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Microbial spoilage can impart non desirable aromas in wine

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This part of the dictionary explores wine aromas due to microbial spoilage occurring during winemaking or aging. Most of these aroma descriptors are considered wine faults; however, at a low concentrations, some wine tasters like to believe they contribute to the overall complexity of the wine sensory profile. 

This is still a work in progress and we will add regularly new descriptors extracted from the wine aroma wheel.

Feel free to leave a comment or question at the bottom of the page.



  • Aroma: Leesy 
  • Category: Microbial 
  • Type: Yeasty 
  • Aroma Definition: Leesy is actually not a wine fault and evokes the aroma of wine lees, which are made of dead and dying yeast cells, which naturally concentrate when the wine fermentation is complete.  
  • Origin: Lees are usually removed from the finished wine by racking the containers used for fermentation. However, some winemaking styles favour “sur lies” (on lees aging) as the wine gains in flavor concentration and mouthfeel characteristics.  The risk is to develop undesirable aromas of rotten egg if the wine is not aerated regularly (operation is called bâtonage, after the French term). 
  • Wine styles: White wines on lees such as Chardonnay or Muscadet, sparkling wines for which the second fermentation in the bottle is made on lees and made keep such an aromatic character.  
  • Aroma Standard: This is a tough one. If you are close to a winery, you can go and ask to smell lees after a tank has been racked. 

Image credit: Agne27 at the English language Wikipedia


  • Aroma: Baker’s yeast
  • Category: Microbial 
  • Type: Yeasty 
  • Aroma Definition: while lees evoke the aroma of dead yeast, baker’s yeast aroma evokes a fresher smell, similar to the bread  starter used to make the bread dough. 
  • Origin: Likely from the yeast strain and its fermentation activities. It's not a wine spoilage per se at low concentration.
  • Wine styles: I often smell baker’s yeast in Chardonnay wines or sparkling wines
  • Aroma Standard: If available, add some active bread yeast into warm water. Let sit for few hours and add to some white wines.

Image credit: images.yourdictionary.com 


Learn more on how to make your own wine aroma kit.


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