2.10 Making Sparkling Wine (Methode Champenoise)

Over the past few decades the production of Sparkling Wine in Australia has made a quantum leap, and to be fair, much of the increased quality is because of the presence of French know-how.
The most prestigious and expensive technique for Sparkling wine production by which any serious Australian sparkling wine is made has  become known as 'Methode Champenoise' (fermentation in the bottle). While the technique of Methode Champenoise is arguably still being refined, the fundamental principles behind bottle fermented sparkling wine were born at the end of the seventeenth century in slightly mysterious circumstances in the depths of the cellars of a Benedictine Abbey, Hautvillers in Epernay.

Monasteries were of course places of prayer, but they were also centres of learning and of wealth, designed to retain light in a world made gloomy by misfortune and misery. Those who entered, far from being excluded from the world, were often involved with cutting edge research while living within a society ordered by piety and ruled over by a patriarchal power. The ingenious monk or monks to whom the credit for the first sparkling wine production is traditionally given must have known how to handle the unpredictable grapes that grow on the slopes of Epernay and Reims in northern France. The autumn weather is very variable in the Champagne region, and the grapes were harvested just as they began to mature, probably in the cool of the morning. The resulting wines were light and slightly sparkling. It was as if the wine had retained some of the greenness and freshness of the grape juice and was continuing with the alchemy of the maturing process in the bottle. This natural fizziness, whilst unusual, did occur in several other regions of France, but the inhabitants of Champagne must have been particularly taken with it. The extremely skillful winemakers of the monastic communities in the Valley of the Marne, where both pleasure and wine had a well-defined place, managed to tame this wonder of nature and succeeded, before others it would seem, in creating a bottle of lightly foaming wine; and this was the birth of champagne. It had a long way to grow up.

The Legacy of Early Sparkling Wines in Australia. On Guy Fawkes Day, 1956, a wine was launched that was to forge a place in Australia's social history. The highly innovative wine company, Orlando, had been working on a sparkling wine of mass appeal produced by the "Charmat process", so named after its inventor. In this process, the still wine is run into a sealed tank, given its dose of yeasts and yeast food, and when fermentation is partly complete, the wine is run into strong bottles under pressure. (The so called pearl wines, a German creation, are made on similar lines). Colin Gramp, of the founding family, sought expert help and secured the services of Guenter Prass, who became renowned, both as winemaker and Managing Director of Orlando. He also maintained the earliest tradition, migrating from Germany and bringing with him a wine background and extensive experience with innovative new wine making equipment. After various samples had been tested "Barossa Pearl", (a now  forgotten Australian legend) was released on November 5, 1956. What very soon became apparent was that many people who had never thought of themselves as sparkling wine drinkers, or any kind of wine drinkers for that matter, were ready for Barossa Pearl and its subsequent cousins, 'Pink Barossa Pearl' and 'Sparkling Star Wine'. Barossa Pearl first sold in the millions and then in the tens of millions until finally being superseded by changes in public tastes that the product itself had generated. The great legacy of Barossa Pearl to the Australian wine industry, was that it introduced a hitherto untapped mass market to the pleasures of civilised wine drinking, at the same time cultivating a new wine and food culture. The Pearl wines as a group were the precursors of other budget priced sparklings in this country. Today, these mass produced wines are made by quickstep methods, apart from the Charmat process,  including the 'transfer system' or simply via carbonation. These techniques are discernable in their end products with the wines usually possessing larger, less long lasting bead (bubbles) than Méthode Champenoise wines, and lack complexity and the flavours of yeast autolysis that can only be achieved via the more costly and lengthy process. In the Transfer System, (invented in Germany), wine is fermented in a bottle, then emptied into a tank under pressure and run through a filter to remove the yeast lees. (This filtering process replaces the time consuming and expensive rémuage, riddling and dégorgement steps of Methode Champenoise production). Finally, a dosage is added and the wine is re-bottled, still under pressure and shipped off to market.   Carbonation is the least sophisticated technique. There is no secondary fermentation; carbon dioxide gas is injected into the wine in a pressure tank. The wine is sweetened and mixed and is usually produced from machine harvested, 'lesser' sparkling wine varieties or even from the juice of black grape varieties. Historically, Seppelt produced a very respectable sparkling wine from Ondenc, whilst Sultana was the basis of many early bulk bubblies. There were and still are other varieties used in Australian Sparkling wine, such as  Muscat Gordo Blanco, Riesling, Chenin blanc, Semillon, Colombard, Trebbiano & Muscadelle. But wines approximating to anything near Champagne  in style and quality only started to appear in Australia when Pinot Noir, Chardonnay and Pinot Meunier - the traditional grape varieties of Champagne, France were adopted as the staple sparkling wine varieties. Why are drinks like Sparkling wine far more appealing than the same liquid once it has gone flat? Bubbles are generally created from C02, (though presurised air also lends some non-commercial spring waters a certain liveliness).  Carbon dioxide dissolves readily at atmospheric pressure, but  high pressure allows more to be dissolved. lt forms carbonic acid in the drink and it is this which gives drinks like sparkling wine or soft drink their appealing "fizzy" taste, rather than the bubbles, as many people believe (although bubbles contribute to mouth feel). Dissolved CO2 actually has a distinct taste of its own, which is slightly sharp.  When the drink goes flat, most of the dissolved CO2, has been released back into the atmosphere, so the amount of carbonic acid is also reduced. Flat beverages have lost this 'bite' without which they tend to taste insipid and overly sweet.

