Wednesday, April 26, 2017

Wine styles: Skin-contact whites

In this series on white wine styles, I have treated Champagne and Sparkling wines, reductive wines, and wines made utilizing the process of hyperoxidation. In this post I cover skin-contact white wines.


Skin-contact white wines are recognized by a combination of their residence on the early part of the orange color spectrum, their earthy flavors, and enhanced mouthfeel. These characteristics are the result of macerating the skin of crushed and de-stemmed white grapes in their own juice (i) prior to pressing and (ii) under controlled time and temperature conditions (The procedure is generally carried out under cool conditions in order to limit the growth of spoilage organisms.).

While white juice fermented on their skins are, obviously, in contact with those skins, we differentiate those wines from the ones treated in this post both on the basis of time -- skin contact wines are macerated for between 2 and 24 hours while the fermented-on-skin wine is macerated for weeks to months -- and phase within the production process -- skin contact is a pre-fermentation process while its compatriot extends beyond that to fermentation and, in many cases, maturation.

Maceration refers to the release of constituents from the pomace following crushing and is facilitated by "the liberation and activation of hydrolytic enzymes from crushed cells." Substances extracted include: aromatic compounds, aromatic precursors, phenols and polyphenols, unsaturated lipids, nitrogen, and potassium. At high enough levels, these extractives will produce earthy flavors and enhanced mouthfeel in the wines and will contribute positively to the fermentation processes. The best results are obtained from fully ripe, aromatic grape varieties such as Gewurtztraminer, Riesling, Muscat, Viognier, Chenin Blanc, and Sauvignon Blanc.

What is the makeup of the grape berry skin and what role do the constituent parts play in the makeup of a skin-contact white wine? The berry skin consists of an outer layer with a wax-like coating (cuticle) and 6 to 10 layers of thick-walled cells (hypodermis) which accumulate phenolic compounds in fairly high concentrations as the berry matures (Dharmadhikari, McGlynn). The main components of the skin are phenols, aromatic substances, potassium, and other minerals.

Phenols
Phenolic compounds are:
  • Responsible for the color of red grapes and wine
  • Involved in the oxidative browning of white wines
  • Contributors to taste and astringency through interactions with salivary proteins.
The two major classes of wine phenolic compounds are flavonoids (defined by a C6-C3-C6 skeleton consisting of two phenolic rings joined by a central, oxygen-containing ring -- Jackson) and nonflavonoids (possessing a C6-C1 or C6-C3 skeleton; all numbers following "C" are subscripts). The sources and roles of the phenolic compounds falling into these two classes are illustrated in the figure below and the relative concentrations of selected classes are provided in the table following.


Table 1. Generalized concentration of various phenolic compounds
present in wine
PhenolicWhite Wine (mg/L)Light Red Wine (mg/L)Full Red Wine (mg/L)
VolatileTrace
10
40
Hydroxycinnamic acids
150
200
200
Other nonflavonoids
25
40
60
Anthocyanins
0
200
400
Catechins
25
150
200
Polymeric catechins
0
600
900
  Totals
200
1200
1800
Source: Kennedy, et al., Grape and wine phenolics: History and perspective,
AJEV, 57(3), September 2006.

Skin contact increases the amount of hydroxycinnamates, gallic acids, and flavonoids. Flavonoids increase slightly with contact time but strongly with temperature. These compounds are of concern because they contribute to bitterness and astringency and also serve as substrates for oxidation in white wines. While there are elevated levels of astringency in skin-contact white wines, they are nowhere near as high as in red wines. First, even though tannin is extracted from the skin of the white grape, the lack of anthocyanins means that only tannin-tannin bonds are formed, a combination that is less soluble in alcohol. Second, during fermentation, most of the tannin will precipitate out, thus limiting its ability to negatively impact the wine's sensory characteristics.

Aromatic Substances
Aromatic substances are located in the skin and layers of cells immediately below it. Examples of these compounds include (Dharmadhikari):
  • 2-methoxy-3-isobutyl pyrazine -- imparts bell pepper odors to Cabernet Sauvignon and Sauvignon Blanc
  • 4-vinylguaiacol and 4-vinylphenol -- spicy, clove-like, and medicinal odors in some Gewurtztraminers
  • Terpenes -- can be found in Muscats and Rieslings.
Fermentation Benefits
While winemakers do not pursue skin-contact because of the benefits that it provides to the fermentation process, they gladly accept what is offered. Maceration (Jackson):
  • Improves juice fermentability and enhances yeast viability through its release of particulate matter, lipids, and soluble nitrogen compounds into the juice
    • Particulate matter provides surfaces for yeast and bacterial growth, adsorption of nutrients, the binding of toxic C10 and C12 carboxylic fatty acids, and the escape of CO₂
  • Improves the production of extra-cellular mannoproteins formed during alcoholic fermentation
    • When combined with reduced concentrations of carboxylic acid, facilitates malolactic fermentation by Oenococcus oeni.
********************************************************************************************************
When contrasted with a more traditional white wine, a skin-contact wine may exhibit lower levels of fruitiness and acidity. In addition, the familiar characteristics of your favorite varietal may be hidden behind a spicy character that may now be present.


