Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
1 · 2 · 3 · 4 · 5 · Microbes Part 1
January/February 2010
WINEMAKING
3. Pediococcus
Some members of this genus (Pediococcus pentosaceous) can grow in wine without residual sugar or malic acid. Sometimes their growth causes a cosmetic problem only (haziness and fine sediment), but sometimes biogenic amines may be produced, or an unpleasant aftertaste (not mousiness) may develop. Reds, especially Pinot Noir, blended shortly before bottling and not sterile-filtered are most at risk.
4. Brettanomyces/Dekkera
Test for Brettanomyces on a regular basis before preparing wine for bottling, to determine whether the population is increasing or declining, unless the wine will be filtered with a 0.65 μ or 0.45 μ membrane. If they grow in the bottle, Brettanomyces
produce a small amount of CO2, which may not be noticed unless the wine is examined carefully. Sensory changes in the bottle can be profound, from 4-EP, 4- EG, and other metabolites.
Bottle variation is common, with some bottles showing little Brett character but other bottles severely affected, their fruity aromas replaced by horse-sweat and Bandaid® odors, accompanied by a bitter, metallic finish. Interestingly, these characters can seem to intensify in the bottle even though the actual levels have not changed.
Non-wine microbes in the bottle
Microbes that are unable to grow in wine may survive the inhospitable environment for a few days to weeks (or sometimes, months). They
make culturing difficult until they die, for they may cover or inhibit wine microbe colonies in culture. Molds and spore-forming bacteria are common bottling contaminants, as are non-wine cocci and some yeasts.
These microbes are important because their presence can indicate problems with bottling sanitation, which can be serious. If more than a few non-winemicrobes grow onmembrane filtration cultures after bottling, a complete evaluation of bottling line sanitation is recommended to find the source(s) of infection.
   
[Lisa Van de Water, the “bad wine” lady, can be reached through the Vinotec group website, www.vinotecnapa.com, or by email: badwinelady@aol.com.]