Wine · Terminology

Lees

The sediment left after fermentation — dead yeast, grape fragments and tartrates.

Lees are the sediment that settles out of wine after fermentation: spent yeast cells above all, plus grape fragments, tartrate crystals and precipitated proteins. They look unpromising and taste of very little on their own — and they are one of the winemaker's most useful tools.

Left in contact with the wine, yeast cells break down over months in a process called autolysis, releasing mannoproteins and amino acids that add body, creaminess and bready, nutty aromas, and that scavenge oxygen, protecting the wine.

In practice

  • Gross lees — the coarse solids that drop in the first day or two — are normally removed by racking; left too long, they can turn reductive and smell of rotten egg.
  • Fine lees are the ones kept for ageing.
  • Bâtonnage stirs them back into suspension to speed the effect.
  • Lees consume oxygen, so a wine on its lees is naturally protected against oxidation.

Where you'll meet it

  • Muscadet sur lie in the Loire, where the term is legally defined.
  • Champagne, where years on the lees in bottle produce the classic brioche character.
  • Barrel-fermented Chardonnay everywhere.

What autolysis contributes

Compound released Sensory effect
Mannoproteins Body, roundness, mouthfeel; also tartrate stability
Amino acids and peptides Savoury depth, umami
Fatty acids and esters Bready, biscuity, hazelnut aromas
Glutathione Antioxidant protection; freshness held longer

In sparkling wine the effect is dramatic because contact lasts years, not months: the EU minimum for non-vintage Champagne is 12 months on lees (15 months total ageing), and prestige cuvées often sit for a decade.

Managing the risk

Lees are biologically active, so they need attention:

  • Reduction. Too much lees, too little oxygen, and the wine develops hydrogen sulfide — struck match sliding into rotten egg. A racking or a stir usually fixes it.
  • Brettanomyces and other spoilage organisms find lees a comfortable home if sulfur is low.
  • Off-flavours from gross lees: the reason coarse solids come off early.

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