"Bad-Brett" management Part II: Repairing contaminated wines

In Part I of this series on Brettanomyces, I laid out the characteristics of the microbe, the contamination routes, and conventional methods employed in controlling its growth. In that post I also referenced some approaches advanced by Dr. Jamie Goode to fix wines that had been contaminated by Brettanomyces. The chart below summarizes both the "control" and "fix" tactics presented by Dr. Goode in the Somm Journal article cited in the chart.

In his book postmodern winemaking, author Clark Smith posits that "... a revolution is taking place within the winemaking industry. Precepts of the modern winemaking system we were taught in school simply don't support the making of the great wines the market demands, and as a result, some of our most successful winemakers have strayed quite far from conventional dogma." These winemakers are using what Smith calls postmodern winemaking to "... merge all of the wine's flavor into a coherent whole like a well-conducted orchestra producing a unified, soulful voice."

As stated in his book, postmodern winemaking does not seek to throw out all elements of modernity and replace them lock, stock, and barrel with a new canon. Rather, postmodern winemaking uses existing pieces where appropriate and substitutes/adds where necessary. Below I provide a graphic representation of wine production under both the modern and Smith's postmodern schemas. The key extensions of postmodern winemaking are provided in red in the below chart.

Two things to note in the chart above: (i) towards the bottom, the introduction of the concept of Integrated Brett Management (that will be the focus of Part III in this series); and (ii) the box at the top right which is labeled Postmodern Tookit. Some of the entries in that box map closely to the "fix" tactics proposed by Dr Goode. These Postmodern Toolkit/Fix mechanisms will be the subject of the remainder of this post.

Sterile Filtration
Dr. Goode mentioned filtration as the first option on his list and it is widely viewed as the most effective method of removing Brett cells. In this method, the wine is passed through a .45µ filter which captures any Brett cells in the filter mechanism. Clark Smith is not in favor of this approach to Brett removal:

The focus of postmodern philosophy is the creation and preservation of beneficial macromolecular structure. This structure manifests in wine as colloidal particles sometimes nearly as large as a bacterial cell. The benefits of good structure -- profundity, aromatic integration, and graceful longevity -- appear to be lost in sterile filtration, despite the fact that no tannin material may be retained by the filter. While this lack of residue has convinced some of my colleagues that filtration cannot be harmful to wine structure, I do not concur. My hypothesis is that the action of tight filtration somehow disrupts rather than removes structure.

It should be noted that Clark does not provide any empirical data or prior scientific studies to bolster this hypothesis.

Velcorin
Both Dr. Goode and Clark Smith mention dimethyldicarbonate (DMDC, trade name Velcorin) favorably. This product is a microbial control agent  (produced by Lanxess) that is effective at eliminating a broad range of yeast, bacteria, and molds from wine. The product works by penetrating the cell wall of the offending micro-organism and deactivating enzymes which then leads to the cell's demise. The manufacturer claims that the product has no effect on wine taste, bouquet, or color and breaks down completely into small amounts of CO₂ and methanol. The downside, according to Clark, is that this is a "nasty chemical" and must be handled carefully.

Tangential Flow Filtration
Dr. Goode refers to cross-flow filtration and nanofiltration in his list but Clark places those technologies into a class he calls the Tangential Flow Family of Filtration and they are classified based on the molecular weight of particles that pass through the pores.

Filtration System	Application	Molecular Weight Range (Daltons)
Crossflow Clarification		200,000 - 500,000
Ultrafiltration		1000 - 200,000
	Tannin and Browning Removal	10,000 - 200,000
	Protein Removal	10,000 - 40,000
	Decolorization	1,000 - 5,000
Nanofiltration		200 - 1000
Reverse Osmosis		50 - 200

Source: Clark Smith, The Crossflow Manifesto, Wine Business, January 2003.

According to Smith, the idea of tangential flow filters developed in the 1960s. One of the major problems with sterile filtration is the fouling of the membrane which occurs when tight pore sizes are used. This fouling prevents the passage of material through the pores. The effective limit of traditional filtration is 0.1µ. Tangential flow filters use the scrubbing action of the flow across the surface of the membrane to keep it clean thus allowing the utilization of ever-smaller pore sizes.

