The wines of Champagne are defined not just by the region’s history, geography, and laws but also by its unique viticultural and winemaking practices. This guide follows Champagne production from the vineyard to the glass, diving into the specific farming practices, decisions made in the cellar, and biological processes that together result in one of the world’s great sparkling wines.
Achieving a vineyard that is balanced year after year to produce sparkling rather than still wine requires adhering to certain criteria. It is not practical to be dogmatic about how each grape variety should be grown in every location within such a large and varied region as Champagne.
But it is true that a variety destined for Champagne production, when compared with the same variety grown in the same place for a still wine, generally requires the following in a classic vineyard:
In Champagne, the space between vines within the same row can range between 0.9 meters and 1.5 meters (roughly 3 feet and 4.9 feet), while the distance between rows must not exceed 1.5 meters. The relatively wide-spaced minimum of 0.9 meters is determined by the space necessary to accommodate all obligatory methods of training and the number of fruiting buds required. There is also a maximum sum of spread—the summation of the distance between each vine and each row—of 2.5 meters (8.2 feet). This is equivalent to, for example, 1 meter (3.3 feet) between vines and 1.5 meters between rows.
The average density in Champagne is 8,000 vines per hectare. There is no maximum vine density, although 10,000 vines per hectare is not uncommon and 18,000 is considered a practical maximum even for nonmechanized vineyards. This practical maximum is lower, however, than pre-phylloxera vineyards planted en foule. French for “in a crowd,” this term refers to a method of planting vines that relies on a layering system; these vineyards would have had a vine density of over 25,000 per hectare. Rare examples survive today, such as Clos Saint-Jacques, a walled vineyard in Aÿ that belongs to Bollinger and is half planted en foule.
Very low vine densities have been allowed by special dispensation for experimental plots, such as Moët’s trialing of the Lyre system, which has a sum of spread of 4.4 meters (14.4 feet) and just 2,750 vines per hectare (although this has been increased to 3,000 to 4,000 vines per hectare in some plots). These trials, which began in the Aube in 1988, are ongoing. Benefits include less ambient humidity, thus less gray rot, and more acidity, resulting in crisper wines. But this comes at a price, because, despite fewer vines per hectare, the Lyre system is significantly more difficult and 30% more expensive to establish. Full cropping levels take six years rather than the usual three, and production levels of the traditional training systems can’t be matched.
Four systems of vine training are allowed in Champagne: Chablis, Cordon, Guyot, and Vallée de la Marne. Guyot is a head-trained system, and the other three are cordon-trained systems. The Chablis and Cordon training systems are the only methods permitted for grand and premier cru vineyards. Generally, the Chablis system is for Chardonnay vines planted in the Côte des Blancs, the Cordon system for Pinot Noir vines in the Montagne de Reims, and the Vallée de la Marne method for Meunier vines grown in the Marne Valley. But since all varieties can be found in each district, the method of training, most clearly identified in the winter, is useful for determining where one variety stops and another begins.
The Chablis system was developed in the Chablis district in the 19th century, and at least 90% of all Chardonnay vines in Champagne are trained by this method. A maximum of five buds are allowed for Chardonnay, Meunier, and Petit Meslier, and up to four are allowed for other grapes. For Chardonnay, four shoots require five buds, as the first bud on this vine is always infertile. Either three, four, or five permanent branches may be cultivated, each grown at yearly intervals. Because vines are not allowed to overlap, when a vine reaches the neighboring plant, it will be removed.
Originally known as Cordon de Royat and now called Cordon, the Cordon-trained, Spur-pruned system was developed in the mid-19th century at the Royat agricultural school, in southwestern France. It is considered the best vine training system for Pinot Noir. Only one main branch is permitted, along which shoots above branch level are spaced at a minimum of 15-centimeter (6-inch) intervals. Each shoot may have two buds (three for Chardonnay, the first being infertile), but the end shoot is also allowed to be an extension of the main branch itself and may have four buds (five for Chardonnay).
Guyot is a cane-pruned system, with a main spur (or spurs if double Guyot is used) that is not permanent but renewed annually. In the version known as single (or simple) Guyot, a single, annually renewable branch is allowed, with 10 productive buds, whereas for double Guyot, two annually renewable branches are permitted, with 8 buds each.
The Vallée de la Marne system is restricted to Meunier vines and vineyards that are not classified as either grand or premier cru. There are four variants of this system, all of which have different shoot requirements. In the basic version, there are six buds on the main permanent spur and nine on the secondary. When the main branch reaches the next plant, it is replaced by the secondary branch.
Champagne’s yields are relatively high compared with those of other regions known for high-quality wines, but yields arguably have less of an impact on Champagne than on other wines. Lower yields are often associated with a grape’s potential to show greater structure as well as weight, color, potential alcohol, pigmentation, and phenolic characters. But for 85% of all Champagne production (primarily nonvintage blends), the structure of a Champagne is defined by the second fermentation and sometimes also chaptalization, making the wine richer and fuller. Champagne is a 12.5% ABV wine with the structure of a 9.7% ABV wine.
If large crops are within reasonable limits, they have certain advantages in Champagne. They can delay flowering beyond the worst ravages of frost and extend ripening into September, when cooler nights will preserve acidity. Most of the best Champagne vintages have been September harvests, whereas most of the worst vintages have been October harvests. (Find a list of harvest dates since 1960 in the Compendium.) If the Champenois must harvest in October, it is usually because of delays caused by a less-than-perfect growing season, after which rot infection becomes highly probable.
Yields are determined by kilograms of grapes harvested per hectare and hectoliters of juice pressed per kilogram of grapes. From this it is possible to convert kilograms per hectare into the more familiar hectoliters per hectare. Until 1990, the maximum pressing limit was 26.6 hectoliters per 4,000 kilograms. In 1991, this was reduced to 25.5 hectoliters per 4,000 kilograms (102 liters per 160 kilograms) at the press and 25 hectoliters after fermentation.
The maximum permitted yield was initially set by a 1935 decree-law. The maximum annual yield should never exceed the maximum permitted yield. Since 2007, the maximum permitted yield has been 15,500 kilograms (96.9 hectoliters per hectare). Hidden in the small print of the maximum permitted yield regulations is a clause under the heading “Double-safeguard to prevent excessive yields,” which states that growers must ensure that no block of vines exceeds 18 bunches per square meter, and, whatever the average yield for their entire viticultural holdings might be, no individual parcel of vines may exceed an average yield of 21,700 kilograms per hectare (138 hectoliters per hectare).
The maximum annual yield is decided each year under the auspices of the Comité interprofessionnel du vin de Champagne (CIVC). In years of plenty, the maximum annual yield may comprise the maximum usable annual yield and maximum reserve (or blocage, stored without the benefit of AOC), but when combined they must not exceed the maximum permitted yield. In small harvests, the maximum usable annual yield will be augmented by the release of the maximum personal reserve (déblocage).
The maximum usable annual yield is classified Champagne AOC and is the proportion of the crop that is immediately usable in a large harvest.
The maximum personal reserve to be stored is a proportion of a large harvest that is not immediately usable. It is not classified Champagne AOC and must be held en blocage by producers as réserve personnelle (or réserve qualitative individuelle). These reserves are not reserve wines kept for blending nonvintage cuvées, which are classified Champagne AOC. The maximum reserve for any vintage will be stored in the form of unclassified vins clairs (clear wines), with reserves of previous harvests. This is Champagne’s strategic emergency stock and, as of 2017, was the equivalent of 270 million bottles. As reserves from better, more recent years become available, it is permissible to replace aging or lesser-quality reserves with excess production, should there be any.
The maximum personal reserve to be released is a proportion of stored reserves that have finally been classified Champagne AOC and authorized for use to combat a shortfall of a small harvest. This is known as déblocage.
The official average yield is the average of all the declared yields made at the pressing centers. It is the average of what can be legally harvested, not the average of what was grown in the vineyards. The latter number, the total volume grown, is known as the actual yield. These numbers can be strikingly different. For example, in 2004 the official average yield was 13,990 kilograms (89 hectoliters per hectare), whereas the actual yield according to the CIVC’s database was 23,000 kilograms (143.8 hectoliters per hectare). The actual yield used to be published by the CIVC but has become increasingly scarce over the past decade or so.
Although it may seem surprising, a high actual yield—even as high as that of 2004—is not intrinsically harmful to the quality of Champagne. It is the interaction of yield with factors such as timing, temperature, and precipitation that can impact quality.