Bibliography
Murli Dharmadhikari, Composition of Grapes, www.extension.iastate.edu.
Ron Jackson, Wine Science, Academic Press.
William McGlynn, Basic Grape Berry Structure, April 15, 2012, www.articles.extension.org.
Tim Patterson, White Wine Skin Contact, August/September 2013, www.winemakermag.com
Nicola Tazzini, Polyphenols in Grape and Wines: Chemical Composition and Biological Activities, August 9, 2015, www.tuscanydiet.net.

©Wine -- Mise en abyme

Thursday, April 20, 2017

The wines of Salvo Foti

Salvo Foti decries the use of the words "natural wine." There is no "all natural" wine he says. "It is a marketing ploy" as vines left to their own designs would seek to maximize reproducibility rather than great winemaking fruit. The wine grape is a human contrivance and there is nothing natural about that.

Yet, if one were to consider the natural-wine bucket in today's winemaking arena, Salvo Foti is as natural as they come. I have previously discussed his traditional, low-impact, sustainable farming practices built on respect for the land and the people who work it. And that philosophy, and those practices, extend into the cellar.

If the laws allowed it, Salvo would make all his wines using the traditional Palmento (he owns a functioning Palmento on the Vigna Caselle property) but, lacking that option, he ferments instead in oak vats using indigenous yeasts and no temperature control (By the time of crush, temperature on the mountain is cold enough to allow that practice without unduly stressing the yeasts and resulting in the production of off-odors or stuck or sluggish fermentations.). Wines are never filtered and minimal SO₂ is used at bottling. Wines are racked and bottles according to the phases of the moon.

After our lengthy promenade among the vines, and being subjected to hundreds of Lidia's must-have picture compositions, we made our way down the hill and across the street to the Palmento in Vigna Caselle. We stepped through the small entry door and negotiated a catwalk-type structure to the crushpad where a table and chairs resided conference-room style. And it was here that we were treated to Salvo's wines and the philosophies and practices that I reported on in previous posts.

Salvo Foti and Author (Picture credit Lidia Rizzo)

In this post I report on Salvo's wines. The tasting group was comprised of Salvo, his son Simone, Brandon Tokash, Lidia Rizzo, a female winemaker, and the author. From time to time visitors would pass through to greet Salvo and he would have to take a small break to go acknowledge them.


I Vigneri vineyards around Mt. Etna (Source: Salvo Foti)

We started out with a 2014 Aurora Etna Bianco Superiore, a blend of 90% Carricante and 10% Minella. This wine was made from grapes sourced from the 5-ha, 5-year-old Caselle Vineyard. Slate, salinity, and eye-popping acidity. Salvo mentioned that this bottle had been opened for a week and offered to open a new one for comparison purposes. We did not object. The new bottle exhibited the same characteristics but with greater freshness. 6500 bottles.

The second wine tasted was the 2014 Vinudilice, made with grapes sourced from Vigna Bosco, a vineyard nestled within the depths of a holly oak forest 1300 meters up. This vineyard lays claim to being the highest in Europe.

100+-year-old vines in Vigna Bosco (Photo courtesy of
Sarah May Grunwald. Used with permission)
The varieties planted here are Alicante, Grecanico, Minella, plus some other unidentified varieties. They are co-vinified to produce a field-blend Rosato. The wines are matured in old oak casks and concrete.

The coloration on this wine was slight. It yielded subtle red fruit on the nose and a density, coupled with freshness and a mineral complexity, on the palate. This is not your grandfather's Rosato. 2,500 bottles.

In addition to the Rosato, we were also treated to a 2014 Vinudilice Metodo Classico. This sparkling wine was stunning but, unfortunately, it is not made every year. This is without a doubt the best sparkling wine I have tasted on the mountain to date and I have not been so excited about a non-Champagne sparkling wine since I tasted the Xinomavro-based Karanika. Fresh and attention-grabbing. Mouth-filling mousse and great persistence. The world deserves to see more of this wine.

Vigna di Milo 2014 is a 100% Carricante Etna Bianco Superiore sourced from a 0.15-ha vineyard located at 950 m asl and planted to 10,000 vines/ha. The wine is matured for one year in stainless steel and then racked into large wooden barrels for further refinement. This wine was fresh to go along with a salinity and slatey minerality. 2500 bottles.

Vinupetra 2014 is an Etna DOC red wine produced from grapes grown in a 0.5-ha plot in the Calderara vineyards of the Feudo di Mezzo district on the mountain's north face. The varieties included in the blend are Nerello Mascalese, Nerello Cappuccio, Alicante, and Francisis. The vines here are in excess of 100 years old and are planted albarello style and at 10,000 vines/ha. This wine had a perfumed nose with plum and cherry notes accompanying spice and sweet vanilla aromas. Focused, with a lengthy finish. This wine was pleasing. 3500 bottles produced annually.


In addition to the wines shown above, Salvo produces two other wines (not a part of this tasting). The first is a white made from Carricante, Rhine Riesling, Grecanico, and Minella grown in a 0.4-ha plot in the Nave Vineyard (1200 m asl) in the Agro di Bronte district. These bush vines were planted 10,000 vines/ha in 2005. The wine is bottled under the Vinjancu label.

The second wine is the I Vigneri Etna DOC which is produced from Nerello Mascalese and Nerello Cappuccio grapes given to the cultivators by vineyard owners to make wine for their personal consumption. This wine is fermented in a Palmento and sees no wood during the maturation process. Four thousand bottles of this wine are produced annually.

