Monday, May 22, 2017

High-level view of Gaja Langhe winemaking process

In my most recent post, I covered changes in the Gaja agronomical practices since 2000. While there have been no meaningful changes in the winemaking processes during that time, providing a rounded picture of the Gaja Langhe environment dictates an overview of those processes. 

The table below shows the range of Gaja Langhe offerings at the point of my first visit a little less than 5 years ago.

In the table, five of the Nebbiolo wines are labeled Langhe Nebbiolo DOC. Angelo felt that a 100% Nebbiolo required bolstering to measure up to his vision and, to that end, added small amounts of Barbera to round out the wines. These additions meant that the wines could not be labeled DOCG. After seeing the quality of grapes that have become almost the norm in the Langhe in recent years, Angelo has made the decision to produce his wines to the DOCG specs beginning with the 2015 vintage.
The cellar is divided into three parts: (i) Fermentation cellar – all stainless steel tanks; (ii) first-year aging – barrique and tonneau, all French oak, and up to 20% new (first-, second-, and third-year passage); and (iii) second-year aging – large oak casks, Austrian and Slavonian oak.

If we look at a blend of the 14 parcels that go into the Barbaresco DOCG, the plots are kept separate through harvesting, destemming, fermentation, and first-year aging. The blend takes place in passage from the small barrels to large barrels. The wine spends one year in large barrels, a 50/50 split between the two regimes. The style, then, is dictated by the length of maceration and the proportion between barrique and tonneau.

This was my second visit to Gaja and the notes on the wines that I tasted on my initial visit can be found here. On this visit we tasted three Langhe wines and one from Montalcino. The notes from the most recent tasting follow.


The first wine tasted was a 2012 Pieve Santa Restituta Brunello di Montalcino. The estate generally draws fruit from south-and north-facing slopes but with the warm temperatures, the south-facing vineyard produced overripe fruit. The wine was opened the morning of the tasting. Sweet, dark, juicy fruit with attractive tannin levels. A food wine. Austere, smoky finish.
The Barbaresco 2014 was opened the day prior to the tasting. Not very concentrated (Sarah talks about a Burgundian style). Sweet, pale fruit with hints of carbonic maceration. Florality. Tar. On the palate strawberries, cherries and aggressive tannins.
The Sperss 1999 showed oak and sweet fruit, tobacco, rust, blackpepper, and a savoriness. Rose tar and spice on the palate. Richness and laid-down tannins.
The Gaia&Rey 2009 showed sweet fruit, oak and baking spices. Curry and tropical fruit. Utilized whole-bunch fermentation in this ripe vintage. Never tried it again. And I can understand why.


©Wine -- Mise en abyme

Friday, May 19, 2017

Gaja Winery agronomical practices aimed at promoting vineyard flexibility

The Gaja wine making process has been the same since 2000 but its agronomical processes have changed within that time frame to accommodate the unpredictability and warming associated with climate change. So said Sarah at the start of our tour and tasting at the Gaja Winery on May 15th of this year. In highlighting this unpredictability, Sarah pointed to the hail that the region experienced in April; hail that came after two weeks of warmth that had encouraged the growth of young, delicate leaves.

To combat this emergent new-normal, the estate has to be flexible in the vineyard. In the course of our conversation Sarah spelt out a number of practices that they have employed in pursuit of this flexibility.

Cover Crops
Grass planted between the rows and tailored to the resident soil. For example, if the soil is compact, cover crops with strong roots will be planted in an effort to open up the soil. One of the many benefits of cover crops is its nitrogen-fixation capability but if the need is to reduce nutrients in the soil, a different type of cover crop can be planted.

In a vintage like 2014, there was a need to reduce the humidity in the soil so the grass was cut three or four times a week in order to remove water. In 2015, a dry period, they did not cut the grass and the carpet of dry grass helped to keep the moisture in the soil.

Most Piemonte vineyard rows are oriented horizontally (Giropoggio), but, since the 1970s, Gaja vineyards have been oriented vertically. This orientation, according to Sarah, slows down sugar production but can contribute to soil erosion during periods of heavy rain. Cover crops are impoprtant in limiting this erosion.

Staffing
Gaja has 96 ha of vineyards spread between Barbaresco and Barolo and applying the estate's agronomical principles consistently requires skilled, competent, and committed employees. Towards this end, Gaja provides housing to its employees in close proximity to their work locale. There are currently 85 employees living in 26 houses distributed across the Langhe holdings. The degree of skill and commitment is reflected in the fact that only eight Gaja employees are allowed to prune the vines; and five of them are second-generation. This degree of focus and specialization allows the estate to maintain high levels of quality over all its holdings for extensive periods of time.