The names of Dom Pierre Perignon and then Fere Jean Oudart have been recorded by history, however these Benedictine monks were probably not alone, and the credit should quite possibly be shared amongst others, but very little information about their lives and their art penetrated the walls of the monastery's cellars. It is believed that Perignon had the idea to harvest selectively, over a period of days rather than all at once, so that only the ripest fruit was taken with each pass. He is also generally credited with inventing the Coquard or "basket" wine press and using it to make the first"Blanc de Noir".Another of his major developments was to blend wines of different vineyards and varieties to achieve better balance between their individual characteristics. He was an excellent taster and his cuvee system is still followed closely to this day by the house of Moet & Chandon to produce their finest Champagne. Although corks had already been used by the Romans as closures for wine bottles, and the seagoing and trading English had corks, and made sparkling wine several decades earlier than in the landlocked Champagne area. It is Dom Perignon who has been credited with the idea of using string to secure these stoppers in the bottles, thus retaining the sparkle for long periods of time.

Whatever the case, these contemplative wine-makers were no doubt as attached to their ideas as they were appreciative of fine wine, and one can imagine them taking the best part of their accumulated knowledge with them to the grave. Their burial by their brothers - by the rules of the monastery - would certainly have been a very quiet occasion, and a particularly sad one on account of such a loss; although the severity of the mourning may have been somewhat relieved by the cellar's reserves of sparkling wine.

Above: Detail of "Le Dejeuner d'Huitres"(Luncheon with Oysters) by Jean Francois de Troy (1735),  the very first known painting of sparkling Champagne. You can see bottles in the ice chest while the diners sip champagne. (Musee Conde in Chantilly)

Methode Champenoise Today

Despite our limited knowledge of this golden monastic period, we do know that the famous 'secret' consisted partly of extremely skillful blending of wines that could vary if the vines were only a stone's throw apart and, partly too, of endless complicated rotations and manipulations of the wine after it had been bottled.
Today, centuries of experience have enabled us to refine the art of bottle-fermented sparkling winemaking to the system known as Methode Champenoise. This system, however, is not a rigid one. Certain steps are prescribed by law in France, while few are required in the New World and there is considerable variation in production philosophy and technique. What is immediately consistent and clear, as we have all learnt to our joy, is that wine produced by Methode Champenoise, as opposed to other sparkling wine production techniques, invariably results in a superior drink. But it is a very difficult wine to make - costly, time consuming, protracted and potentially beset by trouble, as this detailed account of the art of Methode Champenoise illustrates. Compounding the difficulties are a vast array of stylistic decisions, including viticultural practices, cultivars, pressing vs. crushing, types of press and press pressures, phenol levels, use of SO2and the oxidative condition of the base wine, yeast for primary and secondary fermentation, barrel fermentation and aging, fermentation temperatures, lees contact, blending and the nature of the dosage. The following attempts to account for these in as concise a manner as is possible. But before we proceed, it will be helpful to become familiarised with some terms commonly used in Methode Champenoise production:

Terminology used in Methode Champenoise production.

 
Note: For readers looking for a more light-hearted introduction to this wonderful drink,
there is an entertaining introductory article on this site - "Champagne - The Inside Story."

1. Viticultural Considerations

The array of viticultural & environmental parameters affecting methode champenoise palatability are broad and include mesoclimate (site climate), canopy climate, soil moisture, temperature, berry size, rootstock, asynchronous development, fruit maturity and leaf area/fruit weight or fruit weight/pruning weight.

Among the viticultural options affecting grape components either directly or indirectly, mesoclimate is probably one of the most important.  It is generally accepted that a cool climate which allows the fruit to stay on the vine longer while retaining desirable acidities is important in the production of base wine which will develop the needed complexity during sparkling wine maturation. If the field temperatures and heat summation units were the sole parameters affecting the grapevine climate, then we need only consider the macroclimate in analysing the temperature effects on quality. The real situation, of course, is not that simple. Solar radiation, wind velocity, and to a lesser extent, sky temperature can give ranges of berry temperatures of more than 15°C above to 3°C below the air temperature (Kliewer and Lider, 1968).These variables are further influenced by row orientation, training system, trellis height and vine vigour. In warm regions, great care must be given to harvesting early enough to retain desirable acidities and pH values. A primary challenge in warm climates is the production of a base wine that is not too heavy in body or varietal character, too alcoholic, or too coloured. Warm climate wines, by and large, offer more definitive fruit flavours, less complexity and lower acidity than cooler climates, and they tend to develop more quickly.

Grape Varieties

Once the mesoclimate has been established, it is necessary to identify grape varieties which will be best suited to it. Some of the many cultivars utilized in various growing regions for methode champenoise are listed inTable 1below, however Chardonnay, Pinot noir, Pinot Meunier, and Pinot Blanc are among the more popular varieties and almost exclusively used in the Champagne region. 

Chardonnay gives life, acid, freshness and aging potential to methode champenoise, though care must be taken to avoid excess maturity, particularly in warmer climates, which produces a dominant, aggressively varietal character. Warm climate Chardonnay cuvees may suffer from a narrow flavour profile, high "melony" aroma notes and lack of freshness, liveliness and length. Additionally, rich fertile soils can cause this variety to produce foliage and grassy aromas. When combined with Pinot Meunier, Chardonnay has a greater capacity to age harmoniously and for a longer time (Hardy, 1989).
Pinot Noir adds depth, complexity, backbone, strength, and fullness(what the French call "carpentry") to methode champenoise wines but is seldom used by itself, even in Blanc de Noirs. Uneven ripening in Pinot Noir is often a problem for producers trying to minimize excessive colour extraction.

There are two philosophies about sourcing grapes for methode champenoise production. The first is to obtain grapes from a single vineyard (monopole). The second is to obtain grapes from as many vineyards as possible in order to maximise complexity of the base wines. Remy Australie employs the first method with its Blue Pyrenees methode champenoise by using the grapes from up to 50 different blocks it has within its own vineyard area. Domaine Chandon, on the other hand, goes out of its way to source grapes from literally every cool wine growing region in Australia, including Margaret River, the Yarra Valley and Tasmania.

