Malolactic Fermentation (MLF)

 

    Malolactic fermentation, also known as MLF, is a

secondary fermentation process used in wine-making

that is made possible by Oenococcus oeni and

other lactic acid bacteria, (LAB). After initial

fermentation of the wine, be it white or red wine,

malolactic fermentation is an optional process that

some wine-makers use to enhance the flavor and aroma

of their wine. It's not a necessity in wine production, but it

is an option that many wine makers choose.

    The malolactic fermentation process is

initiated soon after primary fermentation,

(the conversion of the sugar in the grapes to alcohol by

(7)

yeast), is completed. The wine-maker inoculates

the wine with the bacteria, but when exactly inoculation is to

be performed is a matter that has been debated for many years.

It's really a matter of preference. Whether the MLF should

occur in the bottle or the barrel is not a matter of debate

however. Wine-makers have stated that the onset

of MLF in the bottle is disastrous as the

wine will appear to the consumer to still be fermenting

(as a result of CO₂ being produced). The wine may also

lose its fruit integrity and take on the unpleasant

lactic aroma of cured meats. MLF in the barrel

integrates the oak and fruit flavors of the wine

and the wood of the barrel, giving it a more complex

and enjoyable flavor. The basic idea here is that

MLF must occur after primary fermentation, when the wine is

most acidic, and the wine must undergo MLF in the barrel

in order for it to have the most desirable flavor and aroma.

    Primary fermentation turns the wine very acidic and

can cause an unpleasant burning sensation in the back

of one's throat when drunk. This is where MLF comes

in. MLF not only enhances flavor and aroma of wine,

but dulls the acidity of it as well.

    The task of malolactic fermentation is undertaken by

the Oenococcus oeni. The O. oeni is commonly selected

by wine-makers for its ability to survive in low pH,

(highly acidic), locations, like newly fermented wine.

This process in a nutshell is the conversion of L-

malic acid to L- lactic acid. Lactic acid has a higher

pH level than malic acid, and adds a smoother finish

to most wines, making them more pleasant to the

drinker.

    Malolactic fermentation is not as effective on some

wines as others. For example, it is quite effective on

Chardonnay and compliments the flavor, finish, and

aroma. On the other hand, it is not as beneficial to

a Riesling and is not commonly used on such types of

wine. In a nutshell, you would have the most luck using

MLF on full-bodied dry whites and medium to full bodied

dry reds.

 

    O. oeni helps to make all of this possible, and the

discovery of the process of MLF has greatly improved

both the quality of wine and the wine business.