The SOMM Journal

February / March 2018

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42 { THE SOMM JOURNAL } FEBRUARY/MARCH 2018 { what somms should know } I LOVE WORKING with lees: After fermentation, it's one of the more signifi- cant ways to guide style in winemaking. Depending on how long a wine sits on the lees (if at all) and how the lees are treated, they can result in a variety of tactile and aromatic changes. The Lifecycle of Lees and Its Effect on Wine When wine settles after fermentation, the lees fall to the bottom of the tank in two layers. Within a day, the heavier particles settle; known as the gross lees, those particles are mostly made up of leftover grape bits, dirt, and seeds. In the following days, the fine lees—the dead yeast cells left from fermentation that are a brighter white in color—settle on top of the gross. It's the fine lees that prove especially im - portant in the winemaking process. In the early life of white wines, a key function lees perform is absorbing oxygen. As a result, they protect a wine from oxidation and preserve fresh, youth - ful characteristics. For wines undergoing malolactic fermentation, ML bacteria prefer anaerobic (oxygen-free) environments; nutrients released from the yeast also aid and encourage this process. Bâttonage, or lees stirring, is most important early after fermentation, as it keeps the lees from compacting and exhibiting undesired hydrogen sulfide odors. While they're beneficial for young white wines, lees can adsorb and indirectly destroy unbound color molecules in young reds—lowering the amount available to bind with and stabilize tannin. Oxygen is also beneficial to color and tannin binding, so lees' oxygen absorption can stifle these functions. Once the main flurry of binding has happened at around six months, lees can safely be added back into the wine. At the risk of ruining sur lie–aged wines for you, what winemakers seek from lees aging is the decay of yeast cells and the emptying of their "guts" into a wine. Ap - petizing, right? This is the famous autolysis process, but because most wines are bottled before the process is complete, it's rarely able to exert its full effect in most wines. Autolysis begins slowly with the degradation of the cell's membrane, which allows its insides to seep little by little into the wine; finally, after about a year, the membrane ruptures and the cell's contents are entirely released. These contents, primarily mannoproteins, end up working much of the magic in lees aging: They incite an increase in mouthfeel and weight, and in red wines, they coat and soften tannins. Bâttonage and warmer tem - peratures can speed up the autolysis pro- cess, and winemakers looking for emerging lees aromatics and their body-enhancing effects often stir every couple weeks. Eventually, over a period of years, the lees break down completely and are fully absorbed into the wine. Lees do a host of other things: They can aid stability, tinker with the intricacies of aromatics, and mitigate susceptibility to spoilage bacteria. They're a useful tool for fine-tuning the style of a wine. SUMMARIZING AND ADVOCATING FOR BÂTONNAGE by Alex Russan Mid-bâtonnage at Jordan Winery in Paso Robles. PHOTO COURTESY OF JORDAN WINERY A Stirring Case for Lees

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