Filtration
A clarification technique that passes wine through a filter to remove yeast, bacteria, particles, and other solids — producing a stable, clear wine but potentially removing some flavour compounds.
In depth
Filtration removes physical particles from wine by passing it through a medium with defined pore sizes. Different types of filtration serve different purposes: coarse filtration removes gross particles; sterile filtration (very fine pore size) removes yeast and bacteria, ensuring microbiological stability without sulphur.
Sterile filtration is required for wines with residual sugar bottled without preservatives — removing all yeast prevents refermentation in the bottle. German Riesling with residual sweetness is a classic example where sterile filtration is essential.
The controversy around filtration mirrors that around fining. Critics argue that filtration strips colour, texture, and aromatic compounds from wine — particularly fine tannin structure in reds. Proponents argue that properly executed filtration has minimal impact while preventing instability issues in bottle.
Many prestige red wine producers avoid filtration entirely, choosing instead to use fining, extended lees contact (which helps clarify naturally), and careful racking. "Unfiltered" on a label signals a hands-off approach that some consumers interpret as a quality indicator.
Related exam topics
Frequently asked questions
- Why do some premium wine labels say "unfiltered"?
- Unfiltered means the wine was not passed through a filter before bottling. Some producers argue that filtration strips flavour compounds and fine tannin structure. Unfiltered wines may have a slight haze or sediment — particularly with bottle age — which is normal. The "unfiltered" label signals a minimalist approach that many premium producers adopt for their finest wines, though it requires careful handling and storage.
Practise questions on this topic
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