Scion Selection
The average Gaja vine is between 50 and 55 years old. At the end of each growing season, vineyard employees will identify the vines which performed best that year. Cuttings will be taken from those vines and planted in the nursery. If there is a need to replace a damaged vine, one of these "superior-performing" cuttings will be deployed.

Biodiversity
There is a concerted program to increase biodiversity in the vineyards. For example, there are 45 beehives scattered around the vineyards. These bees help with the pollination of the cover crops and thus aid in the advancement of the flora and fauna that they support. "The spic and span approach is not the best way to keep balance in the vineyard," Sarah said.

Sarah making one of her many points
Cypress trees are not native to Piemonte but there are in excess of 250 of them scattered across the Gaja vineyards. In addition to Angelo liking the shape of the trees, their compact structure affords protection for smaller birds from marauding larger predator birds. These smaller birds and bats are major consumers of insects.

©Wine -- Mise en abyme

Tuesday, May 16, 2017

Traditional and contemporary: Broad categories of orange wines

In my most recent post I characterized skin-fermented white wines as juice fermented and macerated on the skins, seeds, and, in some cases, stems for periods ranging from weeks to months. These wines, more commonly known as "orange" wines, can be further broken down into two broad classes: traditional and contemporary.

Traditional Orange Wines
The traditional method is primarily employed in the Caucasus region today and represents the manner in which white wines had been made for thousands of years. An example of this is the white Kakhetian wine of Georgia where the juice of the white grapes is macerated for months on the skins, seeds, and stems in buried Kvevri. The method whereby this wine is made is illustrated in the figure below.


The grape varieties used in the process (indicated in the above graphic) are characterized by (domainegeorgia.com):
  • Relatively neutral flavors (low content of terpene compounds)
  • High levels of phenolic compounds in the skin
  • High alcohol potential
  • Moderate acidity.
The lengthy maceration periods associated with the process dictate that the grapes have adequate levels of sugar and acidity and be "perfectly ripe" (phenolic maturity) and that the grapes, skins, and stems be sanitary (domainegeorgia.com).

The result of the Kakhetian method is a wine with a color that is "dark, almost orange, tea, or amber, often with a pink tinge." The wine's polyphenolic content often exceeds 2000 mg/l, a level akin to light red wines and well above the average 300 mg/l for a European white wine. According to domainegeorgia.com, the sources of the polyphenols are seeds (47%), stems (42%), and skins (11%).

Other kvevri-based white wine production methods encountered in Georgia include the Imeretian (from the province of Imereti in western Georgia; 1/10th the chacha and no stems) and Kartli (central Georgia; 1/3 of chacha plus stems). The avoidance of stems renders the Imeretian method less tannic than the Kakhetian while the Kartli method falls somewhere between the two (domainegeorgia.com).

Contemporary Orange Wines
These wines originated in the Italy-Slovenia border area around Friuli-Venezia Giulia, pioneered by producers such as Gravner, Radikon, Movia, and others who were inspired by the ancient winemaking techniques of Georgia. According to Appel, these wines:
  • May be fermented and aged in a variety of vessels, to include wood or clay
  • Are often open to the elements until aging begins
  • Utilize native yeasts for fermentation
  • Undergo long, slow, natural fermentations.
Some of the cultivars employed as raw material for these wines include Ribolla Gialla, Chardonnay, Riesling italico, Malvasia, and Pinot Grigio.

The extended contact with the grape phenolics during the long. slow, maturation and aging results in wines that are characterized by (Appel):
  • Exceptional richness and body
  • Striking, fascinating tannins
  • Ageability
  • Savoriness
  • Intensity
  • Unique flavors to include tea, baked apple, honey, nutcake, sourdough, cider, etc.
Michael Franz points to the region of Collio in the Friulia-Venezia Giulia region for great orange wines. The wines there are made from late-harvested Ribolla Gialla which are macerated for 1 - 4 months, after which they are pressed and placed into large old casks for a number of years before being bottled for sale.

Ribolla Gialla orange wines from the pioneering Stanko Radikon are considered to be among the best of this wine style. Radikon ferments destemmed grapes in oak barrels with natural yeasts and no temperature control. At the conclusion of the fermentation the vats are filled and closed. The wine remains in contact with the skins for 3 to 4 months after which they are aged in large oak casks for 3 years and in bottle for 1 year.

