For example, L. oenos can produce diacetyl. At higher levels though, it can be overpowering and impart rancid overtones. The production of flavor compounds is influenced by the metabolic abilities of the strain and the chemical nature of the wine. Furthermore, they must complement the flavors and aromas already present in the wine. Many compounds produced by malolactic bacteria have not been elucidated but different aromas, including butter, nuts, bread, vanilla, and fruit have been identified.
Malolactic fermentation is more common with red wines than with white wines.
Young red wines become more supple showing a marked decrease in harsh bitterness. Along with the increase in pH, the color becomes a less intense red and the aroma loses some grape-like odor in exchange for increased vinosity. The result is a more full-bodied, mellow wine. However, this may not be desirable, as the loss of the fruit odor also decreases varietal character. While the odor may be somewhat unpleasant, their volatile nature allows them to slowly disappear from the wine, leaving no permanent problem.