2. Harvesting

Methode champenoise producers harvest based upon the flavour and aroma of the juice, as well as analysis of °Brix (approximate concentration of grape sugars), acid and pH, according to the desired style. Producers are generally striving for base wines that are clean, delicate, not varietally assertive, yet not dull or lifeless either. Immature fruit produces wines that are green or grassy while overly ripe fruit can produce a base wine that is excsertive. Early harvest in warmer climates helps minimize excessive varietal character which can be overpowering.

Most producers carefully hand-harvest into small containers to avoid berry breakage and then bring the fruit in from the fields quickly. Grapes must be harvested as cool as possible with the least possible skin contact, particularly with red varieties used for Blanc de Noirs. Reduced skin contact produces a more elegant, less varietally dominant base wine, whereas skin contact releases more aromas, but may also extract coarser components. Proximity to the processing facility is therefore important. Conveyors and delivery systems that may break the berries prior to either pressing and draining, and prolonged transport of warm, machine-harvested fruit is undesirable for methode champenoise production. Oxidation at this stage would reduce desirable aroma / flavour profiles and provide excessive phenols which may cause bitterness and reduced aging capacity.

3. Pressage

For premium methode champenoise, the grapes are usually pressed rather than crushed and pressed. No separation of the stems need occur before pressing. The stems insure efficient and improved draining and pressing of the whole grapes at lower pressures. Ultimately, this aids in obtaining a higher quality, more delicate first-cut press juice. Pressing of the fruit is carried out in three stages, owing to the way in which the sugars and acids are positioned in the grape. The juice flowing out of the berry comes from the juice of the pulp during the early stages of pressing and is usually better suited for méthode champenoise. Figure 1 [right] illustrates the three juice zones in the grape berry: the juice of the pulp (Zone 1), the juice of the pulp area around the seeds (Zone 2), and the juice from just beneath the skins (Zone 3).  The point of rupture is usually opposite the pedicel. The intermediate zone (2) which contains the most fragile cells, is first extracted before the central zone (1) and finally the peripheral zone (3)(Dunsford and Sneyd, 1989). The  concentration of tartaric acid is highest in zone 1 and lowest in zone 3 and hence should be extracted initially. Malic acid concentration decreases from the centre (zone 2) to the skin, and so is also extracted fairly quickly. By contrast, the concentration of potassium, the dominant cation, is highest in zone 3, which is extracted last. A juice extracted from the first two zones will, therefore, have the highest acidity, lowest potassium, lowest pH and the lowest susceptibility to oxidation which will result in a wine of greater freshness.  The goal is usually to preserve the integrity of the berry so that the components of the different zones are not mixed. 

Flavonoids such as catechins are extracted from the skins with increased press pressure and may vary with the type of press employed. Catechins account for most of the flavour in white wines with limited skin contact. Moderate pressures or combining portions of later press fractions are methods of stylistic input that can affect such things as the tactile base of the aroma/flavour character of the cuvee.  The champagne basket press of cocquard [left] is still used by some houses in Europe. This device is unique in that it has a very shallow  press basket, rarely over two feet deep, with a diameter of 10 feet. The shallowness of the base relative to its width allows for grapes to be spread out in a fairly thin layer which reduces skin contact with the juice as it flows through the pressed mass of grapes. Thus, less press pressure is required. Unlike the basket press, newer tank presses are pneumatic, give complete control, higher yields, produce less non soluble solids, low phenols, and require much lower press pressures(Downs, 1983). Low pressure minimizes the chance of macerating the stems and releasing bitter compounds into the juice. Gentle pressing of cool fruit extracts fewer flavonoid phenols. These compounds are responsible for astringency, bitterness and colour. The juice near the skins and seeds, released by heavier press pressures, has more intense aroma / flavours and more flavonoid phenols. A tank press can press to dryness at two atmospheres or less and take cuts.

The juice obtained from the different stages of the pressing cycle is drawn and stored in separate vessels. All or portions of the second press fractions may be blended with the primary fraction due to sensory and economic necessity, but the third fraction is seldom employed in premium methode champenoise production. Most producers are looking for delicacy, which is associated with the initial juice extracted.

Sulphur dioxide is added to the juice expelled from the press but never directly into the press in order to avoid extraction of phenols. The press juice fractions are often clarified then cold-settled The resultant wines are called "base wines". The winemaker thus ends up with at least three base wines from each pressing operation. The different pressings from the different grape varieties and from each vineyard are usually stored and fermented separately. Makers of sparkling wine then have many different wines in their cellars at the end of vintage, increasing their options in the blending process that follows. 

4. Primary Fermentation of the base wines

The base wines may be made in different ways. For example, some producers choose to ferment their cuvees warm (18-21°C) to reduce the floral intensity, thus making a more austere product. Elevated fermentation temperatures are desirable if a malolactic fermentation is sought to decrease perceived acidity. The yeast employed is occasionally the same for the primary and secondary fermentation. Sparkling wine yeasts are selected for their ability, among other things, to produce esters. Those yeasts often used for primary fermentation include Montrachet UCD 522, Pasteur Champagne UCD 595, and California Champagne UCD 505, among others. However, using the same yeasts for both fermentations can result in an end product that is too floral and too high in volatile components.  

The primary fermentation is generally conducted in stainless l, however, European houses use small wooden casks and barrels to ferment all or part of the cuvee. Barrel fermentation results in added structure, often without significant harshness or astringency. But those who suggest that greater finesse and elegance results from wood are countered by the majority who fear the wine will pick up excess tannin and colour. The famous Champagne house "Krug", ferment their entire vintage slowly at low temperatures in oak vats, believing this to add more bouquet. This is consistent with their desired style, which is full flavoured, mature tasting and amongst the most complex of all Champagnes.

