Tuesday, May 12, 2015

Sulfur taint in wine production: Genesis and exodus

A winemaker is continuously on guard to ensure the earliest possible detection of issues that could have potentially negative effects on the quality of in-process or finished wine. One issue that is treated with the utmost respect, and attended to with some alacrity, is sulfur taint, the primarily olfactory manifestation of sulfur compounds in the wine. Sulfur taint is the bane of the winemaker because ( Lansing, Wine defects during fermentation, Wine Busines Monthly, April 2011):
  • It is generally associated with negative aromas
  • It has a low threshold for sensory detection
  • It has high chemical reactivity
  • It is difficult to mask and/or remove.
The sulfur compounds associated with sulfur taint, and the population of odors associated therewith, are illustrated in the figure below.

In this post I will examine the origins of sulfur in must, the creation of sulfur compounds during winemaking, and strategies for minimizing the incidence and/or removing these compounds from the medium.

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.
Environment Source Action Impact
Vineyard Elemental sulfur
used as fungicide 
Reduction during fermentation

Sulfur-containing pesticides do.

Excess of metal ions 

Vine stress

Unsound fruit


Cold soaking

Growth of yeasts such as Kloeckera

Depletion of amino acids and micronutrients

Native Yeasts High hydrogen sulfide production Compete against other yeasts for dominance of fermentation

Excess hydrogen sulfide from sulfate reduction Hydrogen 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 crush Allows sulphur dioxide to bypass the sulfate reduction system Sulfur dioxide enters the yeast cell directly

Vitamin shortage in high YAN musts

Nitrogen limitation Produces sulfur-like off odors Production 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 Class Production Timing Source
Hydrogen Sulfide Early in fermentation (2 - 4 days) Nitrogen/vitamin deficiency

Fermentation end Degradation of sulfur-containing compounds

Sur lie aging Autolysis

In bottle Generally under screw cap
Higher Sulfides Late in fermentation/Sur lie aging Release of compounds by metabolically active yeasts

Degradation of sulfur-containing amino acids

Degradation of cell compounds during autolysis
Source: Compiled from Lansing

There are a number of precautionary steps that can be taken to minimize the potential for sulfur taint (Lansing; Kennedy and Reid):
  • Minimize the use of sulfur in the vineyards and cellar
    • In the vineyard, ensure adequate time spacing between application and harvest
  • Press stressed fruit separately
  • Provide adequate nutrition to support the yeast during alcoholic fermentation
    • The less assimilable nitrogen in the must, the greater the production of hydrogen sulfide
  • Keep yeast cells suspended in the tank during fermentation
    • Allows an even distribution of fermentation
    • Allows the yeast full access to distributed nutrients
  • Manage fermentation temperatures
    • Hydrogen sulfide tends to form more commonly in hot, fast fermentations
  • Mix the tank contents to prevent stratification
    • An especial risk in tall, narrow-diameter tanks
  • Remove wine from lees at the first hint of trouble
  • Smell, smell, smell.
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

Wednesday, May 6, 2015

Non-Nitrogen yeast nutrition requirements during alcoholic fermentation

In addition to their utilization of nitrogen as a nutrient during alcoholic fermentation (AF), yeasts synthesize and/or assimilate a number of factors (growth, co, and survival) that help them compete and survive in the hostile environment that is the active fermentation vessel.

Vitamins are growth factors involved in yeast metabolism with some of the needed species synthesized while others are obtained from the juice/must. The most important vitamins in the AF process are indicated in the table below.

Vitamin Characteristics
Biotin Plays an important role in sugar, nitrogen, and fatty acid metabolism
Yeasts cannot grow without biotin (low concentrations will support growth but 10 microgram/L optimal)
Supplementation of musts with biotin increases the viable yeast population and increases fermentation rate
Thiamine Deficiency leads to accumulation of various products including pyruvic acid which is responsible for much of the non-acetaldehyde sulfite pool
Pantothenate Involved in the biosynthesis of the sulfur-containing amino acids cysteine and methionine
Involved in the formation of acetyl Co-A (acetate donor in esterification)
Deficiency results in increased hydrogen sulfide production as well as higher concentrations of acetic acid and glycerol (the latter two producing negative results when coupled)
Pyridoxine Involved in the biosynthesis of the sulfur-containing amino acids cysteine and methionine
Deficiency results in increased hydrogen sulfide production
Source: Kennedy and Reid

Adequate levels of vitamins are normally available to the yeasts but, in some cases (mold infestation, excessive diammonium phosphate addition), a deficiency is recorded and supplements are required. Inactivated yeasts are an excellent source of vitamins.

