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

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