The most advanced wineries put a lot of effort in perfectly managing their fermentations. Now that alcoholic fermentation is a well-known and managed phenomenon, focus is switching to malolactic fermentation (MLF) management all around the world: from France, Spain and Italy to Chile, South Africa, Australia or USA.
MLF process, summary:
This fermentation step is a natural process whereby lactic acid bacteria transform malic acid into lactic acid (mainly), some fermentation flavours (dairy-like flavours such as diacetyl but also some fruit flavours like red or black-fruit flavours coming from the production of esters) and several other compounds: carbon dioxide, organic acids or even biogenic amines, if the fermentation is managed by lactic-acid bacteria from the endogenous population sometimes also known as “spontaneous bacteria” or “wild bacteria”.
MLF occurs naturally when the initial lactic acid bacteria population grows to a level sufficient to trigger the conversion of malic acid into lactic acid.
Quorum sensing, magic number and concentration factor
One of the key differences from yeast and alcoholic fermentation is that a specific level of viable bacteria per ml of wine has to be reached before MLF starts. With the bacteria species Oenococcus oeni, this level in wine is 1 million cells per ml of wine. Below that level nothing happens.
This concentration level is scientifically called “quorum sensing,” and among MLF specialists this specific level of 1 million active cells per ml is called M, the “Magic number.” Product concentration can be expressed in number of M delivered per bag. This is a good way of comparing the strength of each commercial preparation available on the market and the cost of purchasing 1M.
Three main ways to manage MLF in wines:
In most cases, red wines goes through MLF to get rid of malic acid, which is a common source of carbon for many microorganisms and could therefore be converted at a later transport or storage stage with all the associated problems from bubbles appearing in the bottle to off flavors and sometimes even bottle explosion.
1) Wait and see
Winemakers can wait and let the wild flora degrade malic acid, in that case the winery never knows precisely what type of bacteria will convert malic acid (Oenococcus, Lactobacillus, Pediococcus…), what will be the result in term of flavor profile: positive, neutral or negative, how it will impact the wine’s final quality, what kind of biogenic amines will be produced by wild bacteria populations using amino acids sources present in the wine and, finally, how long the process will take, from a few days to several months! This way of managing MLF is becoming less and less popular, as it represents a high risk for winemakers which may result in degrading and finally downgrading the wine and can severely alter the authenticity of a wine, erasing the distinct flavors from a terroir or the complexity of a specific bin etc.
2) Avoid MLF using massive doses of sulfites
This is what normally happens to most white and rosé wines around the world. To avoid the production of buttery flavors linked to MLF that would mask the fruit flavors originated from the grapes and released during alcoholic fermentation, winemakers tend to block the degradation of malic acid into lactic acid by malolactic bacteria. These lactic acid bacteria populations are stopped using sulfites, the preservative authorized in winemaking.
Thanks to Chr. Hansen, today there is an alternative to this use of sulfites: VINIFLORA® CINE™ developed to manage MLF in wines without producing the buttery, creamy flavors typical from MLF. CINE™ only converts malic acid into lactic acid, stabilizing the wine through a natural and non-flavouring process, very good news for winemakers and consumers!
3) Take control through VINIFLORA® microbial solutions, ideal for bio-protecting, reducing sulfites and preserving wines with natural solutions
Within the very large pool of lactic acid bacteria present in wine, some species and strains have been identified and then selected for their positive contributions to the winemaking process, thanks to their ability to achieve MLF at a fast pace, contribute flavor to the final wine, ability or inability to produce buttery, creamy flavors during fermentation and inability to produce biogenic amines like histamine.