5. Assemblage

Because it is rare that a single wine of a single vintage from a single vineyard will be perfectly balanced in composition and flavour for a premium sparkling wine, blending is often performed from as many as 30-40+ base wines. The selection of the final cuvee components is conducted with three main objectives in view:

It is a very interesting exercise to taste the fermented base wines as they come in, with some of the very cool vineyard areas producing base wines of exceptionally high acidity, and others of wonderful fruit.  The first decision to make is whether the new wines are of sufficient palatability to produce methode champenoise. A desired cuvee is one with body, length, substance and structure with no single varietal character dominating. Chardonnay alone, for example, can be highly perfumey and somewhat candy-like, with intense richness.  Pinot noir often produces a light, earthy, strawberry aroma. Our European colleagues use the analogy: "the Pinot Noir is the frame; the Chardonnay, the picture; and the Pinot Meunier, the dressing for Champagne."
Some prescribed chemical attributes of the cuvee usually include alcohol (between about 10.5%-11.5%), high acid, low pH (less than 3.3), low flavonoid phenol content, low aldehydes, low metal content, low volatile acidity and little colour. Ultimately, however, it is the gifts and talents of the wine maker that will determine a blend in order to create a wine with both finesse and complexity. Indeed, blending was, and still is, considered by most to be the key to the art of great methode champenoise. The supreme challenge for the winemaker is that he or she must blend the wines when they have the better part of their lives yet to come. This requires considerable insight. One can appreciate the difficulty of predicting the final results of blends that will be consumed years later.

6. Reserve Wine

Because the Champagne region's cold climate ripens grapes fully only about once every three years, the solution was to create a non-vintage style that overcomes vintage variability. New World sparkling wine producers have followed suit, sometimes blending hundreds of base wines drawn from subregional vineyard sites and many vintages into a standard, non-vintage wine. The idea is to create a consistent "house style" (light, medium or full bodied) that smells, tastes and feels like the previous year's release.  Reserve wines are key to maintaining consistency in non vintage Champagne, and also in making the wine easier to drink at an early stage.  Generally, at least one eighth of  new wine is put into reserve for this purpose in Champagne. Reserve wine is stored in magnums (as is the case with Bollinger) or in bulk, sometimes under an inert gas environment.  A typical non-vintage Champagne is produced largely from wine of the current vintage augmented by reserve wine. Reserve wine can be added during assemblage or blending and may be a component of the dosage. Such practices are based upon production and vintage dating considerations.

7. Cuvee Filtration

Immediately prior to bottling, many producers filter their cuvees. This occurs, of course, before yeasting. The purpose of such an operation is twofold: to help prevent malolactic fermentation and to begin the secondary fermentation with "clean" wine. Some, such as Krug, do not filter at all, but simply clarify once with isinglass(Duijker, 1980).  Those concerned with the possibility of a malolactic fermentation in the bottle generally sterile filter their cuvees.

8. Yeasts & Preparing for the Secondary Fermentation

After the composition of the cuvee is decided, the selected wines are mixed with an amount of yeast, sugar  and other additives such as riddling aids (see below), and then transferred to the bottles in which the secondary fermentation will take place and in which the wine will be sold.

Yeasts
Because the demands on the yeast are very specific, the vintner must be specific in yeast selection. For  example, Chardonnay is sometimes difficult to ferment to dryness; therefore, a strong fermenter may be desirable. Some yeasts are very delicate, others assertive or defined, with regard to the character they impart to the sparkling wine. This is another stylistic consideration.  Sparkling wine yeasts are available on slants, in liquid, and in active dry forms. Many sparkling-wine makers also employ their own proprietary yeast strains. Some sparkling wine producers use mixed cultures for the secondary fermentation believing that such a procedure adds complexity. 

A common preparation method is as follows:(Bannister, 1983) 500 millilitres of a solution of sterile wine (the cuvee to be fermented) and sterile water are diluted to 7% alcohol. To this, 5% sugar and 12 grams of yeast extract are added. This media is inoculated from a slant yeast culture using strict aseptic techniques and incubated at approximately 80°F. When the sugar is half utilized, the culture is transferred directly into 1.5 litres of undiluted wine to which 5% sugar has been added. This is repeated using a 10% inoculum into a new-wine volume that has 5% sugar added. Transfers are made at 2.5% sugar. This is repeated again until a 5% inoculum volume has been produced (5% of the cuvee volume that is to be fermented). Care be taken not to allow the culture to go to dryness prior to transfer because the alcohol level will increase and begin to inhibit the yeast. When all the sugar has been depleted in the media, the yeasts rapidly begin the death phase. Transferring the growing culture at 2.5% sugar will acclimate the yeast to be able to grow in a 2.5% sugared cuvee. Additionally, during the transfers it is desirable to go from inoculation temperature to the temperature at which the cuvee wie fermented.  To insure secondary bottle fermentation, a minimum of 1 million cells per millilitre should be added to each bottle (Geoffroy and Perin, 1965). 
If equipment is limited, the use of active dried yeast may be considered easier. It is preferable to feed and grow several generations of active dried yeast prior to the addition into the cuvee. This allows the producer to train the yeast to go in the cuvee as well as monitor yeast viability and possible contamination. An increase in the number of yeast cells in the cuvee may give a fuller character and flavour to the sparkling wine(Berti, 19 Care must be  used, however, to avoid rapid secondary fermentation and the development of hydrogen sulphide and other off odours. (For additional information regarding yeast culture preparation, see Fuglesang, 1997.)