As an overall observation, each of the wines tasted was of extremely high quality and fully representative of its place. For the Carricante wines, salinity, acidity, and minerality were not in short supply. I remain blown away by the Vindilice Metodo Classico.

©Wine -- Mise en abyme

Tuesday, April 18, 2017

Aeris Vineyard: An Etna joint venture between Salvo Foti and Kevin Harvey of Rhys Vineyard

A visit with Salvo Foti was the first thing on our Saturday morning agenda so Brandon picked me up in Linguaglossa bright and early in the morning for our trip out to our meeting point at Vigna Caselle, just west of Milo.


We arrived at our destination and turned left into a driveway with a locked gate. Brandon got out and examined the gate which appeared to be latched from the inside. He walked around to the other side of the building but there was no automobile access from that side. There were no signs of humanity so he opened the gate and we drove on into the compound. We looked around, calling out all along, but raised no one. Brandon got on the phone and called Salvo and, lo and behold, they were in the vineyard across the street, half a mile away and 50 meters up.

As I came to find out later, we were in Vigna Caselle, a Salvo Foti property, while they were in Vigna Aeris, the Salvo Foti - Kevin Harvey joint venture. The two properties are separated by a street. We started out in their direction, lifting a pound of volcanic sand with each step, but an exit point from our enclosure was not readily apparent. The view of the volcano was spectacular though.


So we placed another call to Salvo and he said ok, they would come down to us. Brandon is not a guy who can sit still, however, so he continued to poke around and eventually found a gate which provided egress. We crossed over into the Aeris vineyard and met up with the group coming down.


The group was comprised of two men and a woman. As introductions were made, it turned out that the older gentleman was the famed Salvo Foti, the younger was his son Simone. The woman was a visiting winemaker from mainland Italy (or, as the Mt Etneans say, Italy). As the group had completed their circuit of the vineyard, it wad agreed that Salvo would continue on to the Palmento to taste his wines with the winemaker while Simone would show us the vineyard.

The vineyard is 3 ha in size, rising from 800 m at its lowest point to 850 m at the top, and was planted to 20,000 albarello-trained Carricante vines in 2013. This vineyard, as explained by Salvo, lies between the mountain and the sea and the warm air from the latter meets with the cold air from the former over Milo with the result being significant rainfall over the entire growing area. Red grapes do not ripen here. In addition to the rain, growers have to contend with year-round winds which can attain speeds of as much as 50 miles/hour.

There are beneficial aspects to the winds however. Moisture dries out rapidly, keeping vine diseases at bay. As a result, the vineyard makes it through the growing season with only sulfur and copper sprays. In addition, the sea and wind combine to imbue the Carricante grown on this side of the mountain with a saltiness that is not evident in Carricantes grown on the north face.

The soil is sandy and of volcanic origin with a substantial portion of ripiddu (lapilli and eruptive pumice) intermixed with red soils from the Sahara Desert deposited here by the aforementioned winds. The sandy soils drain rapidly, forcing the roots to dig deep in search of moisture and nutrients. A soil profile of the vineyard is shown in the image below.

Aeris soil profile
Foti works this vineyard according to I Vigneri principles. The vines are planted high-density in a quincunx formation with chestnut staves for support. The Quincunx planting system is, essentially, a square planting system with a fifth plant in the center.

Quincunx planting system (http://e-tesda.gov.ph/)
As described in quincunx.it:
In viticulture, the quincunx is a planting pattern: the vines, trained as bushes, are arranged in staggered rows that repeat the lines hinted at in the quincunx. It was the favorite system of the ancient era, because at the same time it met the requirements of order, efficient use of the space and aesthetics: the vineyard looks symmetric regardless of the terrains shape.
It is a way of doing viticulture that is very expensive in terms of energy and economic resources: machinery, in fact, can only be employed to a limited extent. Furthermnore, to grow and maintain a healthy bush vineyard planted in the quincunx pattern, it is essential that the growers have a long experience in the area where they operate. 
According to Salvo, in the original system there was a middle plant (in the Sicilian dialect called "o francisco") but now they no longer place a plant in the middle, but when they make the alignment, they still mark the spot. So, essentially, they have a square planting system with a marker in the middle for esthetic purposes. The diagram below, provided by Salvo, illustrates his point.


The field is worked by hand on the slopes while a small tractor aids in the process on the flatter portions. Lavic stone terraces have been built to ensure that the soils are not washed away by rainfall.

Lavic stone terraces


There is no irrigation and no fertilizers or pesticides are used. The vines are green-pruned in June.

Halfway through our walk we were joined by Lidia Rizzo who lent her formidable expertise to the discussion in the vineyard and the tasting which followed. I will detail that tasting in a follow-up post.

©Wine -- Mise en abyme

Saturday, April 15, 2017

Salvo Foti, the pillar of tradition in Mt Etna winegrowing

For most of it lengthy vinous history, the Mt Etna region has utilized the albarello training system as the foundation of its viticultural regime. This system reigned supreme until growers turned to the Guyot and speranato cordone (cordon spur) systems in the early and middle portions of the 20th century. As explained to me by Salvo Foti during a recent conversation, if you went back 20 years, most new plantings were Guyot, as growers pursued the perceived benefits of mechanization and increased yields. As a result, he said, we (the Etna growers) have lost our patrimonial history. But now things are looking up, he continued, as small producers are going back to albarello for new plantings.

