Continued starch hydrolysis adds fermentable sugar while transpiration removes the water it is dissolved in, so the juice enters the ferment with more sugar per litre and finishes at a higher strength. |
| Body | Raises | Concentrating the whole soluble fraction — sugars, sorbitol, acids and soluble pectin — leaves more non-volatile extract in the finished cider, which reads on the palate as weight rather than as sweetness. |
| Fruit character | Either way | Fresh aldehyde aroma is lost during the hold and replaced by a riper, softer ester profile, so the cider gains mellowness at the cost of the cut-apple lift that a promptly milled crop delivers. |
| Oxidative character | Raises | Softened, wrinkling fruit with a compromised cuticle admits oxygen to tissue rich in polyphenol oxidase, so some phenolic oxidation happens in the fruit before milling rather than in the juice afterwards. |
The chemistry and the organisms
What is actually being changed, and by what. Each entry says what that compound or organism does in cider generally; this page is one place it does it.
Compounds involved
Starch
The fruit’s carbohydrate store, unfermentable until ripening converts it to sugar, and the reason picking early costs alcohol and risks a haze that will not clear.
Glucose
The sugar yeast takes first and the smallest of the three in apple juice, which is why the last sugar left in a slow ferment is almost never glucose.
Fructose
The dominant sugar of apple juice and the sweetest of the common sugars, which is why apple juice tastes sweeter than its total sugar figure implies and why a stuck ferment leaves sweetness behind.
Sorbitol
The unfermentable sugar alcohol that pears carry in quantity and apples carry only in trace, and the single reason a fully fermented perry keeps a sweetness a fully fermented cider cannot.
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.
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.
Total phenolics
The single number used to summarise everything phenolic in a juice, useful for comparing fruit and misleading whenever it is used to predict how a cider will taste.
Patulin
A mycotoxin produced by the blue mould that rots stored apples, regulated in apple juice worldwide, and the clearest food-safety reason not to press rotten fruit.
Organisms involved
Penicillium expansum
The blue mould of stored apples and the principal producer of patulin, the one genuine chemical safety issue that rotten cider fruit raises.
Botrytis cinerea
Grey mould: a broad-host-range fruit rot whose laccase enzyme oxidises phenolics and whose glucans make a juice difficult to clarify.
Monilinia fructigena
The brown rot of apples and pears, recognisable by concentric rings of buff pustules, and a major cause of fruit loss between the orchard and the mill.
Where it is traditional
The places this step belongs to as a matter of practice. It is not a claim of exclusivity — a method can be traditional in one region and perfectly ordinary in another.
What it is done with
What can go wrong
Faults that begin at this step, or that this step makes more likely. Each one is set out with its causes and whether it can be put right.
Patulin contamination
Contamination of juice or cider with patulin, a mycotoxin produced by Penicillium expansum in rotting apples — a genuine food-safety question rather than a flavour one.
Mould taint
Musty, earthy, cellar-damp or rotten-fruit character carried in from mouldy fruit or from mouldy equipment, and a marker that the patulin question needs asking.
Volatile acidity
The measurable fraction of acidity that can be steam-distilled off, dominated by acetic acid and read as vinegar sharpness in the nose and a hard, hot finish.
Enzymatic browning
The rapid darkening of milled fruit and fresh juice as polyphenol oxidase converts phenolics to quinones, taking colour and some tannin structure with it.
Starch haze
A persistent haze caused by starch carried in from under-ripe fruit, which has not yet been converted to sugar and stays suspended in the cider.
Styles it produces
Categories in which this step is characteristic or required. Some name it in their definition; for others it is simply how they have always been made.
Cidre Pays d’Auge
The controlled appellation cider of the Pays d’Auge in Calvados, made by keeving from bitter Norman fruit and bottle-conditioned to a low alcohol and a high residual sugar.
West Country farmhouse cider
Cider made on the farm from tannic bittersweet fruit, wild-fermented in wood and sold still and unfiltered, in a tradition whose variability is one of its defining features.
Cidre fermier
Farm-made French cider, pressed and fermented on the holding that grew the fruit, sold as an agricultural product of that farm rather than as a regional or industrial one.
Single-varietal cider
Cider made wholly or overwhelmingly from one apple cultivar, presented so that the fruit’s own character is the subject of the drink.
Somerset cider
Cider from the Somerset levels and the surrounding hills, built on a locally selected bittersweet fruit population and a tradition of full-bodied, tannic, still cider.
