Molecular Gastronomy: Exploring the Science of Flavor (39 page)

these compounds are dissolved when it is filled with champagne. Although

they do not disturb the wine’s effervescence, they do affect the stability of the

foam, causing the bubbles to burst when they reach the surface. Dishwashing

liquid, though also harmful, is less of a problem because rinsing eliminates

most of it.

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79

Demi Versus Magnum

Champagne ages more quickly in small bottles.

t h e m a g n u m o f c h a m p a g n e 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 Interprofessi-

onnel 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 diox-

ide 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 en-

sures 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 oe-

nologists well know, bottles of champagne lose their pressure over time. This

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phenomenon led them to examine the behavior of corks more closely. In cham-

pagne making, before the familiar mushroom-shaped cork is inserted, produc-

ers 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 block-

ing 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 ques-

tions. 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 Aˆng

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 atmo-

sphere outside the bottle despite its being plugged with a cap? Measurements

showed that the quantity of oxygen that enters through the stopper during

264 | investigations a nd mod el s

aging is proportionally greater when the capacity of the bottle is small: Al-

though 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 oxy-

gen. 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 pre-

cisely, 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.

Demi Versus Magnum
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80

The of Whiskey

Statistical analysis provides guidance in scotch tasting.

s c o t l a n d , b l e s s e d l a n d o f w h i s k e y ! There it is called scotch, and

there are several kinds. Single malts are made from fermented barley at a

single distillery; blended whiskeys are mixtures of different kinds of whiskey

that may come from different parts of the country. Obviously the single malts

are preferred by connoisseurs, who scrutinize them with regard to five crucial

qualities: nose, color, body, mouth, and finish.

Does the provenance of a single malt determine its organoleptic qualities?

If it does, can types of scotch be associated with particular environments (or

terroirs
)? To find out, François-Joseph Lapointe and Pierre Legendre at the Uni-

versity of Montreal analyzed data collected by taster Michael Jackson, who has

described, tasted, and judged the roughly 330 single malt whiskeys produced

by 109 of the most prestigious distilleries in Scotland.

Characteristics of Single Malts

Statistical analysis of single malts proceeds from the fact that their dis-

tinctive characteristics assume several forms. Thus the nose may be aromatic,

peaty, light, sweet, fresh, dry, fruity, grassy, salty, sherry-flavored, spicy, or rich.

The body may be smooth, medium, full, round, honeyed, light, firm, fat, and

so on. What is the best way to divide the population of single malts into groups

of analogous individuals in order to determine whether they come from the

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same
terroir?
The University of Montreal statisticians simplified the problem

by considering only one scotch per distillery, for a total of 109 samples.

To quantify the various sensory impressions, or characteristics, produced

by these scotches, they assigned to each one a value of 1 if it was present in a

single malt and 0 if not. They then displayed the statistical data in the form

of a table by arranging the individual scotches in rows and the characteristics

in columns.

Next they calculated the numerical distance between pairs of single malts

by dividing the number of characteristics common to the two whiskeys by

the total number of characteristics identified in either one of the two; the

distance between them therefore is equal to 1 minus this parameter. The set

of these distances was then used to form a new matrix, where the value of

a given compartment represents the distance between two whiskeys linked

with one another by row and column. The smaller this distance, the closer

the whiskeys to each other.

In order to classify individual whiskeys, Lapointe and Legendre partitioned

the population by aggregating the closest individuals in pairs. This aggregate

is then considered to be a new individual that replaces the two aggregated in-

dividuals, whose characteristics are averaged to arrive at the value of the new

individual’s characteristics. Proceeding in this fashion until all individuals

have been related to one another as members of a single family, one winds up

with a dendrogram (or tree diagram). Different partitions can be obtained by

making a “cut” at a given distance from the root: The nearer to the root the cut

is made, the smaller the number of classes.

In Search of Class

The dendrogram obtained for single malts divides into two branches. On

one side are golden whiskeys having a dry, smoky body. On the other are amber

whiskeys that have a light body, smooth in the mouth with a fruit finish. The

first group, consisting of 69 whiskeys, was then subdivided into amber scotch-

es, which are full-bodied, fruity, fat, and spicy, and golden scotches, which have

a smooth and light body with a grassy finish. The farther away one goes from

the root, the smaller the groups.

Let’s come back to the geographic component. Scotland is divided into three

scotch-producing regions: the Highlands, the Lowlands, and the Isle of Islay.

The
Terroirs
of Whiskey
267

These three regions are divided into thirteen districts. The researchers con-

structed a new table in which the 109 scotches were again arranged by row and

column. The compartment at the intersection of a row and column contains a

0 if the corresponding scotches are from the same district, otherwise a 1.

Comparing this matrix with the one that generated the dendrogram, one

observes that the division into regions of production corresponds to the tree

diagram division, whether six or twelve groups are considered. These groups

correspond to
terroirs
. What is more, this distribution confirms that the water,

soil, microclimate, temperature, and overall environment are indeed the deter-

mining factors of the characteristics of single malt whiskeys, as upholders of

the
terroir
theory maintain. The secrets and traditions of individual distillers

account for only small differences by comparison.

Finally, the Canadian researchers sought to relate the five types of character-

istic to one another. It was clear that nose, color, body, and mouth are not inde-

pendent characteristics: The color of a scotch is related to its nose and its body,

and the nose is related to the mouth and, to a lesser degree, the body. The fin-

ish, on the other hand, which is to say the impression that is left in the mouth

when one has finished drinking, depends on neither the nose, the mouth, the

body, nor the color. The familiar method of tasting that consists of spitting out

the beverage after its color, nose, body, and mouth have been judged therefore

is open to criticism because it neglects a fundamental parameter.

268 | investigations a nd mod el s