Champagne grapes cannot be picked until the annual ouverture de la vendange is published. This dictates when the harvest is allowed to begin on a village-by-village, variety-by-variety basis. The dates are determined by a committee but are essentially based on a system of fieldwork that was introduced in 1956, whereby samples are taken twice a week, starting at veraison, from 450 control plots spread throughout Champagne. The selected clusters are checked for rate of change in weight, sugar, and total acidity, and for any incidence of botrytis. These findings indicate the degree of grape ripeness by village and variety, and eventually lead to the CIVC establishing when the harvest should begin. The findings also determine the quantity of grapes per hectare that will be approved for AOC production and the minimum potential alcohol level.
Hand-harvesting is required by law in Champagne. Bunches are deposited into small crates that, when stacked, prevent the grapes from being crushed. The crates are delivered to the press house quickly to avoid oxidation.
Most producers still believe that, despite the technological advances of the latest machine harvesters, the harvest in Champagne will always be by hand, but not everyone is convinced. A small but growing number of more technically minded producers have gradually conceded that mechanical harvesters will be permitted in Champagne in the future. The obstacle is that such harvesters will have to pick whole clusters, which they have not yet achieved on a commercial scale.
It is a myth that grapes in Champagne are harvested early or underripe. On average, the harvest in Champagne starts two weeks after the harvest in Bordeaux. Because of the long, drawn-out veraison and final ripening period, the grapes attain acid ripeness when their average potential alcohol is just 9.5% ABV, sometimes even less.
In Champagne, acid ripeness begins at 50-50 tartaric-malic. After this point, the degree of ripeness at which grapes are picked is determined by the style of wine required. The data for the past 30 years demonstrates that Champagne grapes have averaged 9.7% ABV with 53.2% tartaric acid. For vintage, prestige, and other special cuvées, the vins clairs chosen undergo an increasingly stricter selection; consequently, the final cuvées tend to average 10.5% to 11% ABV, with most components not requiring chaptalization. Such Champagnes are generally richer, with a fuller structure, qualities that can interfere with maintaining a classic lean structure. This is the primary reason why the construction of the supposedly best-quality, most expensive Champagnes is not as simple as selecting the best-quality components, as these may end up bigger, not better.
Ripeness levels have increased significantly since 1970, but total acidity and pH remain optimal. Although the increase in ripeness is primarily the result of warmer growing seasons, particularly since 2003, other factors are involved, such as the cultivation of earlier-ripening clones.
Champagne grapes are never destemmed, because the fibrous material of the stems and stalks creates a network of canals through which the juice rapidly drains. This is particularly advantageous for black grape varieties, as it helps avoid coloration. Champagne’s traditional Coquard press is essentially 17th-century technology (which itself was merely a flattened adaptation of the basket press of the Middle Ages) powered by electricity, yet it is still one of the very best presses for sparkling wine in the world. Modern pneumatic presses are also excellent, particularly those that press in a sealed, inert-gas environment, as they reduce oxidation, a process that is unavoidable as soon as a grape is crushed. All pneumatic presses have a large central or lateral rubber balloon that inflates, gently yet rapidly crushing the grapes against the inner surface of the press, and the juice swiftly drains away along channels and through ducts. When Coquard brought out its radically new model, the PAI (an acronym for pressoir automatique à plateau incliné), it stood the original 17th-century design not on its head but on its side. The reason for this, and the clever part of the press’s design, is the inclusion of an inclined plate, which allows the pomace to fall by gravity. The improved press is less likely to bruise skins, doesn’t crush seeds, saves time, and reduces oxidation.
Most presses are programmed with a CIVC chip to replicate the Coquard’s complex series of pressing and breaking-up operations, the ultimate objective of which is to separate the cuvée (used in this sense to mean the first pressing, rather than in the sense of a blend) from the taille (the second and any subsequent pressings). The best producers seek the cleanest and richest juice—containing the most sugar, acids, minerals, and vitamins, but the least tannin—which is found only in the first pressing. The longer the grapes are pressed, the more colored the juice becomes (even from white grapes), the higher its pH (thus the lower its acidity), and the more tannin it will contain (from the skins as well as the stalks and the rachis, or skeletal remains of the cluster).
Traditionally, the comparative volumes of cuvée and taille were based on the capacity of a classic Coquard press, which could hold 4,000 kilograms of grapes. Each fill of the press historically yielded 2,666 liters of juice. This capacity was used to define a unit of volume called a marc, which measures the weight of the grapes (not juice). This was the basis on which the AOC for Champagne was initially established, with the first 2,050 liters extracted classified as the cuvée, the next 500 liters called the taille, and the last 116 liters the rebêche.
Most producers make their wines exclusively from the cuvée—or at least they say they do, although even some top-quality producers claim that a little taille from Chardonnay can be interesting and useful in a blend. If the grapes are wet with rain or contain rot, or if no rain has fallen since they were last sprayed, quality-conscious producers will run off the first 50 to 65 liters of every marc into the taille and run on the cuvée for an additional equivalent amount, effectively upgrading the first 50 to 65 liters of taille. In these cases, the taille will consist of the first 50 to 65 liters and the final 435 to 450 liters. Some producers have created special cuvées from the coeur de cuvée (heart of the cuvée), while, at the other extreme, the producers of own-label products and premier prix Champagnes will use high percentages (sometimes 100%) of the taille.
Following pressing, the juice is piped to cleansing vats for débourbage, or settling. It typically remains in the vats for 12 to 24 hours while any solids (particles of skin, stalk, pips, and more) settle on the bottom as bourbes. The settled juice is then piped to the fermenting vessel. Some producers like to perform a double débourbage (devised by James Coffinet when he was cellar master at Billecart-Salmon in the 1970s), which can reduce the amount of sulfur required.
Champagne goes through two separate fermentations, neither of which should yield a complete or balanced wine. Indeed, the objective of both fermentations is the opposite: to produce a wine that is intentionally incomplete and precisely unbalanced. The winemaker must keep in mind how the balance will be affected by additional alcohol from a second fermentation, the altered chemical composition that results, the tactile effect of the mousse on the balance of the final wine, the “fattening” effect of several years of lees contact, the oxidative punch of disgorgement, and the dosage (if there is to be one). The wine cannot be either complete or balanced before manipulation by all these additional factors.
Most wines are fermented separately by village and grape variety, and, whether vin de cuvée or vin de taille, the degree of separation depends on the ratio of vats (and their respective sizes) to the total volume of production. Some producers vinify their wines by lieux-dits or lots within each village.
Although fermentation temperatures in Champagne are generally lower now than they were prior to the 1960s, when temperature control was introduced, the ability to control the temperature rather than the temperature itself is most important. The first fermentation should be relatively fast and furious, as its job is to produce a comparatively basic wine. The second fermentation should be significantly longer and cooler, because it unlocks more biochemical reactions that result in a finished product of greater complexity.
Chaptalization is necessary for most Champagne to achieve the classic, recognized structure of the category. As the average potential ABV from grapes grown in Champagne is 9.7% and the maximum amount of liqueur de tirage would contribute an additional 1.5%, the total average ABV for Champagne is no more than 11.2% without chaptalization. With chaptalization, an average of between 0.8% and 1.3% is added, with a finished strength of 12% to 12.5% ABV (this covers almost all Champagne sold).
The initial fermentation usually takes place in temperature-controlled stainless steel vats. Some producers vinify their Champagnes in new or used oak, using large foudres, small casks (known locally as pièces and 205 liters in capacity), or 228-liter Burgundian barriques. Concrete tanks lined with either glass tiles or epoxy resin are still used, even though they date from the 1940s and 1950s. These often remain in place because they cannot be removed without demolishing the cellars. Egg-shaped concrete vessels are occasionally used, as are similarly shaped vessels constructed from oak.
Historically, every Champagne was fermented in old oak—not just pièces but also much larger vessels, such as foudres, muids, and demi-muids—because it was the only suitable material available. When producers began replacing oak with large concrete tanks lined with glass or epoxy, in the mid-1940s, and started introducing stainless steel beginning in 1959, the most noticeable effect was one of mouthfeel: the loss of a midpalate ampleness and a textural creaminess on the finish, which had been created by micro-oxygenation. By the 1960s, some chefs de caves were becoming concerned about how the change in fermentation vessels had affected the style of Champagne.
The work of the French researcher and enologist Émile Peynaud, who had made malolactic fermentation a practical and repeatable option on a commercial scale in the late 1950s, filtered through to chefs de caves in Champagne when he was consulting for Mercier in the 1950s. This was at the same time that the Champenois adopted temperature-control technology (using it for new stainless steel vats and old concrete ones, too). The CIVC soon developed a bespoke malolactic fermentation cocktail that delivered exceptionally low volumes of diacetyl, which has a distinctly buttery aroma not considered appropriate for the classic style of Champagne. Malolactic fermentation became, for the first time, not just a style choice but a controllable style choice. This enabled Champagne’s chefs de caves to mitigate the loss of the textural effect from micro-oxygenation in oak vessels on a variable, year-by-year basis as they were decommissioned.
