Loss of Pinot noir wine color and polymeric pigment due to malolactic fermentation (MLF) and potential causes for this loss were studied. Delaying MLF was investigated as a method to minimize loss of color and polymeric pigment as Pinot noir wines were held at 13°C for 0, 14, 28, 100, and 200 days before inoculation with O. oeni VFO.
Delaying MLF did not impact loss of color at 520 nm but delaying MLF for increasing time periods reduced the loss of polymeric pigment to the point that after 200 days no loss was noted compared to the control.
The role of acetaldehyde and/or pyruvic acid degradation by O. oeni during MLF was investigated as a cause for reduced polymeric pigment formation. Wines that had undergone MLF were supplemented with acetaldehyde and/or pyruvic acid to the levels measured in control wines that did not undergo MLF.
Wines with acetaldehyde additions had higher color and polymeric pigment than MLF wines with no additions while addition of pyruvic acid resulted in no improvement in color or polymeric pigment.
However, acetaldehyde additions did not completely prevent loss of color after MLF and the possibility that this color loss was due to fining by O. oeni was explored.
Wines that did not undergo MLF but were exposed to inactivated O. oeni cells showed no difference in color, polymeric pigment, and monomeric anthocyanin compared to the control suggesting that loss of color during MLF was not due to fining by O. oeni cells.
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