Compound
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.
Also called Laevulose, Fruit sugar.
- Class
- Sugars
- Formula
- C6H12O6
- How often it matters
- Central to how cider behaves
What it does in cider
- Supplies the majority of the fermentable sugar in apple and pear juice, and therefore most of the potential alcohol.
- Tastes distinctly sweeter than glucose or sucrose at the same concentration, so the sweetness of a juice depends on its sugar composition and not only its Brix.
- Is taken up more slowly than glucose by Saccharomyces, so it dominates the residual sugar of any ferment that slows or stops.
- Increases in perceived sweetness as the drink is chilled, unlike glucose, which is part of why serving temperature changes how sweet a cider seems.
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.
- sweet
- clean
- fruit-sugar sweetness
Conventionally the sweetest of the common dietary sugars at equal concentration, and unusual in that its relative sweetness rises as temperature falls.
Descriptors it is responsible for
Sensory records that name Fructose as a cause. Each states the perception and the mechanism behind it.
- Butterscotch — Diacetyl at higher concentration with a caramel edge, sitting at the boundary between character and fault.
- Cooked apple — The soft, sweet, aldehyde-stripped apple character of heated fruit or heated juice, the base note of the whole cooked family.
- Pressed apple juice — The full, sweet, unfermented smell of fresh juice, met in cider where residual sugar and surviving fruit esters combine.
- Sweet apple — An impression of sweet fruit produced by aroma rather than by sugar, common in dry ciders with a high ester load and low acidity.
- Apricot — A concentrated, faintly honeyed stone-fruit note from lactones at higher concentration, common in ice cider and sweet styles.
- Baked apple — Cooked apple with a browned, Maillard-derived layer over it, met in ice cider and in long-matured sweet styles.
- Caramelised apple — Burnt-sugar sweetness over cooked fruit, from sugar breaking down under heat or high concentration.
- Cooked juice — The flat, jammy, slightly sulphurous character of over-heated juice or concentrate, recorded as a processing fault.
- Dried fruit — Raisin and sultana character from long oxidative ageing, most often met in concentrated and fortified styles.
- Maderised — Heat-and-air damage together: cooked, browned, flat character from cider stored warm in the presence of oxygen.
- Raspberry — A raspberry aroma arising in unfruited cider from bacterial spoilage — the French *framboisé* — as well as from added fruit.
- Russet apple — A dry, nutty, faintly pear-like apple character associated with russeted skin and high soluble solids.
- Stewed apple — Soft, wet, low-definition cooked fruit without browning, from prolonged gentle heat or long warm storage.
- Strawberry — A soft red-fruit note from furanone and ester chemistry, arising in fermentation or from added fruit.
- Toffee apple — Dense Maillard character — butter, brown sugar, slight roast — over concentrated apple, characteristic of ice cider and pommeau.
- Apple sauce — Cooked culinary-apple character with the sharpness retained, met where high-acid fruit has been heat-treated.
- Candied peel — Sweet, concentrated citrus-and-sugar character from terpene release during long maturation of a sweet cider.
- Cooked pear — Soft, sweet, heat-treated pear character, with the decadienoate top note stripped and a lactone-like weight left behind.
- Honeycomb — Honey with a caramelised, slightly burnt-sugar edge, met where oxidative honey notes coincide with Maillard character.
- Nectar — A light, sweet, floral-sugary impression from phenylethyl acetate and residual sugar together.
The structure it moves
| Dimension | What it is |
|---|---|
| Sweetness | How sweet the drink tastes, which is not the same as how much sugar it contains. |
| Body | How much weight and viscosity the drink has in the mouth. |
Measured figures
Shown as they were measured, with the context each was taken in. They are not averaged: a concentration recorded in one country's fruit in one decade is not a constant.
2 separate analyses of sugar. They are shown as they were measured, in their own contexts, and are not averaged — the same fruit grown somewhere else can genuinely give a different number.
Sugar50.0–80.0 g/L
context not recorded · Fructose fraction of total juice sugars · Andrew Lea
The fructose share of apple juice, not the total sugar. Cultivar and season move it substantially, and the figure for any one pressing should be measured rather than assumed.
