Glossary · Chemistry
Fermentable sugars
Definition
The sugars yeast can consume — in apple juice principally fructose, with glucose and sucrose in smaller proportion. Fructose usually dominates, which is unusual among fermentable fruit juices.
- Subject
- Chemistry
In more detail
The fructose-rich profile matters because Saccharomyces ferments glucose preferentially, leaving fructose towards the end. A ferment that stalls late therefore stalls on fructose, the sweeter of the two sugars, so a stuck cider tastes sweeter than its residual sugar figure alone would suggest.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Chemistry
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.
Chemistry
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.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Chemistry
Residual sugar
The fermentable sugar remaining in a finished cider, usually expressed in grams per litre. It is what sweetness legislation and style bands are written against.
Fermentation
Attenuation
The proportion of the original sugar that fermentation has consumed, calculated from the fall in gravity from the starting to the current reading and expressed as a percentage.
Fermentation
Stuck fermentation
A fermentation that has halted before the sugar is used up and will not restart on its own. It is distinct from a deliberately arrested ferment and from a merely sluggish one.
Chemistry
Specific gravity
The density of a liquid relative to water at the same temperature. In cider it is the routine measure of dissolved sugar before fermentation and of progress during it.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
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.
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.