Malolactic Fermentation (MF) in My Cellar

Wine Making 201

If you have ever made wine from fresh grapes or from fresh grape juice (not Welches frozen concentrate) late winter becomes an interesting time of the year. Your wine has been in the secondary for several months and is nice and clear. Not much is going on...the holiday season is over, the grapes from the southern hemisphere have not yet arrived (Chilean grapes and juices) and you begin thinking about filtering and bottling your wine.

The picture to the left is Malolactic Fermentation currently going on in the wine one of the wines in my cellar.  The little white ring is an accumulation of tiny bubbles.

This is the time of year that something interesting can happen to your wines. If the acid has a good amount of MALIC acid and fairly low amounts of sulfite, AND the temperature of your cellar goes up a few degrees, Malolactic Fermentation (MLF) can begin. That's the MLF you occasionally see in the winemaking publications and books you may have read.

This can be a good thing given the right circumstances. If your wine is a bit high in acid, the MLF will reduce the acid by converting the harsher MALIC acid into the softer LACTIC acid. It happens when bacteria that is naturally in your wine wakes up and begins a new kind of fermentation. You may find that your wine is nice and clear, but there is a low level fermentation activity in you air lock. You may also see a fine band of bubbles around the neck of your carboy. If you shake the carboy, you WILL blow off a bit of carbonation! During this fermentation, the wine will of course have a reduced titratable acid level AND it may take on a slight buttery/butterscotch aroma and flavor. A nice combination for a Chardonnay!