For particularly the higher price point wine market segments, wine maturation is a very significant step. Some factors to consider are: the tank or barrel size, the use of oak or not, the length of maturing and ageing conditions and to micro-oxygenate or not. Wine transfers and managing “wine lees” is one of the most important dimensions of enhancing “wine quality through mastering wine maturation”.
What is “wine lees?” I guess it depends on who you are talking to… The official definition of lees is the “residue that forms at the bottom of recipients containing wine, after fermentation during storage or after authorized treatments, as well as the residue obtained following the filtration or centrifugation of this product” (if you are ever inclined to read the EU Regulations)…
I suppose lees for me as a winemaker, is a tool to potentially reach a stylistic goal, i.e. to enhance the structure and mouth feel of the wine, to enhance body and increase the aromatic complexity, and ultimately to achieve longevity.
There are a few technicalities to consider whenever lees is discussed. Heavy lees in red wines is considered to be a combination of yeast cells, tartrate crystals and precipitated color matter and tannins; or involve compounds made up of proteins, tannins and polysaccharides. In white or rosé wines heavy lees may consist of solid grape particles (depending on the clarity of the juice prior to primary fermentation), yeast cells, tartrate crystals and precipitated colloidal matter. It may even include residues of settling treatments such as PVPP, bentonite and casein.
The technical definition of light lees (or “functional lees” as I call it) is: “particles which remain suspended 24 hours after a wine has been moved, and consist mainly of yeast cells and lactic acid bacteria.”
The truth is that, no matter the semantics, optimal lees management will contribute to quality in one or more of the following ways:
1. Increased polysaccharides benefits
-A direct sensorial effect on wine structure – roundness, volume and coating. (Polysaccharides, of different origins, are added to numerous products such as sweets and dairy desserts, in the food industry.)
-Some released colloids or mannoproteins block the reactions of tartrate crystallization and thus enhance tartrate stability.
-Enhanced protein stability
-Binding reactions between tannins, color pigments, proteins and volatile compounds stabilize some of these compounds, which “protects” them against polymerization and precipitation.
-Mannoproteins may have an indirect effect on astringency when they combine with phenolic compounds from grapes or oak, thus acting as protective colloids that decrease the intensity of tannin.
2. Amino acids and nucleic acids are released. The cell content of yeast is rich in amino acids and nucleic acids and is regarded in the food industry as flavor enhancers. This may intensify various taste sensations and complex aromas according to Delteil, as the concentrations of these compounds can be affected by lees contact.
3. Esters & other volatiles are released, especially the esters of fatty acids with sweet and spicy aromas. Primary grape aromas are complemented by the sweeter and spicy aromas of the ethyl esters.
Many wines from around the world and even dimensions of marketing are built upon this simple term – “sur lie.” From wonderful, rich Muscadets from the Loire, great Burgundies, to two of South Africa’s greatest unwooded Chardonnays and Chenins – the Jordan Chardonnay “Sur lie” and the Bosman Family Vineyards Chenin blanc “Sur lie.”
Look out for The (Colloidal) Matrix Part II