The Role of Lees in Maturation Flashcards
Define lees.
Lees are the sediment that settles at the bottom of a wine vessel.
It is made up of dead yeast, dying yeast and bacteria, grape fragments, precipitated tannins, nutrients, and other insoluble compounds.
Define gross lees.
Lees that are made up of large particles that settle within the first 24 hours after fermentation finishes.
Define fine lees.
The lees made up from smaller particles that settle slowly.
Define racking.
Removal of the lees from a wine by transferring the liquid away from the sediment.
What positive effects are generated by maturing wine on the lees?
- autolytic flavors
- modification of flavors and tannins
- stabilization
- protection against oxidation
Which flavors are associated with yeast autolysis?
Yogurt, dough, biscuit, and toasted bread
How does lees maturation affect the tannins in red wine?
Compounds from autolysis of the yeast bind to the tannins from the grapes and oak wood, and make them softer and less astringent.
How does lees maturation affect the color in red wine?
Autolysis derived compounds bind to phenolic compounds, and can reduce color.
How do the lees stabilize the wine during maturation?
Lees aging prevents unstable proteins from causing haze in the wines.
Lees also help protect the wine against oxidation, and reduce the need for SO2.
What negative impact can lees maturation have on a wine?
If the lees are too thick, the wine can produce volatile reductive sulfur compounds.
What effect do the lees have on microbial activity?
Lees can provide nutrients for both malolactic bacteria, but also unwanted microbes including brettanomyces.
What is the main disadvantage of lees maturation for the wine business?
Lees aging costs additional money to maintain and monitor, however it is often performed simultaneously with barrel aging, and so these costs may be minimal.
In addition to removing yeast, what effect does racking have on a wine?
Racking can introduce oxygen to the wine. This may be advantageous for certain styles of wine, but may be avoided with aromatic wines by using inert gas to push the wine.