A contemporary, non-Friuli orange-wine producer is the Etna-based Frank Cornelissen. The core objective of Frank's viticultural regime is the production of grapes that lead to profound wines. The practices to promote this goal include: crop management through pruning; tailoring of  bunches to concentrate sugar; handpicking of defective grapes; late harvests; and multiple passes through the vineyards to ensure harvesting of fully ripened grapes.

In the cellar, Frank does not add sulfur either to combat oxidation or to combat micro-organisms. Wines are fermented by indigenous yeasts in small, food-grade plastic tubs. To ensure vintage integrity, all yeasts resident in the cellar are killed prior to the start of wine production. Fermentation is conducted with yeasts brought in from the vineyards on the grapes.

Both white and red wines are fermented with skin contact. His Munjebel bianco 2014 is a white wine made from 60% Grecanico Dorato and 40% Carricante. The grapes for this wine are grown on 40+-year-old vines grown in the Calderara soprano and Borriglione vineyards. A total of 4000 bottles of this wine is produced annually. This wine is amber in color and, when tasted, exhibited florality, spice, and a savoriness on the nose. Savoriness flows through to the palate. A textured wine with great acidity and a long finish.
**********************************************************************************************************
Skin-fermented wines have spread way beyond the "old world" into every nook and cranny of wine production. While these wines will probably always occupy a relatively small niche of the white wine world, they have long thrown off the coat of "oddity."

Bibliography
Joe Appel, Skin-contact in winemaking turns an ordinary white into a tantalizing orange, Portland Press Herald, 8/31/16.
Domaine Georgia, Winemaking in Kvevri, domainegeorgia.com
Michael Franz, Collio, Italy's Best Region for White Wines, Wine Review Online.

©Wine -- Mise en abyme

Sunday, May 14, 2017

Skin-fermented white (orange) wines: Another arrow in the winemaker's quiver

In my post on skin-contact white wines, I differentiated between that specific style and the more expansive skin-fermented style. I characterized the former as juice macerated on the skins for between 2 and 24 hours, during the pre-fermentation phase, while the latter is macerated for weeks to months, extending through the fermentation and, in some cases, maturation phases. I examine skin-fermented wines in this post.

Skin-fermented white wines are treated in the same manner as are red wines; that is, fermentation of the juice in the presence of grape skins, seeds, and, in some cases, stems. The key difference between these wines and conventional white wines are the extractives from the skins, seeds, and stems (if stems are included). The key difference between these wines and skin-contact wines are the greater concentration of extractives from the skin and the extractives from the seeds and, if utilized, the stems.

The figure below illustrates the flavonoid phenolic compounds in wines and their sources. I have described the skin and its extractives in the previously mentioned post. I will provide a brief summary of the seeds and stems in the following.


Seeds
Grape seeds are comprised of an outer seed coat, an endosperm, and an embryo, with the seed coat containing relatively large concentrations of tannin. Jackson stipulates that the predominant phenolics in seeds are the flavan-3-ols catechin, epicatechin, and procyanidin polymers (the latter a condensed tannin).  The tannins in the seed walls are more polymerized, and contain a higher proportion of epicatechin gallate, than those in the inner portions. Phenol levels in the seed are higher than in the skin or stems (60% versus 20% each) but they are seldom extracted to their "full potential" during wine production due to the lipid coating which retards tannin extraction until alcohol content becomes a facilitator (Jackson).

Seed tannins weigh, on average, 3.5 - 5 mg per berry while skin tannins weigh in between 0.5 and 0.9 mg. Seed tannin polymers are shorter than skin tannin polymers (the longer the tannin chain the higher the astringency) yet seed tannins are perceived as harsher, greener, and more astringent due to a greater degree of galloylation.

Grape tannins accumulate during the first period of berry growth with skin tannin synthesis beginning earlier than seed tannin synthesis and then ending with the conclusion of the first phase of growth. Seed tannin synthesis continues into the early period of berry ripening before concluding. Both skin and seed tannins continue to mature during the berry ripening phase.

Skin tannins release early and easily but then plateau. Seed tannin release is slow, steady, and long and requires alcohol as a solvent. Tannin extraction will continue throughout fermentation with the ratio tilting in favor of seed tannin somtime during the process.

Stems
Grape stems are comprised of cellulose (approximately 30%), hemicellulose (21%), lignin(17%), tannin (16%), proteins (6%), and other constituents. As was the case for seeds, stem flavan-3-ols occur primarily as catechin, epicatechin, epigallocatechin, epicatechin-gallate, and condensed tannins (procyanidin oligomers and polymers).