To sum up then, for the secondary fermentation (prise de mousse), a yeast with the following attributes is desirable: pressure tolerance, alcohol tolerance, cold tolerance, SO2 tolerance, one that produces little SO2, ferments to dryness, dies or becomes inactive following fermentation, does not stain the wall of the bottle, has desirable flocculating or agglutinating ability, produces no off flavours or odours, and has a desirable effect on carbonation.

Liqueur de Tirage (Sugar) & Sparkling Wine Styles

Different wineries use various sugar sources for the 'prise de mousse' (or capturing the sparkle). Bottler graded sucrose or dextrose are perhaps the most common in the New World. arger operations may choose to employ sugar syrups. Many French producers use high quality beet sugar. Some use a 50% sugar solution - 500 grams/litre (g/L) of sugar in wine, with 1.5% citric acid frequently added to invert the sugar if sucrose is used. The various champagne styles with their corresponding degrees of sugar are as follows:

Extra Brut or Brut de Brut (not dosed). A less common style these days, resulting in a very dry wine.
The sugar content or dosage is from 0-6 g/L.
Brut. (Dry) Most Champagnes fall into this category. The sugar content is from 0-15 g/L. In exceptional vintages the grapes have enough natural sugar to be a "Brut" style without any dosage.
Cremants, produced by the addition of 15-18 g/L sugar, were first made in 1850 as meal compliments and possess a creamy mouthfeel. They should be consumed young as they age quickly.
Extra-Sec. (Off-Dry to Medium Dry) A very unusual style with 12-20 g/L sugar.
Sec. (Medium-Dry) 17-35 g/L sugar.
Demi-Sec. (Quite Sweet) This style is ideal with desserts and foie gras. Most houses do a Demi-Sec. The sugar content is between 35-50 g/L.
Doux. (Rich and Sweet) This style is intensely sweet at over 50 grammes of sugar per litre, and quite rare. The early Champagnes, particularly those favoured in Russia (which was a major Champagne market until the revolution in 1917) were of this style.

Riddling Aids
To enhance riddling ability during maturation, disgorgement, and even the potential wine palatability, some vintners add riddling aids at the time of cuvee bottling. Such aids (fining agents) may enhance the riddler's ability to convey the yeast to the neck of the bottle. When there is sedimentation of the yeast with the proper fining agent, riddling can be much easier. Some common riddling aids are:

Bentonite is, perhaps, the most popular riddling aid in countries like the U.S.A. because of its relatively inert nature. It seldom has a detrimental effect on product palatability at the levels employed (usually less than 6 g/HL or 2 pound/ 1000 gallons). In Europe, calcium bentonite (3.5 g/HL (1/4 lb per 1000 gallons) is frequently used. Care must be taken to avoid the addition of too much riddling aid, which can make riddling, and particularly disgorgement, difficult (Zoecklein, 1987a).The choice of riddling aids should ale based upon the expected time sur lie. Clays are often preferred for young wines while gelatins are aged or older wines. The major disadvantage with the use of riddling aids is that their effects on both riddling ease and sparkling wine palatability are not predictable. Riddling aids may influence foam and/or bubbles as well as wine clarity. Tirage tannin, for example, may positively influence mousse quality (Munksgard, 1998). Because each cuvee is different, the winemaker must wait until riddling and disgorgement to review the merits or deficiencies of the riddling aid(s) employed.

Bottling
Finally we arrive at the cuvee bottling line. Here are added to the bottle the afore-mentioned ingredients, as a uniform mixture of wine yeast, dissolved sugar, sulphur dioxide, possibly riddling aids and nutrients too. The bottle fill level should be based upon an understanding of disgorgement volume loss and desired dosage volume. Disgorgement volume loss should not exceed 2%. In Europe, the minimum pressure for sparkling wines recommended by l'Office International de la Vigne et du Vin is 51 psig at 20°C in bottles over 250 mL capacity. Accurate determination is  critical. The bottles themselves must  be heavy weight, and pressure tested.

After the cuvee has been placed in the bottle, a bedule is inserted into the bottle either by hand or by machine. This is a hollow polyethylene cup usually 17 mm dia x 14 mm high. Bedules help prevent leakage and metal contact from caps; further, they give a better seal and aid in disgorgement.  A closure is then placed on the bottle - usually a specially designed, stainless steel or aluminium crown cap with a  liner and sufficient skirt length to grip over the bead of the bottle for a proper seal.

9. Bottle Fermentation

Following sealing, sparkling wines are stored for the secondary fermentation. The storage method is dictated by general economics, the intended riddling system and space considerations. There are several bottle storage systems(Zoecklein, 1986d).'Sur lattes' (stacking bottles on the floor) is labour-intensive, although it can add an aesthetic appeal to the cellar. One person can stack approximately 2000 bottles a day.(Berti, 1981) This system requires considerable bottle handling going from cuvee line to stack, to poinitage (bottle shaking), then to the riddling system. Another choice is to use bins. Wooden or caged bins, often holding from 380-504 bottles, are available. These can be stacked, thus requiring much less floor space. A third method of bottle storage is to place bottles into cartons (the same cartons that will go to market) and allow the secondary fermentation and riddling to transpire in those cartons. This is a system designed and patented by California's 'Korbel' winery. Twenty pallet loads at a time are tied down on a conveyor that employs a shaft to shake the wine gently and evenly on a programmed cycle and air bags that inflate and tilt the bottles by lifting one side of the pallet.

During binning, in either cases or cartons, most producers at some time store their bottles with the neck slightly down so the air bubble in the bottle moves away from the neck toward the back of the bottle. This helps avoid any bottle staining in the neck and allows the winemaker to use the bubble as a 'scrubber' to free k yeast deposits prio remuage (riddling). Of course, the bottle storage area should be cool and have minimum temperature fluctuations and minimum lighting.

