Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
1 · 2 · 3 · 4 · 5 · Microbes Part 1
January/February 2010
Monitoring microbes during cellaring/bottling
Monitoring methods: Sensory evaluation, microscopic exam, culturing, polymerase chain reaction (PCR)- based genetic techniques
We use the name Brettanomyces for the physiologically and morphologically disparate group of yeasts that comprise the species best known as Brettanomyces bruxellensis. Some yeast taxonomists consider all the winerelated yeasts to be the sporulating form Dekkera bruxellensis, the sporulating form of the same microbe (though it does not sporulate in wine). Dekkera anomala, found in European cider, has been isolated in fruit juice from the U.S.
Cellared wines, mostly red, are at risk of becoming infected with Brettanomyces in cellars that have populations of the yeast. Ageing in infected wood is the most common means of contamination, but equipment and topping wine can also spread the yeasts through the cellar. New barrels often have more active “Brett” infections because cellobiose (a byproduct of oak toasting), can support more growth, and because free SO2 binds much more quickly in new oak.
White wines are not usually infected, partly because they seldom go into infected oak, and also because they are kept at lower pH and higher SO2 levels than red wines during cellaring. White wines have been infected with “Brett” when aged in shaved red wine barrels or old wooden uprights, or through winery equipment.
Lisa Van de Water,
Vinotec Napa
fter yeast and malolactic fermentation have completed, and wines settle down for varying periods of cellaring in tanks or barrels, they are still susceptible to spoilage microbes. Some of these are aerobic; some are anaerobic and do not require oxygen for their metabolism.
At bottling, wines should be evaluated carefully for microbial stability, to decide whether filtration or other bottling preparation options are necessary. Bottling wines with active microbes, and with substrates to nurture them, risks disaster. Aerobic microbes are seldom a problem in the bottle, but anaerobic microbes may wreak havoc.
Microbes to watch out for: Dekkera/ Brettanomyces, film-forming yeast (e.g. Pichia, Candida), and Acetobacter, and lactic
Monitoring microbes during cellaring/bottling
Cultures of contaminants from bottling line
acid bacteria; if residual sugar is present, Saccharomyces and Zygosaccharomyces Danger signals: Unexpected change in color, aroma, or flavor, CO2 production, film on surface, clouding of wine that was clear, pH change, volatile acidity (VA) rise, 4-ethyl phenol (4-EP) and 4-ethyl guaiacol (4-EG)
Candida cantarelli (common cycloheximide-resistant cellar yeast)
Candida cantarelli (common cycloheximide-resistant cellar yeast)
Monitoring microbes during cellaring/bottling
Typical cells of Dekkera/Brettanomyces
Monitoring microbes during cellaring/bottling
Conjugating Zygosaccharomyces and ‘shmoo tips’
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