Molecular Gastronomy: Exploring the Science of Flavor (30 page)

ists have decoded the alphabet of algal polysaccharides, it remains for them to

learn how to form words and put them together.

Algal Fibers
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58

Cheeses

Commercial protection requires several kinds of analysis.

t o p r o t e c t t h e i r c a m e m b e r t s and other raw milk cheeses against leg-

islation that would prohibit the use of raw milk in fabrication, countries such

as France must demonstrate the gastronomic superiority of these cheeses by

comparison with ones made from pasteurized milk. To do this they must per-

form a detailed comparison of the chemical composition, texture, and aroma of

the different types, which will take quite a while. In the meantime, the Institut

National de la Recherche Agronomique and the Comité Interprofessionnel du

Gruyère de Comté, in collaboration with food research institutes elsewhere

in Europe, have been analyzing cheese with the aid of a very efficient system:

human beings.

The chemical analysis of cheeses, as by chromatography, often is insuffi-

cient. As a device for detecting trace amounts of molecular compounds, which

sometimes are aromatically preponderant, the human nose has no rival. Nor

are measurements of mechanical properties very helpful in characterizing cer-

tain cheeses that are pasty, crumbly, and heterogeneous.

On the other hand, tasting—an essentially subjective activity—integrates

various pieces of sensory information that human beings sometimes have a

hard time dissociating. A group of experts in the sensory analysis of cheeses,

assembled under the auspices of a European Union program called Food

Link Agro-Industrial Research (flair), has sought to set standards for the

training of tasting juries and to define norms for characterizing hard and

200 |

semihard cheeses. Six cheeses awarded a protected designation of origin were

tested: Comté (from the French Jura), Beaufort (from the French Savoie),

Parmagiano-Reggiano and Fontina (Italy), Mahon (Spain), and Appenzeller

(Switzerland).

The Texture of Cheeses

The texture of cheese is a crucial property, as anyone who has eaten a chalky

Camembert or a rubbery Gruyère knows. Unlike the organoleptic qualities of

shortbread biscuits, gum arabic candies, or puffed cocktail crackers, those of

cheeses cannot be described in terms of a single textural characteristic, for the

flavor of a cheese depends in complex ways on its overall texture.

The European laboratories participating in the flair study evaluated the

texture of the six selected cheeses by comparing their superficial, mechanical,

and geometric characteristics in addition to various sensations they produce in

the mouth. To specify perceptions and intensities, the researchers character-

ized the samples in terms of a reference class of basic textures associated with

a particular kind of apple, a cracker, a banana peel, and so on.

In the 1960s American food researchers proposed a general classification

of the textural properties of foods, but the study of cheeses has since shown it

to be inadequate. Which sensory characteristics must be considered in order to

define the texture of a food? And how can they be systematically recognized?

Specialists in sensory analysis have devised a range of methods for evaluat-

ing products: analysis by untrained judges, by trained judges on the basis of

predetermined categories, and by trained judges using intuitive criteria. The

attempt to establish international norms required a strict methodology. The

protocol finally chosen involved predetermined categories with trained judges

conducting blindfold tests.

Sensory evaluation consisted of the following steps: looking at the sample,

touching it, chewing it, deforming it, and shaping it into a ball before swal-

lowing. Because the overall assessment of texture was to be made with refer-

ence to surface, mechanical, geometric, and other objective measurements,

each phase of tasting was classified under one of these four categories. The

intensity of each sensation was evaluated on a scale of 1 to 7, with a minimum

of three basic textures serving as points of reference. Tasting was done at a

temperature of 16°c (61°f).

Cheeses
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Parallelepipedal slices of cheese having an area of 150 square centimeters

(about 24 square inches) and a thickness of 2 centimeters (about three-quar-

ters of an inch) were visually inspected to assess the smoothness of their sur-

faces and the presence of any openings, tears, crystalline deposits, and droplets

of water or oil. Tactile information regarding superficial quality was collected

next: Samples were put on a plate, and the judges ran their index fingers over

each slice to feel the grain and the degree of moistness. Mechanical character-

istics were noted by examining strips 1.5 cm (about half an inch) wide and 5–8

cm (about 2–3 inches) long that had been cut along the grain of the cheese. The

judges then evaluated elasticity (by pressing down with the thumb), firmness

(by gently pressing down with the teeth), deformability (the maximum defor-

mation achieved before breaking), friability, and adhesivity. Finally, geometric

characteristics related to the shape, size, and nature of the particles perceived

in the course of chewing (sandiness, granularity, fibrousness, and so on) were

analyzed, along with other textural characteristics resulting from complex and

residual perceptions such as solubility, impression of humidity (dry or moist),

and astringency.

Cultural References

The products used as bases for comparison in evaluating all these charac-

teristics were chosen because they are readily available in European countries

and because, in the case of prepared dishes, they are simple to make using

standardized procedures. For example, roughness was determined by compari-

son with the outer surfaces of a Granny Smith apple, a banana peel, a ladyfin-

ger, and a Breton cake; solubility was determined by comparison with a long

madeleine, a cooked egg yolk, and a small meringue; and so on.