All of the systems mentioned in the table employ the strategy of pumping the wine across the membrane at high velocity. As the wine flows across the membrane it continually scrubs the surface, removing fouling material. The majority of the feed stream does not pass through the filter but is retained upstream and returned to the tank. This stream, called the retentate, contains all of the high-molecular-weight components. The low-molecular-weight material that passes through the filter is called the permeate. A reverse osmosis application is illustrated below.

Reverse osmosis (Source: memstar.com.au)

It should be noted that, of the tangential flow systems mentioned in the table above, reverse osmosis is the only one specifically noted for Brett removal by Clark Smith.

Fungal-Source Chitosan
A Brett-repair technology that was not mentioned by either Jamie Goode or Clark Smith is fungal-source Chitosan. Chitosan is a deacetylated version of chitin, a compound found in the exoskeletons of crustaceans and insects as well as in the cell walls of fungi. According to Olivier Pillet (Chitosan and Brettanomyces: Origin, Impact, and Mode of Action), "the innovation that led to the use of chitosan in oenology is the process for obtaining chitin from a non-animal fungi source, Aspergillus niger." This process provides natural-source chitosan that is both biodegradable and non-allergenic and has been accepted as an oenological process by both the International Organization of Vine and Wine (July 2009) and the European Union (December 2010).

Chitosan has been documented for its antimicrobial properties which depends on the degree of deacetlylation and its molecular weight. Studies have shown that the homogenous incorporation of 4 g/hl dose of the commercial product (No Brett Inside) will "result in the total destruction of the Brettanomyces populations, or, in certain cases, a significant reduction of the contaminating populations" (Pillet).

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These then are some of the tactical tools that can be employed in the fight against Brett. In my final post in the series I will treat Clark Smith's Integrated Brett Management.


©Wine -- Mise en abyme

Management of "Bad Brett": Part I, the conventional approach

Writing about Brettanomyces in Decanter, Linda Murphy stated thusly:

... at best, Brettanomyces can give wine what many believe to be positive attributes that add complexity and depth: earthy flavours of glove leather, smoked meat, bacon fat, tobacco, truffle, clove and other savoury spices. Yet when B(rett) turns bad, it can give wine the offensive stink of barnyard, manure, plasters, wet dog, sweaty horse blanket, mouse droppings and antiseptic.

Remarking about this contrast in character, Clark Smith (postmodern winemaking) stated: "... most connoisseurs have experienced on different occasions both faces of Brett: the sultry, profound earthiness and the repulsive barnyard stench." It is the latter characteristic that is of most concern to winemakers and it is that character that will be the focus of this post.

In a recent Somm Journal article, noted wine writer Dr. Jamie Goode laid out the issues associated with Brettanomyces (Brett) contamination of wines and offered up a number of control measures and fixes to combat same. Clark Smith, in his book postmodern winemaking, takes the conventional view of Brett and Brett management to task and, instead, proposes a schema he calls Integrated Brett Management. I present these competing views in three posts beginning with this one. But first, some background

Brettanomyces bruxellensis falls within the Fermentative class of wine-associated yeasts (the other classes are Basidiomycetous and Ascomycetes), the most dangerous of the wine-spoiler yeasts. According to Woolford, et al., (Genome Survey Sequencing of the Wine Spoilage Yeast Dekkera (Brettanomyces) bruxellensis, Eukaryotic Cell 6(4), April 2007), Brettanomyces bruxellensis is a major microbial cause of wine spoilage worldwide and results in significant economic loss. Brettanomyces is exceptionally dangerous because it has all of the characteristics of Saccharomyces cerevisiae but extends beyond it in that, while slower growing, "it can assimilate a wider variety of carbon choices."  The key characteristics of Brettanomyces bruxellensis are presented in the chart below and its contamination mechanism in the one following.

