Impact of Malolactic Fermentation on Red Wine Color

The color of a red wine is an important sensory attribute that originates primarily from anthocyanins. However, development of stable red wine color is impacted by compounds such as p-coumaric acid, caffeic acid, catechin, and quercetin that are involved in copigmentation reactions as well as acetaldehyde and pyruvic acid. While it is known that yeast can alter the concentrations of some of these compounds, little is known regarding the impact malolactic bacteria may have on red wine color development. This project investigates the effect of the malolactic fermentation (MLF) on red wine color and the ability of malolactic bacteria to degrade compounds important to the development of stable red wine color. Pinot noir and Merlot wines were produced in 2009. A portion of the Pinot noir and Merlot wines underwent a simultaneous alcoholic and malolactic fermentation (S. cerevisiae VQ15 + O. oeni VFO) while the remainder were only inoculated with S. cerevisiae VQ15. At dryness, all wines were pressed and sterile filtered (0.45 ?m). For both the Pinot noir and Merlot wines, three carboys were inoculated with either O. oeni strain VFO, Alpha (Lallemand), or VP-41 (Lallemand) at approximately1 x 106 cfu/mL. The remaining carboys of wine were not inoculated with O. oeni. All wines were kept at 20°C. Some of the wine that had not undergone MLF was pH adjusted to the same final pH of wines that had completed MLF. Samples were taken before and after MLF for analysis and wines were sterile filtered, bottled, and stored at 13°C. As had been seen with wines produced in 2008, wines that underwent MLF, including wine produced with a simultaneous alcoholic and MLF had the lowest color throughout storage. MLF (+) Pinot noir wines had significantly lower color after completion of MLF (day 0) and this difference remained after 180 days with close to a 20{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} difference in color @ 520 nm being observed. This trend was also seen for the Merlot wines although the differences were larger with a 30-35{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} difference in color @ 520nm after 180 days storage. Color differences appear to be related to pigmented polymer formation as after MLF both Pinot noir and Merlot wines had significantly lower pigmented polymers than wines that had not undergone MLF. Differences increased over time and by day 180 there was a 30-35{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} difference between MLF (+) and MLF (-) Pinot noir wines and a 40{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} difference for Merlot MLF (+) wines. Furthermore, there were significant differences between the monomeric anthocyanin content of MLF (+) and MLF (-) wines. Pinot noir and Merlot MLF (+) wines contained significantly higher concentrations of monomeric anthocyanins than MLF (-) wines. These differences increased after 90 days storage with Pinot MLF (+) wines having 30-40{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} greater monomeric anthocyanin content than control pH wines and a 30-48{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} difference for Merlot MLF (+) wines. Overall, different O. oeni strains did not cause a significant difference in color @ 520 or polymeric pigment indicating that O. oeni strains did not impact red wine color differently.