Yeast cell membrane integrity will be affected by the toxicity of ethanol and the increase in permeability associated with higher ethanol levels will have a negative impact on sugar and amino acid uptake. So-called survival factors, comprised primarily of sterols and long chain fatty acids, are responsible for cell membrane integrity and fending off the ethanol effects until fermentation is complete. Survival factors are formed only in the presence of oxygen and grape musts normally contain enough dissolved oxygen which, when combined with the use of active dry yeast, allows the synthesis of adequate amounts of these factors.

If ascorbic acid is added to the must for any reason, no additional survival factors will be synthesized. Naturally occurring sterols and fatty acids will be depleted by excessive must clarification. In the case of a deficiency of these survival factors, the addition of inactivated yeast cells or yeast hulls will provide a rich source of sterols and fatty acids. Such additions should be adde at the beginning of fermentation and should utilize fresh material to avoid the negative effects associated with lipid oxidation.

Minerals are used as co-factors in enzymatic reactions in the yeast cell with the most important ones being magnesium, potassium, manganese, zinc, iron, and copper. The grape must normally contains adequate levels of these minerals to support AF to its conclusion.

©Wine -- Mise en abyme

Tuesday, May 5, 2015

Nitrogen as a yeast nutrient in alcoholic fermentation

Wine is a result of using yeasts in an anaerobic (oxygen-free) environment to convert sugars from pressed grape juice into ethanol in the two-step process illustrated in the figure below. The first step -- glycolysis -- results in the 6-carbon glucose being split into two 3-carbon pyruvate molecules. In the next step --- alcoholic fermentation (AF) - four atoms of oxygen and two atoms of carbon leave the pyruvate, resulting in acetaldehyde, which is subsequently converted into ethanol.

Alcoholic fermentation (Source: http://alcoholicfermentation.net/)
According to Fugelsang (Overview of yeast selection and malolactic fermentation on aroma, flavor and phenols), the yeasts (i) extract compounds from the solids in the must/juice in order to form the "characteristic metabolites of fermentation (alcohols, esters, fatty acids, carbonyls, etc.) and (ii) cleave cysteine-containing precursors such that volatile thiols (aroma component of several varieties) can be released. The yeast that receives most of the credit -- and does most of the work -- in alcoholic fermentations is a species called Saccharomyces cerevisiae (SC) which is "specialized in metabolizing media with high sugar content and small quantities of nitrogenous compounds" (Suárez-Lepe and A. Marota, New trends in yeast selection for winemaking, Trends in Food Science and Technology 23 (2012), 39-50.). Yeasts require nutritive support to allow the performance of the above functions in the hostile environment (ethanol-rich, acidic) of the fermentation tank. It is the nitrogenous aspect of that support that is the focus of this blog post.

Proteins are used by the yeast as (i) enzymes for the glycolytic pathway (indicated above), (ii) permeases in the cell membrane responsible for the transportation of compounds into the cells, (iii) cellular constituents (Kennedy and Reid, Yeast nutrient management in winemaking, The Australian and New Zealand Grapegrower and Winemaker, 537, October 2008). These proteins are synthesized by the yeast and nitrogen (N) is a key component in that process. According to Kennedy and Reid, "Efficient protein synthesis is needed for efficient sugar transport and overall yeast metabolism."

According to Schwarcz and Schoeninger (Stable Isotope Analysis in Human Nutrition, Yearbook of Physical Anthropology 34, pp. 293-321), almost 100% of exchangeable nitrogen is found in the atmosphere or dissolved in the world's oceans and is transferred from these environments into the biological system through the processes illustrated in the figure below.  Grape vine plants receive their nitrogen through this terrestrial nitrogen cycle.

