Molecular Gastronomy: Exploring the Science of Flavor (50 page)

cooking: A marvelous activity because it is infinitely variable. The cooking of an egg

white is not the same as the preparation of a fish with acids in the Tahitian manner

or the same as subjecting a fish to the pressure of several hundreds of thousands of

Glossary
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atmospheres. Even if one limits oneself to cooking by heating, cooking is a vast phe-

nomenon. For example, a roast of beef is considered cooked even when it is raw in the

center (although in this case the temperature of the meat in the center is actually a little

lower than if you were to put the meat out in the sun during the summer). At what point

can a food be said to be cooked? Rainwater is the product of prior evaporation. Should

we therefore considered it cooked?

custard: An example of the sort of complex physicochemical systems whose study draws

extensively on the work of two Nobel Prize winners, the physicist Pierre-Gilles de

Gennes (custard is an example of a suspension–emulsion) and the chemist Jean-Marie

Lehn (its proteins combine into supramolecular aggregates).

decanting: One of the operations that chemists have learned to master and that cooks

could perform more expertly if only they were willing to depart from tradition. But who

is prepared to assume responsibility for breaking with the ancients?

decoction: Both very ancient chemistry and cooking—even modern cooking—distin-

guish between maceration, which involves placing a substance in cold water; decoction,

which puts it in boiling water; and infusion, which puts it in boiling water and then

quickly removes it. This distinction no longer holds when the solvent is oil, which de-

composes before the boiling point is reached.

dehydration: Water may be drawn out from the tissues of vegetables, meats, and fish

with sugar or salt, often in order to make the surface dry and to protect foods against

deterioration.

denaturation: Proteins are said to be denatured when their form changes, for example

by unfolding.

diffusion: An important phenomenon in the kitchen. It is because of the diffusion of

light that milk is perceived to be white and because of the diffusion of water molecules

that fluids are drawn out from the tissues of salted vegetables and meat.

dough: From the physicochemical point of view, doughs are wonderfully complex sys-

tems: solid suspensions in which a solid (starch) is dispersed into another solid (a glu-

ten network formed by kneading).

egg: A food that consists of a shell (accounting for about 10% of the mass of the egg),

white (57%), and yolk (33%).

egg white: A transparent yellow—not white—liquid containing areas of differing vis-

cosity. If one looks closely one also sees slender white strands and a few bubbles. When

heated it solidifies, becoming opaque and white. A first microscopic approximation

indicates that it is composed of 90% water and 10% proteins. On closer inspection, it

can be seen to contain different proteins, including ovalbumin (58% of the total), ovo-

transferrin (3%), ovomucoid (1%), ovoglobulin (8%), and lysozyme (3.5%). Coagulation

begins at 62°c (144°f); at this temperature the ovotransferrin is denatured, forming

a delicate, white, almost transparent network that barely retains the liquid trapped

inside it.

342 | gloss ar y

egg yolk: A remarkable substance composed of approximately 50% water and 15% pro-

teins, with a great many lipids. It has a powerful taste and an unusual texture that

changes at temperatures above 68°c (154°f).

emulsion: A dispersion of droplets of one liquid in another liquid that does not mix with

it. Mayonnaise is an emulsion of oil in water.

enhancers: Certain preparations are said to be flavor enhancers, but physiological anal-

ysis does not yet justify use of this term.

enzymes: Proteins that are responsible for the reactions of other molecules.

ethanol: An important molecule because it is found in concentrations exceeding 10%

in wines and contributes significantly to their gastronomic interest. The discovery of

distillation, which allowed higher concentrations of ethanol to be achieved in the form

of
eaux-de-vie
or brandies, was a major event in human history. Certain animals apart

from human beings have a sort of language, and some have a form of laughter, but

none of them knows how to distill.

evapor at ion: Not the same thing as boiling, as I remarked earlier.

expansion: There is an old idea that boiled meat cooks by expansion. But boiled meat

does not expand. On the contrary, it contracts, and it is this contraction that causes its

juices to be expelled into the surrounding liquid.

extraction: Cooking extracts aromatic and taste molecules from various foods. None-

theless the flavor of dishes sometimes is wrongly attributed to extraction. For example,

a stock owes its flavor to chemical reactions between the molecules extracted from the

meat; contrary to what is often said, however, it is not an example of cooking by extrac-

tion.

fl avor: A term that describes the synthetic sensation produced by eating and drinking

(including odor, taste, texture, heat, mechanical properties, and so on) that corresponds

to the French
goût
. It is a pity that the English word has been imported into French

(
flaveur
) and that
goût
usually is translated in English as “taste”! But let us persevere in

our campaign against error: The world of tomorrow will be the one that we create today.

