Thursday, February 28, 2013

Part VI -- Fermentation and Aging: The definitive comparison of Champagne, Franciacorta, Prosecco, and Cava

All four of the wines under consideration obtain the desired bubbles in a two-step process: (i) development of base wines through alcoholic fermentation and (ii) creation of the bubbles in a secondary fermentation process.  Champagne, Franciacorta, and Cava conduct that secondary fermentation in-bottle and that overall process is called the Champagne method (or methode traditionelle) while the large-tank method utilized by Prosecco is called the Charmat method.  I consider these two methods of production in this post beginning with the steps associated with alcoholic fermentation and then looking at the steps associated with secondary fermentation.

Base-Wine Creation

Harvest

In all the cases, rapid picking and crushing of the grapes are required to preserve freshness.

In the case of Champagne, the starting date for picking the grapes is set by the CIVC (the organization that "coordinates the common interests of wine growers and producers in Champagne") which bases its decision on input from the ripening observation network which was initially established in 1956.  This network allows input variables from 450 control plots to be analyzed and the grapes tracked for ripeness by cru and variety.  Decisions on picking dates, quantities, and alcohol levels are a direct result of this analysis. Over 100,000 pickers are involved in harvesting the ripe grapes and moving them from the field to one of the 1900 pressing stations that are located throughout the region.  The grapes are picked in clusters and then placed gently into waiting plastic bins.  Picking normally begins in the cool of dawn in order to preserve as much of the grapes' freshness as possible.  Chardonnay is generally picked one or two weeks later than Pinot Noir and Pinot Meunier.

In the case of Franciacorta, harvesting begins around the middle of August with picking of grapes around the base of Franciacorta.  Berlucchi, one of the leading Franciacorta producers, hand-harvests on a lot-by-lot basis using over 1000 pickers. Careful harvesting is designed to retain the freshness and flavors of the grapes.  Given the variability of the zones, harvesting can extend over 3 weeks on occasion.  Chardonnay is harvested first followed by Pinot Noir and then Pinot Bianco. The picked grapes are transported to the crushers in 18-kg crates to keep the bunches perfectly intact during transportation to the winery.

The Glera grapes (Prosecco) are handpicked and transported to the winery for further processing. The grapes from the Cartizze area are the last to be harvested as, coming from the steepest hills, they are the most difficult to be accessed. The grape stalks are removed and the grapes crushed after which the must is moved to a press for separation of the juice from the skin and seeds. The grapes are pressed gently in order to ensure that only the most desirable juice makes it into the wine. The remaining material is set aside to be used in the production of grappa.

The Cava harvest runs from mid-August to the end of October and the picked grapes are quickly transported from the vineyards to the cellars either in 25-kg-capacity boxes or in stainless steel trailers.

Pressing

The Champagne grapes are weighed at the pressing center and relevant information recorded in the pressing logbook.  The grapes are then pressed as whole bunches in a process that is called fractionated winemaking.  In this process, the free-run juice is drawn-off first in three successive pressings.  The product of these pressings is called the cuvée and the middle of the three is called the coeur de  cuvée (heart of the cuvee) and is said to possess an ideal balance of purity and structure. The maximum amount of juice that can be harvested during the cuvée pressing is 20.5 hl. The second component of this fractionated winemaking is the heavier press called the taille.  In this stage the juice is harvested in two or three high-force presses that occur subsequent to the removal of the cuvée.  The juice collected at this point is darker due to the impurities extracted from the grape skins.  A total of 5 hl of juice can be legally harvested at this stage. The cuvée and taille have similar levels of sugar but the cuvée has higher levels of malic and tartaric acids while the taille has higher levels of oxidants, minerals, and pigments.  A total of 25.5 hl of juice can be legally harvested from a 4000-kg marc of fruit.

After harvesting, the Franciacorta grapes are placed into special presses for a soft, gradual crushing. The first-press must is used for alcoholic fermentation.

Unlike the Champagne case, only free-run juice is used in the production of Prosecco and the allowed yield is 70 liters of wine from 100 kilogram of grapes, almost 10% greater than the yield allowed in Champagne.

Once harvested, Cava grapes are subjected to quality inspections and then transported rapidly to the winery to ensure freshness retention. Must is extracted with gentle pressing in order to obtain highest quality juice.

Coquard presses at Berlucchi in Franciacorta

Addition of Sulphites

The fruit extracted during the press of the Champagne grapes flows into open tanks which are separated by cru, variety, and pressing (If the intent is to make Rosé Champagne via maceration, then the juice stays in contact with destemmed black-skinned grapes  for 24 to 72 hours until the desired color is obtained.).  Sulphites are added to the juice at between 6 and 10 g/hl in order to combat mold and bacteria and reduce the risk of flavor-killing oxidation.

Settling

Impurities are removed from the Champagne must in a process called débourbage where the solids fall to the bottom of the tanks while the clear juice is drawn off from the top.

