Skip to content
CiderHQ
Search

Cider science

Where cider flavour comes from

Does cider taste of the apples it was made from?

In short

Partly, and less than most people assume. The fruit contributes the acid, nearly all the tannin, the sugar and a set of aroma compounds, but a large part of the fruit’s own volatile aroma is lost during fermentation, stripped out by escaping carbon dioxide or metabolised by yeast.

What replaces it is fermentation aroma: esters, higher alcohols and their combinations, produced by the yeast from precursors in the juice. Much of what reads as apple in a finished cider is an ester made during fermentation that happens to smell of apple.

Two further layers sit on top. Bacteria may add lactic and phenolic characters after the ferment, and oxygen adds oxidative ones over time.

The four sources

Where the components of cider flavour originate.
SourceWhat it contributesAroma families involved
The fruitSugars, malic acid, procyanidins and other phenolics, some volatile aldehydes and esters, and the aroma precursors the yeast will act onFresh apple, ripe apple, pear, citrus, herbal
The fermentationEthanol, glycerol, higher alcohols, acetate and ethyl esters, acetaldehyde, and sulphur compounds where nitrogen is shortFermentation-derived, tropical, floral, stone fruit, sulphur
Post-fermentation microbiologyLactic acid and diacetyl from malolactic conversion; volatile phenols from Brettanomyces and some lactic bacteria; acetic acid and ethyl acetate from acetic bacteriaLactic, phenolic, earthy, fault-volatile
Time and oxygenAcetaldehyde and phenolic oxidation products; ester hydrolysis; tannin polymerisation; wood compounds where a barrel is involvedOxidative, cooked apple, honeyed, woody, spice

What survives from the apple, and what does not

The non-volatile fruit components survive well. Malic acid is unchanged unless bacteria convert it; the phenolic material is rearranged but largely retained; sugars are consumed but that is the point of the exercise. So the structure of a cider — its acidity, its tannin, its body — is genuinely inherited from the fruit, and this is the strongest sense in which apple variety matters.

The volatile fruit aroma survives much less well. Fresh apple aroma depends on six-carbon aldehydes and alcohols formed when fruit tissue is damaged, and on esters accumulated during ripening. Fermentation strips a large part of this: carbon dioxide streaming out of the vessel carries volatiles with it, and yeast reduces many aldehydes to their corresponding alcohols.

The upshot is that a cider does not smell of its apples in the way that a pressed juice does. What it retains from the fruit is the frame, and what it presents as aroma is mostly new.

How yeast makes the aroma

Higher alcohols are made from amino acids by the Ehrlich pathway: the amino group is removed, the resulting keto acid decarboxylated, and the product reduced to an alcohol. Leucine gives isoamyl alcohol, phenylalanine gives 2-phenylethanol with its rose aroma, and so on. The alcohols themselves are pungent and solvent-like in quantity.

Esters are then formed enzymatically from those alcohols. Acetate esters combine an alcohol with acetyl-CoA — isoamyl alcohol plus acetate gives isoamyl acetate, which smells of banana and pear drop. Ethyl esters combine ethanol with medium-chain fatty acids, giving ethyl hexanoate and ethyl octanoate with their apple and tropical characters. Several of these have detection thresholds in the parts-per-billion range, so very small quantities dominate the impression.

Which esters predominate depends on the yeast strain, the temperature and the nitrogen supply rather than on the apple. This is the honest reason two ciders from the same juice can smell quite unlike each other, and the reason that yeast selection is a stylistic decision.

Where variety does show through

None of this means apple variety is irrelevant, and the evidence that it is not is straightforward: trained panels distinguish single-varietal ciders reliably, and the differences are consistent across seasons and producers.

The mechanisms are several. Structure is inherited directly. Phenolic composition, including the chain-length distribution that governs bitterness against astringency, is a varietal property. Aroma precursor content differs between varieties, so the same yeast produces different quantities of the same esters from different juices. And some varietal volatiles do survive, particularly in perry, where the pear-specific decadienoate esters are distinctive and durable.

The reasonable summary is that variety sets the frame and constrains the aroma, and fermentation decides most of what the aroma actually is. Both statements are needed; either alone is misleading.

Also answered on this page

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

Related

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.

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.