Impact of Malolactic Fermentation on the Color and Color Stability of Pinot noir and Merlot Wine

Malolactic fermentation (MLF) is an integral step in red winemaking that results in a decrease in acidity and can also influence additional wine quality parameters. This study examined the impact of MLF on red wine color and the ability of Oenococcus oeni to degrade compounds important to the development of polymeric pigments. Pinot noir and Merlot wines were produced where a portion of the wines underwent a simultaneous alcoholic and malolactic fermentations with O. oeni strain VFO. Post-alcoholic MLFs were conducted using VFO and two additional O. oeni strains in sterile filtered wines. A control wine that did not undergo MLF was pH adjusted to the same pH as wines that had undergone MLF. Wines that underwent MLF (MLF+) contained lower concentrations of acetaldehyde and pyruvic acid than wines that did not undergo MLF (MLF+). Wines that underwent MLF with O. oeni VFO also had higher concentrations of caffeic and trans-p-coumaric acids. MLF+ wines had significantly lower color and polymeric pigment content than MLF-wines and contained significantly higher monomeric anthocyanins. Vitisin B concentrations were also significantly lower in wines that underwent MLF. These differences remained throughout nine months of storage, demonstrating that MLF can affect red wine color independent of pH change. While O. oeni influenced the concentration of phenolic and nonphenolic compounds involved in red wine color development there were no strain specific differences in color and polymeric pigment content.