Fermentation within the bottle can often be observed as a ring of CO2bubbles around the base of the air bubble and its progress is usually noted by examination of either the reducing sugar, the bottle pressure, or both. A secondary fermentation at 12-15°C can be expected to last 0.5-1.5 months, though sometimes it will continue over several months.  The rate of the secondary fermentation is a function of the yeast, yeast volume, the temperature, and cuvee chemistry. The rate is increased by high pH, high yeast nutrients, a low phenol content, a low alcohol content, low sulphur, and low carbon dioxide pressure(Reed and Peppler, 1973). The fermentation temperature is usually not lower than 48°F (8.89°C) and not greater than 55°F (12.78°C). Some prefer a cool secondary fermentation temperature of 12°C (54°F) believing this to affect the amount of carbon dioxide chemically and physically bound (Merzhanian, 1963). Growth at low temperatures is believed to increase the production of lipids which favour bubble retention. A high secondary fermentation temperature is believed to result in coarse bubbles that are larger with less retention(Brusilovski et al., 1977).  Other factors affecting bubble retention include yeast strain, the nature of the still wine, and the length of time under pressure in contact with yeast (Berti, 1981). When poor fermentation in the bottle occurs it can usually be attributed to a poor starter (low inoculum, low temperatures, and/or undesirable cuvee chemistry).

As a result of storing wine in contact with yeast, there is an enrichment of the wine with amino acids(Bergner and Wagner, 1965).However other compounds are known to be increasing too: Esters, amides, fatty acids, and terpenoids are all shown to increase due to yeast autolysis. The products of yeast autolysis and aging not only improve flavour, bouquet, complexity, and depth, but possibly also CO2 retention and bubble size.

10. Aging Surlie

During the secondary fermentation there is an accumulation of amino acids from the cuvee into the yeast cell. At the end of fermentation, when the sugar has been depleted, the yeast restores the amino acids back to the medium. This is not autolysis but simply a free exchange back to the wine.  After this excretion of amino acids by the yeast at the end of the secondary fermentation, the concentration of amino acids remains stable for several months. Yeast autolysis then begins with a slow rise in the amino acid concentration, particularly between the 12th to the 43rd month sur lie.  The proline, lysine, leucine, glutamic acid, isoleucine, phenylalanine, serine, and valine content also significantly increase with age in bottle-fermented sparkling wine. (Bergner and Wagner, 1965)
Influences contributing to the increased rate of autolysis include elevated pH levels and temperatures. However to have a detrimental effect on both bubble retention and sensory attributes of the final wine.

The chemical changes in from the cuvee to the final wine contribute to the character and complexity of Methode Champenoise wines(Schanderl, 1943).These along with the changes that occur during aging, help explain the sensory differences between methode champenoise and charmat produced champagne.(Janke and Rohr, 1960). Adequate aging sur lie is, in particular, needed to develop roundness in the body and general flavour and complexity. (The 'yeasty' character does not refer to bread-type yeasty fermentation aromas, but to a toasty-like note that is the result of aging and yeast autolysis).  If maturation is not carried out during the aging in contact with the yeast, it cannot be attained later. The dosage liqueur can add only a slight attenuation to the sparkling wine palatability. (In fact, wines cannot be sold as Champagnes in France if they have not been kept on the yeast for at least nine months).

All of the critical factors that influence bubble size conditions of the secondary fermentation, concentration of nitrogenous compounds in the cuvée and yeast autolysis appear to play an important role.

11. Remuage (Riddling)

When the winemaker considers that his wine has matured for a significant length of time sur lie, the process of removing the sediment is begun.  Most believe that the wine should be left in contact with the yeast deposit at least a year before disgorging in order to allow the yeast cells to die and to permit the development of the 'champagne bouquet'.  Remuage (riddling) is the process by which gravity conveys the sediment the neck of the bottle, causing the heavy particles to ride over and bring down the lighter more flocculent particles. The sediment in the bottle is not quite homogenous, being composed of yeast, protein material and possibly some bitartrate and riddling aids. The heavy substances are fairly willing to descend, but the lighter particles tend to easily float up into the wine, adding a significant degree of difficulty to the riddling process. However,  the longer the yeast has been in contact with the wine, the more homogeneous is the sediment and the easier it is to remove.  As to why certain wines and certain vintages riddle easier than others is not fully understood (Zoecklein, 1987).

Riddling is performed by hand, automatically, or semi-automatically. (The widow Clicquot is credited with pioneering a way of removing the yeast sediment from mature bottles which has changed little to this day.)  After shaking, the bottles are allowed to rest before riddling to allow the lees to settle. It is important that air currents in the riddling area be minimized. Air movement will cause convection currents within the bottle, which will make riddling more difficult. The use of air conditioning, therefore, is not encouraged. In the hand-riddling operation, bottles are loaded into 'pupitres' (A-frames) that are about 6-feet high & 10-feet wide, spread out to approximately 40-42 inches,  holding 60 bottles per side. Hand remuage is said to have 3 phases. The bottles are first rotated, then oscillated, and finally tilted slightly. It is said to take years to learn how to properly perform these steps efficiently and effectively.

The bottles begin at an angle approximately 25-30° from the horizontal. Generally, two bottles are grasped, lifted approximately 1/4 inch from the rack and twisted rapidly 1/8 turn to the right then back to the left. The bottles are then placed back into the rack 1/4 inch to the right of the original position and at a steeper angle. The 'twist-counter-twist' is designed to create a backspin by causing the liquid to move one way and the glass another, and then stop abruptly. This rotative movement ensures that the main mass of sediment as it descends toward the neck does so at a different point on the circumference of t of the gla oscillation. The bottle is placed back into the rack at a slightly steeper angle and ends up at approximately 50-55° from the horizontal. Gravity causes the the sediment to slide down a fraction of an inch toward the crown. Each bottle is turned every 8 hours or once per day. A skilled hand-riddler may turn as many as 25,000 bottles per day(Reventos, 1982).The process may take 1 week to 3 months or longer depending upon the nature of the sparkling wine and the skill of the remueur.

