malolactic

Malolactic refers to malolactic fermentation (MLF), a secondary microbial process in winemaking in which lactic acid bacteria convert malic acid into lactic acid and carbon dioxide. This transformation lowers total acidity and can raise pH, affecting mouthfeel, balance, and perceived freshness.

MLF is most commonly carried out by Oenococcus oeni, though other lactic acid bacteria such as Lactobacillus, Pediococcus, and Leuconostoc can contribute under certain conditions. The process typically follows alcoholic fermentation and can occur spontaneously or be initiated by inoculation with a commercial bacterial culture.

Flavor and aroma changes accompany MLF. In addition to acidity reduction, it can produce diacetyl, leading to buttery or creamy notes, and may alter ester profiles. By softening sharp malic acidity, MLF can influence the overall impression of freshness and roundness. In some cases, however, off-flavors or undesirable aromas may develop if non-desirable bacteria dominate.

Control and management are important in winemaking. Winemakers regulate MLF by selecting bacterial strains, adjusting temperature (roughly 18–22°C for faster performance), managing pH and sulfur dioxide levels, and monitoring progress through malic acid measurements. MLF can be slowed or halted by cold stabilization, filtration, or, in some situations, higher SO2 levels, depending on grape and style.

Outcomes and considerations. Whether to encourage or avoid MLF depends on the wine style, grape variety, and vintage. When desired, MLF can soften acidity, add complexity, and influence mouthfeel; when not, it is prevented to preserve crispness and brightness. It is a common tool in modern winemaking and a key factor in shaping wine profiles.