MALOLACTIC FERMENTATION

Malolactic fermentation (MLF) is an integral step in red winemaking, which not only is wine de-acidification, as it will also influence the composition of volatile fermentation-derived compounds with concomitant effects on wine sensory properties and the wine color profile. Long-established winemaking protocols for MLF induction generally involve inoculation of bacteria starter cultures post-alcoholic fermentation, however, more recently there has been a trend to introduce bacteria earlier in the fermentation process. Co-inoculation greatly reduces the overall fermentation time, and the rate of alcoholic fermentation is generally not affected by the presence of bacteria. In addition, the fermentation-derived wine volatiles profile is distinct in wines where bacteria were inoculated at a later stage of alcoholic fermentation. Most red wine studies have shown an overall slight decrease in wine colour density following MLF, but this is not influenced by the MLF inoculation regime.
However, there can be differences in anthocyanin and pigmented polymer composition, with co-inoculation exhibiting the most distinct profile. Studies in Pinot Noir have shown some more significant loss in color following MLF. The color stability in Pinot noir wines following MLF can be influenced by several parameters and winemaking practices; onset and speed of MLF, time length of a planned MLF delay and the species of LAB used for MLF (Oenococcus oeni or Lactobacillus plantarum). Acetaldehyde is important in color formation and MLF can influence this process.