However, the Remueurs are slowly becoming an endangered species. Automatic riddling machines are now more common. The gyropallete, is one such machine, which  consists of a pallet basket that holds approximately 504 bottles. The pallet basket can shift in all directions up and down as well as from side to side- and stop abruptly. These units can be controlled by a computer system that can operate many units under different riddling cycles. California's Korbel winery perfected an early auto-riddling system consisting of 7 layers of dntal racks. The upper rack in each level is stationary, the lower movable. Bottles are placed into this system by hand and are at about 20° angle from the vertical. The bottles are then flip-flopped back and forth four times a day by moving the lower movable rack and are vibrated for several minutes. Riddling is often accomplished within 7 days (Berti, 1981). Korbel's second innovation was a system allowing wine to be riddled in the same case that goes to market. Bottles undergo 12-18 months in the carton, neck-up. The cartons are then inverted and moved to special pallets that tilt 25° and vibrate briefly to loosen the yeast from the walls of the bottles. The elevated side of the pallet abruptly falls, thus jolting the bottles. One thousand cases at a time are riddled, which takes 5-7 days (Stashak, 1983).Some small producers, on the other hand, use a batch, semi-automatic system that consists of a metal frame rotated on a pivot. Each rocker holds approximately 500 a metal bin that has a bottom which is mounted on an eight-sided fulcrum that enables the bin to revolve by one-eighth of a turn in one movement.  Other innovators  have adapted such things as paint shakers. But neither the auto-riddler nor the rocker systems universally do as good a job as the hand-riddler. This is principally due to the fact that in bin-riddlers, bottles are usually not given the same jolting action received by hand-riddling and even those sparkling-wine houses that have  heavily invested in auto-riddlers also rely on hand riddling for difficult bottles.  When riddling is complete the winemaker  reviews the clarity of the riddled bottles. When the sediment has been fully convoyed to the neck of each bottle, they wine is ready to be disgorged.

12. Disgorgement

The next bit of action will be a mystery to many wine lovers: How to get the dead yeast cells and other sediments out of the bottle? This relatively simple process is known as 'disgorgement'. Prior to disgorging, the wine is usually chilled to about 4-10°C. This aids in preventing any significant loss of either product or carbon dioxide. (The lower the temperature, the less carbon dioxide will be lost). The chilled bottles are placed neck first into a brine of calcium chloride or a glycol solution (-15°C or 5°F) which freezes the sediment and a small portion of the liquid in the top one inch of the bottle neck. Care must be taken to avoid freezing too much liquid, which may make disgorging difficult.
The yeast & sediment is entrapped in the bedule and ice plug. (The bedule, as described before, helps to insure that the plug will be ejected uniformly and that no yeast residue will be left). If disgorgement is not properly executed, refermentation may occur. Small producers disgorge by hand:  Holding a single bottle, neck-up, at about a 45° angle, the crown cap is lifted from the bottle. The pressure within the bottle ejects the bedule and ice plug. The disgorger places his thumb over the mouth of the bottle to prevent pressure loss. He then evaluates the wine for clarity,  checks that all the yeast sediment has been expelled and smells it to ensure there are no off odours.  Wines with a reductive character (hydrogen sulphide, mercaptans, etc.) are separated and often discarded. When done properly, only about 2% of the bottle's volume is lost and 1-2 atmospheres of carbon dioxide pressure. One person can hand-disgorge about 1,500-2,000 bottles per day (Fowler, 1983b). Automatic units are also employed which can disgorge in excess of 2,700 bottles per hour. After disgorgement, the bottle is then placed on a tourniquet device for the dosage.

13. Dosage

The dosage (or 'liqueur d'expedition') material is any that alters the taste and composition of the sparkling wine and its addition permits a certain 'rounding of the edges' of the final wine. It should be noted, however, that while excessive sweetening can help to mask the defects of a sparkling wine, it can also conceal qualities.

Each firm has a slightly different formula for the dosage, and some use no dosage at all in certain products. The dosage may consist of wine, sugar, brandy, sulphur dioxide, ascorbic acid, citric acid or copper sulphate amongst other substances. The dosage liqueur must be filtered until brilliantly clear and free from suspended materials. If this is not done, gushing will occur (see below). With a hand-operated dosage machine, a piston adds a given amount of dosage to each bottle (0-45 mL). These machines also add sparkling wine from another bottle to bring the volume to the proper fill level. Having the dosage and the sparkling wine at the same temperature and chilling the bottle helps reduce gushing. Following the dosage and corking, bottles are shaken to distribute the dosage liqueur. Mnay sparkling wine houses allow the wine and dosage to marry prior to release with such 'empilage' periods  frequently lasting up to six months.