Exceptionally restrained malolactic fermentation contributes to textural creaminess. This is almost always carried out using neutral, low-diacetyl, low-VA strains of Oenococcus oeni. The higher the inoculation rate, the shorter the duration of malolactic fermentation, and the less diacetyl produced. Less diacetyl is also produced the longer a base wine is left on its lees prior to the second fermentation, because the yeast and bacteria break down diacetyl. For partial malolactic fermentation, the process must be stopped either through chilling or by adding SO2.
By the 1980s, almost all Champagnes were being produced with full malolactic fermentation. But, by the 1990s, partial malolactic fermentation had become fashionable, and, by the 2000s, the ability to use at least some nonmalolactic fermentation wines at assemblage was considered a necessary tool under Champagne’s changing climatic conditions. With the advent of warmer seasons and riper grapes, exacerbated by the move to earlier-ripening clones, an industry-wide move away from malolactic fermentation ensued.
While tartrate stability is purely an aesthetic consideration for still wines, it is essential for fully sparkling wines. This is because the crystals serve as nucleation points for CO2, which causes gushing on opening (as opposed to random gushing, which occurs only when a bottle has imperfections on its inner surface). Champagne must therefore be tartrate stable at the time of bottling.
Rarely admitted, let alone discussed, in Champagne is the use of carbon to remove unwanted color from base wines, particularly from blanc de noirs or when blending with any of the taille of Pinot varieties. Many producers never use carbon, especially if they are making a premium blanc de noirs, when the skill is to produce naturally as pale a cuvée as possible. But there are many active carbon products that can legally be used to remove color from tinted juice and wine.
Initially, the product of the first fermentation is known as a vin clair (clear wine), although, because of the method of production and even the type of fermentation vessel, it can be anything but clear, depending on how early it is looked at. Generally, wines fermented in pièces or any other small casks are not temperature controlled and will be the first to clear. The last wines to clear are usually those fermented in stainless steel, as they are temperature controlled.
Before becoming clear, most Chardonnay vins clairs are cloudy and light in color, while Pinot Noir and Meunier vins clairs show a pink tinge. As they clear, much of the color drops out, but any black-grape vins clairs that are almost indistinguishable from the same producer’s Chardonnay vins clairs indicate the use of carbon. Vins clairs are very simple, somewhat crude, and definitively incomplete and unbalanced. One of the main reasons why chefs de caves are coy about making pronouncements about the quality of a vintage is that stark changes can occur in specific vins clairs.
After racking, the vins clairs are ready for assemblage. It can be helpful to make a distinction between base wines and reserve wines: vins clairs are base wines, and reserve wines are not. But it is equally correct to describe the entire blend after assemblage (containing both vins clairs and reserve wines) as the base wine.
Assemblage usually occurs in the first few months of the year following the harvest. At its most basic, and without taking into consideration house style, assemblage is the blending of different wines produced in different places, usually from different grape varieties and, in the case of a nonvintage or so-called multivintage wine, from different years.
There are many approaches to assemblage, but producers generally agree that it is best to have the widest possible palette of different wines with which to blend, even when making single-vineyard cuvées. The greatest Champagne producers vinify wines separately according to their origin and grape variety but also inject other variables, such as vinifying in oak as well as stainless steel, or putting some wines through malolactic fermentation.
While a few chefs de caves might determine the final blend on their own, most involve a panel that consists of other enologists or otherwise extremely experienced tasters within the company. If the company is family owned, the final blend will be approved with at least one senior member of the family participating in the exercise. This is, however, a laboratory exercise, whereas bringing together the component parts for each blend can be a logistical challenge, particularly for larger houses, which often have their wines stored at 20 or more locations spread across a wide area. Some of these wines can be housed at various co-operatives. The larger houses effectively rent space wherever they can, although most of them are working toward reducing the number of off-site locations.
For nonvintage Champagne, assemblage involves the use of reserve wines. These are wines that are kept in reserve from previous years and can be used only in the blending of Champagnes that are nonvintage.
Reserve wines are often perceived as a means of evening out quality and creating a particular house style. While reserve wines do serve these purposes, their original role was much simpler. By adding a touch of mellowness and complexity that could otherwise be achieved only over time, reserve wines made an entry-level cuvée more agreeable at a relatively young age.
Reserve wines are kept in various vessels, from stainless steel to oak of all sizes, and even in magnums (famously by Bollinger, but other producers, such as AR Lenoble, have followed suit). The types of storage vessels might not necessarily fit the image of the house’s style. There is, for example, a growing trend among producers of stainless steel–fermented Champagnes to keep at least a part of their reserve wine stock in oak, whereas the reserve wines for a barrique-fermented Champagne, such as Krug Grande Cuvée, can be stored in temperature-controlled stainless steel vats (the reserves for Krug Private Cuvée used to be kept in fiberglass tanks).
Whatever the storage vessel, unless reserve wines are kept on their fine lees and occasionally stirred, the lees can reduce the autolytic process; the older they are, the more protein that drops out, and it is the protein that helps kick-start the process of autolysis. The older the reserves are, the more they should be regarded as seasoning rather than a primary ingredient.
At the more modest end, many producers add just 10% to 15% reserve wine from the previous two or three years, and some add none at all. Although dwindling, there is an old grower custom of selling Champagne as nonvintage when the stocks are young, then labeling exactly the same cuvée as a vintage when it reaches the legal minimum age of three years. At the other end, some open-minded and quality-driven growers have started to build up stocks of reserve wines and make use of a considerable proportion in truly bespoke nonvintage cuvées (for example, Paul Bara with 50% reserve wine and Larmandier-Bernier with 40%).
Even producers who add relatively large volumes of reserve wine do so in different ways. Some use reserves from one or more recent harvests, while others will add less in volume, but what they use is of greater age. These percentages vary not only from producer to producer, but also from year to year for the same producer.
There have always been two situations when producers will use a significantly higher proportion of reserve wine than usual. One is in a particularly poor year, to bolster an otherwise weak base wine. The other is the extreme opposite, when a great vintage produces wines that are too distinctive and so imbued with the character of the year that a normal amount of reserve wine would have little effect.
Recently, however, a third situation has developed: when hot years and early harvests produce base wines that require an exceptionally large proportion of reserve wine from a lighter, very recent year. This has turned the concept of reserve wine on its head, encouraging producers to store extremely young reserves for their lightness, freshness, and crispness. For a growing number of producers, it has also altered the distinction between base wines and reserve wines, as they move the concept of base wine from that of the current year’s wine to that of the current year and the preceding year. For some, this will be a 50-50 blend, while for others the blend could be two-thirds to one-third. Others have stretched the base wine over three years, using either equal volumes from each or progressively smaller amounts.
Some preblended reserve wines known as réserves perpetuelles or soleras are produced (primarily) by growers and a few houses. The terms are used synonymously, but some producers make a distinction and, in certain cases, keep and use both perpetuelles and soleras separately. An authentic solera is a true fractional-blending system, where exactly the same volume is removed and replaced with new wine each year. For a réserve perpetuelle, however, the proportion will vary each year according to the size of the crop, although the amount added must be the same as the amount withdrawn.
Traditionally, Champagne is bottled between February and May following the harvest, with the nonvintage blends bottled first. Before bottling, the liqueur de tirage, which incorporates precisely calculated amounts of sugar, yeast, and nutrients, is added to the fully fermented dry base wine to create a second alcoholic fermentation.
The second fermentation (prise de mousse) is the essence of Champagne. Its duration varies according to temperature, the yeast deployed, and bottle size, taking between three weeks and three months. The legal minimum for élevage (the maturation period) is 15 months for nonvintage Champagne and three years for vintage Champagne, although most nonvintage Champagnes are aged for two to three years (some notably longer), and many vintage Champagnes are aged for eight years or more.
During any alcoholic fermentation, not just the second fermentation, there are two overlapping phases: aerobic and anaerobic. In the aerobic phase, oxygen stimulates yeast growth. In the anaerobic phase, yeast cells enzymatically break down sugar molecules to alcohol and CO2 (and various by-products). As the second fermentation takes place inside a sealed container (the bottle), the CO2 created remains dissolved in the wine, causing pressure, which is released in the form of bubbles only when the closure is removed.
