It is really is up to the winemaker to decide to what extent he or she will allow a wine to go through Malolactic Fermentation (MLF).
MLF is the transformation of malic acid into lactic acid by specific strains of bacteria during secondary fermentation.
Malolactic Fermentation is a series of metabolic effects carried out by a group of bacteria that breaks down malic acid into lactic in wines. Lactic acid is the acid profile found in smooth creamy milk. Mostly it happens spontaneously throughout a wine’s life.
The theory though is… by depleting the malic acid early on; the less chances there are of fermentation spoilage later.
MLF usually happens on its own and if not controlled can end up with wine smelling leathery, sweaty and cheesy and even spritzy because of extra carbon dioxide.
A lot of New World reds and white wines get smells like artificial popcorn butter and desirable aromas that fit well together like buttery oaky chardonnay that not only consumers like the taste of. The critics do too. This aromatic profile especially desirable in quality red-wines. It adds a rounded feel, glycerin, even chewiness to the fruit to the wine when done right.
Just consider different food and combinations like Crab or Salmon and California Chardonnay. A Rich and Oaky Red Zinfandel and BBQ Grilled Steak...or a moist Mushroom Risotto with an Australian Shiraz.
From French Wine to California Wine and beyond; when you hear subjective wine sensory terms referring to feeling of fullness, viscosity and astringency the MLF has had an effect on the wine.
With that said Red Wines like Merlot, Cabernet Sauvignon, Pinot Noir and almost any dry table wine that will be aged for more than 6 months for consumption at least a year after it’s first fermented are encouraged to go through MLF.
In White Wines, Chardonnays makes good candidate for malolactic fermentation for stylistic reasons. Other whites like Riesling are not much… They are better when they retain their freshness, fruity zippy acidity.
So again, it’s up to the winemaker how much if any malolactic fermentation is allowed in a wine.
How do they stop it?
How do they prevent Malolactic Fermentation?
MLF is usually arrested by chilling, adding Sulfur dioxide (SO2) and filtering. Some winemakers want to discourage Malolactic Fermentation at all costs. Even many consumers feel the same way, so they always keep the wine cool and cellars under 62 degrees F. Malolactic Bacteria does not thrive in cold temperatures, it flourishes less in high alcohol, High SO2 and the use of fresh cultures.
That’s a strong reason for making and storing and monitoring wine in cooler environments. It helps fight off potential spoilage.
Malolactic Fermentation has a lot of other things to it that can affect it including racking, enzyme analysis, PH levels, different malic acid powders, concoctions, egg whites, etc. Sometimes MLF bacteria is hard to control and just doesn’t convert into lactic acid as expected.
When you drink a white. Ask if it has MLF. It might start an interesting conversation.
What’s interesting is that sometimes-experienced winemakers just use their ears during MLF you hear popping and burping and once the popping and burping is done the bacteria is probably finished their job.