Sugar90.0–160.0 g/L
context not recorded · Total fermentable sugars in pressed juice · Andrew Lea
Total of all three sugars, given for context. It corresponds roughly to a specific gravity of 1.040 to 1.065, and therefore to a fully fermented strength somewhere in the region of 5% to 9% ABV.
Fermentable sugar available to yeast, and therefore potential alcohol. Measured in grams per litre.
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
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.
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.
Ice concentration
Freezing pressed juice and drawing off the unfrozen fraction, so that water is removed as ice and everything else in the juice is left behind more concentrated.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
Wild fermentation
Letting the microflora already present on the fruit and in the press house carry the ferment, in a succession rather than as a single organism.
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
Secondary fermentation
Any fermentative event that follows the primary ferment — residual sugar refermenting, a deliberate second alcoholic fermentation, or the malolactic conversion of the maturation phase.
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.
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.
Sluggish fermentation
A fermentation that is still moving but far more slowly than it should, extending the period during which the cider is weak, sweet and exposed.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
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.
Cooked character
A stewed-apple, caramel or jam-like character from heat applied to juice or cider, most often through pasteurisation or hot storage.
Framboise
A raspberry-and-rotten-fruit character with sulphurous overtones, produced by *Zymomonas mobilis* in sweet ciders that still contain sugar.
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.
Zygosaccharomyces bailii
A preservative-resistant spoilage yeast that refements sweetened cider and juice, and one of very few organisms able to grow through sorbate and benzoate at cider strength.
Saccharomycodes ludwigii
A large, sulphite-resistant yeast that refements sweet cider in bottle and is one of the classic causes of unwanted secondary fermentation.
About Fructose
Apple juice is unusual among fermentation feedstocks in being fructose-dominant. Grape must is roughly half glucose and half fructose; apple juice is heavily weighted towards fructose, with glucose and sucrose sharing the remainder. This has two consequences a cidermaker meets directly. The first is that apple juice tastes sweeter than a grape must of the same sugar content, because fructose is the sweeter molecule. The second is more awkward: fructose is the sugar Saccharomyces finds hardest to finish.
Yeast takes glucose and fructose through the same transporters but with a marked preference for glucose. Early in a healthy ferment this is invisible, because there is plenty of both. Late in a ferment, when alcohol is high, nitrogen is exhausted and the cells are stressed, the remaining sugar is almost entirely fructose and the transport preference becomes a real obstacle. A cider that stops at 10 or 15 g/L of residual sugar has stopped on fructose, and restarting it requires an acclimatised yeast rather than simply more yeast.
The same chemistry works in the maker’s favour when sweetness is wanted. An arrested fermentation, whether achieved by keeving, by repeated racking off the yeast or by chilling and filtering, leaves fructose rather than glucose, which is the sweeter-tasting outcome. And because fructose sweetness increases as temperature drops, a medium cider served cold tastes appreciably sweeter than the same cider at cellar temperature — a point worth knowing before adjusting a blend on a warm bench.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Sugars
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.
Sugars
Sucrose
The disaccharide of apple juice and the sugar most often added to it, split into glucose and fructose by the yeast’s own invertase before any of it is fermented.
Sugar alcohols
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.
Alcohols
Ethanol
The alcohol yeast makes from fruit sugar, which converts a perishable juice into a keepable drink and carries most of its aroma to the nose.
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 many calories are in cider — Roughly 40 to 60 kcal per 100 ml for most ciders, so a UK pint falls somewhere around 200 to 250 kcal. Alcohol contributes about 7 kcal per gram and residual sugar about 4, so both strength and sweetness matter.
- 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.
- Why did my sweetened cider start fermenting again — Live yeast met the sugar that was added back. Sweetening is only stable if the yeast has been removed by sterile filtration, killed by pasteurisation, or held in check by sorbate together with sufficient sulphite.
- Why is my cider fermenting so slowly
- Why is sorbitol important in perry — Sorbitol is a sugar alcohol that pears carry in quantity and that Saccharomyces cannot ferment. It passes through the whole fermentation untouched, so a perry can taste sweet while being dry by measurement.
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.
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.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.