A common misconception about the liqueur de tirage is that the ingredients are mixed together and added to the base wine at once. Rather than being a single addition, the liqueur de tirage is an umbrella name for a series of operations, in which several individual ingredients are prepared separately and progressively, and each is added to the base wine at the appropriate moment. Simply adding the yeast and sugar together with sufficient wine to form a liqueur would create such a sugar-dense, high-alcohol environment that the yeast would be overwhelmed almost instantaneously, causing the second fermentation to fail before it could even begin.
To ensure success, the yeast must go through three phases: activation (kick-starting from dehydrated form), assimilation (acclimatizing to high concentrations of sugar and alcohol), and proliferation (fully fermenting in bottle). First, for activation, the yeast is rehydrated with base wine diluted to around 7% ABV and a small amount of sugar. When half the sugar has been converted to alcohol by the yeast, it is added to undiluted base wine with a little more sugar; when half of that sugar has been consumed, the process is repeated, and this goes on until 5% of the volume of the base wine to be bottled has been achieved (assimilation). During this process, nitrogen and other nutrients might be added.
This daylong tank method of preparing and bottling the base wine and liqueur de tirage is the most classic and widely practiced bottling procedure, but it has the disadvantage of creating an uneven amount of oxygen pickup. The further along in the process, the longer the wine has been subjected to agitation, and the more oxygen it will contain. These are minute but significant differences.
To solve this oxygen variation, some producers have been administering the liqueur de tirage directly to bottle for decades. This solution is technologically demanding and, consequently, very complex and expensive, but it is well worth the investment for those who can afford it (there are fewer than 20 bottling lines equipped with this technology in Champagne today). Up to five components (liqueur, assimilated yeasts, riddling agent, base wine, and, if required, nutrients) are developed to their optimum condition, then fed continuously in precise volumes to a fixed tubular chamber, where they are mixed.
Sugar and yeast are the most important components of the liqueur de tirage, as without them no second alcoholic fermentation would be possible. One yeast cell converts one molecule of sugar into two molecules of ethanol (alcohol), two molecules of CO2, and a dash of residual energy.
The most typical amount of sugar is 24 grams per liter of blended wine (compared with 18 to 22 grams in New World sparkling wines), which provides a pressure of six atmospheres, or 6.08 bars, creating a grand mousseux (fully sparkling) Champagne. If there is any residual fermentable sugar in the base wine, it is deducted from the required level of sugar for the liqueur de tirage. Some producers, such as Louis Roederer, have lowered the liqueur de tirage to 21 grams in recent years. As a prudent safety measure, even lower levels are used for some large formats to reduce the pressure. For example, a Jeroboam of Perrier-Jouët Belle Époque receives 18 grams, while a 750-milliliter bottle of the cuvée receives 24 grams.
Many would agree today that a nonvintage cuvée with six atmospheres of pressure can have a rather aggressive tactile quality, especially when the wines are young and have received minimal aging between disgorgement and shipping. As these cuvées account for 80% of all Champagnes sold, producers who are reducing pressure levels could lead a trend. It should not be forgotten that the crémant style originated in Champagne, in the 18th century, and designated a softly sparkling style, whose lower pressure resulted from the use of less sugar.
In theory, it takes 3.84 grams per liter of sucrose (disaccharide), or 4.04 grams per liter of glucose (monosaccharide), to create one atmosphere of CO2. In practical terms, the production of CO2 is less, because the basic formula does not take into account the creation of small amounts of aldehydes, volatile acids, fixed acids, esters, glycerol, and other by-products. In practical terms, it takes 4 to 4.3 grams of sucrose to produce one atmosphere of CO2 pressure, and most Champagne producers base their calculations on 4.2 grams (any residual fermentable sugar must be taken into consideration). Producers have a range of choices for the sugar source for the liqueur de tirage, as for chaptalization of the base wine and dosage of the finished wine. Most Champagne producers opt for sucrose (from beet rather than cane sugar), along with a little citric acid to help invert the sugar. Rectified concentrated grape must (RCGM) is, like ordinary concentrated grape must, a combination of natural grape sugars, glucose, and fructose, but, unlike ordinary concentrated grape must, it is clear, odorless, tasteless, and neutral in acidity. It is possible to use virtually zero SO2 in the liqueur de tirage when relying on RCGM, as the rectification process yields a stable solution of just glucose and fructose, and this lack of SO2 is beneficial for the yeast.
Yeast was once considered little more than a fermentation agent, but science has shown that each yeast strain can produce a range of aromas and flavors, and the choice of which strain to use will depend on the environment in which it is to be deployed and the end results that are desired. For sparkling wine, two distinctly different yeasts are required for distinctly different requirements: first fermentation and second fermentation. The first fermentation is short and classically conducted at a relatively higher temperature. The second fermentation is typically conducted over a longer period at a lower temperature and under extreme duress, to produce a more complex end product that will shed debris suitable for clean autolysis.
Prior to autolysis, the existing amino acid content is determined by the composition of the wine itself, while during autolysis the creation and consumption of amino acids differ according to the properties of the second-fermentation yeast and the timing of disgorgement. Since amino acids are the precursors to volatile aromatic compounds, the choice of second-fermentation yeast is important. Using the same yeast for both first and second fermentations is usually the worst choice of all, with excess levels of volatile acidity the most common result.
Although some producers reject the uncertainty of wild yeast, some smaller growers consider it part of the expression of their terroir. In such cases, it is reasonable to encourage wild yeast for the first fermentation but never for the second. During any fermentation, most wild yeasts never survive beyond 2.5% ABV, the point at which they are overwhelmed by the yeast that dominates the production facility.
Most of the top Champagne houses culture their own second-fermentation yeast, which will often be a blend of yeasts reared in-house and proprietary yeasts. The propagation and maintenance of yeast require strict monitoring if the yeast’s viability is to be maintained and contamination avoided.
To prepare yeast, it is progressively revived in a mixture of still wine, water, sugar, and a source of nitrogen, such as diammonium phosphate. The wine feeds the yeast, while the water, present in very small quantities, ensures that the alcohol level will not exceed 11% to 12% ABV. The diammonium phosphate provides the nitrates necessary for cell growth.
The second fermentation is conducted in a hostile, reductive environment. Some stress factors are similar to those found in the first fermentation, such as low pH and high acid content, but others are unique to bottle fermentations, such as very little oxygen availability, low nitrogen content, high CO2 pressure, and high alcohol. Under such stressful conditions, yeast cells require a guaranteed supply of nutrients to work well, yet the yeast assimilable nitrogen (YAN) and other yeast nutrients will be at an all-time low, having already been depleted by the first fermentation. It is therefore important to check whether yeast nutrients will be required when rehydrating yeast for assimilation and combining it with the liqueur de tirage.
The amount of nitrogen required for the second fermentation is significantly lower than that needed for the first fermentation, as the second fermentation produces just 1.5% ABV, which involves much less cell growth, with the yeast having to replicate only two to three times during the whole process. Inorganic nitrogen, however, encourages a much shorter and faster second fermentation, whereas organic nitrogen (that is, inactive yeast-based nitrogen) drives a longer, slower, and more complete fermentation. Furthermore, active yeast cells require amino acids for the formation of esters, which provide clean, fruity, and floral aromas, which contribute to freshness, elegance, and finesse. Many chefs de caves opt for a mix of base wine and liqueur de tirage that has sufficient (not overloaded) YAN of at least two parts organic nitrogen to one part inorganic nitrogen. The usual sources for organic nitrogen are inactive yeast-based products, such as yeast cell wall, yeast extract, yeast hulls, or yeast autolysate, all of which include a complex range of essential amino acids, minerals, lipids, and sterols.
Controlling the SO2 level of the base wine prior to bottling is also vital. If SO2 is more than 50 parts per million (ppm), any thiamine, whether preexisting or added through the liqueur de tirage, will be deactivated, and that will result in high levels of acetaldehyde (via decarboxylation of pyruvate acid).
Despite all this, some producers, including some of the very finest in Champagne, do not add nutrients, either because they believe that their base wines have sufficient nutrients to complete a second fermentation or because they want the yeast to struggle and stretch the second fermentation as long as possible—or a bit of both.
In the rare cases when the secondary fermentation is ineffective, or when a batch of wine is technically correct but a decision has been made not to commercialize, the wine must be returned to the vat and reblended. French winemakers call this procedure remise en cercles (return to hoops), a reference to the hoops around a wooden barrel.
It is standard to add a fining agent, a riddling aid, or both, a practice that began in 1947.