Source: http://tolweb.org/notes/?note_id=3920
The nitrogen content of grapes are affected by variety, rootstock, climatic conditions, soil composition, vineyard management practices, fertilization, irrigation, rot incidence, and grape maturity (Kennedy and Reid). The yeast cells extract yeast assimilable nitrogen (YAN) from the grape must in the form of ammonia (preferred source of nitrogen for yeast growth as most easily assimilated) and amino acids and these are stored in the cell walls for later use. This extraction and storage of YAN is front-loaded in the AF process.

Nitrogen is required throughout the fermentation process with larger amounts being utilized during the exponential growth phase of the yesats and small amounts during the stationary phase. In some cases the grape must does not provide adequate amounts of assimilable nitrogen and is supplemented by added nitrogen in the form of diammonium phosphate (DAP). Juice levels of < 25 mg/L ammonia or < 150 mg N/L (measured as YAN) is considered nitrogen-deficient (UCDavis). Insufficient nitrogen can result in sluggish/stuck fermentations or sulfide formation (sulfur-like off-odors, mercaptans, and sulfur-containing acetic esters; the less assimilable nitrogen in the must, the more hydrogen sulfide will be produced). Supplements are best added incrementally and proportional to yeast growth (UCDavis).

Excessive nitrogen in the must can lead to elevated levels of ethyl carbamate (a supposed carcinogen) or urea excretion. The levels of nitrogen required for a successful AF is dependent on (Kennedy and Reid):
  • Initial must YAN
  • Yeast strain
  • Fermentation temperature
  • Initial grape sugar
  • Other factors.
Amino acids are the building blocks of proteins and, when brought into the yeast cell, can be incorporated as is, transformed into a different amino acid, or broken down as a source of nitrogen or sulfur. The amino acids taken up by the yeasts from the grape must is primarily stored in the vacuole to be used for protein synthesis during yeast growth. Once access to inorganic nitrogen becomes difficult, the yeast begins to break down the stored amino acids to provide nitrogen for protein synthesis. The most important amino acids taken up by the yeasts are shown in the table below.

Amino Acid Characteristics
Proline Not metabolized appreciably by yeasts under winemaking conditions
One of the predominant amino acids along with Arginine and Glutamine
Main amino acid from low-fertilization vineyards
Arginine One of the predominant amino acids
Breakdown results in formation of urea and ammonia (During wine storage, urea can react with ethanol to form ethyl carbamate, a carcinogen).
Located mostly in grape skin so processing practices could influence content in juice
Main amino acid from low-fertilization vineyards
Glutamine One of the predominant amino acids
Favored by yeasts because it can be broken down to glutamate and ammonia

The less-important amino acids taken up by the yeast cells are alanine, serine, and theronine.

©Wine -- Mise en abyme

Tuesday, April 28, 2015

Characteristics of high-quality wine grapes

As the starting point for the production of a quality wine, it is imperative that high-quality grapes be delivered to the cellar door. I posit that high quality grapes are a funcntion of both what is within and what is without. Further, what is within can be divided into two broad classes: objective and subjective.

The objective criteria revolve around the components of grape juice at maturity, with soluble solids (major component being sugar), acid, and pH being the primary indicators based on (i) abundance and (ii) ease of measurement.
  • Soluble solids -- 6-carbon sugars (glucose and fructose; 90 - 95% of total), non-fermentable sugars (inclusive of 5-carbon pentose sugars), pectins, acids and their salts, tannins, pigments, and dry extract.
  • Acid – primarily tartaric acid (5 - 10 g/l in grapes) but also includes malic (2 - 4 g/l), citric, and other acids.
  • pH – measure of the amount of hydrogen ions in a solution. Regarded as the acidic strength of the solution.. Increases with increases in sugar concentration. According to Wynboer, not a reliable measure on its own. Should be between 3.1 and 3.3 for white grapes and 3.3 - 3.5 for red grapes.
  Table 1. Summary of objective grape quality measures (Source: UCDavis)
Wine Type
Soluble Solids (%)
Tartaric Acid (g/L)
18 - 20
7 - 9
2.8 – 3.2
White Table
19 - 23
7 - 8
3 – 3.3
Red Table
20 - 25
6 – 7.5
3.2 – 3.4
Sweet Table
22 - 25
6.5 - 8
3.2 – 3.4
23 - 26
5 – 7.5
3.3 – 3.7