Viticulture on the mountain is a mix of the traditional and these "newer" training systems and associated practices. There is no fiercer proponent and advocate of the traditional approach than the aforementioned Salvo Foti.  I provide some insight into Mr Foti's philosophy and practices in this post.

In their seminal work on Sicilian wine (The World of Sicilian Wine), Nesto and di Savino describe the subject thusly: "Salvo Foti stands out, by himself, as Sicily's greatest homegrown consulting enologist ..." who "... more than any other person, ... has fostered an awareness of (Etna's) unique wine culture."

Salvo Foti with Lidia Rizzo, Contrada Caselle
According to Nesto and di Savino, Foti's grandparents owned vineyards on the slopes of Etna. Salvo gained a technical degree in enology on the 1980s and began consulting work with a number of producers in Sicily. He continued his studies and eventually received a specialized degree in enology from the University of Catania. When Giuseppe Benanti made the commitment to the production of high-quality wine on Etna, he turned to the young Foti to work with him on the needed experiments. Foti was Benanti's enologist until they parted ways in 2011.

In his writings (Foti has written a couple of books and a number of pamphlets on wine-related topics), Foti draws a sharp contrast between "producing Etna wines" and "making wine on Etna." Producing an Etna wine results in a product that "captures the essence of the land, the environment, and the people;" requires a winemaker who is "committed to improving and preserving the land where she or he operates," and a vineyard that is ...
in harmony with the terroir, is naturally integrated with the Etna volcano and is expressed in vertical: lives and grows upwards (leaves and shoots to the sky, in lavic stone terraces) and down in the depth (roots), in opposite directions but complementary between them (Salvo Foti, Applied Viticulture, Book 4, The Etnean Palmento: the traditional vinification).
Foti's core mission, as described by Nesto and di Savino, is:
  • Protection of the land
  • Preservation of albarello viticulture
  • Cultivation of indigenous vine varieties
  • Emphasizing the humanity of the grower
  • Conservation of Sicilian culture.
His key viticultural principles are:
  • The use of the albarello training system
  • Dense vine spacing
  • Avoidance of systemic sprays and synthetic soil additives
  • Chestnut poles for vine support.
Foti's key principles on display at Aeris Vineyard

In Foti's view (expressed in my conversation with him), albarello is perfect for grape maturity: (i) the leaves cover the grapes, affording protection from the sun's direct rays and (ii) it affords the capability of working around the vine. He is not a big fan of non-albarello training systems (Foti, The Verticality of Etna):
In the Etna, the vineyard cultivated in the horizontal way (destruction of the terraces to make flat the land, cultivation of the vineyards in the espalier system) is a forcing system for the vine, intended only for the mechanization and for the quantity. 
Foti has been very proactive in disseminating his thoughts and practices:
  • I previously mentioned the books and pamphlets
  • Salvo has formed an organization called I Vigneri which is comprised of like-minded grape growers and producers operating in Etna and eastern Sicily. In addition to work on their personal properties (if so endowed), members of the organization are available to work the vineyards of clients, all work based on the I Vigneri principles.
  • He has guided new Etna winemakers, such as Ciro Biondi and Alice Bonaccorsi, and has served as consultant to Edomé, Romeo del Castello, and Il Cantante, among others.
  • Salvo's work on Pietra Marina caught the eye of Kevin Harvey of US-based Rhys Vineyards and they eventually entered into a partnership to grow Carricante grapes at the Aeris Vineyard in Contrada Caselle. But that is not the end of the story. Salvo is also planting a Carricante vineyard for Harvey in California, using I Vigneri practices and personnel.
In our conversation Salvo emphasized that his focus was on respect for the people and the environment. In the Mt Etna region they have been doing the same thing for over 200 years. The viticulture and the people have evolved together and he sees no reason to change that dynamic. He feels strongly that he has a responsibility to the people and the native varieties of the region to ensure their continuity.

And that continuity extends to his farming and management of the land. His grandfather and father worked Carricante. He is farming the way they did. They passed the practices and principles on to him and he is passing it on to his son Simone. And hopefully Simone will pass it on to his son. Continuity.

Foti with his son Simone

Simone, Salvo, Lidia Rizzo, and Brandon Tokash

Salvo Foti and author (Photo credit Lidia Rizzo)

Foti is a quiet and soft-spoken man. At least those were the characteristics that he projected during the course of our meeting. But he also impressed as being extremely knowledgeable, having a strong sense of self, commitment to a set of ideals, and intensity of purpose. Albarello could not have happened upon a stronger proponent.

©Wine -- Mise en abyme

Wednesday, April 12, 2017

The major Etna DOC grape varieties

The Etna DOC has established the following wine and labeling requirements:
  • Etna DOC Rosso -- to be made from the indigenous varieties Nerello Mascalese (> 80%) and Nerello Cappuccio (< 20%) plus up to 10% of other non-aromatic grape varieties (red or white)
  • Etna DOC Rosato -- same as for Rosso
  • Etna DOC Bianco -- to be made from Carricante (> 60%), Catarratto (< 40%), and up to 15% of other non-aromatic grapes such as Minella or Trebbiano
  • Etna DOC Bianco Superiore -- to be made from Carricante (> 80%) and Catarratto or Minnella (< 20%). All grapes to be sourced exclusively from the area of Milo on the eastern side of the volcano.
I continue to flesh out my understanding of the Etna DOC viticultural  environment with the following post on the main grape varieties included in the DOC specification.


