Monitoring methods: Sensory evaluation, microscopic exam, culturing, polymerase chain reaction (PCR)- based genetic techniques

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.

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.

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)