Soluble solids are reported in Brix, specific gravity, Baume, or Oeschle, depending on preferences, and are measured by refractometry (juice in the vineyard) or hydrometry (during fermentation). Anthocyanin and total phenolic levels are measured using Near-infrared and Spectrophotometry, equipment that is not readily available to most wineries. Titratable acidity (TA) is measured by acid-base titrations while pH is measured using a pH meter.

It should be noted that, depending on winemaker preferences or climatic conditions, some of the soluble solids and acidity level metrics may be over- or under-shot and is then adjusted during the winemaking process by acid/sugar addition or subtraction.

The subjective criteria for quality are as follows: color; ease of removal of berries from pedicel; texture; aroma; and flavor. These tests should be conducted by the winemaker during vineyard walk-throughs. Of the objective tests mentioned, the test for flavor is the most important. Bisson (UCDavis) sees optimal maturity as assessable only by monitoring flavorants themselves but such a task is laborious and expensive and has to be approximated through tasting.

But all of the quality elements associated with the grape are not subcutaneous. Grapes in a vineyard are hosts to what Gourrand (Using non-Saccharomyces yeasts during alcoholic fermentations: taking advantage of yeast biodiversity) calls native microflora -- molds, lactic bacteria, acetic bacteria, Saccharomyces spp, and non-Saccharomyces yeasts (Pichia, Metchnikowia, Kloeckera, Kluyveromyces, Candida, Zygosaccharomyces, Torulaspora, Cryptoccus, Brettanomyces, and Hanseniaspora). According to Loureiro and Malfeito-Ferreira (Spoilage yeasts in the wine industry, International Journal of Food Microbiology 86, 2003), mature, healthy grapes harbor microbial populations at levels of 103 - 105 CFU/g (colony forming unit -- a measure used in microbiology that indicates the number of micro-organisms present in a water sample (www.legionella.com/cfu)), levels that vary based on environmental conditions (rainfall, temperature, grape variety, the application of chemicals in the vineyard).

It is the yeast element of this microflora that natural-yeast winemaking adherents seek to exploit. Wild yeasts accumulate on the grapes from flowering through harvest with the presence of SC being pegged at 1 in 1000 grapes (Robert Mortimer, Vineyard Theory of Wild Yeast, UC Berkeley). At harvest, SC is the least prevalent of the grape-resident yeast strains.

Wine-associated yeasts are identified in the table below.

©Wine -- Mise en abyme

Thursday, April 23, 2015

Penfolds and the Pinnacle of Australian Wine: A Pebble Beach Food and Wine tasting panel

I love to participate in tastings where Paolo Basso is lead because, not only is he a pure taster, he is also elegant, clear, and precise in describing the sensory characteristices of the wine "under the microscope." But I also love participating in tastings led by DLynn Proctor because he is unmatched in describing the technical characteristics of the wine and the conditions under which it was produced; a style in marked contrast to the Basso approach. DLynn recently headlined a panel at Pebble Beach Food and Wine (April 9 - 12, 2015) titled Penfolds and the Pinnacle of Australian Wine and I report on that tasting in this post.

The tasting was scheduled to be held at 3:30 pm on April 10th in the St Andrews East Room at The Inn at Spanish Bay. I had driven around in the town of Monterey for a bit after picking my car up at the San Jose Airport and, after a brief lunch, headed north on Lighthouse Avenue and then southwest on David Avenue before making a right into Congress Road and into the grounds of The Inn.

The overall setting at The Inn is one of elegance, both outside and in, and conversations seemed to be conducted in hushed tones. No drunken throngs here. I inquired after the St Andrews Room and made my way there and mingled with the other attendees awaiting entry and the start of the tasting. The room, once the doors were opened, was rather expansive and was occupied by rows of tablecloth-bedecked tables oriented towards a raised platform at the front. The platform was occupied by a table and four chairs and would be the home of the panelists for the duration of the event.

