Sensory descriptor
Rose
The rose-petal note of 2-phenylethanol, a higher alcohol produced by yeast from phenylalanine.
- Aroma family
- Floral
- Does it indicate a fault?
- No — a normal part of cider and perry aroma
What causes it
Yeast deaminates and decarboxylates phenylalanine and reduces the resulting aldehyde to 2-phenylethanol, an alcohol whose odour is unmistakably rose. Production is highest where assimilable nitrogen is limited enough that yeast must catabolise amino acids for nitrogen, and where fermentation is slow; non-Saccharomyces yeasts active in the early phase of a wild ferment, particularly Torulaspora delbrueckii, are notable producers. Its acetate ester, 2-phenylethyl acetate, carries a related honeyed-floral note and rises under the same conditions.
At low concentration 2-phenylethanol reads as a floral lift and contributes to perceived sweetness. As it rises with other higher alcohols it stops being floral and joins the general fusel impression, which is heavy and warming rather than perfumed.
The compounds responsible
Where the molecule is established. Some descriptors in this lexicon name a compound the compound register does not yet hold a record for; those are named in the cause above instead.
2-Phenylethanol
The yeast-made alcohol responsible for the rose and honey note in cider, produced from phenylalanine and one of the few floral aromas that is not carried in from the fruit.
Higher alcohols
The group of larger alcohols yeast makes from amino acids, welcome as background complexity in trace and harsh and solvent-like in quantity.
Amino acids
The largest usable nitrogen fraction in apple juice, and the raw material from which yeast builds both its own protein and most of the aroma compounds a cider carries.
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.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
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.
Yeast selection
Choosing which cultured strain to pitch, on the basis of the temperature, nitrogen, alcohol and aroma behaviour that separates one commercial yeast from another.
Yeast nutrition
What a fermenting yeast population actually needs from apple juice — assimilable nitrogen, vitamins and membrane lipids — and what goes wrong when the juice cannot supply it.
Fermentation temperature control
Managing the temperature at which a ferment runs, which sets not only how fast it goes but which aromatics survive it and what the finished cider tastes of.
Where it is usually met
Fruit and styles this character is recorded in. A record here is where the descriptor is commonly found, not a claim that every example shows it.
About Rose
Rose is one of the cleanest examples of a descriptor with a single named cause, and its presence is a reasonably direct report on nitrogen status during fermentation. Musts short of assimilable nitrogen produce more of it, which is why it is common in traditional low-nitrogen keeved ciders and in wild ferments.
It should be separated from the geranium note, which is a fault with a different chemistry entirely, and from general perfumed impressions that no compound accounts for.
Others in the floral family
Blossom, rose, elderflower, hawthorn.
Apple blossom
A light, sweet floral note from terpene alcohols and 2-phenylethanol, distinct from the fruit character of the same tree.
Elderflower
A green-tinged floral note from terpene alcohols and cis-rose oxide, or from direct botanical addition.
Geranium
The crushed-geranium-leaf note produced when lactic bacteria metabolise added sorbate — a fault with one cause and no remedy.
Hawthorn
A heavy, faintly fishy hedgerow-blossom note from trimethylamine and phenylacetaldehyde in ageing cider.
Violet
A powdery floral note from β-ionone, formed by degradation of carotenoids carried in from the fruit.
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 does cider ferment — Yeast consumes the sugar in apple juice and produces roughly equal masses of ethanol and carbon dioxide, along with the esters and higher alcohols that give cider much of its aroma. In a wild ferment several yeast species take turns before *Saccharomyces* finishes the job.
- What temperature should cider ferment at — Most cider is fermented cool, commonly between about 12 and 18 °C. Cooler ferments keep more fruit aroma and run slower; above the low twenties the cider tends towards hot, solvent-like higher alcohols.
- What yeast should i use for cider — CiderHQ does not recommend brands. The choice is between a neutral, reliable strain that lets the fruit show, an aromatic wine strain that adds its own esters, and no addition at all. Alcohol tolerance, cold tolerance and nitrogen demand are the properties worth comparing.
- 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 sidra natural — Sidra natural is the still, dry, unfiltered cider of Asturias and the Basque Country, bottled without added carbonation and poured from a height to rouse it. It is tart, funky and made to be drunk in small measures poured one at a time.
- 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.
Where to go next
- The sensory model — The thirteen structural dimensions and the twenty aroma families, in full.
- Compounds — The chemistry behind the words.
- Troubleshooting — When a perception turns out to be a problem, this is where it is diagnosed.
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.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.
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.