It was long thought that Brettanomyces contamination was a result of poor hygiene in wineries but contamination persists even in the face of intensive hygiene efforts (Renouf et al., Interactions between Brettanomyces and other yeast species during the initial stages of winemaking, Journal of Applied Microbiology 100 (6), June 2006).  Research seems to indicate that Brettanomyces can enter the winery through sour rot and can then take up residence within the facility and contaminate batches of wine essentially at will. The chart below shows Brett potential contamination sources and pathways. In the case of sour rot grapes, it can be a direct source (that is, mixed in with healthy grapes brought into the cellar) or via bees interacting with sour rot grapes in the field and then bringing Brett into the winery.

According to Clark Smith:

Except in new cellars, Brettanomyces is a ubiquitous organism, a fact of life. Like athlete's foot, one cannot usually hope to eradicate it. Like keeping one's feet dry, control of this organism based on suppressing growth by denying it facile growth conditions is the most realistic solution. Keep in mind that the goal is to facilitate a truce with Brett so a stable condition exists at bottling.

Central to this growth-suppression approach "... is the maintenance of free SO₂ at a level of around 30 ppm at relatively low pH's in order to maximize its effectiveness by increasing the percentage of the free SO₂ that is in the un-ionized molecular form." This approach greatly reduces the number of colonies of Brett that grow on a petri dish but according to Clark, may actually be reducing the culturability rather than actually killing cells.

In his Somm Journal article, Jamie Goode identified a number of actions that can be taken in the fight against Brett. The actions in the left part of the chart below are conventional growth-suppression activities.

Lisa Van de Water (Monitoring microbes during cellaring/bottling, Practical Winery and Vineyard Journal, January/February 2010) recommends testing the wine in the cellar in order to minimize the opportunity for Brett contamination manifesting in the bottle. According to Ms. Van de Water, 100 cells/ml can lead to visible Brett haze in the bottle and the production of small amounts of CO₂. Sensory changes are "profound" with compounds such as 4-EP and 4-EG present manifested by horse sweat and Band Aid odors and a bitter, metallic finish. Bottle variation is common with some bottles showing the clear evidence of "bad Brett" while others show little impact.

Ms. Van de water recommends culturing the wine on media containing 50 ppm of the antibiotic cycloheximide (to inhibit growth of other yeasts) and, if Brettanomyces is present, the culture will manifest white, hemispherical colonies in three to seven days. The culture will, in addition, produce a strong acetic acid smell.

If Brett is determined to exist in the wine at levels between 1 and 50 cells per ml, then we switch to the right side of the chart above and attempt to "fix" the problem. The most common approach has been to pass the wine through a .45µ membrane (this approach can be used both as a control and fix mechanism) but Clark Smith is opposed to this because he feels that filtration disrupts the structure of the wine.

The other wine fixes mentioned by Dr. Goode are identified as key elements of the postmodern toolkit by Clark Smith and so serves as  a bridge between the conventional and postmodern approaches. I will cover them in the next post on the topic.


©Wine -- Mise en abyme

Part III of my review of Jamie Goode's "Rescuing Minerality"

This is the final installment of a three-part review of Jamie Goode's post titled "Rescuing Minerality." Where the first and second installments examined Jamie's discussions of terroir and the contribution of soils to wine quality, respectively, this post hones in on the elemental core of the article, minerality.

Jamie begins this section of his post by remarking on the relative youth of the term minerality in relation to wine. In this he is aligned with Alex Maltman (Minerality in Wine: A Geological Perspective, Journal of Wine Research, 2013) who, as I described in my post on the topic, sees minerality as "... a thoroughly modern invention which had received no mention in the works of the 'masters' (Peynaud 1987 and Vine 1997, for example) or the science-based tasting schemes (Jackson 2009 and Noble et al., Aroma Wheel 1987, for example).

Jamie takes issue with a "literal view" of minerality where it is characterized as "... the perception of the rocks in the soil, by the palate." In taking that position, he is aligned with the aforementioned Maltman. The two charts below (derived from Maltman) show (i) the differences between the types of minerals found in wine and geological minerals and (ii) an example of the path ("protracted, rocky, and time-variant") that a geologic mineral has to traverse in order to be usable to a vine.