In a study of wines made with varying levels of stem inclusion, Suriano, et al., came to the following conclusions:
  • Wines vinified in the presence of stems were higher in tannins, flavans, vanillin, and proanthocyanidins
  • Stems conferred more structure and flavor to the wines
  • Stems facilitated must aeration thus promoting synthesis of higher alcohols and ethyl esters by the yeast.
In addition to the foregoing, it should be mentioned that the stems reduce the compactness of the cap thus providing pathways for carbon dioxide escape during fermentation and wine flow-through during pumpovers. On the minus side, stems in the cap increase the difficulty of manual punchdowns.

Stem condensed tannins are also considered to be very bitter and astringent and fall between skin and seed tannins in size. Green stems should be avoided as it will take years for the wine in which it is included to mellow out (Pambianchi).

Summary
To summarize (Gil, et al.):
  • Seeds and stems are major sources of phenolic compounds that condition the final composition of the wine
    • Seeds release significant amounts of flavan-3-ol monomers as well as proanthocyanidins with relatively low mean degree of polymerization and a high percentage of galloylation
    • Seeds also increase astringency and bitterness and generate a slight but significant decrease in ethanol content, probably through the release of potassium and water
    • Stems also release flavan-3-ol monomers and proanthocyanidins but their composition differs from those of the seeds
      • (+)-gallocatechin replaces (-)-epicatechin
      • Procyanidins had a higher mean degree of polymerization than those from seeds and a higher percentage of prodelphinidins
  • Stems significantly increased the pH and decreased the titratable acidity and ethanol content (probably through the solubilization of potassium and water) of the finished wine.
In my next post I will discuss two broad categorizations of skin-fermented white wines.

Bibliography
Mariona Gil, et al., Influence of Grape Seeds and Stem on Wine Composition and Astringency, Journal of Agricultural and Food Chemistry, August 2016.
Herraiz, et al., Effects of the presence of skin during alcoholic fermentation on the composition of new volatiles, Vitis 29, 1990.
Ronald Jackson, Wine Science, 3rd ed., Academic Press.
M. Jose Jara-Palacios, et al., Detailed phenolic composition of white grape by-products by RRLC/MS and measurement of antioxidant activity, Talanta, 2014.
James A. Kennedy, Grape and wine phenolics: Observations and recent findings, Ciencia e Investigacion Agraria 35, 2008.
William McGlynn, Basic Grape Berry Structure, articles.extension.org, April 15, 2012.
Daniel Pambianchi, Tannin Chemistry: Techniques, winemakermag.com, April/May 2011.
Jean-Marc Souquet, et al., Phenolic Composition of Grape Stems, Journal of Agricultural and Food Chemistry, May 2000.
S. Suriano, et al., Major phenolic and volatile compounds and their influence on sensorial aspects in stem-contact fermentation winemakingof Primitivo red wines, J Food Sci Technol 53, 2016.


©Wine -- Mise en abyme

Thursday, May 4, 2017

"Oxo-Reductive": An emergent Burgundian white wine style*

I am in the midst of a series on white wine styles and most recently wrote on barrel-fermented and -aged white wines. The process I described therein mapped tightly to the process described on the Burgundy Wines website. I also wrote (earlier) on reductive winemaking, some aspects of which Jancis Robinson associated with Burgundian whites in a 2015 article. Now Jon Bonne has written an article (post-Premox: A Quiet Revolution in the Côte de Beaune, Wine&Spirits, April 18, 2017) which pushes the Burgundy white wine envelope out beyond the boundaries established by Jancis to a new style that I am referring to as "Oxo-Reductive."

Both Jancis and Jon point to the premox issue as the engine driving the change in Burgundy. Prior to the recognition of a problem, "'buttery,' 'rich,' and even 'toasty' used to be the terms of approbation for these sort of wines, but no longer." Instead, these wines were now characterized by (Jancis):
  • High levels of acidity
  • No trace of the toastiness of obvious oak
  • Leanness on the palate
  • The tell-tale flinty smell of recently struck matches.
This new style was driven, according to Jancis, by work done in the cellar. In her words, "it is only very rarely shaped by what goes on in the vineyard." The cellar activities that she identified were as follows:
  • Minimize the amount of new oak influence
  • Eschew stirring of lees in the barrel (minimize O₂ exposure)
  • Minimize racking (minimize O₂ exposure)
  • Complete aging in tanks (process invented by Roulot and identified in the article as being utilized by Roulot and Leflaive)
  • Top up space left by evaporation with contents of a particularly reductive one
  • Add a bit more SO₂ at bottling
This process is not fully reductive but it is stingier with O₂ than the full barrel-aging process described in my prior post.

