A couple of weeks ago, I reviewed a Sauvignon Blanc from Chile. The tech sheet that came with it described how the wine was made including the terms 'maceration,' 'lees,' and 'battonage.' We took a brief look at 'maceration' last time where, simply put, it is a term for allowing the grape skins, seeds and stems to soak in the juice (the must) either prior to fermentation or during fermentation.
After the yeast does its job during fermentation by 'eating' the natural sugar in the must and transforming it to alcohol, fermentation is complete and the yeast dies. These dead yeast cells that remain in the wine, along with bits of grape seeds and solids, are called 'lees.'
At this point, the lees can either be removed from the wine (by racking or fining methods) or they may remain in the wine. If they are left in the wine, they will break down and release compounds that interact with the fermented wine. This interaction can create additional complexity, aroma and flavor.
But, with time, the lees tend to settle at the bottom of the aging vessel. If the lees are just left in the bottom of the aging vessel, they can clump up and actually become detrimental. So, if a wine maker wants to age their wine 'on lees,' they need to periodically stir the wine to keep the lees mixed in with the aging wine. Battonage (or Bâtonnage) is this periodic stirring of the wine. Battonage essentially helps redistribute all these positive lees compounds into the wine, making sure all the wine comes in contact with them.
The term battonage derives from the stirring stick, a baton. The baton is placed in the top opening of a barrel (bung hole) and gentle rotated within the barrel to stir the wine and re-distribute the lees during aging.
So, there you have it. Many wine makers use maceration, lees and battonage in their wine making process. A bit technical, yet important parts of making all the great wines we enjoy. Cheers!