The above shows some of the difficulty in tasting geologic rock in wine but, further, absorption and distribution of the cations by the vine plant, and cellar activities associated with winemaking, further dis-associate the minuscule amounts of minerals found in wine from the geologic minerals in the vineyard.

Jamie identifies aroma and taste as the areas in which minerality has been mentioned (I will add "texture" to that list.). In his discussion, Jamie specifically refers to a matchstick/mineral character in white wines and then dismisses it as a volatile sulfur compound created during alcoholic fermentation. I have not researched this particular area. I have, however, looked at the aroma described as "earthy minerality" and my research shows this to be an off-odor caused by geosmin, a secondary metabolite produced by the fungus species Penicillum expansum. The final nail in the aroma coffin is Maltman's assertion that aroma requires volatilization in order to register on the organs of the olfactory bulb. Neither rocks nor minerals possess this capability.

Before turning to Jamie's discussion on taste I would like to explore the category which I have contributed -- texture -- and relate it to the term "chalky minerality." Based on the work done by an Australian and French research team (S. Vidal et al., Use of an experimental design approach for evaluation of key wine components on mouth-feel perception, Food Quality and Preference 15, 2004) and reported on in Wine Business Monthly (Bibiana Guerra, Key Wine Components in Mouthfeel Perception, November 2011), we learn that chalkiness is an astringency categorization (along with pucker, adhesive, dry, medium-surface smoothness, and coarse-surface smoothness). According to sensorysociety.org (and Richard Gawel, Secret of the Spit Bucket Revealed, aromadictionary.com), astringency is a tactile sensation, rather than a taste, and is primarily caused by polyphenolic compounds contained in certain foods (including wine) but can also be caused by acids, metal salts (such as alum), and alcohols. A key characteristic of astringency is the fact that it is difficult to clear from the mouth and, as such, builds in intensity on repeated exposure to the source. The source of astringency in wines is tannins.

Jamie divides taste in minerality into two areas: those associated with high-acid whites and those having a taste of "salty minerality." The "mineral" taste associated with "high-acid" white wines is quickly dispatched with an admonition that they should be so described. The "salty minerality" is described by Jamie as being the "best use of the term" and he asks whether this could be "caused by mineral salts in wine, absorbed by vine roots." He posits that the minerality of wine fluctuates between 1.5 g/L and 4 g/L "which may be enough to confer some flavour on the wine." The Waterhouse Labs at UCDavis places that range at 0.2 to 2 g/l while winesofczechrepublic.cz places the range at 1.8 g/l to 2.8 g/l. Second, it seems (and please correct me if I am wrong) that there is an attempt here to equate mineral salts with saltiness but, according to Wikipedia: magnesium ions are sour to the taste; dilute solutions of potassium taste sweet; and calcium ions vary to human taste, being reported as mildly salty, sour, "mineral-like," and "soothing." Further, if there were to be a mineral taste imparted by these salts it would most likely be aligned with the potassium ion (sweet) as that ion comprises 50-70% of the mineral concentration in grape juice.

Jamie points to two cases as evidence that the soil type influences the mineral composition of the wine. He did not have to go that far. We know that different soils have differing CEC and will result in more or less minerals being available in the soil. But that does not prove that the wine tastes mineral. He shows where Anders Pueke grew Riesling in three different soils and then found chemical differences when the sap was analyzed. Notice here he said chemical differences. I am not sure if he meant mineral differences. Because chemical analysis does not advance the point. Further, was minerality (salty) found moreso or less so in the wines? He also mentioned Randall Grahm placing rocks into wines and getting a textural change. As Stephen Mense points out in his post (Rocks in our wine ... or just our heads? tableintime.com, 10/31/12), Grahm's intent was to "determine if minerally flavors and aromas would be communicated" from the rocks to the wines. Mission unaccomplished as "the alterations did not have the effect of making the wines taste more like rocks or gravel."