Raj Parr and Jean-Marc Roulot during our 2014 visit
to Domaine Guy Roulot
Jon characterized the 1990s Burgundies as "wines that were riper, fuller, and more enjoyable when young." And the most reputable appellations went along for the ride: "Puligny-Montrachet, Chassagne-Montrachet, and Meursault gravitated towards the richer, early drinking style gaining favor elsewhere, especially California."

When the Burgundian winemakers realized that they had a problem on their hands, they went back and took stock of every aspect of the winemaking process. To the extent that they could not identify a single causative factor for premox, they tightened all aspects of their winemaking. In Jon's words, "Where once the goal was richness and opulence, the new plan was to prepare wines for a long and prosperous life -- namely by making them as bulletproof as possible to oxidation."

Where Jancis identified "reductive-associated" winemaking as the solution pursued by the winemakers, Jon saw it as extending beyond the cellar to include grape growing and handling. He identified a number of farming changes that have taken place but did not, to my satisfaction, directly link these to the fight against premox. Changes like movement to biodynamic farming, yield reduction, picking earlier, and massal selection, in the words of Dominique Lafon, contributed to greater clarity and length in the wines.

Jon concedes that the "greatest revolution has come in the cellar." They are more or less in agreement on the winemaking activities -- except where he mentions leaving the wines in barrel longer (15 months or more) -- but it is in the area of grape and juice handling, an area unexplored by Jancis, where we see the greatest departure. Jon has noted the following handling initiatives:
  • The pressing of the grapes is less delicate (in some cases the grapes are lightly crushed)
  • The resurgence of upright mechanical presses (to the detriment of the pneumatic presses)
    • These presses tend to expose the grapes to air and O₂
  • Oxidation that occurs at pressing is allowed to continue through the next day
    • Juice browning.
As described to Jon by one of the winemakers, he wants to oxidize at the must stage so that the substrates do not make it into the wine.

Except for scope and scale, this is exactly the process that I described in my post on hyperoxidation. Thus, given the mix of oxygen exposure and the reductive tendencies described in these two articles, I will refer to this emergent white Burgundy style as "Oxo-Reductive."

*Author's Note: I had originally referred to this style as Hyperoxo-Reductive. After giving it some thought overnight, I have come to the conclusion that the name prefix "hyper" is not warranted due to a lack of direct infusion of O₂ into the juice. Based on that thinking, I have modified the name to Oxo-Reductive.

©Wine -- Mise en abyme

Sunday, April 30, 2017

Barrel-fermented and -aged white wines

Oak was the primary fermentation vehicle prior to the post-war inroads made by stainless steel tanks, inroads driven by the latter's perceived advantages:
  • Provides an anaerobic environment
  • Easier to clean, thus reducing the risk of bacterial contamination
  • Increased durability
  • Allowed fermentation temperature control
    • White wines could be fermented cool and thus preserve floral and fruity aromas
    • Cooler fermentation temperatures lowered the risk of off-flavor production
  • Allowed control of fermentation rate.
With all of these advantages arrayed against it, oak had to have some overriding benefits for winemakers to continue using it as a vehicle. And it did. According to Ibern-Gomez, et al*., "Fermentation in oak barrels leads to wines with much more complex sensory properties, largely attributed to the phenols extracted from oak wood."


I will examine these substances and their impacts on barrel-fermented wine in this post.

Oak Wood
As a result of its "strength, resilience, workability, and lack of undesirable flavor," oak is the wood of choice for most wine cooperage applications.


The oak used in the maturation of alcoholic beverages fall into one of three species: Quercus albaQuercus robur, and Quercus sessilis.  Q. robur and Q. sessilis, and their respective subspecies, are European white oaks while Q. alba is the source of 45% of the white oak lumber produced in the US.  American oak used in barrel production is sourced from Kentucky, Missouri, Arkansas, and Michigan but there is no apparent regional distinction.  European oak, on the other hand, may have designations which reach all the way to the forest from which the oak originated.  For example, French oak from the department of Alliers may be sourced from a forest named Tronçais.

Sources: enologyinternational.com; Dr. Murli Dharmadikari; Principles and Applications in Wine Science

The journey from oak tree to wine barrel is shown in the graphic below.


