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Winemaker Greg La Follette of La Follette Wines uses batonnage for pinot noir as well as chardonnay. into wine in a good and useful way rather than being deleterious." CHEMICAL AND MICROBIOLOGICAL IMPACTS When yeast cells die at the end of alcoholic fermentation, their cell walls break down and undergo yeast autolysis to release compounds into wine such as amino acids, proteins, peptides, and cell wall polysaccharides such as mannoproteins. Batonnage stirs the settled lees back into suspension to increase wine contact and the release of these yeast compounds into the wine. La Follette said a major benefit of batonnage is that it breaks up stratification of the settled lees that tend to have a lower pH at the bottom than the top, which also affects the wine's oxidation-reduction potential. This practice is recommended only with wines made from clean, sound fruit. Some winemakers use sur lie and batonnage with particular yeasts and yeast strains. Some commercial yeast strains are designed for better polysaccharide production, and some yeasts promote early autolysis after fermentation. UC Davis professor of enology and microbiologist Dr. Linda Bisson said a benefit of sur lie aging is that it can reduce astringency to soften and improve mouthfeel. "During sur lie, the release of compounds from yeast cells can provide nutrients and stimulate the growth of other microbes," she said. "This w w w. v w m m ed i a .com w mm e d a.com co o can be desirable if it helps promote bacteria for malolactic fermentation (ML), but if it promotes unwanted microbes, such as Brettanomyces, then it's not." She also noted that reduction, and hydrogen sulfide offaromas, are potential issues. Regular evaluation of the lees and the wine as it develops guides winemaking decisions on the frequency of stirring, and when to end stirring and sur lie. La Follette takes a lees sample from the bottom of each barrel prior to sur lie, using a plexiglass racking tube to assess the lees visually and by smell and taste. "When I sample lees, I look for off-aromas such as mercaptans and sulfides," he explained. "If I find a little reductive character, I may still go with it, as it may add to the aromatic complexity, and I know that stirring will provide oxygen to help control reduction. "When I taste lees, I look for bitterness, and if they don't taste good, I'll rack off and not use them." La Follette also evaluates the lees' freshness during elevage. "If they're dark in color and have a gloppy consistency, they've been absorbing oxygen, and if they have a barbecue smell, then it's probably time to take the wine off," he said. Feb 2014 J a n - Fe b 2014 F 4 | V INE YA RD & W INE RY M A N A G EM E N T IN R NE Y E AG E EN 63 6