Monday, June 12, 2017

"Bad-Brett" management Part III: Clark Smith's Integrated Brettanomyces Management

Brettanomyces, according to Clark Smith (postmodern winemaking), can allow a wine to show "sultry, profound earthiness" or a "repulsive barnyard stench." And it is this latter characteristic -- the "bad Brett" -- that is of concern to winemakers. Conventional approaches to combating Brett fall into the "contain" or "repair" camps but Clark sees these approaches as falling short of the requirements of postmodern wine. Instead, he has proposed an approach which he labels Integrated Brettanomyces Management (IBM), an approach I describe below.

Clark has taken the position that, given the ubiquity of Brettanomyces, one cannot hope to eradicate it. Rather, the strategy should be one of "suppressing growth by denying it facile growth conditions." And that is precisely the course pursued in the first two legs of the three-legged IBM stool (ashown below). The third leg strives to utilize the capabilities afforded by structured wines to integrate microbial aromas in a supporting role to a varietal-fruit-led aroma without "apparent aromatic expression."


Creating a Nutrient Desert
Clark Smith characterizes the Brett existence strategy as insidious: rather than competing with Saccharomyces during the fermentation stage, it emerges later, during wine aging. The old adage is that if you don't grow, you die. Brett has two growth modes: fermentative and respiratory, the former requiring sugar and the latter, oxygen.

According to Clark, we can assess the risk of Brett fermentation by measuring the levels of enzymatic glucose + fructose:

               < 500 g/l - preferred
               > 1000 g/l = unsafe

It is hoped that primary fermentation activities will result in safe levels of fermentable sugar.

Brett lacks the ability to synthesize many micronutrients for itself, depending, instead, on material resident in the environment. In order to deprive Brett of this growth source, all available micronutrients should be consumed during primary fermentation. Key to this goal is the delivery of "healthy, nutrient rich fruit" to the cellar. The fruit should have enough nutrients to allow a vigorous fermentation by healthy yeast cells. Important considerations (Clark Smith):

  • Fertilize only in deficient hot spots rather than over the entire vineyard
  • Minimize the addition of simple refined chemicals such as DAP.

If the yeast cells have easy access to nutrients -- such as provided by excessive fertilization or excessive DAP addition -- they will not work to make enzymes to digest micronutrients as a food source, leaving them available to be exploited by Brett. According to Clark, "If you feed them Twinkies they won't eat their oatmeal."

The primary ally in suppressing respiratory growth is the wine's reductive strength (Clark defines reductive strength as "the rate at which a given wine can consume oxygen without a resulting buildup in dissolved oxygen.). It has been shown that Brett can metabolize the amino acid proline to meet its carbon and nitrogen needs if oxygen and micronutrients are available in the environment. If the wine maintains its ability to consume oxygen, it will deprive Brett of this very valuable growth engine. Tannins are natural antioxidants given their affinity for binding with oxygen. Tannin content is maximized by actions in the vineyard as well as extraction strategies. According to Mark Downey (Tannin Management in the Vineyard, GWRDC), there is a demonstrated correlation between tannin concentration in the fruit and vine vigor: high-vigor vines have lower tannin levels while low-vigor vines have higher tannin levels.

Microbial Equilibrium in the Cellar
The key takeaway of this leg of the stool is that the natural competitiveness of the ecological system will keep all microbial activity at acceptable levels.
It seeks to play out in the cellar any metabolic conversions to which the wine os prone, so that sterile filtration is unnecessary. Any influence inhibitory to this goal should be dialed back to the point where microbial processes achieve completion.
Based on studies carried out at Oenodev, Smith has come to the conclusion that "our greatest ally in controlling Brett has been the presence of other microbes."

Aromatic Integration
Aromatic integration, according to Clark, occurs in wines of good structure. Structure, as used by Clark, refers to the outcome when macromolecules such as tannins and proteins form into colloids suspended in the wine. Smith sees the size and shape of these colloids affecting the aroma and texture of the wine.

A properly formed colloidal structure is capable of integrating the array of aromas (varietal fruit and vegetal elements, nuts and phenolic aromas, oak constituents, and microbial by-products) into "an aroma that is primarily varietal fruit, with oak, vegetal, and microbial notes in a supporting role as muted, integrated elements."

The process for building structured wines is shown in the figure below.


The figure below shows ring-stacking and polymer formation when anthocyanins and tannins are extracted from the fruit. Tannin are hydrophobic and this ring-stacking protects the innermost elements from the water. Tannin molecules will continue to stack until they are capped at either end by anthocyanin molecules. 

Source: micro-ox.com
These capped tannin chains are the base of Smith's colloids.
A properly formed tannin colloidal structure is capable of providing a home within the wine for these aromatic compounds. The shorter the tannin chains, the finer the colloids and the greater the the interactive surface area for intercollating these compounds ...
According to Clark, structured wines can carry many times the supposed threshold of 400 ppb of the Brett metabolic marker 4 EP without apparent aromatic expression.

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Clark is the first person to tell you that his postmodern winemaking schema has not garnered acclaim from most mainstream enologists. It has been arrived at through careful observation in the real world and those views have been curated in a number of magazine articles and then consolidated in his book postmodern winemaking. There are a number of areas of departure: his view of the colloidal structure of wine and the functio of those colloids has not received scientific blessing; micro-oxygenation is still viewed as an aberration by many winemakers; and his open views on wine manipulation caused great concern at a jointly attended conference in Rioja a few years ago.

If his postmodern views have not yet gained broad-based acceptance, then his schema for Integrated Brettanomyces Management will not be mainstream either. That being said, they do have some internal consistency issues.

First off, it is not clear whether the integration part refers to being integrated into the winemaking process or whether the three elements are themselves integrated. If it is the latter, then that integration is not spelt out in the writings. In other words, what is the seat to which the legs are attached.

Second, if you look at the three legs, the descriptors become less action-oriented as you go from 1 to 3 (Create, foster, achieve) with no specific Brett-related actions required by the winemaker in the third case. As a matter of fact, as laid out, if you adhere to the construct for making structured wines, you will get the benefits of aromatic integration.

Fostering microbial balance is less ephemeral but speaks to the actions that you should not take and seems to be somewhat risky for a naturally risk-averse profession.

It will be interesting to see the future adoption curve for this approach to managing Brett.

©Wine -- Mise en abyme

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