Alcoholic Fermentation in Oak Barrels
Grapes are pressed and the resulting juice is deposited into oak barrels (In many Burgundy white wines the grapes are pressed "whole-cluster"). The juice levels do not fill the tank as space has to be left for expansion of the contents during alcoholic fermentation.

In a study on barrel-fermentation of white wines (S. Herjavec, et al., The quality of white wines fermented in Croatian Oak, Food Chemistry, 100, 2007), the authors stated thusly:
One of the practices used to intensify the aroma and flavor characteristics of white wines is to ferment the must in oak barrels, and Chardonnay is one of the most suitable varieties for this. Wines produced by fermentation and maturation in oak barrels have different flavor characteristics to those which have undergone barrel maturation only after fermentation in stainless steel. One reason for this is that actively growing yeasts are capable of transforming volatile flavor components, extracted from oak wood, into other volatile metabolites.
This metabolite transformation results in what Zac Brown, Winemaker at Alderlea Vineyards, describes as "better integration of the oak and softer mouthfeel when compared to a white that is finished and then transferred into oak barrel to age."

In the case of reductive winemaking, we seek to prevent the rich varietal aromas of Riesling, Petit Manseng, and Gewurtztraminer from oxidizing effects. This environment will be subjected to oxygen effects and it is not recommended that these varietal types be barrel-fermented.

Malolactic Fermentation
According to Sauvageot and Vivier (Effects of Malolactic Fermentation on Sensory Properties of Four Burgundy Wines, AJEV 48(2), 1997), malolactic fermentation (MLF) is a bacterial conversion -- most commonly performed by Leuconostoc strains, due to their tolerance of the high acid and alcohol content associated with wine -- of L-malic acid to L-lactic acid and CO₂.

The main effects of MLF on wine are (i) a reduction in titratable acidity (by 0.1 to 0.3%) and an increase in pH (0.15 to 0.30). In addition, dramatic organoleptic changes to the wine are evidenced (Lonvaud-Funel, Microbiology of the Malolactic Fermentation: Molecular Aspects, FEMS Microbiology Letters):
  • The specific taste of malic acid disappears
  • Sugars are catabolized to produce mainly lactic and acetic acid
  • Citric acid is transformed into acetic acid and carbonyl compounds, notably the butter-flavored diacetyl
  • Wine taste and color are modified due to the metabolic activity of bacteria on phenolic compounds (tannins, anthocyannins).
By synthesizing anti-bacterial compounds and depriving the wine of nutrients, MLF also contributes to its microbial stability (Lonvaud-Funel).

The process is encouraged (Bauer and Dicks, Control of Malolactic Fermentation in Wine, S. Afr. J. Enol. Vitic. 25(2), 2004): in cooler areas where grapes have high malic acid content; in cases where the wine is aged in oak barrels; and when the wine style calls for long-term aging in bottle. The practice is sometimes forsworn in warmer, lower-acid areas and in the cases where undesirable organoleptic changes or the production of biogenic amines result.

Lees Aging
Murli Dharmadhikan (Yeast Autolysis, extension.iastste.edu) defines yeast autolysis as "... self-destruction of the cellular constituents of a cell by its own enzymes" following its death. Figure 1 below shows the component parts of a healthy yeast cell while Figure 2 shows an overview of the process  -- autolysis -- that occurs once that yeast cell has consumed all of the available nutrients and dies. At a high level, autolysis encompasses (i) the degradation of intracellular materials and (ii) degradation of the cell wall.



The detailed autolysis process is shown in Figure 3 below. The yeast extract, product of the degradation of intra-cellular material, is confined to the cell until such time as the cell wall becomes porous enough to allow the material to seep out. It should be noted that degradation and compound creation continues outside the degraded cell walls.

Figure 3. Details of yeast autolysis
The lees-aged wine is enriched by the compounds released during the constituent-degradation process. Compounds released during autolysis include (Thierry Binder, Cremant d'Alsace, TONG #13; Dharmadhikan):
  • Nitrogenous compounds
    • Amino acids -- known to enrich mouthfeel; aroma precursors of acacia honey notes
    • Polypeptides -- sweet and bitter taste; precursors of the autolytic aromas of brioche and toast
    • Peptides
    • Nucleic acid components
  • Polysaccharides -- originates from breakdown of cell wall components
    • Degradation products are glucose and mannose
    • Mannoproteins increase mouthfeel and foam stability as well as contributing to fineness and persistence of bubbles
  • Fatty acids -- important for foam stability, mouthfeel, and flavor. Can be involved in the formation of esters, aldehydes, and other volatile compounds
  • Volatile components
    • Heavy esters
    • Terpene components
    • Higher alcohols
    • Other volatile components.
In order to ensure distribution of the beneficial autolysis products evenly throughout the wine, a process called batonnage -- stirring of the lees -- is undertaken. Batonnage is generally conducted once or twice per week.