In the case of Prosecco, the cloudy must is chilled to 5 - 10℃ and kept in stainless steel tanks for 10 to 12 hours during which time the solids settle to the bottom. The Cava must is also clarified prior to alcoholic fermentation.

Alcoholic Fermentation

The resulting clear juice is transported to the vat room for alcoholic fermentation.  Today most fermentation is carried out in stainless steel tanks, a change from the prior norm of oak fermentation  (Oak seems to be making a comeback in Champagne).  In Champagne, the juice is chaptalized as necessary to bring it up to 11% potential alcohol after which yeast is added to initiate alcoholic fermentation. Fermentation runs between 10 and 20 days (10 - 14 in Champagne and 15 - 20 in Franciacorta) before all the sugar in solution is converted to alcohol and carbon dioxide.  The carbon dioxide produced at this phase is allowed to escape. Malolactic fermentation is initiated if is a part of the house style.

In the case of Berlucchi in Franciacorta, the result of the vinification process is 200 base wines, some of which undergo battonage in order to stir up the lees.

Cold Stabilization and Clarification

The base wine is cold stabilized to prevent tartrate precipitation later in the life of the wine.  The wine is then racked off the solids and clarified further through fining and/or filtering.

Secondary Fermentation

Blending

The next step in the process sets Champagne apart from other sparkling wines.  In order to produce Champagne that aligns with the House style, the Chef de Cave has to memorize and blend wines from a broad array of crus from the current vintage plus wines from the reserve as necessary.  The other sparkling wines, on the other hand, draw from a smaller number of "crus" and a far smaller number of vintages as the base wines for their blends.  In the case of a vintage sparklers, the blend can only contain wines sourced from grapes that have been harvested and fermented in the vintage year.

Fermentation

For Champagne, Franciacorta, and Cava, the blended wines are placed into Champagne-style bottles to which liqueur de tirage (a solution of wine, sugar, and yeast) is added and then the bottle is capped with a crown cork seal.  This addition precipitates a second fermentation, this time in the bottle.  As the bottle is capped, the carbon dioxide created during fermentation cannot escape and the bubbles formed as a result are absorbed into the liquid.  The process by which these bubbles are formed is called prise de mousse and the longer the period, the more refined the bubbles.

At the conclusion of alcoholic fermentation, the Prosecco base wines are assembled into batches and pumped into large, sealed tanks (autoclaves) for the secondary fermentation. Sugar and yeast are added to the tanks and the consumption of the sugar by the yeast results in the Carbon Dioxide that gives the sparkling characteristic to the finished wine.  This method of sparkling wine production is called the Italian (because it was first demonstrated as industrially viable by an Italian, Martinotti) or Charmat (the name of the Frenchman who refined the process such that it became feasible for large-scale industrial production), or Martinotti-Charmat method.  It is felt that this method preserves the aroma of the grapes yielding fruity, floral wines. This second fermentation can run between 20 days and 3 months after which the wine is bottled.

Aging

After the sugar has been exhausted, the yeasts die.  The breakdown of the dead yeast cells by enzymes -- autolysis -- adds complexity to the aroma, flavors, and mouthfeel of the Champagne if residency is maintained.  Aging on lees (Aromas and Flavors: Explanatory Notes, wine-pages.com):
    • Releases reducing enzymes that inhibit oxidation
    • Absorbs certain essential yeast nutrients (limits potential for refermentation at dosage)
    • Increases amino acids and other nitrogenous matter, precursors to "Champagne character"
    • Produces acetal which possibly adds a biscuity or brandy-like complexity
    • Produces MP32 which reduces tartrate precipitation.
Champagne is legally required to remain on the lees for at least 16 months if a non-vintage and at least 3 years if designated as vintage.  Quality houses normally age their non-vintage wines for 3 to 4 years and their vintage wines for 7 to 8.

Non-vintage Franciacorta wines are aged for a minimum of 25 months with 18 of those months being on the lees in the bottle.  Vintage wines are aged for a minimum of 37 months with 30 of those months being in the bottle on the lees.  Riserva wines are aged for 5 years on the lees.

In order to be called Cava, the sparkling wine made in the region has to be aged a minimum of 9 months before being taken to market.  Many producers age their wines for 2 to 4 years in order to provide wines with more character.  To be classified as Gran Reserva, a Cava has to be aged for at least 30 months.

The Prosecco aging requirement is the shortest for the sparkling wines under consideration in that the wine rests in bottle for between 20 and 40 days before being shipped.

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In the next installment of the series I will be examining the styles of wines offered by these brands. For a look back at previous posts in the series, please click on the appropriate link below.


Part I -- Origins
Part II -- Regulatory histories
Part III -- Macro-Level characteristics
Part IV -- Production zones
Part V -- The vineyards


©Wine -- Mise en abyme

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