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Friday, January 15, 2021

Wine Sensory Defects---Brettanomyces

I recently came across some lecture notes given by George Vierra called "Sensory Defects in Wine". I was familiar with most of what he was talking about but there was an entire section on Brettanomyces and this intrigued me.
I haven't really written about Brettanomyces in detail, only this post 2009 Bernard Baudry Chinon where I wrote a small blurb on the Janus-faced nature of Brettanomyces. So, this is a closer look at Brettanomyces.
Have you ever smelled barnyard or band aid aromas coming from your wine? I distinctly recall one red wine tasting that we had at our home decades ago where one of our friends thought that an old Bordeaux wine we opened smelled like band aids to her! Those aromas come from the yeast Brettanomyces bruxellensis also known as Dekerra, which is the spore forming “perfect” sexual form of Brettanomyces.
Currently there are five known species of Dekkera/Brettanomyces:
  • D. (B.) bruxelllensis
  • B. custersianus
  • D. anomalus
  • B. naardenensis
  • B. nanus
The conditions that allow Brettanomyces to multiply include:
  • cellar hygiene not under control
  • SO2 not used appropriately
  • barrels and infected containers neglected and allowed to absorb oxygen from the air
  • more common in red wine because it contains a higher level of polyphenols as well as a high pH
  • growth is slow but much faster above 68 oF and essentially stops below 46 oF
  • resistance to sulfur dioxide, alcohol and low sugar levels give it great potential to spoil wine
  • filtration can physically remove Brettanomyces
Compound Aroma/Flavor
4-ethylphenol medicinal
valeric acid green apple
isovaleric acid wet goat; rancid, horsey aroma
4-ethylphenol aromas of stables, barnyards and sweaty saddles; bandaid; chemical signature of Brettanomyces infection
isomers of 2-acetyl-tetrahydropyridine and 2-acetyl-1-pyrroline, experienced retro-nasally mousiness; bread crust, stale popcorn, and mouse urine
4-ethylguiacol leather and spice
The following are recommendations if you don't want Brettanomyces tainted red wine:3
  • avoid barrels; use stainless steel
  • avoid cross contamination; when taking barrel samples, use plastic thiefs that are used just once
  • avoid doing rack and return where the wine would go from several barrels to be mixed up in one tank: instead, rack each barrel separately to tank and return, clean the tank before repeating the procedure with the next barrel
  • keep the acidity low, either by acidifying or harvesting earlier
  • avoid lees ageing, keep barrels topped up, and aggressively clean new and used barrels

References:
1. George Vierra, "Sensory Defects in Wine".
2. Jamie Goode, Brettanomyces.
3. Jamie Goode, Brettanomyces Master Class.

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