A naturally occurring clay known as bentonite (aka montmorillonite) is the most traditional fining agent for the liqueur de tirage in Champagne. There are four primary types of bentonite: aluminum, calcium, potassium, and sodium. Only sodium and calcium are relevant, and, over the past 10 years or so, a number of producers have shifted from sodium bentonite to calcium bentonite, which results in better lees compaction and finer bubbles. In more recent years, some have moved to a mix of calcium and sodium bentonites to avoid calcium tartrate instability.
The use of an adjuvant, and even a coadjuvant, is also very popular. An adjuvant is far more than its literal meaning, “additive.” It is a highly elaborate combination of mineral (bentonite) and organic (alginate) colloids designed to create a filmed deposit that forms thin layers of latex-like consistency and never adheres to the glass, facilitating a much easier remuage (riddling). Adjuvants are all created for fast riddling via gyropalette, but many high-quality, high-volume producers manage easily enough without them.
Exposure to light waves, primarily but not exclusively in the ultraviolet (UV) range, will quickly have a devastating and irreversible effect on the quality of any wine, creating volatile light-struck (goût de lumière) aromas. The primary culprit of the light-struck aroma is a volatile sulfur compound called dimethyl disulfide (DMDS). At its very lowest detectable threshold, this compound inflicts a hint of something not quite fresh to a wine aroma. Even if not initially noticeable, it will eventually evolve into extremely unpleasant aromas. This is particularly relevant to sparkling wines, because the foul-smelling compounds created are elevated in the presence of CO2. The choice of bottle color is of paramount importance to all quality-conscious Champagne producers.
The protection afforded by different colors of glass varies considerably, but the precise degree of protection depends on not just the color of the glass but also its specific hue, how deep or dark the color is, and, crucially, the thickness of the glass. Heavier bottles of the same hue and depth of color are significantly more protective than lighter bottles. As producers move toward the use of lighter bottles to reduce their carbon footprint, however, heavier ones have become a far less attractive option. This leaves color, hue, and depth of color as the only variables producers can realistically adjust.
If quality is foremost in the mind of Champagne producers, the fastest-growing category of Champagne bottle should be deeper and darker amber. The dark-amber bottles used by a few forward-thinking producers today do not offer complete protection, but, with above 90% protection, they are highly effective. Yet the vast majority of Champagne is sold in traditional, green-colored bottles, even though they offer just 50% protection. The only challenge to the dominance of green bottles is in the wrong direction; the use of clear-glass bottles has increased significantly over the past 20 years, especially for blanc de blancs and rosé styles.
As the first step in Champagne’s strategy to reduce its carbon footprint by 75% before 2050, the average weight of a Champagne bottle has been reduced from 900 grams to 835 grams, a reduction of 7%, which equates to an emissions reduction of 8,000 metric tons of CO2 per year—the equivalent of removing 4,000 vehicles from the road.
The range of Champagne bottle sizes, particularly those in the larger formats, began to increase in the late 19th century, when Champagne had achieved global recognition and the sight of such enormous bottles helped market its glamour. Most of the large-format names and all the names of the historically traditional large formats are etymologically of Biblical origin, though the reason why is uncertain. The law requires Champagne be sold in the bottle in which it underwent its second fermentation, but there are exceptions for bottles that are 375 milliliters or less (primarily for the lucrative airline market), and bottles that are larger in size than the Jeroboam (primarily for publicity events). Such bottles are typically filled by transversage (or by transfer method), from a tank or through the process of decanting multiple smaller bottles.
It has long been understood that the greater ratio of wine to oxygen in a magnum (1,500 milliliters) is the reason for its superior aging capacity compared with that of a standard bottle (750 milliliters). Both have a neck of the same diameter and are sealed with a cork of the same size, thus the ratio of wine to oxygen is almost exactly double in a magnum. For a wine in magnum, the potential for and rate of oxidation are almost half those of a wine in standard bottle. The ratio of wine to oxygen is why wines in magnum age far more slowly.
What has become more broadly understood in recent years, however, is that the magnum effect begins with the second fermentation, which starts on average two days later than it would for the same wine in a 750-milliliter bottle, and takes almost one week (about 33%) longer. The yeast cells must convert twice as much sugar to alcohol in a magnum compared with a standard bottle, but with the equivalent oxygen availability. Thus, they stall the fermentation occasionally while the last dregs of oxygen are sought. It can be argued not only that magnums are superior to 750-milliliter bottles for bottle-fermented wines, but that the wines produced in magnums are intrinsically different because of the different biochemical reactions and by-products involved in the longer, stop-start fermentation process.
Some producers still use corks rather than a crown cap for the second fermentation and subsequent yeast aging. The cork (bouchon de tirage) is secured by a clip called an agrafe. There is evidence that natural cork is superior for aging beyond 10 years, but it comes with the risk of the chemical 2,4,6-trichloroanisole (TCA), which causes musty aromas. Most producers who believe it is worth the risk cite the permeability of cork as their reason. The risk-free Mytik Diam cork closures (used by Bollinger) offer this same benefit while also ensuring a consistent rate of development prior to disgorgement because of their uniformity of oxygen ingress.
Although the crown cap (capsule couronne) was patented in the US by the Irish-born William Painter as early as 1892, it was not used in Champagne until the 1960s and did not become widely adopted until the 1970s.
Today, crown caps are constructed from standard steel (usually tin plated) for use in short-term storage, while those made from 5052 aluminum (alloyed with magnesium and chromium for strength) are for short-to-midterm storage. Both are suitable only for cellars with less than 70% humidity. Crown caps made from AISI 430 are for long-term storage and can withstand cellars of more than 70% humidity.
The crown cap is not the seal, temporary or otherwise—the liner is the seal. The crown cap is a mechanical device to keep the liner in place. The liner sits between the crown cap and the glass, providing cushioning and a medium through which gases may be exchanged or restricted. It is the ability to tweak this exchange of gases (particularly the oxygen transfer rate, or OTR) that has made crown cap liners one of the most creative tools for chefs de caves in recent years. The crown cap also keeps the bidule, a small silicone pot that collects the sediment during riddling, in place.
After the second fermentation, a deposit of spent yeast cells, known as lees, is left behind. Clinically dead yeast cells are not lifeless. Rather, they undergo an activity known as autolysis, which involves an enzymatic breakdown that imparts much of the classic character considered integral to Champagne. This biochemical process begins two to four months after the second fermentation has finished, and its most active period usually ends after four or five years. There is very little autolytic contribution after 10 years, although enzymatic activity has been detected in yeast cells after as long as 80 years (this activity was so limited, however, that it would have had little effect on the character of the Champagne).
During autolysis, yeasts decompose proteins into simpler amino acids, which are also in the wine prior to autolysis. Amino acids are essential precursors to many of the aromas that typify fine-quality Champagne. In autolysis, because amino acids are both created and consumed, with levels of each rising or falling continuously, the potential aromas are equally in a state of flux. This is why the date of disgorgement can have a profound effect on how a Champagne’s aromatic profile will develop.
There is no such thing as an optimum duration for yeast aging, although there are optimum moments for disgorgements. Champagne can benefit from being disgorged at various intervals over its lifetime, but the first window of opportunity is the most critical one.
The first window of opportunity is relatively easy to spot for a chef de cave, who will taste the cuvée regularly and recognize when it shifts from an exclusively crisp mode to one that shows the first hint of creamy mellowness on the palate. The creamy-mellow note can be very subtle, and, after the Champagne has received dosage, the palate will revert to a crisp mode, requiring a couple of years of postdisgorgement aging before it will once again start to reveal a creamy mellowness on the palate. The two most common reasons why the first window might be missed are corporate decisions around a release date and chefs de caves focused on minimum yeast aging.
If the decision to disgorge is made purely for the benefit of the mousse, then 18 months on yeast is optimum, as this is the scientifically established peak for mousse retention, and it is when the bubbles are smallest. Many Champagnes need more time to show their full aromatic potential or develop a taste profile, while some may continue to improve for several decades. But most Champagnes (that is, entry-level nonvintage cuvées) have little to gain from longer than 18 months on yeast—other than the additional cost. And not all consumers want to drink the most complex Champagne, particularly at entry level. The taste preference of any Champagne’s most loyal and regular consumers may be the most important factor for a chef de cave to consider when deciding on disgorgement.
Although the influence of autolysis is relatively subtle, it is far more complex than the production and consumption of amino acids. Indeed, some researchers suggest that the role of amino acids has been overstated. When the cell breaks down, it releases many other compounds from inside the cells and cell walls. The same compound may also be present in the wine prior to autolysis, whether detectable or not, and can evoke different aromas, depending on the level found and the presence of other compounds. This can influence how each compound is perceived by enhancing or lowering—or even negating—its aroma, an effect known as positive synergism or antagonism.