White Varieties
Carricante
Carricante is an ancient white variety -- prevalent on Mt Etna's eastern face -- that yields low-potassium, low-pH, high acidity wines (benanti.it). The bunches are of average length at ripening, with medium-sized berries of a green-yellowish color.

Carricante (tenutaterrenere.com)
Frank Cornelissen, one of the leading winemakers on the mountain, has historically viewed the variety as too acidic to produce world-class wine. Ian d'Agata, author of Native Wine Grapes of Italy, on the other hand, is quoted in Szabo's Volcanic Wines thusly: "potentially one of Italy's greatest cultivars ..." that "... when properly tended to, yields wines of great longevity and intense mineral character."

According to Salvo Foti, long-famed viticulturist, Carricante vines have to be somewhere between 10- and 15-years old in order to begin giving great concentration. Salvo said that both his father and grandfather worked Carricante and the wine's high acidity was extremely important in the days before widespread access to refrigeration. The wine is also great for raw fish, the main dish in the area.

There is a saltiness in the east side Carricante that is lacking in wines made from grapes grown on the north side of the mountain. For Salvo, typicity is the key; and he sees Carricante as the grape for this place.

There are some 100% Carricante wines on the market but the grape is usually the primary varietal in an Etna DOC wine. It is also used, at lower elevations, to lighten the color and body of Nerello Mascalese and Nerello Cappucchio blends.

Catarratto
Catarratto is a high-yielding, low-acidity Sicilian grape variety. It is the main grape used in the production of Marsala but on Etna is primarily blended with Carricante. There are two clones -- Commune and Lucido -- with the former having more acid and less sugar than the latter as well as being the clone of choice on the mountain.

Catarratto (etnawine.it)
Catarratto does not engender as much discussion on the mountain as does Carricante.

Minnella
Minnella is a white-berry vine that is indigenous to Etna where it is mostly found in old vineyards interplanted with Nerello Mascalese and Carricante. This is an early ripening variety.

Reds
Nerello Mascalese
Nerello Mascalese is the most important variety on Mt Etna. In older vineyards in can be found interplanted with Nerello Cappucchio while newer plantings position these varieties into separate rows or blocks to facilitate cellar rather than field blends.

Nerello Mascalese (tenutaterrenere.com)
The vine is vigorous and is readily affected by:
  • Vintage conditions
  • Cultivation area
  • Training system
  • Density
  • Cultural practices.
The wines from the variety are mildly sweet and "distinctively tannic." Szabo compares it to Pinot Noir and Nebbiolo both in color and the ability to reflect even minor variations in terroir.

Benanti sees the best training system for the variety as follows:
  • Free standing bush with 2 - 3 branches per tree
  • High vine density -- 6000 - 9000 vines /ha
  • Spacing of 1 x 1 or 1.25 x 1.25.
Nerello Cappuccio
This variety's medium-to-small-sized bunches and medium-sized grapes produce wines with good acid and tannin levels. The variety buds and ripens earlier than Nerello Mascalese with the former characteristic bringing the negative effects of late spring frosts into play.

Used primarily in a blend with Nerello Mascalese, this grape brings color and perfume to the blend as well as serving to soften up some of the harder edges of its partner.


©Wine -- Mise en abyme

Tuesday, March 28, 2017

Hyperoxidation: White winemaking jujitsu

According to dictionary.com, jujitsu (or jiujitsu) is "a method developed in Japan of defending oneself without the use of weapons by using the strength and weight of an adversary to disable him."

Jujitsu training at an agricultural school in
Japan circa 1920 (Source: wikipedia.com)
Hyperoxidation, a white winemaking mechanism which utilizes oxidation effects during the juice phase of winemaking in order to avoid its effects later on in the bottle, is winemaking jujitsu.

I previously described the process whereby white wines are oxidized and the resulting effects. To summarize, the enzyme Tyrosinase (laccase in the case of botrytized must) catalyzes the formation of caftaric acid quinone, the result of the oxidation of the phenol caftaric acid. The quinone reacts with glutathione (a naturally occurring tripeptide found in grapes; and itself a powerful antioxidant) in the juice to form the colorless complex Grape Reduction Product (GRP). Once the glutathione is fully ustilized, GRP is no longer formed and oxidation proceeds unencumbered (This process is called enzymatic oxidation. For a fuller description of this process, as well as the non-enzymatic oxidation of wine, see here.). The results of oxidation in white wines are browning, loss of fruity aromas, and gain of aldehydic aromas.

According to Jackson (Wine Science), "In contrast to red wines, the limited antioxidant character of white wines (ed: tannins and anthocyanins provide substantive antioxidant capability in red wines) make them more susceptible to oxidative browning." Further, grape varieties differ markedly in the amount of phenolics released during crushing or extracted during maceration (an extremely important consideration given that phenolics are the main substrate for oxidation activity). The table below shows the levels of flavonoid accumulation during crushing or maceration of selected white varieties.

