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Sometimes a glass of wine smells like dark fruit and spice. Other times, something unexpected appears — leather, earth, even a hint of barnyard. For some wine lovers, those aromas add intrigue. For others, they signal a flaw.

In this episode of The Wine Lab, Dr. Andreea Botezatu explores one of the most debated microorganisms in wine: Brettanomyces.

Why do some wines develop these distinctive aromas? Why have certain traditional European wines historically embraced them while many modern wineries work hard to avoid them? And what is actually happening inside the wine at the chemical and microbiological level?

From cellar history in France to volatile phenols and modern detection methods, this episode unpacks the science and culture behind the yeast that continues to divide the wine world.

Open a bottle, take a careful smell, and join the conversation.

Glossary

Brettanomyces
A genus of yeast considered a spoilage organism in wine. The species most associated with wine is Brettanomyces bruxellensis, which produces aromatic compounds known as volatile phenols.

Volatile Phenols
Aromatic compounds responsible for Brett-related aromas in wine, often described as leather, barnyard, smoke, or spice.

4-Ethylphenol (4-EP)
One of the primary volatile phenols produced by Brettanomyces. Commonly associated with aromas described as stable, leather, or medicinal.

4-Ethylguaiacol (4-EG)
Another volatile phenol produced by Brett. Often contributes smoky, clove-like, or spicy notes.

Hydroxycinnamic Acids
Naturally occurring phenolic compounds in grapes, including p-coumaric acid and ferulic acid. These act as precursors that Brett converts into volatile phenols.

Terroir
A concept in wine describing how a wine reflects its place of origin, including climate, soil, vineyard practices, and sometimes traditional cellar environments.

Spoilage Yeast
A microorganism that can negatively affect wine quality by producing undesirable compounds.

PCR (Polymerase Chain Reaction)
A molecular technique used to detect specific microorganisms, including Brettanomyces, by identifying their DNA.

GC-MS (Gas Chromatography–Mass Spectrometry)
An analytical technique used to identify and quantify volatile compounds in wine, including Brett-related phenols.

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