Many windows of opportunity for disgorgement will result in very similar aromatic profiles, but some will be significantly better or worse than others.
When autolysis stops, further aging on lees will have very little effect on the complexity of a Champagne, which essentially will remain fresher than had it been disgorged at an earlier date and aged after disgorgement. But this freshness comes at a price. The longer a Champagne is kept on its lees, the more dependent it is on its almost completely anaerobic environment, and the more sensitive it will be to the oxidative shock of disgorgement. It is initially fresher but declines at a faster rate.
The environment is not completely anaerobic, however, because a tiny trickle of oxygen still flows through the temporary closure against the pressure (because it is CO2 pressure, not O2 pressure), enabling a glacially slow micro-oxygenation. When small lots of Champagne are cellared long term, they are usually stored sur pointe, stacked in an inverted vertical position, with the sediment in the bidule or at the base of the cork. When corks and agrafes are used for temporary closures, there is no means of securing a bidule, so the sediment builds up on the base of the cork, coating it with a sludge of dead yeast cells that act as an antioxidant barrier. This sweeps up O2 molecules at the only possible point of ingress, further reducing the already minuscule flow of oxygen, ensuring graceful maturation. The slower the oxidation, the more finesse and complexity achieved. The antioxidant effects of the sediment constrained in a bidule include consuming some of the incoming O2 molecules, but dead yeast cells do not completely cover the only point of ingress, thus cannot work as efficiently as the sediment that builds up on cork. This could be one reason for cork’s supposed superiority as a temporary closure.
Traditionally, déplacements—the stacking, unstacking, and restacking of bottles resting horizontally, or sur latte—take place throughout yeast aging, when bottles are transported from one stack to another, and deliberately shaken before building a new stack. This shaking redistributes the sediment to encourage autolysis and prevent the deposit from forming sticky layers, although this has been much less of a problem since the introduction of agglomerating yeasts and adjuvants. Most producers now stack bottles in pallets, which are quickly moved from place to place by forklifts.
At some point, it’s necessary to shift the bottles from storage sur latte to storage sur pointe, an essential prerequisite to disgorgement. To achieve this, the bottles undergo the process of remuage (literally, “stir”), also known as riddling.
Remuage was traditionally an eight-week manual operation that took place on pupitres (racks). But because of the relative ease with which the sediment slides down the bottle, thanks to the specialized second-fermentation yeasts and riddling agents available, the few producers who manually riddle bottles today can complete the process in just four to five weeks. Most Champagne producers have moved to gyropalettes, which work constantly and perform the same function, initially in just eight days and now in four to five. With the very recent developments involving the use of ultrasonic vibrations, however, the duration of riddling, once the most labor-intensive and drawn-out cellar operation in the entire méthode champenoise, can be reduced to one hour.
A literal translation of pupitre is “desk,” as in a school desk with a hinged lid, and it is specifically the hinged lid that Champagne’s pupitre alludes to. Traditionally, pupitres were made of wood, with concrete casted boards also quite common. The pupitre as it is known today was patented by Michelot in 1864 and consists of two hinged, heavy rectangular boards, each containing 60 holes that have been bored at an angle of 45 degrees. The angled cut of each hole allows a bottle to be held by the neck, starting almost horizontally and gradually going through any number of intermediate angles to a practically vertical, inverted position.
Moving from bottle to bottle, the remueur or manipulateur swiftly performs two operations on each bottle: oscillating it clockwise and counterclockwise, leaving each bottle a final turn to the left or right of maybe an eighth of a revolution (to ensure that the sediment settles on a different section of the bottle’s inner surface), and then nudging the bottle slightly upward. The oscillation slides the inner bottle surface under the sediment, momentarily detaching it, thus enabling the sediment to slide down the length of the bottle toward the closure when the remueur nudges the bottle upward.
Some remueurs perform the oscillation and tilting in two separate operations, while others combine the two in what is known as a coup de poignet, but they all glide over the contents of a pupitre with astounding accuracy in just a few seconds. After numerous nudges upward, the bottle will eventually reach an almost upright, inverted position, with the sediment neatly deposited in the bidule or at the base of the cork. This leaves the wine ready for disgorgement, although some Champagne is left sur pointe for many years.
With the advent of palletizing in the 1950s (reaching Champagne by the 1960s) and the use of forklifts to move the pallets around, the concept of riddling by the pallet load was not far behind. All that was required was a means to shake a pallet and gradually invert the bottles, guiding the deposit to the base of the cork or crown cap. The first manual device was presumed to be the Catalan girasol (sunflower), invented by Codorníu, in Sant Sadurní d’Anoia. Codorníu also invented the ticono, the supposed precursor to the actual girasol, which was itself believed to be the precursor to the gyropalette. Yet the gyropalette was first patented in 1968, and the true girasol was registered with the Registro de la Propiedad Industrial in 1974, while the ticono was registered in 1972. There is no proof that the Catalans actually did make a precursor to the gyropalette, although research in Codorníu’s archives remains active.
The mechanization of riddling was not a straightforward jump from the Catalan girasol to the gyropalette in the early 1970s. The first mechanical remuage device was patented by a German (Hassemer) in 1903 and 1905. Various French inventors came up with their own apparatuses, mostly crank or lever operated, while the first automated remuage device was invented by François Chiaverini (patented in 1931). None of these devices had much impact on the Champagne industry, as most producers continued to riddle the old-fashioned way with Michelot’s pupitres.
Indeed, until the arrival of computer-controlled gyropalettes, which eventually revolutionized riddling throughout the Champagne industry, the only device that made an impression was the Pupi-Matic. Of all the weird and wonderful riddling contraptions invented, this is the most interesting and longest lasting. The Pupi-Matic is an automated system introduced in 1966 and still used by some smaller producers. It can hold 240 bottles in vibrating cups, at angles of incline between 25 and 75 degrees. The odd machine has even been spotted in the cellars of some large houses, although they have long since moved on to gyropalettes. This is because the Pupi-Matic can do something the gyropalette can’t: riddle just a few bottles, making it ideal for riddling trial bottlings.
In the 1960s, the Champagne grower Claude Cazals (Le Mesnil-sur-Oger) and his friend Jacques Ducoin wanted to invent a riddling system that would turn as many bottles as they could possibly manage. In 1968, they patented a “gyro-palette”: a 504-bottle-capacity stackable cage that could be manipulated. In 1970, they patented and registered the gyropalette: an all-steel frame that could be loaded with a cage, manually manipulated, unloaded, and reloaded. The first prototype was produced in 1973, in partnership with Pierre Martin, a grower in Bouzy, and the enologist Georges Hardy.
The ultraconservative Champenois were slow to adopt the gyropalette. They had to be convinced to invest in expensive machinery to replicate an operation that was already being performed adequately by hand, and cellars had to be reconfigured to accommodate the equipment. Those who held out against this form of mechanization would often claim that the clarity achieved by gyropalettes was inferior to that managed by manual remuage. It is a misconception that still exists; there is plenty of hard science showing the contrary. Another hurdle to the acceptance of gyropalettes was the concern that it would result in redundancy for one of Champagne’s most skilled workers and raise the specter of trade union disputes.
Although the first order for the gyropalette came from Italy, the next came in 1978 from Piper-Heidsieck, followed by Taittinger and eventually Louis Roederer, giving others the confidence to follow as well. The widespread installation of the gyropalette was a well-kept secret into the late 1990s, as tours of Champagne houses using this technology would make elaborate detours to avoid the slightest glimpse of it.
After remuage, the bottles are ready for disgorging, although many might undergo further yeast aging sur pointe. The benefit of aging sur pointe is twofold: first, the wine’s flavor and bouquet can benefit from extended contact with the yeast; second, its overall longevity is improved. When a bottle is stored sur pointe, there is less capacity for the yeast cells to undergo autolysis compared with storage sur latte, but the process still acts as an antioxidant against the glacially slow ingress of oxygen, through either a cork or a bidule.
While some technologies have tried to compete with gyropalettes over the years, none have succeeded. Today, however, the low-cost ultrasonic technology is gaining a notable following. It was invented and patented not in France but in Italy, by a team of scientists at the University of Milan, and can riddle bottles in one to four hours. Ultrasonic riddling is still in the prototype stage. It will likely be much easier to introduce ultrasonic riddling to a gyropalette-dominated industry than it was to replace pupitres with mechanization. Many cellars are already configured to house and service this type of machinery, though this also indicates just how heavily producers have invested in gyropalettes, with some possessing several hundred. The inventors of ultrasonic riddling realized this dilemma and concurrently developed conversion kits that could be attached to existing gyropalettes, which, eventually, will be replaced by dedicated ultrasonic units.
