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Bubble, Bubble, Toil and Trouble – Sparkling Wines
Champagne is no witch’s brew, but it does bubble, demands more toil than most wines, and gave trouble in the past (exploding bottles). Sparkling wine begins its life as a table wine, but undergoes a second fermentation that generates the entrapped carbon dioxide. There are several methods by which this can be achieved, but the most common is the appropriately named méthode champenoise.
All wines are mildly bubbly at the end of fermentation (being supersaturated with carbon dioxide), but this usually dissipates before bottling. In the past, wine that had not completed its fermentation in the fall would recommence it in the spring. If shipped and poured out of the barrel (formerly common practices), or transferred early to bottle, the wine would be frothy on pouring. This is the origin of the bubbles in the original vinho verde wines of Portugal, and the imported still champagne, turned bubbly, in mid-17th century England. The value of adding sugar to producing effervescence was first reported in 1662 by Dr. C. Merrit (Royal Society of London). Advances in glass production had permitted the production of bottles capable of withstanding pressures up to 6 atmospheres. However, when producers in Champagne began to purposely manufacture effervescent champagnes is unclear. But it may coincide with the 1728 repeal of a French law forbidding wine bottling; the first recorded Champagne firms producing sparkling champagne appearing about this time. Nonetheless, inability to accurately measure how much sugar was needed to produce the desired (and safe) carbon dioxide content lead to extensive bottle losses, and production amounts remained limited. This problem was solved only about a century later when in 1837 André Francois produced a densimeter that could measure the sugar content of the base wine, and thus permitting accurate calculation of the amount of sugar needed to achieve the desired carbonation.
That the sparkling wine industry first became established in Champagne may be due to the particularly cold grape-growing conditions during the late 1600s. Champagne, being a cool grape growing region was particularly affected, producing grapes that rarely reached maturity. As a consequence, the wines were low in alcohol content (≤9%), a possessed limited aroma, and had poor color (if made from Pinot noir/Pinot meunier). The wines were derogatively referred to as vin gris. These attributes, serendipitously, were ideal for producing sparkling wine, with the sensory attributes that now typify and are desired in champagne-style wines. For example, the low alcohol content of the base wine minimizes the difficult conditions under which yeasts must recommence fermentation (an alcoholic, acidic, low nutrient wine and at about 10 ̊C). In addition, as carbon dioxide accumulates, it tends to suppress yeast growth and metabolism. Although slow to commence, the second fermentation does come to completion, generating the desired carbon dioxide and raises the alcohol content to a value once typical of most wines (11–12.5%). The minimal fragrance of the base wine is also beneficial as it does not compete with, or mask the subtle, toasty, fermentation aromas now expected in this style of wine. That the red grapes, often used to make white champagne, were pale colored (due to immaturity) was not a problem. This undesirable attribute, for making a red wine, made it easier to extract colorless juice to produce a white champagne. In addition, immature grapes were more likely to be harvested disease-free.
Dom Pérignon may be generally presented as the ‘father’ of champagne, but documentary evidence of his role in producing (or championing) the sparkling version is nonexistent. His activity also predated known production of sparkling wine in Champagne. Nonetheless, he does seem to have had a beneficial influence in advocating reduced grape yields, whole-cluster pressing, and the blending of wines from different locations and/or vintages. Skillful blending can mollify the faults of individual wines while accentuating their desirable attributes. Blending is still a central component in preparing the base wine for the second fermentation.
Subsequent discoveries demonstrated the role of yeasts in fermentation (now added to ensure the second fermentation) as well as discovering means to efficiently remove the spent yeast cells from the bottle (yielding a crystal-clear wine). Evolution of consumer preferences also drove a shift from a sweet (doux) to the dry (brut) style currently favored (by reducing the sugar sirup added immediately after removal of the spent yeast). The wine is typically left on the dead yeast cells for up to three years after the second fermentation. During this period, some of the distinctive aromatic compounds that characterize champagne escape into the wine from the yeasts (e.g., thiols, decanoic acid, m-cresol, and furaneol). Also released are cell-wall constituents (mannoproteins) that favor the formation of chains of miniature bubbles in the glass.
If for no other reason than due to the wine’s expense, it behooves the consumer to fully savor the sensory attributes achieved with so much effort. To characterize the bubbles, clear flutes are essential. Those with an elongated tulip shape are preferred as they help concentrate the wine’s subtle fragrance. Chilling the wine (most conveniently done in a refrigerator) increases the solubility of carbon dioxide, slowing and prolonging bubble generation. Although proper rinsing to remove any detergent (if used in cleaning the glasses) is critical, drying with towels is beneficial. Residual lint fibers provide sites within which microscopic air pockets are trapped when wine is poured into the glass. These, and minor imperfections on the glass surface, act as nucleation sites for bubble initiation. Finally, the wine should be poured slowly down the sides of the flute, to minimize foaming and a regrettable reduction in the duration of effervescence.
Unlike many wines, sparkling wines are best consumed shortly after purchase. Although tightly sealed, carbon dioxide does slowly escape, with the wine eventually turning flat. Admittedly, there may still be a small coterie of aficionados who savor the attributes of long-aged, flat champagne. Nonetheless, most of us purchase sparkling wine because of its effervescent property.
Although champagne gets most of the press, many other sparkling wines of similar quality and characteristics are produced, some in France, but also in other countries. These may or may not be produced from the same grape cultivars as champagne (Chardonnay, Pinot noir and Pinot meunier). Typically, this is of relative unimportance as the base wines should have limited varietal aroma (to avoid masking the wine’s subtle fermentation fragrance). A significant exception relates to sparkling wine based on Muscat grapes, such as Asti Spumante. It this instance, a marked muscaty fragrance is expected. Most sparkling wines are produced by the traditional champenoise method, but other techniques can be almost as effective and may be less costly. Typically they can be differentiated from traditionally produced wine only on detailed sensory analysis. Thus, in most situations, it is a moot point whether the price premium paid for champagne is worth the expense.
About the Author
Ronald S. Jackson received his bachelor’s and master’s degrees from Queen’s University and the doctorate from the University of Toronto. His time in Vineland, Ontario, and subsequently at Cornell University, redirected his interest in plant disease toward viticulture and enology. As part of his regular teaching duties at Brandon University, he developed the first wine technology course in Canada. For many years, Dr. Jackson was a technical advisor to the Manitoba Liquor Control Commission, developed sensory tests to assess the tasting skills of members of its Sensory Panel, and was a member of its External Tasting Panel.
Dr. Jackson has left his position as a professor and the chair of the Botany Department at Brandon University to concentrate on writing. He is allied with the Cool Climate Oenology and Viticulture Institute, Brock University.
He is also the author of Elsevier books Wine Science: Principles and Applications, Fourth Edition, which won the prestigious OIV Award in 2015, and the forthcoming Wine Tasting: A Professional Handbook, Third Edition.
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Additionally, please click one the links below to listen to Dr. Jackson’s lectures and learn more.
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