According to Jamie, "It follows that increased soil microlife could lead to more mineral wines." I am missing something. I can agree that increased soil microlife could be beneficial in a number of ways but I do not see how it leads to more mineral wines. I would be willing to say that increased soil microlife would eventually result in increased mineral levels in the soil but it is not clear that that automatically translates into increased mineral uptake by the vine plant. Nor does it show that these additional minerals would be delivered to the fruit versus other parts of the plant. And, why is this not a constant. Why are not all wines (red or white) that are subjected to organic/biodynamiic treatments exhibiting this salty minerality?

I am not sure but this looks like an awesome leap of faith to me.

©Wine -- Mise en abyme

Jamie Goode's "Rescuing Minerality" Post as viewed through the lens of my research: Part I

Jamie Goode, one of the most prolific and respected wine writers of the day, recently wrote a post on his blog (wineanorak.com) titled Rescuing Minerality. As this is a topic in which I have great interest, I have read the article a number of times since its publication and finally decided to write a review piece which examines Jamie's post through the lens of the research which I have conducted and reported on in these pages. The original post can be viewed as having three major components -- terroir, soil science, and minerality -- with the latter two being tightly coupled. I will review each of the components in separate posts beginning with terroir in the current instance.

Jamie begins the post with four definitions of terroir which comprehensively capture the major streams of thought that swirl around the topic today. Based on my past work, I have developed the below timeline which shows the evolution of sense-of-"placedness" as it relates to wine.

                                                        Terroir Timeline

Period/ Year	"Terroir-Advancing" Event
Classical Greece	Preference for wines from Aegean Isles
Rome (Early)	Preference for wines from the south
Rome (Late)	Preference for wines from the sub-regions of the Bay of Naples and Latium
Middle Ages	Burgundy -- “First wines prized for their ability to display ... individualized aromas and flavors”. Cru as a vineyard plot
1660	Arnaud III de Pontac doubling the price of Haut Brion wines because -- he said -- they were “special”
1800s	Word terroir -- which originally meant territory or land in France -- was extended to describe “an area of land valued specifically for agricultural properties”
1816	Quality being extended to tradition first mentioned in Julien’s Topographie. Cru as a Chateau
1843	Barolo, Gattinara, Asti, Montalcino, and Rioja begin to adopt Bordeaux principles
1850s	Bordeaux proprietors define quality as cru (estate) + grapes + tradition
1900s	Word terroir used as a designator for a vineyard’s natural environment and to characterize the wines from the grapes grown therein
1905	French Frauds and Falsification Law -- French wines sold commercially had to indicate its origin on the label
1906 - 1912	Bordeaux, Cognac, Armagnac, and Champagne demarcated
1919	Law made it illegal for an unauthorized producer to use an appellation name
1927	Champagne boundaries finalized to include Aube
1927	Law restricting the varieties and viticultural practices that could be used for appellation wine
1935	Law creating the AOC system. It combined earlier legislation and stipulated regions, varieties, minimum alcohol levels, and maximum vineyard yields

Table constructed from the following posts:
Book Review: Inventing Wine
French wine quality: From thin air to a weapon of war
The rise of the Algerian wine industry
Decline and fall of the Algerian wine industry: Filling in the study gaps
A brief history of terroir (After Lukacs)
Part II -- Regulatory histories: The definitive comparison of Champagne, Franciacorta, Prosecco, and Cava

Based on the foregoing, terroir, as construed today, differs significantly from its origins and intent. The Cistercians demarcated their vineyards to show differences in grapes grown there and, as a result, established a tradition of Burgundian wines. I maintain that they initially established a tradition of Burgundian vineyards -- because the wines should have been indistinguishable from others due to oxidation and sourness -- and that evolved into a tradition of Burgundian wines. Somewhere along the way there was a successful marketing effort to monetize that tradition. Bordeaux recognized the pecuniary benefits of traditions and sought, successfully, to establish its own. They did not spend the hundreds of years getting to understand the characteristics of their vineyards -- as the Burgundians had done. They just claimed it. The AOC system, set up to deter counterfeit wines, evolved into a "deviser" of taste and quality. It was not set up around terroir. Rather, terroir was devolved upon it. To my mind, terroir is all about tradition and monetization of same.