Table 1. Phenolics released/extracted during crushing/maceration
Variety Flavonoid Accumulation
Palomino Low
Sauvignon Blanc Low
Riesling Moderate
Semillon Moderate
Chardonnay Moderate
Muscat Gordo Extensive
Colombard Extensive
Trebbiano Extensive
Pedro Ximinez Extensive

In the case of hyperoxidation, the deliberate introduction of oxygen into the juice causes enzymatic oxidation of the phenols. The process entails adding large amounts of oxygen to the wine, allowing the juice to settle, and then racking the juice from the brown precipitate just prior to fermentation. This oxidation will cause browning of the juice but the phenols will have been polymerized and will precipitate out.  

Clarification is required to reduce the suspended solids to less than 1% by weight in order to remove the major part of the phenolic precipitate. This clarification must be completed before fermentation begins as the precipitate will redissolve in alcohol. The clarified juice will retain retain a brown color but this residual browning will be eliminated by the reducing conditions of alcoholic fermentation and absorption by yeasts (Schneider, Hyperoxidation: A Review, AJEV, 1998).

The brown pigment absorbed by the yeasts during alcohol fermentation will fall to the bottom of the tank with the lees and can be removed in a post-fermentation racking. Fining and/or filtration can be utilized for additional clarification if required.This process renders the wine less susceptible to in-bottle browning (due to the elimination of the phenols) as well as reduces bitterness in the wine.

Hyperoxidation requires that SO2 additions be withheld from the must as the oxidative enzymes are inhibited in its presence. For example, tyrosinase registers a 90% decrease in activity when 50 mg/L of SO is added to the must. SO2 also reduces caftaric acid quinone and enhances the solubility of phenolic molecules. . These effects will limit the extent and effectiveness of the hyperoxidation. The implementation of hyperoxidation can thus allow for the production of low-sulfur wines.

Hyperoxidation, then, uses the strength of oxidation in the early stages of winemaking to neuter the substrate in the early stages of winemaking and prevent it from becoming an oxidation resource in the bottle. Jujitsu.

©Wine -- Mise en abyme

Thursday, March 23, 2017

An architecture for the production of reductive white wines

Traditionally, wine has been made in an oxidative style. But, beginning in the 1950s and 1960s, grape growers and winemakers began to employ new tools to attain specific "stylistic and qualitative ends."

Based on Clark Smith's interpretation of the history of that period, the "tools of 20th century winemaking" were stainless steel, inert gas, refrigeration, and sterile filtration (a product of nuclear energy) and this "modern winemaking revolution exploded out of Germany" in the form of Rieslings that were fresh, sterile-filtered, and completely without oxidative characters. According to Smith: "the idea of a light, sweet, fresh, fruity wine like Blue Nun was as world changing as color television." 

These tools and techniques were adopted by Emile Peynaud and other scientists in France and, from there, migrated to the US. According to Smith, prior to the 1960s, 95% of California wines were either port or sherry styles. With the introduction of Blue Nunn, and the adoption of the associated technologies in Bordeaux, US winemakers followed suit such that, by 1970, the majority of California wine contained less than 14% alcohol. These tools and techniques allowed the introduction and use of a reductive style of winemaking.

Hydrogen sulfide is the result of a severe case of reduction in wine but, lower down on the scale, Benzene thiol and furfural thiol contribute bread crust, smoke, and struck flint aromas. Fruity thiols provide notes of passion fruit, citrus zest/cat pee, and grapefruit, aromas associated with Sauvignon Blanc (Remy Charest, Fashionable Chemistry ..., nomacorc.com; Jackson, Wine Science). But it is preservation of freshness and fruit aromas and flavor that the winemaker pursues when he/she decides to employ a reductive winemaking style.

The essence of reductive winemaking is the production of wine without the presence of oxygen. Grapes are harvested from cool regions and the juice is fermented cold in closed stainless steel tanks. Juice is protected as is the wine through maturation and bottling. This method is particularly beneficial for grape varieties such as Sauvignon Blanc, Petit Manseng, Chenin Blanc, and Gewurtztraminer that are rich in varietal aromas that can be placed at risk in the face of oxidizing effects.

The winemaker's plight in producing a reductive white wine
(Underlying picture source: http://cdn.pcwallart.com/)

Before I get into the elements of the architecture, I would like to highlight a Remy Charest report wherein he illustrated a shift to reductive winemaking among Burgundy producers. According to Remy, Jancis Robinson had written about in a shift in Burgundy from buttery, rich, toasty Chardonnays to Chardonnays that exhibited:
  • High acidity
  • No trace of toastiness or obvious oak
  • Leanness on the palate
  • The flinty smell of recently struck match.
In her discussions with Jean-Marc Roulot (Domaine Roulot), she was told that this result was largely due to a more reductive style of winemaking, itself a reaction to the premox crisis that rocked the region's white wines in the 1990s.

Remy described the reductive program as:
  • Long, slow, delicate pressing
  • Protection from oxygen through vinification and aging
  • Finishing the aging in tank
Some additional (and widely accepted, though not necessarily reductive) characteristics of these wines include:
  • Relatively high SO2 addition (Probably related to the battle against oxidation but may also be linked to the appearance of the struck-match character in some of the wines.
  • Fresher, crisper wines resulting from earlier pick dates and moving vineyards to cooler sites.
Reductive white wines are all the rage today but, as Lance Cutler (Achieving Balance in Reductive Winemaking, Wine Business) points out, "Keeping wine away from oxygen can create some vibrantly fruity wines, but this same lack of oxygen might encourage the development of reduced sulfur compounds."