In the case of hard and semihard cheeses, further study will be needed to

examine correlations between sensory descriptions of texture and mechani-

cal and biochemical analyses. New European Union research programs have

been proposed for soft cheeses, for there remains a great deal to learn about

the reasons for the distinctive character of raw milk products. However, Cam-

embert is not included in these programs, for lack of a commercial sponsor

(in Europe the costs of such research fall on industry). For the moment, then,

Camembert’s superiority is a fact only in the minds of connoisseurs.

202 | investigations a nd mod el s

59

From Grass to Cheese

Diet contributes to the quality of cows’ milk cheeses.

l e t e r r oi r
— t h e l a n d. For several years food producers have been talk-

ing of nothing else, often out of a desire to protect or expand their markets.

If they are to be believed, there is a special relationship between a region and

its products; no version of a product made elsewhere is as good as the origi-

nal, which for this reason is the only one to merit a protected designation of

origin.

Agronomic analysis has demonstrated the effects of climate, soil, and ex-

posure in the case of wine, but cheese proved to be a trickier proposition.

Working with producers in the northern French Alps and the Massif Cen-

tral, Jean-Baptiste Coulon and his colleagues at the Institut National de la

Recherche Agronomique station at Clermont-Ferrand recently succeeded not

only in illuminating the relationship between the land and the quality of its

cheeses but also in proposing objective criteria for according them certain

legal protections.

Taste and Reôn

What makes a cheese good? The distinctive characteristics of a cheese may

result from the physical features of the region in which it is produced, the

types of animals that provide the milk from which it is made, and the people

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who make it. Producers who talk about
terroir
emphasize the importance of the

cows’ environment and, in particular, of their diet: green grass, hay, and silage

(wet grass stored in silos, where it ferments). Does this diet really determine

the quality of a cheese?

The first attempts to answer this question, beginning in 1990, involved

twenty makers of Gruyère in the Franche-Comté region of France and revealed

a significant correlation between the taste of their products and the geographic

site of their operations. In other words, one can give a rigorous definition of

what “raw milk” means in Franche-Comté. Subsequent analysis of the volatile

components of Gruyère made in Switzerland showed that mountain pasture

cheeses are distinct from those of the plains: Fragrant molecules belonging

to the class of terpenes (limonene, pinene, nerol), for example, are present in

much higher quantities in mountain pasture cheeses. What accounts for these

variations? Agronomists initially supposed that they resulted from differences

in vegetation.

However, in these early studies methods of production and the character-

istics of the animals had not been taken into account. Would the observed

differences not have been found if the type of cow or the type of fabrication

had been modified? In other words, can cheeses typical of mountain pastures

be obtained by treating milk from alpine cows with production methods used

at lower elevations?

The
of Reblochon

Coulon and his colleagues decided to use Reblochon as a case study. Ex-

amining samples taken from several producers who used comparable fabrica-

tion techniques, they demonstrated that dietary characteristics determined the

sensory characteristics of the cheese. They showed that cows grazing in two

different parts of the same mountain pasture—one a southerly slope covered

mainly by
Dactylis glomerata
and
Festuca rubra
and the other a northerly slope

sparsely planted with
Agrostys vulgaris
and
Nardus stricta
along with unproduc-

tive patches of moss and
Carex davalliana
—gave cheeses that differed notably

with regard to taste and color. The cheeses from the south-facing precincts

were shinier and less yellow, and their taste was more intense, fruitier, and

spicier.

204 | investigations a nd mod el s

The sensory differences between cheeses may be a direct result of the mo-

lecular content of the cows’ forage. Carotene, which is present in vegetables,

gives cheese their color. It is also known that ingestion of certain subtoxic

plants (such as
Ranonculus
and
Caltha palustris,
which seem to be more com-

mon in north-facing mountain pastures) changes the cellular permeability of

mammary tissue and facilitates passage into the milk of enzymes that alter the

quality of cheese made from it. Moreover, it is possible that microorganisms

typically found in the soil of grazing lands may have a significant influence on

the characteristics of cheeses, but this remains to be demonstrated.

The E‡ects of Silage

Finally, more recent studies have examined the effects of silage, which

in certain regions is a matter of controversy (some say it produces mediocre

cheese). The new studies involved more than twenty farms producing raw milk

Saint-Nectaire of recognized quality. More than sixty cheeses were analyzed by

means of sensory studies, with judges instructed to evaluate taste, odor, and

texture.

It was discovered that the principal differences between these cheeses re-

sulted from methods of fabrication and the diet of the cows rather than the

manner in which their forage was stored. In particular, cows feeding on hay

did not always produce cheeses that differed notably from ones made from

the milk of cows that were fed on silage. The stocking of forage under con-