After some additional socializing within the room, the meeting was called to order and DLynn introduced the panel members. In addition to himself, they were:
  • Greg Harrington MS, Founder and Winemaker, Gramercy Cellars
  • Ray Isle, Executive Wine Editor, Food & Wine
  • Kim Beto, Vice President of Key Accounts, Southern Wine and Spirits of Northern California.

Once the introductions were out of the way, DLynn gave a brief overview of the history of Penfolds. My notes regarding this particular discourse was "He understands and disseminates the story of Penfolds like no other ..." A little bit of that Penfolds history (with a Grange bent) can be found here.

The tasting was divided into non-Grange and Grange flights, the former consisting of six bottles and the latter of five. The non-Grange labels, drawn from the Penfolds Collection, were RWT, Magill Estate, and St. Henri. Of the three, I had only previously tasted the RWT. The defining characteristics of the three non-Grange labels are presented below. Similar data for Grange can be found here.

Initial Vintage
Fruit Source(s)
Barossa Valley, South Australia
Stainless Steel (SS) tanks with wax-lined wooden header boards; finished in barrels
12 – 15 months in 50 – 70% new French oak hogsheads (300L)
Magill Estate Shiraz
Magill Estate, Adelaide. Single-vineyard blocks to include Blocks 1, 2, and 3
Wax-lined, open concrete fermenters with wooden header boards; after basket pressing, components complete fermentation in barrels
12 – 15 months in 65% new French and 35% new American oak hogsheads
St Henri
1953 – 1956 experimental; commercial in 1957
Cabernet Sauvignon; Shiraz
CS from Coonawarra and Barossa Valley; Shiraz from Barossa Valley, Eden Valley, Clare Valley, McLaren Vale, Langhorne Creek, Robe, and Bordertown
Stainless Steel (SS) tanks with wax-lined wooden header boards; finished in barrels; somer componenets vinified at Magill Estate
18 months in large (1400L), old oak vats

The first tastings within the non-Grange flight were of the 1998 and 2009 St. Henris. According to DLynn, St. Henri predates Grange and was actually purchased by Penfolds in the 1940s. During the 1950s and 1960s, the label rivaled Grange.

According to DLynn, these wines were double-decanted 1 hour before the tasting. The 1998 exhibited notes of spice, leather, tobacco, smoked meat, burnt toffee, chocolate, and mint. On the palate a savoriness and surprising youth. Intense, bright, some salinity, spiciness, and slightly grippy tannins. Long, spicy finish. According to DLynn, 2.4% Cabernet Sauvignon included. The nose on the 2009 was unyielding. Slight vegetality. Weighty on the palate with a great core of fruit. Intense. Eucalyptus notes. It is not as structured as the 1998 but a beautiful wine nonetheless.

The 1997 RWT had a layered complexity with a perfumed nose and accompanying notes of eucalyptus, mint, earth, spice, and dried tree bark. Delivers on the palate but not on the promise of the nose. Rich and powerful with blackberry, cedar, and truffles dominant. Long, drying finish. The 2012 RWT had a core of blackberry fruit supporting notes of dark chocolate, soy, and mahagony. Concentrated fruit on the palate along with a saline character. Balanced by appropriate tannin structure and acidity. Lengthy finish.

Magill Estate is a 5.1 ha property and is, according to DLynn, the spiritual home of Penfolds. The wine is 100% Shiraz and the 2004 exhibited notes of green bark, coconut, petrol, smoke, charcoal, and toffee along with a hint of phenolics. On the palate elegant and balanced with a drying finish. The 2012 was more "in your face" than was the 2004. Same nose as for the 2004 but with more intensity. Dark fruits and brightness on the palate.

The Grange flight consisted of wines from the 1986, 1989, 1998, 2008, and 2010 vintages. I had tasted the 1986 as a part of our Five Decades of Penfolds Grange tasting and had described it as having aromas of dill, bay leaf, thyme, phenolics and a little greenness. I had also described it as balanced and savory and having integrated tannins and a long finish. Similar characteristics exhibited at this tasting except for a hint of portiness taht I had not evidenced previously.

