Champagne ages more quickly in small bottles.
THE MAGNUM OF CHAMPAGNE is a prince among princes: Connoisseurs ascribe virtues to it that they do not detect in regular or half-bottles of the same wine. Are they correct? And are they correct in supposing that champagne should be stored lying down because the cork remains moist and so better preserves its hermetic properties? Experiments performed recently by Michel Valade, Isabelle Tribaut-Sohier, and Félix Bocquet at the Centre Interprofessionnel des Vins de Champagne (CIVC) in Épernay led to a new understanding of the role of corks in the aging of sparkling wines.
Champagne is a wine that foams, by contrast with still wines, in which the presence of bubbles is considered almost a flaw. Why does champagne foam? Because the yeast put into the wine consumes its sugar, releasing carbon dioxide in the space enclosed by the bottle. This gas is then dissolved in the liquid, causing it to bubble when the cork is popped. Along with the bottle itself, the cork is the key to preserving the qualities of a good champagne because it ensures that the wine retains its gas.
Cork Scrutinized
For a long time it was supposed that corks are perfectly hermetic. After all, the wine does stay in the bottle. The wine, yes, but not the gas: As oenologists well know, bottles of champagne lose their pressure over time. This phenomenon led them to examine the behavior of corks more closely. In champagne making, before the familiar mushroom-shaped cork is inserted, producers use crown caps equipped with a temporary seal that can be removed to add sugar. This seal comes in either cork or plastic (a synthetic polymer derivative). The CIVC team studied the two types of material and found that cork seals were not uniformly impermeable, which explains the variations that are observed from bottle to bottle.
Synthetic seals displayed a consistently higher degree of impermeability, but this fact alone does not establish that they are the best device for blocking the escape of gas. However, tasting juries have unanimously found that wines with plastic stoppers change less quickly and have less of the cooked fruit taste that is often associated with oxidation. This raises a series of questions. Why does oxidation occur in the first place? Does oxygen diffuse through the stopper? Does the surface area of the stopper in relation to the volume of liquid explain the differences tasters detect between half-bottles, bottles, and magnums?
Tests of Aging
An impression—even a highly educated one—is not the same thing as a controlled experiment. To determine whether the size of the bottle really makes a difference, the Épernay oenologists compared samples of the same champagne, drawn and bottled under identical conditions, and plugged in the classic fashion using crown caps with cork seals. Then, after a year of aging, they submitted the wines to the judgment of a panel of tasters. Consistent with earlier results, the wine in the magnums seemed younger than that in the regular (75-centiliter) bottles, and the wine in these bottles seemed less developed than that in the half-bottles.
Could these differences have resulted from a chemical reaction between the wine and the oxygen present in the small volume of gas trapped when the bottle was capped? No, for measurements showed that the oxygen trapped in this volume and subsequently dissolved in the wine is completely consumed by the yeast, leaving only a residue of nitrogen and carbon dioxide.
Are the changes in the wine caused by a gaseous exchange with the atmosphere outside the bottle despite its being plugged with a cap? Measurements showed that the quantity of oxygen that enters through the stopper during aging is proportionally greater when the capacity of the bottle is small: Although the quantity of oxygen is roughly identical for the three types of bottles, the smaller the bottle, the smaller the volume of liquid that reacts with this oxygen. This is the advantage of the magnum: The larger the bottle, the less effect oxidation has on the wine. But even if it is clear why carbon dioxide manages to escape the bottle, why does oxygen get in? Because its partial pressure outside the bottle (about a fifth of an atmosphere) is greater than the partial pressure inside the champagne (equal to zero).
The Position of the Bottle
As for the position in which a bottle is kept after it has been purchased, this has no influence at all—except on the cork, whose mechanical properties are better preserved when the bottle is standing rather than lying down. More precisely, the force needed to extract the cork is greater in this case, with the cork reassuming its mushroom shape on being removed from the bottle. When the wine is in contact with the cork, by contrast, it gradually penetrates the cork and alters its mechanical properties.
Finally, the CIVC team explored the influence of the moon on the increase in sugar in grapes before harvest. Preliminary findings confirmed what had long been suspected: It has no effect whatever.