Ultrasonic riddling relies on the piezoelectric effect, in which mechanical energy is converted into electrical energy. Piezoelectric transducers are coupled to the bottles and generate ultrasonic vibrations to speed up the rate at which the sediment slides down the glass. The frequency of the vibration can be adjusted by dial to move the oscillation through a range of 20 to 50 kilohertz, with 25 to 30 kilohertz and 35 to 45 kilohertz currently thought to be optimal. Different wines produced in different areas could be more responsive to different frequencies, so the producer must be able to fine-tune the oscillation for the wine.
With the bottle inverted and the sediment resting on the closure at the tip of the neck, the next step is disgorgement, which ensures a clear and bright wine. The most common method of disgorgement is known as dégorgement à la glace, a process that was invented in the late 19th century (by Armand Walfard, in 1884, and patented in 1892). It involves immersion of about four centimeters (1.5 inches) of the bottle’s neck in a shallow, freezing bath (between minus 25 degrees Celsius and minus 30 degrees Celsius, or minus 13 degrees Fahrenheit and minus 22 degrees Fahrenheit), which causes the deposit to become a semifrozen slush that adheres stubbornly to the base of a cork or bidule and the inner surface of the neck. The bottle can then be turned upright and placed on the disgorging line without disturbing the sediment. When the closure is removed, the semifrozen sediment is ejected by the pressure built up in the headspace. Very little wine is lost, as the wine’s pressure is reduced by its lowered temperature. The freezing bath formerly consisted of brine (salt water), but that caused corrosion of the bottling line equipment and, by transfer, corrosion of the wire cage and muselet. Producers now use propylene glycol, which is not corrosive and, as a legally permitted food additive, presents no health risk in the unlikely event of any cross contamination.
Champagne sealed with a cork and agrafe will be disgorged by hand in an operation known as à la volée, so-called because the noise it makes sounds like the discharge, or volley, of a rifle. If the dégorgeur is skillful, the technique can even be performed on bottles that have not been frozen, with very little loss of wine. Champagnes sealed with a crown cap are also occasionally disgorged à la volée, particularly for tasting purposes.
The addition of at least a modest dosage (six grams) is essential for the graceful maturation of most ageworthy Champagnes. The question of dosage has very little to do with sweetness itself and everything to do with balance. Brut nature should never be used as an excuse for an austere mouthfeel, nor should a gradual increase in perceptible sweetness in ascending order of residual sugar (RS) be anticipated.
Note that when sugar is indicated for Champagne, some of the grams of sugar indicated as the dosage can include RS, and some indicated as the RS can be from the dosage. To further confuse the issue, the regulations in Champagne permit a variation of three grams between the stated and actual RS to cover the margin of error in the different types of analysis performed, and producers indicating the dosage rather than the RS do not take account of the one to two grams of RS commonly left after the second fermentation. Consequently, a Champagne claiming 6 grams could contain more sugar than another claiming 10 grams, or anything in between.
The dosage is added via the liqueur d’expédition. The most important ingredients of the liqueur d’expédition are sugar (unless it is for a brut nature), base wine, and SO2. This liqueur might be developed months in advance because of its dense concentration of sugar (600 grams per liter), and it will eventually be microfiltered. In most cases, the composition of the base wine used for this liqueur will be neutral, deliberately designed to blend in with as little effect on the aroma or flavor of a cuvée as possible.
The liqueur d’expédition is the final opportunity to make any corrections to the wine—for example, if the wine has developed unexpectedly, or if the wine is being released earlier or later than originally intended. The liqueur d’expédition can also be used to reinforce the house style and to ensure longevity (through the use of SO2). The list of permitted ingredients is far more limited in Champagne than elsewhere.
Although acetaldehyde is the principal aldehyde in any wine, only a tiny amount is present in all but a few, mostly fortified, wines. While a soupçon of acetaldehyde can contribute background complexity to many wines, detectable amounts are a fault (except in wines that utilize flor, where the layer of yeast oxidizes ethanol).
In nonfortified wines of any longevity, acetaldehyde is the key aromatic compound of premature oxidation (premox). It strips away the expected fruit and freshness to reveal the harsh, bare bones of a wine. The definition of longevity is not how old a wine tastes but how young. The greatness of that longevity is determined by how much fruit and freshness has been retained.
Some people can detect acetaldehyde at concentrations of 70 milligrams per liter, but the general threshold of perception is 100 to 125 milligrams per liter. This is the level at which acetaldehyde usually starts to develop its characteristic nutty, bruised-apple aromas. On average, Champagne is said to have 50 to 100 milligrams per liter of acetaldehyde, whereas flor styles of Sherry can have 500 to 1,000 milligrams per liter. These are all free acetaldehyde levels. Acetaldehyde bound to SO2 is not aromatically detectable, and total (free and bound) acetaldehyde is never measured.
Every responsible winemaker tries to minimize the amount of sulfur added, and even the Champagnes with the highest amounts of sulfur are among the wines with the lowest. Champagne is one of the few wines for which it is normal practice to open a bottle immediately before shipping and expose it to air. Despite the many precautions taken to limit the ingress of air into the bottle during disgorgement and corking, it is impossible to prevent some additional oxygen (such as that dissolved in the dosage wine itself) from entering at this extremely critical stage of the wine’s life. That is why it is essential for the liqueur d’expédition to include SO2, especially for producers operating low-sulfur regimes. There are ways of lowering SO2 levels, but they require adjustments at every phase of the winemaking operation, from grape to bottle, with the focus on reducing SO2 at the earliest juncture, not the final stage. If Champagne is to retain its freshness as long as possible, there is no alternative to SO2.
There is a general misconception that SO2 protects against oxidation, but only a fraction of the SO2 added will interact directly with O2 molecules. The problem is that the speed at which sulfur reacts is glacially slow compared with that of oxygen. Its main role is to bind with the aftermath of oxygen’s presence: acetaldehyde. Consequently, SO2 does not stop oxidation; rather, it neutralizes its key aromatic compound by binding with it. Thus, the SO2 found in wine consists of free and (mostly) bound SO2. When SO2 is added, it is initially free SO2, but much of it quickly binds with sugars, pigments, and other compounds to become bound SO2. It is often said that, once bound, SO2 is no longer available to protect a wine against oxidation, but this is not entirely accurate. The only compound to which SO2 is tightly bound is aldehyde (primarily acetaldehyde itself), whereas among the unstable compounds loosely bound to SO2, the most important is sugar. When only loosely bound, SO2 can be freed to bind acetaldehyde, so only Champagnes with a dosage possess an additional line of defense against oxidation.
Champagne producers who do not use jetting (described below) must allow for an ingress of 2.7 milligrams per liter of oxygen during disgorgement and corking. The theoretical minimum of SO2 required to neutralize that amount of O2 would be 10.8 milligrams per liter, but that would be nowhere near sufficient. The winemaker must overcompensate, because SO2 is slow and inefficient (even more so in a brut nature sparkling wine) and will be diverted elsewhere to bind with other compounds. The dose should be calculated to leave at least five milligrams per liter of free SO2 after 12 months. Much depends on the chemistry of the Champagne in question, but, as a very rough rule of thumb, a minimum dose of SO2 for producers who use jetting is around 15 milligrams per liter; for those who do not, it is 25 milligrams per liter. Again, this is the dose added at disgorgement—not free or total.
When bottles are corked, despite whatever precautions have been taken to reduce potential oxidation (such as jetting and using Mytik Diam corks), the Champagne has already been exposed to the air—it has received dissolved oxygen from both the dosage base wine and the top-up wine. The Champagne will receive more oxygen during oxygen initial release, when air is forced out of the cork as it is squeezed into the bottle. Consequently, producers generally add SO2 at this stage.
The Champenois had long recognized the potential effects of oxidation resulting from exposing Champagne to air during the disgorgement process, but they did not know the precise volume of oxygen ingress until a groundbreaking paper was published by the CIVC in 2003. The research showed that the problem was not only oxidation from the volume of oxygen that enters a Champagne at each step (disgorgement, dosage, topping up, and corking) but also the extreme difference in oxygen entering each bottle (between 1.8 and 2.7 milligrams per liter), which is responsible for unacceptable bottle variation in the finished product.
As soon as the CIVC study revealed how large and varied the oxygen uptake was, it became imperative to devise an appropriate defense. The obvious answer was jetting, which had been used in the brewing industry since the 1960s.
In the process of jetting, a precise amount of sulfited water is injected into the wine, exciting the CO2 on the wine’s surface. The bubbles rise, pushing oxygen out of the bottle, and then the cork is inserted, compressing the CO2.
