Malolactic fermentation is a conversion of sharp malic acid to smoother lactic acid. It typically takes place after primary fermentation*, accounting for the smooth texture in most red wine and the ‘buttery’ character of some white wines. The process is performed by Lactobacillaceae, a group of bacteria integral to sauerkraut, beer, wine, and the many other faces of fermentation.
We are currently in the process of inoculating our 2011 reds with lactic bacteria (Lactobacillaceae) using measured portions of the starter* wine pictured above. The starter was created by combining 9 parts wine at a sugar level of 18 brix with 1 part bacteria. Once this small 10 gallon batch kicked into malolactic fermentation* we combined it with a 90 gallon lot of Zinfandel that had finished primary fermentation to create the final starter culture.
The lactic bacteria eventually consume all of the malic acid present in the wine and begin seeking other sources of food, this action can result in volatile acids* so we measure the remaining amount of malic acid every few days. Once the malic acid has been consumed, we ‘feed’ the starter by adding measured portions of another wine that still contains malic acid to maintain ideal conditions for inoculation.
As we barrel down* the 2011 wines we add a small portion of the starter culture to each barrel. These inoculated barrels are then placed in a slightly heated storage room (pictured here) to take each wine through malolactic fermentation. To this point, only red wines have been put through ML at Halter Ranch though we may see at least a partial secondary fermentation on one or two of our white wines in the future. A fun detail: the smell of a wine undergoing malolactic fermentation is reminiscent of movie theater popcorn.
*a conversion of sugar to alcohol performed by yeasts, accountable for the distinction between wine and grape juice
*in the same sense as sourdough starter
*confirmed by periodic measurement of malic content in the inoculated batch, if the amount of malic acid is on the decrease, the wine is undergoing secondary fermentation
*check back in to Geek Flight next week for definition and discussion of volatile acidity
*move fermented wines from tank to barrel