Oak Aging
Wine is aged in wooden barrels to: (i) enhance its flavor, aroma, and complexity through transfer of substances from the wood to the wine; and (ii) allow gradual oxidation of the wine.

In the first instance, many of the wood's native aromatic compounds, as well as the aromatic compounds created during seasoning and toasting, are absorbed, and integrated, into the wine, thus contributing to wine richness and aromatic complexity.  For example, hemicellulose will hydrolyze upon exposure to wine, creating, as a result, sugars and acetyl groups.  The sugars are further converted to furanaldehydes and ketones while the acetyl groups are converted to acetic acid during maturation.  A small proportion of lignin will dissolve in wine (these are called native lignins) while some undergo ethanolysis and are oxidized to aromatic compounds.  These compounds have low olfactory thresholds and will, therefore, impact the wine's aromatic profile. As noted by Dr. Murli Dharmadikari, common descriptors of oak-aged wines are oaky, vanilla, smoky, toasty, spicy, and coconut.

In terms of gradual oxidation, wine loss from barrels amount to approximately 2% per year, resulting from the fact that water and ethanol are smaller molecules and will diffuse into the wood and, ultimately, escape as vapor.  If the air in the cellar is dry, more water is lost and the wine is more concentrated in terms of alcohol.  If the environment is too humid then more alcohol is lost, reducing the ethanol content in the remaining wine.  This loss of liquid opens up a space between the wine surface and the barrel which the winemaker generally "tops up" in order to prevent oxidation and acetic spoilage.  During this "topping-up" process, small amounts of oxygen are dissolved in the wine.  Oxygen is also introduced into the wine during winery operations such as filtering and racking.

The oxygen which is now in the wine reacts with resident phenolic compounds in a manner such that: (i) tannins are softened (polymerization and precipitation as well as tannin-polysaccharide combinations); (ii) complex aromas develop; and (iii) there is improvement in the wine's body and mouthfeel.  It should be noted here that the tannin resident in the wine at this time is the oak tannin absorbed from the barrel (30% from the innermost four millimeters of wood).

In the aforementioned Herjavec, et al., study, the authors found that the sensorial characteristics of barrel-aged wines were modified, due to the wood-derived compounds. These wines manifested roundness in taste with a complex retro nasal aroma." Barrel toast also affected flavor perception: aging in medium-toast barrels yielded a smoky, roasted, and raw oak flavor while light toast resulted in a more fruity aroma.

Comparison of Barrel- and Stainless Steel-Fermented White Wines
According to Ibern-Gomez, et al., "wines fermented in wood barrels are distinguished by the cession of oak wood compounds to the wine." The figure below shows the phenolic compounds found in wine fermented in oak barrels.


Further, the authors compared control wines fermented in stainless steel to wines fermented in oak barrels and noted the following differences:
  • Total phenolic content was higher for white wines fermented in oak barrels than for wines fermented in stainless steel tanks
  • New phenolic compounds which are characteristic of oak wood (syringaldehyde, coniferaldehyde, sinapinaldehyde, scopoletin, 4-ethyl-guaicol, and eugenol (the latter two being volatile phenols)) were found in the white wines fermented in oak
  • The gallic acid and 4-vinylguaiacol increased in white wines fermented in oak
  • Browning in oak wood white wines was higher than for stainless steel white wines.
  • Furfural, 5-methylfurfural, and furfuryl alcohol from thermal degradation of cellulose and hemicellulose were found in the white wines fermented in oak.
As it relates to sensorial analyses, the following was reported:
  • Tasters described white wines fermented in oak as having golden hues
  • White wines fermented in oak were described as having toasty and spicy aromas
    • Probably due to the 4-ethyl-guaiacol and eugenol
  • Tasters also described a coconut aroma for the barrel fermented wines
    • Probably due to the cis-β-methyl-γ-octalactone detected.
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While the process described herein is identified as being associated with oak fermented and aged white wines, it is not exclusive, in its entirety, to that style of wine. For example, a wine fermented in stainless steel could also be subjected to malolactic fermentation and lees residence in the tank or could have those two procedures completed in oak barrels and subsequent aging in same.

