page_title: Wine fault
section_title: Bitterness taint
hierarchical_section_title: Wine fault / Microbiological / Lactic acid bacteria / Bitterness taint
caption_attribution_description: Español: Estructura química de la Acroleína Description: Skeletal formula of acrolein (2-propenal, C3H8O). Author, date of creation: self made by Ben Mills at 15:01, 9 March 2006 (UTC). Source: user-created image Comments: high-resolution black and white PNG; ChemDraw / Photoshop.
context_page_description: A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine but at insufficient concentrations to be of issue. In fact, depending on perception, these concentrations may impart positive characters to the wine. However, when the concentration of these compounds greatly exceeds the sensory threshold, they replace or obscure the flavors and aromas that the wine should be expressing. Ultimately the quality of the wine is reduced, making it less appealing and sometimes undrinkable.
  There are many causes for the perception in wine faults, including poor hygiene at the winery, excessive or insufficient exposure of the wine to oxygen, excessive or insufficient exposure of the wine to sulphur, overextended maceration of the wine either pre- or post-fermentation, faulty fining, filtering and stabilization of the wine, the use of dirty oak barrels, over-extended barrel aging and the use of poor quality corks.
context_section_description: Bitterness taint or amertume is rather uncommon and is produced by certain strains of bacteria from the genera Pediococcus, Lactobacillus, and Oenococcus. It begins by the degradation of glycerol, a compound naturally found in wine at levels of 5-8 g/L, via a dehydratase enzyme to 3-hydroxypropionaldehyde. During ageing this is further dehydrated to acrolein which reacts with the anthocyanins and other phenols present within the wine to form the taint. As red wines contain high levels of anthocyanins they are generally more susceptible.
caption: Acrolein
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