In theory, jetting should be able to eliminate all externally sourced oxygen, but in practice it is reduced to less than 0.5 milligrams per liter. Further, the equipment is usually calibrated to 80% to 90% efficiency to prevent overfoaming (which causes fallback, sucking air into the bottle, exacerbating rather than eliminating the problem). Most chefs de caves are enthusiastic about jetting, but a small number say that it leaves the Champagne too closed for their style. All jetting equipment, however, can be calibrated on site. Thus, instead of setting it to 0.5 milligrams per liter of oxygen, it could be fine-tuned to provide a consistent degree of openness.
For any type of wine, a cork must be compressed from all sides to fit inside the neck of a bottle, and it is the natural elasticity of cork trying to resume its normal size that forces it to press evenly against the inner surface of the neck, creating its hermetic seal. In a still wine, this pressure against the inside of the neck will be sufficient to keep the wine from being exposed to the air outside. For Champagne, however, there is also pressure from underneath the cork, trying to push it out. At six atmospheres, the equivalent pressure of a double-decker bus tire, this is a significant amount of pressure, which is why one-third of the cork is left exposed, outside the bottle. When the metal capsule, called a plaque, is pushed onto the top of the protruding portion, it molds the cork into its iconic mushroom shape. The plaque is necessary to protect the cork from the wire cage (muselet or, in full, muselet de fil de fer) that is used to secure the cork against the internal pressure of the bottle.
What is perceived today as the classic Champagne cork consists of an agglomerate body faced with one, two, or (occasionally) three pure cork disks (also known as mirrors or rondelles). Champagne corks used to be solid cork, but as the general demand for cork rose during the 19th century, the interval between cork harvests dropped to increase supply, which led to a reduction in the thickness and quality of the cork bark stripped. Since the bark required for a Champagne cork (31 millimeters, or 1.2 inches) must be 30% thicker than that used for a still wine cork (24 millimeters, or 0.95 inches), the thicker, higher-quality cork bark required by Champagne became too rare and costly to sustain the entire industry.
The initial alternative was made by gluing halves together vertically, then cutting the corks shorter and adding disks made from remnants that would not normally be of any use. It was at this time that such disks first appeared, on the end of solid corks, not agglomerates. Interestingly, and rarely discussed, this was the only time when the disks were cut correctly (parallel to the bark, not at a right angle). Eventually, thick cork bark became so scarce that the main body was replaced by agglomerate cork, a product that had been available for other uses since the end of the 19th century. For economy, the disks were stamped perpendicular to the bark—rendering this closure fatally flawed. The shaft of a regular cork is cut parallel to the bark to ensure the lenticels (raised pores in woody plants that allow for gas exchange) are kept horizontal to the width of the cork, not its length. The purpose of lenticular channels is to permit both an ingress of O2 through the cork bark to the tree’s interior and an egress of CO2. With lenticels horizontal to the width, a regular still-wine cork is almost completely impermeable. Yet in sparkling-wine disks, the lenticular airways form a network running from one end of a cork to the other, almost guaranteeing its permeability.
The more obvious and prolific the lenticels, the shorter the life of the disk. The wetter and more pinched the disk, or disks, of a classic agglomerate cork becomes, the less effective the cork is as a closure. Over time, the wine may come into direct contact with the agglomerate, and the danger of loss in pressure, oxygen ingress, and TCA increases.
Strictly speaking, any cork that is not a single piece of natural cork might be classified as a technical cork. But since oxygen ingress for an agglomerate cork can vary by as much as 300-fold (3,000%), the agglomerate cork’s efficiency does not differ significantly from that of the cork closures used by the ancient Romans and Egyptians. A more appropriate definition of a technical cork is that, at the very minimum, it ensures a consistent and effective level of oxygen ingress.
Among the dozens of technical corks, Mytik Diam is the gold standard in Champagne. It is made from microagglomerated cork that has been subjected to a supercritical CO2 extraction process to guarantee that it is TCA free, with uniform CO2 retention and oxygen ingress. There are two basic, commercial Mytik Diam formats, each visibly recognizable by its size of granule: Mytik Diam 5 (formerly Classic), which has the tiniest granules and offers the lowest oxygen ingress; and Mytik Diam 3 (formerly Access), with slightly coarser granules (although much finer than those found in classic agglomerate closures) for a more open permeability. The numbers in the closures’ names refer to Diam’s aging guarantee. The size of the granules alone is not the determining factor for oxygen ingress, as microspheres possess great elasticity and are impervious to oxygen. The ratio of microspheres to cork affects oxygen ingress, as does the proportion of food-grade glue. By tweaking all these elements, DIAM can create bespoke Mytik closures to suit the specific requirements of any producer. Note that MDC and MDA are sometimes printed on these closures to denote Mytik Diam Classic and Mytik Diam Access, respectively.
There is also a newer closure in the Mytik range, Mytik Diam 10, released in 2022. Diam claims this cork has improved oxygen management and mechanical performance, and aging is guaranteed for 10 years.
Postdisgorgement aging covers the period between the insertion of the final cork and the moment when the wine is consumed. How Champagne evolves after disgorgement is very different from the process before disgorgement. Prior to disgorgement, the aging process is primarily about retaining freshness, with any mellowing effect playing a relatively minor role. After disgorgement, it is the opposite, with mellowing being of primary importance and any retention of freshness playing the minor role. Micro-oxygenation mellows reductive aromas in postdisgorgement aging long before it begins what is, ideally, a long and smooth oxidation of the wine.
Virtually all postdisgorgement aromas are sulfidic, but some sulfidic aromas are more obvious and typically less enjoyable than others. If the sulfur regime is a healthy one, and every aspect of the winemaking has been finely tuned, it is possible to achieve a Champagne with sulfidic aromas that are subthreshold and take many years to evolve. Not all sulfidic aromas come from added SO2. Some can be by-products of the second-fermentation yeast. A combination of yeast- and dosage-derived sulfidic aromas can be extreme, going well beyond the burnt match aroma of molecular sulfur, to gunpowder or fireworks. SO2 has a flavor, and most commonly that flavor is loosely described as gunpowder. Sometimes the SO2 aromas and flavors are so strong that they obscure the house style, yet at other times they can be of such a distinctive character that they easily evoke the name of the producer (probably a result of the use of an equally distinctive in-house second-fermentation yeast culture).
True toasty aromas are soft and mellow and take time to evolve. Typical gunpowder aromas are far more immediate and aggressive. Gunpowder can be the precursor to a certain type of toasty aroma, but it has a hard edge and takes just two or three years to emerge, compared with a decade or more for much softer notes of true post-disgorgement toastiness. The more gunpowdery a Champagne is, the further from optimum drinking it will be, whereas the more toasty aromas a Champagne has, the more ready it is to drink.
To produce a Champagne that respects the reductive style yet avoids sulfidic aromas is no easy task. When deciding whether to use SO2 after disgorgement, the producer must choose between ending up with no protection at all and achieving adequate protection. In terms of the appropriate amount of SO2 to use, there is a very fine line between achieving adequate protection and shutting the wine down. If SO2 is rightly used, however, the pure, pristine style of Champagne that can be achieved will be neither reductive nor oxidative. Such Champagnes provide an ideal medium for the subtle nuances of autolysis to shine through and can achieve the holy grail of longevity, drinking well in their youth, middle age, and old age.
It takes 3 to 6 months for the dosage to settle and a further 12 months for the degree of softness in the mouthfeel to return to the pre-dosage level. Postdisgorgement development typically begins after this period, initially as a creamy-floral influence on the nose before yeast-complexed fruit becomes apparent on the palate. It will take at least another three years before any hints of real toastiness begin to build, although gunpowdery toastiness can be present from day one.
Also important are Maillard reactions, which take place between amino acids created during autolysis and fructose from the dosage (thus not possible in brut nature styles unless the Champagne has sufficient residual sugar from the second fermentation). These biochemical interactions are responsible for many of the mellow, complex postdisgorgement aromas that appeal to drinkers of mature Champagne. At low concentrations, they add to the complexity of Champagne, but some reactions can introduce browning, oxidation, and oxidation-like aromas. These effects, however, should not detract from the overall importance of Maillard reactions; comparatively, autolysis is associated with many more negative effects, and that process is generally accepted as positive.
Read the Champagne Part I: Introduction expert guide.
Read the Champagne Part III: History expert guide.
Some material in this guide was previously published in The World of Fine Wine.
Compiled by Tom Stevenson (2023)
Edited by Stacy Ladenburger and Sandra Ban