The main considerations in producing a reductive white wine are as follows:
  1. Healthy fruit from a cool vineyard. The climate in the vineyard will help to preserve freshness and crispness of aromas while healthy fruit will have an adequate supply of the vitamins and minerals to ensure a successful fermentation. The viticultural factors affecting the supply of yeast assimilable nitrogen include: cultivars, rot incidence, block, vineyard mulch, crop load, moisture stress, and grape maturity level (Zoecklein)
  2. Minimize the use of sulfur in the vineyard and ensure adequate time spacing between application and harvest
  3. Harvest at night to preserve freshness and flavors
  4. Application of inert gases during harvest (mainly CO₂ in dry-ice form)
  5. Provide antioxidant treatment to the free-run juice. Most normally ascorbic acid and sulfur dioxide but there is some concern that ascorbic acid switches from protection to oxidative mode over the long term and, as such, is not suited for wines destined for aging. In many cases inert gases such as CO₂ and N₂ are used to protect the juice from oxygen.
  6. Measure fermentable nitrogen as too high, or too low, concentrations can result in the formation of undesirable sulfur compounds during fermentation. According to Zoecklein these measurements can be carried out with either Formol titration or a NOPA test.
  7. Turbidity should be adjusted such that stylistic goals and aromatic finesse of the wine is achieved. Juice clarity should be measured in Nephol units and should fall between 100 and 150 (Zoecklein)
  8. Non-soluble solids concentration should be monitored as both high and low concentrations can result in the production of undesirable sulfur compounds
  9. The appropriate yeasts should be selected for the effort as strains differ in their capacity to transform the non-volatile grape derived precursors to odor-active volatiles (Zoecklein)
  10. Keep yeast cells suspended in the tank during fermentation in order to allow an even distribution of fermentation as well as to allow full access to distributed nutrients
  11. Rack gently under a carbon dioxide or nitrogen blanket. Use an in-line sparging device to sparge the wine with CO₂ or N₂. Add SO₂ to the wie as it is being racked to prevent oxidation
  12. No malolactic fermentation inorder to preserve varietal character, flavors, and freshness
  13. No oak aging in order top continue to continue to deny oxygen access to the wine
  14. Select an appropriate closure. According to Remy Charest, "Precise control of oxygen in the bottle, for example by selecting a closure allowing small and consistent amounts of oxygen, can prevent extreme reduction without compromising the more interesting flinty and fruity aromas."
In the cases where the odors are manifested in the wine, remedies include (i) blowing it off through volatility; (ii) inert gas sparging; (iii) precipitating with copper additions; and (iv) fining.

©Wine -- Mise en abyme

Tuesday, March 21, 2017

Walking the tightrope between oxidation and reduction in white wine production: Reduction

Reduction is the other side of the oxidation/reduction coin. When elemental oxygen combines with wine compounds, it can take a pair of electrons from the compound. The compound losing the electrons is said to have been "oxidized" while the oxygen, which has gained two electrons, is said to be "reduced."

Reduction is of principal importance to the winemaker as it relates to sulfur compounds. According to Jackson (Wine Science):
When present, elemental sulfur can be assimilated and used in the synthesis of sulfur-containing amino acids and coenzymes. It also may be oxidized to sulfate and sulfur dioxide or reduced to hydrogen sulfide. The reduction of sulfide to hydrogen sulfide may be a means, albeit aromatically unpleasant, of maintaining a favorable redox balance in yeast cells under anaerobic conditions.
According to Zoecklin (Enology Notes #96, 12/20/2004, vtwines.info):
Since wine is fermented by yeast through an anaerobic process (without oxygen), a number of reduced compounds are produced. Reduced sulfur and and nitrogen compounds, in the form of hydrogen sulfide and mercaptans (ammonia and amines), are known particularly for the negative characters they impart to wines. Thus, it is possible to have a wine with an unpleasant and undesirable reduced character.
The sulfur compounds associated with sulfur taint, and the population of odors associated therewith, are illustrated in the figure below.


Sulfur taint has its origins in either the vineyard, the cellar, or both. In the vineyard, elemental sulfur is sprayed on the vines to combat the potential effects of powdery mildew. If this spraying is conducted too close to harvest, portions of the sulfur will remain on the grapes and make its way into the fermentation process. An example of sulfur-like off odors created in the cellar is the case of hydrogen sulfide production by the yeast to synthesize the sulfur-containing amino acids methionine and cysteine. This process is facilitated by the reduction of sulfates via the sulfur-reduction pathway. A lack of intracellular nitrogen will not curtail the process and the excess hydrogen thus created cannot be incorporated into the amino acid. Rather, it is secreted into the medium (Kennedy and Reid, Yeast nutrient management in winemaking, The Australian and New Zealand Grapegrower and Winemaker, 537, October 2008).

A listing of the sources of sulfur-like off odors is presented in Table 1.

Table 1: Sources of sulfur taint in wine production.
EnvironmentSourceActionImpact
VineyardElemental sulfur
used as fungicide 
Reduction during fermentation


Sulfur-containing pesticidesdo.