The 1989 wine had also been tasted earlier and in that case I described it as having ripe fruit, molasses, savoriness, beef broth with dark fruit and molasses on the palate. The notes for this tasting aligned somewhat in that I evidenced an aromatic high tone along with pyrazine, sugar cane, and molasses on the nose to go along with dark fruit, pyrazine, and molasses on the palate.

The 1998 had rich, dark, ripe fruit along with baking spices and pepper on the nose. Palate-filling. Rich and concentrated with a long creamy finish. Hint of port.

The 2008 was perfumed on the nose with baby talcum powder, sawdust, chocolate dust, and cocoa dust. Elegant on the palate with sweet ripe fruit and a hint of green. Toffee, coffee, chocolate, and a long smooth finish.

The 2010 also exhibited an elegant nose. On the palate thick, rich dark fruit. As Yogi Berra would say, "Its future ahead of it."

All in all this was a fun tasting. Dlynn and Greg made stellar contributions to the affair with DLynn being "always on" and Greg having taken the necessary steps to be prepared for the event. I wish that the audience member who sucked up most of the oxygen had been a little more knowledgeable.

©Wine -- Mise en abyme

Thursday, April 9, 2015

The Châteauneuf-du-Pape AOC

The Châteauneuf-du-Pape AOC is known for "rich red wines redolent of the heat and herbs of the south" and "full aromatic white wines with a crisp freshness," with both styles complexed by blending; up to 13 varieties for the reds and five for the whites. I was pleased to be invited by the Fédération des Syndicats de Producteurs Châteauneuf-du-Pape to explore the region and its wines as part of a 2014 Digital Wine Communications Conference pre-conference Press Trip. The trip itinerary is presented below.

Meals and Tastings
Terroir of Chateauneuf-du-Pape with geologist Georges Truc (treated previously)
Lunch at La Mère Germaine with a tasting of CdP whites
Domaine La Barroche
Dinner at La Table de Sorgue and tasting of older CdP vintages
Domaine de Nalys

Chateau Fortier

Ogier – Clos de l’Oratoire

It is from this visit, plus subsequent secondary research, that I have crafted this description of the Châteauneuf-du-Pape AOC.

The Châteauneuf-du-Pape AOC, the largest and most important of the Southern Rhone AOCs, is located in the westernmost portion of the Vauclause region, 19 km north of Avignon and 10 km south of Orange. Its 3200 ha of vineyards renders it the largest appellation in the Southern Rhone (and almost equal to the size of the entire Northern Rhone, which comes in at 3264 ha) and its annual production surpasses the total of all of the Northern Rhone appellations.

The appellation is distributed over five communes and 134 lieux-dits.

Size (ha)
# of Lieux-dits
Percent of Lieux-dits

The appellation's climate is Mediterranean with approximately 2800 hours of sunshine and 650 mm of rain annually. The mistral, a strong, cold, dry wind from the north or mortheast, is a striking feature of the environment. It blows annually for approximately 120 days per year, primarily in the spring and winter. It is advantageous, viticulturally speaking, in that it (i) prevents fungus growth in the vineyards, (ii) rapidly dissipates water from grapes after rainfall, and (iii) protects against late spring frosts. However, it also dries out the soils and can do physical damage to young, unprotected vines.

There is a growing trend in Châteauneuf-du-Pape away from traditional viticulture and towards more sustainable approaches. Many of the vineyards are either organic or biodynamic, or are in the process of converting to one or the other. Syrah vines are trained Guyot while all other varieties are either gobelet or bilateral cordon de royat. Vineyard plantings of the various varieties are as shown below.

Size (ha)
Grenache Noir








Terret Noir

Red Total
Grenache Blanc




Clairette Rosé

Picpoul Blanc


Grenache Gris

White Total
Source: Karis, The Chateauneuf-du-Pape Wine Book

The generalized Chateauneuf-du-Pape winemaking process for red wines is illustrated below.

©Wine -- Mise en abyme