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62 WINES&VINES February 2016 WINEMAKING PRACTICAL WINERY & VINEYARD content and monomeric anthocy- anin concentrations were the same as the control wine that did not undergo MLF. From a practical winemaking point of view, delay- ing the MLF for 200 days to im- prove color does carry some risk. No SO 2 additions can be made until MLF has been completed. Wine would therefore be at risk for microbial spoilage during this time, and so it would need to be stored cool (under 55 o F) to mini- mize the risk of microbial growth. The risk of delaying the addition of SO 2 versus improving wine color would have to be carefully considered by the winemaker on a case-by-case basis. The improved polymeric pig- ment formation in wines where MLF was delayed was likely due to acetaldehyde being present in the wine for an extended period of time. A number of studies have reported the ability of O. oeni to degrade acetaldehyde in wine, 16,19 and acetaldehyde is known to play a role in the formation of poly- meric pigments. This is also sup- ported by improved color and polymeric pigment content when acetaldehyde was added back to the wine post-MLF. While metabolism of acetalde- hyde by O. oeni explained some color loss, it did not explain all of it. Therefore, an experiment was conducted to investigate the ad- sorption of anthocyanins to O. oeni cell walls (as has been shown to occur with yeast cell walls), 12,15 to determine whether this could account for the remainder of the observed color loss. Addition of inactivated O. oeni cells at a high cell population that would be found at the end of MLF did not, however, cause a loss in color at 520 nm or monomeric anthocyanin concentration. This is in contrast to what has been reported for wine yeast but may be due to the smaller relative sur- face area of the bacteria or due to the likely different electrostatic nature of a bacterial cell wall com- pared to a yeast cell wall. Conclusions Anecdotally, winemakers have reported that MLF can cause a loss of color in red wines, but the cause of this has not been known. In the present study it was dem- onstrated that MLF can cause a significant loss of color indepen- dent of the pH change that always accompanies this metabolic pro- cess. The color loss corresponded with lower polymeric pigments in wine that underwent MLF and may be related to the degradation of acetaldehyde by O. oeni. Lower color and polymeric pigment con- tent was observed regardless of whether MLF occurred simultane- ously or after alcoholic fermenta- tion, and no differences between O. oeni strains were noted. Results from this study suggest that winemakers may be able to improve the polymeric pigment content of Pinot Noir by delaying MLF. The wine would, however, be at risk for microbial spoilage during this time and should be stored at a cool temperature (under 55° F) to minimize the risk of microbial growth. 21 Research will continue into additional techniques that may add to the formation of polymeric pigment prior to MLF. As only three O. oeni strains were utilized in the present study, additional malolactic bacteria strains will be tested to determine if strain selec- tion can aid in the retention of color and polymeric pigments during the MLF process. James Osborne is an associate professor and enology extension specialist in the Department of Food Science and Tech- nology at Oregon State University. His research focuses on the impact of wine microorganisms such as wine lactic acid bacteria and Brettanomyces on wine quality. Osborne also teaches under- graduate and graduate classes in wine production and analysis. This work was made possible by grants from the Oregon Wine Board and the American Vineyard Foundation. The authors would like to acknowledge support from the Oregon Wine Research Institute and OSU. Tonnellerie Saint Martin North America PO Box 5268 Paso Robles, CA 93447 O. 805-226-5622 F. 805-226-5623 M. 805-550-8937 E. info@saintmartinusa.com W. www.tonnelleriesaintmartin.com Tonnellerie Saint Martin When tradition meets the highest standard of quality The risk of delaying the addition of SO 2 versus improving wine color would have to be carefully considered.