*M. Ibern-Gomez, et al., Differences in Phenolic Profile between Oak Wood and Stainless Steel Fermentation in White Wines, Am. J, Enol. Vitic, 52:2 (2001).

©Wine -- Mise en abyme

Saturday, April 29, 2017

A visit to Pietradolce Winery (Solicchiata, Mt Etna, Sicily)

“A model small estate making top-level, authentically regional wines from mostly old vines, including several pre-phylloxera parcels. Michele Faro’s grandfather grew grapes and made wine on Etna, and some of the oldest parcels were in family hands, so he got off to a running start in 2005.” Thusly was Pietradolce described in John Szabo’s Volcanic Wines. With this full-throated endorsement of the Pietradolce estate and wines, I was anxious to pay them a visit. Sensing my urgency during our pre-trip communications, Brandon arranged for me to go directly from the airport (after an overnight, intercontinental flight) to the estate in Solicchiata.


After a great “catch-up” ride, we arrived at the Pietradolce (“sweet stone”) estate. The winery building dominates the zone, appearing as an oversized lava terrace overseeing the smaller terraces that fell away before it. We were met in the driveway between the vineyards by Giuseppe Parlavecchio, the vineyard manager, who, after the introductions were made, proposed that we go walk in the vineyard. I agreed. I needed to keep walking to stay awake.



The estate sits on 11 ha that is subdivided into three vineyard plots (two of the plots fall within the Rampante Contrada while the other is in Zottorinoto. The location experiences cool nights, warm days, and a 20-degree day night temperature variance (Such variances are widely held to be beneficial to grape quality.). The area is also subject to steady winds flowing over the Nebrodi Mountains and they serve to keep the vineyard, which faces in that direction, relatively free of vineyard diseases (2015 was a very difficult year in that they experienced higher-than-normal rainfall). 

The soil is comprised of a stony, light sandy loam infused with a bounty of minerals. According to Giuseppe, the soil is very rocky up to depths of 2 - 3 meters over the entirety of the property.

The  vineyard follows the natural lay of the land. Because of the amount of stone that had to be removed during vineyard establishment, they opted for two large terraces, rather than a larger number of smaller terraces. 

The vineyard is farmed organically. Vine training is a mix of albarello (legacy and youngest vines) and espalier. Albarello is cropped shorter here than on other Etna estates. The estate’s position is that albarello affords the best expression of Etna wines in that it forces the roots to dig deep in search of nutrients and water.

The lowest vineyard is laid out between 600 and 800 meters and is simply called Pietradolce. It is planted 4000 vines/ha to Carricante (2.5 ha) and Nerello Mascalese (0.5 ha). The Archineri cru is 2.5 ha in size and is home to 70-year-old Nerello Mascales vines. The Barbagalli vineyard is the highest of the vineyards (900 m) and is populated with 80 - 100-year-old Nerello Mascalese vines.






The estate’s first vintage was the 2007 Archineri — a total of 300 bottles — followed by the Barbagalli in 2010 and the Rosato and Etna Bianco in 2011. The white wine is subjected to a lengthy maceration. The reds are fermented/macerated over 20 days in 500 - 700 hl barrels and then undergo a natural malolactic fermentation. Entry-level wines are aged for 3 months while the more complex wines are aged between 14 and 20 months.




The Pietradolce Etna Rosato 2010 is a Nerello Mascalese wine which saw no maceration. Perfumed cherry nose along with spice and butterscotch. Focused, with great acidity and a lengthy finish. Slight yeastiness attributable to lees with no battonage. Beautiful wine. 9000 - 10,000 bottles per year.



The Etna Rosso 2015 is a 100% Nerello Mascalese which spends 3 months in wood. Cherry, spice, aggressive tannins and searing acidity. Great attack and mid-palate with reticence on the finish. 10,000 - 11,000 bottles.

The Archineri 2014 spent 14 months in wood and 6 months in bottle. Pine notes, dried bramble, tar, and mahagony on the nose. Mint, green herbs, silky tannins on the palate. Balanced. 7000 bottles.

Archineri 2010 showed spice, polished wood, caramel, sweet tobacco, and burnt orange. Cigar and leather on the palate. Lengthy finish.

We did not taste the white on this visit, a gap which I intend to address in the near future. Overall I was pleased with the wines on offer and especially so with the Rosato.

©Wine -- Mise en abyme