Excess of metal ions 



Vine stress



Unsound fruit



Cellar

Cold soaking

Growth of yeasts such as Kloeckera

Depletion of amino acids and micronutrients

Native YeastsHigh hydrogen sulfide productionCompete against other yeasts for dominance of fermentation

Excess hydrogen sulfide from sulfate reductionHydrogen sulfide used to synthesize Absence of nitrogen causes produced hydrogen sulfide  to be secreted into the medium

High levels of sulphur dioxide added to must at crushAllows sulphur dioxide to bypass the sulfate reduction systemSulfur dioxide enters the yeast cell directly

Vitamin shortage in high YAN musts



Nitrogen limitationProduces sulfur-like off odorsProduction begins 30 minutes after ammonia starvation initiates
Source: Compiled from Lansing and Kennedy and Reid)

The timing of the production of sulfur-like off odors is shown in Table 2 below.

Table 2. Production timing of sulfur taint by sulfur class.
Sulfur ClassProduction TimingSource
Hydrogen SulfideEarly in fermentation (2 - 4 days)Nitrogen/vitamin deficiency

Fermentation endDegradation of sulfur-containing compounds

Sur lie agingAutolysis

In bottleGenerally under screw cap
Higher SulfidesLate in fermentation/Sur lie agingRelease of compounds by metabolically active yeasts

Degradation of sulfur-containing amino acids

Degradation of cell compounds during autolysis
Source: Compiled from Lansing

In the cases where the odors are manifested in the wine, remedies include (i) blowing it off through volatility; (ii) inert gas sparging; (iii) precipitating with copper additions; and (iv) fining.

Oxidation and reduction are twin evils in the world of (especially) white wine production but there are aspects of both that are beneficial to the final product. Making wines which call on these qualities is called oxidative and reductive winemaking, respectively, and I will cover those styles in upcoming posts.


©Wine -- Mise en abyme

Sunday, March 19, 2017

Walking the tightrope between oxidation and reduction in white wine production: Oxidation

In this series I will be examining the winemaker's challenge in navigating between the twin evils of reduction and oxidation, both faults but both having potentially desirable characteristics close to the center of the continuum. I begin with this post on oxidation.

According to Lukacs' research (Inventing Wine), modern wine did not arise until the advent of the relevant scientific and technological advances of the Enlightenment. Prior to that period, wine drinkers consumed oxidized, sour wines which were "fortified" with all manner of additives designed to either slow its decay or make it more "palatable." Lukacs points out that winemaking in the first half of the 20th century was a reprise of thousands of years past -- "a process of letting nature run its course."

When Emile Peynaud (famed Bourdeaux enologist) began his work in the early 1950s, growers were harvesting early and, as a result, the wines were "excessively green or vegetal." He observed that there was a further striking uniformity about the wines: they were all oxidized.

Wine oxidizes when exposed to air via two primary mechanisms: enzymic and non-enzymic oxidation.  The effects of oxidation on white wine are browning, loss of fruity aromas, and aldehydic aromas. Because of these characteristics, oxidization is widely viewed as a wine fault.

Enzymic Oxidation
Enzymic oxidation (which primarily afflicts wine must) requires the presence of the enzyme Tyrosinase* (or Laccase**, in the case of botrytized must), phenolic compounds (hydroxycinnamic acids, with the main player being caftaric acid but others — including coumaroyl, tartaric acid, and catechin — as alternates) to perform the role of substrate, oxygen, and metallic co-factors (iron, copper, etc.). These enzymes interact with the substrates to form caftaric acid quinone which, in turn, reacts with glutathione (normally a powerful anti-oxidant) in the must to form Grape Reduction Product (GRP). The conversion of the oxidized quinone to GRP limits the browning of the juice to some extent (duToit and Kritzinger). Once the glutathione is depleted, the remaining caftaric acid quinone reacts with other must constituents to form caftaric acid and begins the oxidation process anew. Browning occurs when the flavanols oxidized by caftaric acid quinones polymerize and precipitate out. Unlike the case of wines, these brown pigments are insoluble in must.

Because tyrosinase is associated with grape solids, its enzymic activity is significantly diminished once the solids have been removed from the equation. Laccase is difficult to eliminate from grape juice.

The activity of these enzymes will be impacted by (Boulton, et al, Principles and Practices of Winemaking):
  • The concentration of major phenols
  • Competition between substrates for binding and reaction
  • The caftaric and glutathione content of cultivar (the state at which glutathione is depleted will determine the level of potential browning)
  • The ascorbic acid content
  • Temperature
  •  Wine pH.
Both tyrosinase and laccase use catechin, anthocyanin, flavanols, and flavanone as substrates but, as indicated in Table 2.1 of Boulton et al., laccase acts on a far wider range of substrates than does tyrosinase. UCDavis pegs the added scope of laccase as encompassing anthocyanin pigments and ascorbic acid, the latter of which is itself used as an antioxidant

Non-Enzymic Oxidation
Non-enzymic oxidation, also known as chemical oxidation, occurs in fermented wine. In this case, oxygen does not react directly with phenolic compounds. Rather, it functions through a reaction catalyzed by Cu+ or Fe+ that converts oxygen into a highly reactive radical capable of oxidizing organic compounds.

Non-enzymic oxidation in white wines can result in premature aging, browning, and pinking, all resulting in wine deterioration and loss of quality. Strategies for combating this fault include removing metals -- oxidation catalysts -- and reducing the concentration of phenolic compounds -- oxidation precursors --in wines.

©Wine -- Mise en abyme