More on sweating the fruit
What the practitioner is actually doing is running a controlled decline and stopping it at the right moment. Every change that makes the fruit better to press — softer flesh, higher gravity, converted starch — is a step along the same path that ends in rot, and the skill lies in reading the heap rather than counting days. A maker turns the fruit or looks through it, watches for the first musty smell, notices when the surface of the heap starts to look damp rather than dry, and mills before the population of lesions starts to climb. Because warmth accelerates both the wanted and the unwanted changes together, the same crop might be ready in a fortnight in a mild autumn and take much longer in a cold one, and there is no defensible general figure for how long it should take.
Traditions handle this quite differently, and the differences are substantive. French practice treats the post-harvest hold as a named stage of production, with fruit held in a cool building until it reaches the softness and gravity the maker wants; the French institute’s guidance discusses it as a management decision with a target, not as storage. English farm practice has traditionally been rougher — fruit heaped on a barn floor or even outdoors under a straw cover, judged by hand and eye, and the West Country cultivar literature notes which bittersweets sweat well and which go to rot too fast to be worth holding. Asturian practice heaps gathered fruit at the llagar before milling, but the crop has already begun softening on the orchard floor, so the hold does less work. In German-speaking Most production, mixed Streuobst fruit of variable condition is commonly milled soon after gathering, because a heap of fruit gathered from many trees of unknown history is a poor candidate for a long hold.
It is also, importantly, not universal and not always desirable. A maker aiming at bright fresh-apple aroma in a modern single-varietal or a fruit-forward cider has every reason to mill promptly, because the hold trades exactly the aromatics that style depends on for weight and mellowness that it does not want. Large commercial operations working to a schedule with washed, sorted, mechanically harvested fruit generally do not sweat at all, and the character of that cider reflects it. And where a crop contains a meaningful proportion of drops, damaged fruit or fruit from a wet gathering, sweating is the wrong choice outright: the heap will multiply the problem rather than mature the crop, and the visible result — a warm heap running with juice, smelling of mould and attracting vinegar flies — is a food-safety failure rather than a stylistic one.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Harvest
Fruit storage before milling
Holding a gathered crop between harvest and the mill, and managing what respiration, water loss and spoilage do to it while it waits.
Harvest
Ripeness assessment
Judging when cider fruit has converted enough starch, loosened enough on the spur and hardened enough for the store to be worth gathering.
Harvest
Starch–iodine testing
Staining a cut apple with iodine solution so that remaining starch turns blue-black, giving a visible map of how far conversion to sugar has progressed.
Harvest
Fruit sorting
Taking rotten, mouldy and damaged fruit and foreign material out of the crop before it reaches the mill, which is the primary control on patulin in cider.
Fruit preparation
Milling
Reducing whole fruit to a pulp so that the press has cell walls it can drain, rather than intact apples it can only bruise.
Juice treatment
Patulin control
Managing the mycotoxin produced by rot fungi in damaged apples, which is controlled by fruit selection rather than by any treatment applied to juice.
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 are apples milled for cider
- How do cider makers keep patulin out — By sorting rotten fruit out before milling, because patulin comes from moulds growing on damaged apples. Fermentation reduces what gets through, so fermented cider carries no limit where juice does.
- When are cider apples harvested — In the northern hemisphere the cider harvest runs from about September to November, with late bittersweets such as Dabinett and Vilberie coming in last. Cider fruit is generally picked riper than dessert fruit, and often gathered from the ground.
- Can you fix a cider that has gone vinegary — Not really. Volatile acidity cannot be removed at small scale, and blending it away only dilutes it. The realistic options are to accept it, to blend a lightly affected batch into a much larger sound one, or to let it finish becoming vinegar.
- 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.
- Which sugar is most of the sugar in apple juice — Fructose, by a long way. Apple juice carries roughly twice as much fructose as glucose, with a smaller amount of sucrose, and fructose is the sweetest of the three on the tongue.
Where to go next
- How cider is made — The whole sequence, stage by stage, with the choices open at each one.
- Cider science — The chemistry and microbiology the methods on this page rest on.
- Troubleshooting — What goes wrong, how to recognise it, and whether it can be reversed.
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.
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.
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.
A Somerset Pomona: The Cider Apples of Somerset
Liz Copas, The Dovecote Press, 2001. ISBN 9781874336877 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against Open Library: Liz Copas, The Dovecote Press, 2001, ISBN 9781874336877. The author was Long Ashton’s cider pomologist, which is why this work is registered for Somerset cultivar identity at all — it is the nearest thing to a successor to the station’s own descriptions. No copy was opened. Not digitised in any open collection.