The Vintners Voice

I managed to sneak out of town for a couple of weeks over the holidays. I missed out on a monster snow storm (by Willamette Valley standards), got married, got the flu and enjoyed fog and rain in San Diego.

It isn’t as if the winemaking just stopped, it was still happening while I was gone. My red wines were going through the Malolactic Fermentation (MLF). This is a crucial step in the process and MLF is quite misunderstood by the wine drinking public (and in some unfortunate cases, the winemaking community as well).

The MLF is a ‘fermentation’ carried out by bacteria that convert Malic Acid into Lactic acid. Malic acid is the acid of green apples and has a very tart character. Many variables can impact levels of malic acid in grapes, notably climate, vintage, varietal, canopy management, picking decisions. Lactic acid is milk acid, is much softer and rounder than Malic acid and therefore has a ‘softening’ effect on the wine. Another important feature of the MLF is that as the Malic acid is converted to Lactic acid, the pH of the wine shifts upward ( the more Malic acid present the greater the shift, which further contributes to the softening effect but also has some other potentially undesired effects as well. This shift can also reduce color of red wines and may create an environment more favorable to spoilage organisms.

The MLF can be carried out by a vast number of bacterial species. Oenococcus is the preferred bacteria of conducting MLF and is the bacteria that is contained in most, if not all, commercial malolactic bacterial cultures. Native or Wild MLF’s may be carried out by Oenococcus or other bacteria such as pedioccus or Lactobacillus. In addition to the conversion of malic to lactic acid, the bacteria can also produce a great assortment of other molecules that may or may not impact the organoleptic qualities of the wine. One such molecule is acetic acid, the acid found in vinegar. Diacetyl is another; it generally imparts an odor commonly described as ‘buttery’. Some of the ‘wild’ bacteria produce molecules such as putracine and cadaverine, which as the names imply may not exactly be the sort of thing one wants in wine. Another class of compounds, the biogenic amines, are similar to histamine and have been known to contribute to hangovers or allergic reactions.

The concept of Malolactic fermentation entered the consumer jargon a number of years back when the Napa Valley style of Chardonnay came into prominence, the fat, buttery character of the style heavily marked by the MLF. Now many chardonnays are being touted as “no-malo” because inhibiting the MLF can maintain a brightness and edginess that would be lost if MLF were to take place. So weather or not MLF takes place in a white wine is an important winemaking descion. Generally speaking most red wines, those produced via carbonic maceration excepted, are put through the MLF to round and soften the acid-tannin structure of the wines.

Though I utilize spontaneous primary fermentations for my pinot noir, and find great returns for the risk, I do not employ spontaneous MLF’s. Part of what I attempt to do in my winemaking is reflect a sense of place, a feature easily covered up by VA (acetic acid) and the various compounds generated by the spoilage organisms that can flourish during MLF. By knowing what bacteria are conducting my MLF I feel I produce a cleaner wine that is more reflective of place. In some cases, my Rose for example, I feel are best when the MLF is inhibited. I love the zippy, tight acid structure for that wine and want to preserve it.