Sugar
Sugar in the dosage is added for the purpose of sweetening, balancing the acidity, masking astringency/bitterness and slightly modifying flavour.  The sugar source is often sucrose, invert sugar, or sugar syrup. Corn sugar is reported to add a candied-fruit character, whereas beet sugar may affect palatability. The sugar is dissolved in wine or occasionally deionised water. The volume of sugar syrup will alter not only the sugar/acid perception but also the character of the wine.  Most wines are dosed with sucrose which, with time, will be inverted to glucose and fructose which might change the level of perceptible sweetness or dryness. Carbon dioxide can cause a reduction of one's perception of sugar. Only the best wines have the gentleness to be 'perfect' without some added sweetness. (Perhaps the best known naturals are the 'Brut Sauvage' of Piper Heidsieck and the 'la Brut Zero of Laurent Perier'). Sugar dosages are often produced from secondary and later press fractions. The use of wine in the dosage allows for minor attenuationacter. The addition of a recent of the dosage can aighten up the finished product. Oak-aged wine can be used to add depth and complexity. A red wine in the dosage can be used to add depth and brightness to the colour of sparkling roses. (Some sparkling roses are made by cuvaison, a method in which the colour comes from keeping the juice in contact with the skins for some time. The rather pale hue that develops can be corrected by adding red wine to the dosage. The advantage of such a prstomization of the desired colour.)

Spirit
There are varying opinions about the desirability of espirit de cognac and its effects on methode champenoise palatability. The limited use reflects the desire for natural grape flavours. In years when the cuvee alcohol is low, addition of spirits may be desirable. The cognac or brandy should be chosen with great care. Diluted with deionized, distilled water, cognacs or brandies more readily reveal their true character. Usually, only very small quantities of brandy are now employed whereas previously, brandy was added to a level of 5-6%.  Cognac additions can have  dramatic effects on the sensory quality of the finished product. The dosed wine will change quickly over a period of months, therefore, dosage trials should be conducted.

Citric Acid
Some makers add limited amounts of citric acid as an aid to increasing the freshness of older wines.

Ascorbic Acid
Ascorbic acid is an antioxidant added in a range of 60 mg/L in conjunction with sulphur dioxide in the range of 40 mg/L. The use of ascorbic acid allows for a reduction in the amount of sulphur dioxide required. This may be a benefit due to the fact that CO2 will magnify one's perception of SO2.

14. Gushing

The appearance of sparkling wines is a very important quality feature affected by foaming and effervescence (amount, size and duration of bubble formation). There are some 250 million bubbles waiting to gush out of the average bottle of sparkling wine. In such wines, some of the gas is free and some is fixed with an equilibrium between free dissolved gas and combined gas(Miller, 1966). Gushing in sparkling wine is a sporadic but significant problem. Particulate matter in the form of case dust, cork dust, fibres or particles from packaging materials, and possibly particles from the wine or dosage itself, can cause gushing(Rankine, 1979).Such particles, particularly those present in the bottle before filling, occlude very small air bubbles that act as nuclei on which carbon dioxide comes out of solution when the pressure is released. The sharpness or jaggedness of particles appears to be important in the occlusion of fine air bubbles(Rankine, 1979).Such conditions as incomplete yeast riddling and potassium bitartrate crystal formation can contribute to gushing. When bottles have imperfections on their inside walls, bubbles will originate from this area, due again to occluded air. The need for strict control of glass and cork quality cannot be overemphasized. Shrink-wrapped glass and predusted corks are an asset.
(Lovers of Sparkling Reds will know that gushing of red often occurs when they are opened. To help reduce this potential problem, some producers fine their young cuvees with gelatin to lower the tannin content.)

A note on 'Light struck' bottles

Light struck is a sensory defect occasionally noted in wines as a result of methionine decomposition. In the presence of UV light, methionine can be broken down to yield the following odour compounds: hydrogen sulphide, methane thiol, dimethyl disulfide,  dimethyl sulphide, and ethyl methyl sulphide. Light struck wines are characterized as having cheese, plastic, vegetable and/or honey-like aromas. Due to the magnifying effect of carbon dioxide, these compounds can pose a serious quality loss. Green glass is reported to help filter out ultraviolet light that can produce "off" compounds but does not assure control(Thoukis and Stern, 1962).Even limited exposure to light (including fluorescent) can result in the production of light struck aromas. Some Champagnes, such as Roederer Cristal, are shipped with a yellow anti UV wrapping, which should be left on during storage. Brown glass bottles offer better protection against ultra-violet than green glass bottles.

15. Champagne Bottle Sizes

Early sparkling wines were stoppered in relatively brittle, thin-walled bottles. When the wine went through a secondary fermentation, in which carbon dioxide increased and back pressure built up,  monks were left at the mercy of potentially lethal time bombs (one can imagine monastic debates over who was to fetch the next bottle from the cellar!) The 17th century English had developed a fondness for Champagne, but wisely preferred bringing it over in barrels rather than risk the unwelcome surprise associated with French glass. At about this time, a new form of harder, thicker glass was developed in the super-hot, coke-fired kilns of northern England. Capable of withstanding the pressure of secondary fermentation, this new bottle allowed sparkling wine to be produced, contained and transported reliably for the first time. With the stronger glass, bottle sizes also increased, as pictured below.  Today, bottles of different sizes and shapes are used for special occasions or for special cuvees. For example, extremely rare is the 18 litre Solomon, and even rarer is the gigantic 36 litre Primat bottle (pronounced "preemah"), which weighs in at 65 kg. Big bottles have a novelty and theatrical value, but because of the difficulty in moving such a large mass for riddling and disgorgement (a full Nebuchadnezzar weighs 38 kg), in most houses the secondary fermentation is carried out in magnums. The wine is then decanted into the larger bottles. This inevitably results in a loss of pressure. Some would say that there is a chance of more oxidation as a result of this, and that Champagne from a giant bottle is inferior to that from the magnum it was fermented in.

Acknowledgement:  The above account of modern Champagne production is an abridged version of "A Review of Methode Champenoise Production" by Bruce Zoecklein (2002), Associate Professor & Enology Specialist, Dept. of Food Science & Technology, Virginia Polytechnic & State University and describes the general production philosophy and practices of méthode champenoise producers. Introductory notes on champagne history partly sourced from http://www.maisons-champagne.com