Editing Malolactic fermentation (section)

===Acrolein and mannitol taint===
[[File:Raisin botrytisé.JPG|left|thumb|Wine grapes infected with ''Botrytis'' bunch rot tend to have higher levels of glycerol which can be metabolized by LAB into acrolein. Especially in red wine grapes with their high phenolic content, this can lead to the development of bitter-tasting wines as the acrolein interacts with these phenolics.]]
The degradation of glycerol by some strains of LAB can yield the compound [[acrolein]]. Glycerol is a sweet-tasting [[polyol]] present in all wines, but at higher levels in wines that have been infected with ''[[Botrytis cinerea]]''. An "active-[[aldehyde]]", acrolein can interact with some [[phenolic compounds in wine]] to create highly bitter-tasting wines, described as ''amertume'' by Pasteur. While at least one strain of ''O. oeni'' has been shown to produce acrolein, it is more commonly found in wines that have been infected by strains of ''Lactobacillus'' and ''Pediococcus'' species such as ''L. brevis, L. buchneri'', and ''P. parvulus''. Acrolein taint has also shown to be more common in wines that have been fermented at high temperatures and/or made from grapes that have been harvested at high [[Brix]] levels.<ref name="Wine Micro"/>

Heterofermenting species from the genus ''Lactobacillus'', as well as some wild strains of ''O. oeni'', have the potential to metabolize fructose (one of the main sugars in wine) into the sugar alcohols [[mannitol]] and (less commonly) [[erythritol]]. These are sweet-tasting compounds can add sweetness to a wine where it is not desired (such as [[Cabernet Sauvignon]]). Mannitol taint, described as ''mannite'' by Pasteur, in wines is often accompanied by other wine faults, including the presence of excessive levels of acetic acid, diacetyl, lactic acid, and [[2-butanol]], which can contribute to a "vinegary-[[ester]]y" aroma. The wine may also have a slimy sheen on the surface.<ref name="Zoecklein"/>