Winemaking
Biological ageing and flor
Ageing wine beneath a living film of yeast, which protects it and transforms it.
Overview
When wine is fortified to around 15% — low enough for yeast to survive — a film called flor can grow on the surface.
The flor consumes oxygen, glycerol and alcohol, and produces acetaldehyde. It shields the wine from oxidation while fundamentally changing its character, giving the saline, bread-dough, green-olive profile of Fino and Manzanilla.
It is a living thing, which is why Fino must be drunk fresh and why an opened bottle behaves like white wine rather than like Port.
Sources
Sources consulted
- Consejo Regulador de las Denominaciones de Origen Jerez-Xérès-Sherry — Consejo Regulador del Jerez
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Fermentation
Yeast converting sugar into alcohol and carbon dioxide — the step that makes wine wine.
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How red wine is made
Fermenting grape juice in contact with the skins, which is where colour and tannin come from.
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How white wine is made
Pressing the juice off the skins before fermentation, then fermenting the clear juice.