Prevalence and effects of skin contact in Timorasso wine production

As shown in the table below, a significant number of Timorasso producers macerate the must on the skins prior to alcoholic fermentation. Why are they doing so? and why is the Timorasso cultivar a prime candidate for participation in such an activity?

Table 1. Instances of Maceration on skins: Selected Timorasso producers

Producer	Wine	Maceration Period (Hours)
Massa	Piccolo Derthona’ Timorasso	N/A
	Timorasso ‘Derthona’	48 - 60
	Timorasso Cru ‘Costa del Vento’	60
	Timorasso Cru ‘Montecitorio’	60
	Timorasso Cru ‘Sterpi’	60
La Colombera	Derthona	3
	Il Montino	3
Franco M. Martinetti	Martin	36
Ricci	Derthona	72
	San Leto	72
Teralba	Derthona	48 - 72
	Stato	72
Morgassi Superior di Gavi	Timograsso	12
Cascina Gentile	Derthona	24
i Carpini	Ruggiada del Mattino	48
	Brezza d’Estate	48
Massimo Pastura	Timian	16 - 18
Cantina Botazzi	Italo	N/A
	Monterosso	N/A

Based on the figures above, Timorasso producers macerate their grapes for an average of 44 hours prior to alcoholic fermentation. In the case of Massa, the cold maceration is carried out in cement containers, after which the must is transferred to stainless steel tanks for fermentation. Massa is the only producer whom I could identify as also including stems in the maceration.

Skin-Contact Whites

Skin-contact white wines are recognized by 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.). Skin-contact white wines are macerated for hours while skin-fermented whites are macerated for weeks to months. Further, skin contact is a pre-fermentation process while its compatriot extends beyond that to fermentation and, in many cases, maturation.

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.

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 have historically been obtained from fully ripe, aromatic grape varieties such as Gewurtztraminer, Riesling, Muscat, Viognier, Chenin Blanc, and Sauvignon Blanc.

Phenols
Skin contact increases the amount of hydroxycinnamates, gallic acids, and flavonoids in the wine. 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.

The Timorasso Case
Writing in openingabottle.com, Kevin Day characterizes the Timorasso variety thusly: "Timorasso has a rich phenolic character, meaning the natural phenols and polyphenols in the grape yield a lot of aromas, flavors, textures, and characters." In other words, these factors, when coupled with the variety's thick skin, renders Timorasso an ideal candidate for skin contact.

Of the wines I have tasted to date, the one with the most evidence of skin contact was the Cascina Gentile, with its color, tangerine aromas, tannins, spice, and texture attesting to its residence. There is a little bit of a curve ball in this case as the producer ages 1/3 of the production in untoasted French oak barriques of unknown age.

The La Colombera is only exposed to its skins for 3 hours but the color, phenolics, and spice are indicators of this experience. 

I will continue to update this post as I tatse additional skin-contact Timorasso wines.

©Wine -- Mise en abyme

A summary of the various dry white wine styles

In this series I examined the winemaker's challenge in navigating between the twin evils of reduction and oxidation in the construction of white wines; both faults but both having desirable characteristics as you move further away from the edges. The below chart illustrates the dry white wine styles that have been covered in this series. Below the chart are short descriptors of each of the styles along with links to the posts in which they are detailed.

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 that 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."

But, beginning in the 1950s and 1960s, grape growers and winemakers began to employ new tools to attain specific "stylistic and qualitative ends." On the technical side, the introduction of temperature control and regular chemical analysis allowed greater control over the fermentation and this gave greater impetus to the concept that humans "could and should assume control" of the winemaking process.

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 allowed the introduction and use of a reductive style of winemaking. 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.

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 juice, allowing it to settle, and then racking it 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.

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.

White juice fermented on their skins are differentiated from skin-contact wines 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. These skin-fermented wines, more commonly known as "orange" wines, can be further broken down into two broad classes: traditional and contemporary.

With all of the advantages associated with stainless steel fermentation, oak had to have some overriding benefits for winemakers to continue using it as a fermentation 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." Further, 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.

The premature oxidation issue in white Burgundies has been identified by both Jancis Robinson and and Jon Bonne as the engine driving the change in Burgundy from 'buttery,' 'rich,' and 'toasty' Chardonnays to wines that are 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.

I have named this style of winemaking oxo-reductive.

The final style-specific installment in my discourse on white wine styles was the non-ouillé (evaporative loss during aging not topped up) Savagnin wines of the Jura. These oxidatively styled wines are unique to both the region and the cultivar.

©Wine -- Mise en abyme

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

Phenolic	White Wine (mg/L)	Light Red Wine (mg/L)	Full Red Wine (mg/L)
Volatile	Trace	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