Kendall-Jackson Blog > Wine Education > A Primer On Malolactic Fermentation

A Primer On Malolactic Fermentation

Tasting Fermentations

Last week we talked about how busy we are in the winery, despite crush being past us.  I also mentioned that the wines are going through malolactic fermentation (ML).  I thought it would be worthwhile to give an overview of what that term actually means.

Wine is perhaps the most blessed of any commercially produced product.  Due to the very nature of wine, it is not susceptible to infection from any organism that could be harmful to people.  Unlike milk or even fresh fruit juice, once fermented, no pathogen can survive in wine to make someone sick.  This is because of two main characteristics of wine: high alcohol content and low pH level (an indicator of the acidity in a solution – like wine).  As a result of these two factors, only a very small number of organisms can possibly survive in the wine environment.

One of the most successful of these organisms is the yeast, Saccharomyces, which is responsible for converting sugar to alcohol in the primary fermentation.  Another organism that is found around grapes and wine is the Lactic Acid Bacteria Oenococcus Oeni.  This special type of bacteria provides two valuable services to the winemaker: first by bestowing greater stability on the finished wine, and second by softening it and making it more approachable.

When I say the wine becomes more stable, I mean that it is no longer subject to this process taking place.  As I mentioned, ML bacteria are ubiquitous in the winery.  If the conversion does not take place at this time, it could very easily take place later in the bottle.  This would turn our valuable product into a fizzy, hazy one that would be off-putting to the consumer.  Once all the malic acid is converted, we no longer run the risk of this happening.  The second effect, one of softening, happens as the bacteria convert Malic acid, a tart, green apple-like acid common to most fruit, into Lactic acid, a softer, mellower tasting acid.

We desire this effect in most wines that we produce.  One notable exception to this is Sauvignon Blanc.  Where the wine style dictates a crisp, somewhat tart, fresh and lively product, ML is avoided by the use of sulfites and ultimately filtration prior to bottling.  Most wine styles encourage the conversion for the softening effect I already mentioned; but there can be other flavor or aroma contributions as well.

For example, one byproduct of the malo-lactic conversion is a compound that smells just like butter. Some strains produce more of this compound than others.  The winemaker can choose his strain to avoid it, or choose one that produces it in abundance.  This would be the choice made in order to create the more buttery style of Chardonnay.

In the past several wineries have discovered a beneficial ML bacteria strain whose flavor and aroma contributions are just right, and they have isolated it to keep it for future use.  One such strain was isolated at the Matanzas Creek Winery.  This strain is still used by some wineries today.

Next week we’ll talk more on the actual nuts and bolts.  Feel free to post any questions you might have in the comments section of this blog, and I’ll do my best to answer them.  Happy holidays!  I hope your celebrations are joyous and with them you enjoy a great bottle of wine!

CATEGORY: Wine Education, Winemaker

  • Ed Bavais

    I can taste the buttery flavor you mentioned in several of the KJ wines especially your Grand Reserve Chard. I also note other flavors like a slight almond and sometimes molasses hints. It truly is my favorite Chard. So my question: Can you (or do you) use more than one strain of ML bacteria to develop more complex flavors or would they compete with each other as most bacteria do?

    • Winemaker Matt

      Ed,

      You are correct, and the white winemakers at KJ use primarily one strain of ML bacteria to achieve their stylistic goal.

      You are right that it might not work for complexity to have several strains competing against each other. At KJ, we tend to keep our barrel lots separate by vineyard blocks to keep an eye on quality levels from different vineyard sites. If a unique bacteria strain was used per lot, but many different strains were used overall, we might see some interesting results. Once the ML is complete and we add sulfites, there is no more activity, so theoretically that complexity could be preserved in the blend. However, while we could use many different strains, one in each different lot, we tend to focus on our tried and true.

      This is very different when it comes to the KJ Avant Chardonnay. Here we are aiming for a Chardonnay wine that emphasizes the fruit characteristics of the grape, keeping it lighter and fresher. So a buttery ML strain is not used, or ML is avoided.

      Also, the molasses and almond characteristics you mention come from the interaction of the barrel fermentation and the ML flavors with the toasting of the oak barrels we use.

      Glad you love the GR Chardonnay. I think it is exceptional too!

      Thanks,

      Matt

  • Thomas Jordan

    Matt: I like your eduacating reports! There is always more to learn – well done!

    Happy Holidays! Thomas

    • Winemaker Matt

      Good to hear from you Thomas. Thanks! Have a great holiday.

      Matt

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