That being said, it must be noted that there are differences in wine depending on where the grapes are grown. Jamie refers to these as macro- and micro-scale effects and uses differences within a vineyard and similarities across a region to illustrate his point. I will use differences across a region and differences between vineyards compared to a model to illustrate the same point.

According to UC Davis, regional differences in grape quality are evidenced by:

• Earlier maturity in warmer regions
• Lower tonnage in cooler regions
• Less color, acid, and varietal flavor in warmer regions
• Lower price in warmer regions

The color and acid assertions are shown in an Amerine and Winkler (1938) study which reported on similar varieties grown in each of the degree-day Regions (I - V) and showed a decline in both measures as the study progressed from cooler to warmer regions. The regional differences are further borne out by the table below which shows grape production and price in each of the California regions (The state of California can be divided into 5 broad regions -- North Coast, Central Coast, Northern Interior, Central Interior, and Southern Interior -- with the coast being cooler than the interior.).

Region	2003 Total Grape Crush	2003 Percent	Cabernet Sauvignon Ton/Acre	Cabernet Sauvignon $/Ton
North Coast	410,000	12.2	4.3	1800
Central Coast	352,000	10.5	7.9	920
Northern Interior	143,000	4.2	6.3	500
Central Interior	2,025,000	60.1	11.9	300
Southern Interior	440,000	13.1	10.2	550

Data Source: UC Davis

The table shows the highest production in the warmer central interior but the lowest prices per ton of Cabernet Sauvignon fruit. Cabernet Sauvignon fruit from the North Coast are widely perceived to be some of the best Cabernet Sauvignon fruit in the world. So, an example of a macro-scale difference in quality depending on where your grapes are grown.

In terms of the micro-scale, I have recently developed a viticultural architecture model and then sought to flesh out the elements of an ideal vineyard based on this architecture. My contention here is that differences in the variation from this ideal would reflect "terroir" differences between vineyards. The architecture and model elements are provided below.

Model 

The ideal climates for vitis vinifera are Mediterranean and marine west-coast climates, both of which are characterized by mild, wet winters and warm, dry summers.

Vitis vinifera requires a minimum of 1250 hours of sunshine to provide ripe fruit.

In cool climates, slopes with southern aspects (S, SE, SW) allow vines to accumulate the maximum amount of sunshine as they pursue growth and fruit maturity. In continental climes, on the other hand, eastern, northern, and northeastern exposures are preferred.

In cooler regions a vine needs approximately 500 mm water/year while the need increases to 750 mm/year in hotter climates.

Planting at or near the highest feasible points in the vineyard allows the viticulturist to meet the grapevine's need for good air and water drainage.  A slight to moderate incline is desirable for air and water drainage.

The optimal soil type also has a moderate content of low cation exchange capability (CEC) clay.

The best vineyard soils "permit deep and spreading root growth" and provide a moderate supply of water year-round.  Wine grapes do best in moderately fertile soils that are unsupportive of vigorous vine growth. 

Vineyards sited on convex land patterns are preferable to those on concave landforms.

Soil pH between 6.0 and 6.8 is considered optimal for vine plant growth as most of the needed nutrients and micro-organisms are available in that range.

The most effective means of combating diseases are (i) a good canopy management program and (ii) a rigorous preventative fungicide treatment program.

It is important that there be a balance between the vine root system and its canopy. In that regards, vines should be planted with higher density in poorer soils and less-densely in fertile soils. Many of the high-quality European vineyards are planted at between 5,000 and 10,000 vines/ha.

A well-managed canopy should have one grape cluster per shoot --assuming an average size of 5 to 8 ounces per cluster -- and 10 - 15 leaves per shoot in order to ensure proper ripening.

©Wine -- Mise en abyme