See also
Gustation, Sapiction.

foam: A dispersion of air bubbles in a liquid or a solid. A stiffly whipped egg white is a

foam. A soufflé is also a foam, but the liquid phase is a suspension–emulsion. The

sweetened dessert known as a mousse is an example of an uncooked foam.

fructose: A sugar found in certain fruits and in the aisles of your local supermarket. It

has a remarkable taste.

gel: A liquid immobilized by molecules that are linked together to form a network. A

cooked egg white, for example, is a chemical gel, for the network formed by the pro-

teins is permanent. By contrast, jams and preserves form a physical—that is, revers-

ible—gel.

gel atin: Proteins extracted from meat that are reassembled in the form of sheets or pow-

der. In hot water these molecules are dispersed; when the liquid cools, their extremities

Glossary
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are linked in threes as segments of a triple helical strand, forming a network known as

a gel in physics and, in cooking, as a gelatinous stock or jelly.

glucides: Molecules formerly considered carbohydrates because the first ones to be

discovered had the general structure c (h o) , containing as much water as carbon.

n

2

n

Nonetheless, it is a mistake to believe that these molecules are composed of water mol-

ecules attached to carbon atoms. The various atoms of glucides are arranged in a differ-

ent manner, with the result that the molecules they compose have numerous hydroxyl

(–oh) chemical groups that determine their capacities for combination. It would not be

imprecise to call these molecules sugars.

glucose: A very simple sugar that is found particularly in our bloodstream. The blood

carries it to the body’s cells, which use it as fuel.

gus t ation: Flavor (
goût
) is the sensation experienced when one eats and drinks—a syn-

thetic, global sensation produced not only by taste and olfactory and visual perception

but also by the perception of textures and various trigeminal stimuli. Nor should the

papillae be called gustatory, because they communicate only the small part of the overall

sensation known as taste. I propose instead to call the papillae sapictive because they

detect tastes (
saveurs
).
See also
Sapiction.

heat: A form of energy that is characterized in terms of temperature. Strictly speaking, ex-

pressions such as “Heat propagates toward the center of a roast” are mistaken. It is more

accurate to say that, in each part of a roasted piece of meat, the temperature increases

during the course of cooking or that the rate of molecular agitation of the molecules

increases in the meat during roasting, with greater average agitation on the periphery.

infrared rays: Invisible radiation that is abundantly emitted by hot bodies. Infrared

rays are detectable with the aid of a thermometer in the spectrum of sunlight dispersed

by a prism, where they come after red. You can perceive them by putting your hand next

to your cheek without touching it: The warm sensation you feel is created by infrared

rays emitted by your hand.

infusion: Tea is an infusion.
See also
Decoction.

iodine: In alcohol solution a very useful substance for detecting the presence of starch:

After a few seconds starch granules turn blue (rather than brown).

kurti: The Oxford physicist Nicholas Kurti (1908–1998), known for his discovery of

nuclear adiabatic demagnetization. In 1988 Kurti and I gave the name “molecular and

physical gastronomy” to the scientific discipline that studies the chemical, physical,

and biological transformations produced by cooking and eating foods. After his death

I shortened it to “molecular gastronomy” and gave Nicholas’s own name to the work-

shops devoted to this subject that are held every two or three years in Sicily.

l actic acid: Produced by lactic bacteria from the lactose found in milk. The characteris-

tic sourness of foods such as sauerkraut is caused by lactic acid.

lactose: A milk sugar. Milk sometimes is said to be sweet on account of its presence, but

if you pay close attention you will find it has a salty taste.

344 | gloss ar y

lipids: Dictionaries of biochemistry make a point of defining them because several types

of related molecules are grouped under this term. Many alimentary lipids are triglycer-

ides or phospholipids.

lump: A disagreeable structure, the prototype of which is obtained by putting flour in hot

water. The starched periphery of the resulting agglomerations prevents the diffusion of

water toward the center, which remains dry.

maceration:
See
Decoction.

magnetic resonance imaging (mri): Common name for an imaging process that

exploits the phenomenon of nuclear magnetic resonance. In hospitals, the term is a eu-

phemism: In deference to public fears of imagined radioactive dangers associated with

nuclear magnetic resonance, one speaks instead of magnetic resonance imaging.

maillard: French biochemist Louis-Camille Maillard (1878–1936). Maillard studied

medicine and chemistry at Nancy, writing his medical thesis on urinary indoxyl; his

thesis in chemistry, on the action of glycerine and sugars on alpha-amino acids, earned

him an international reputation. After volunteering for service in World War I, Maillard

joined the medical faculty of the University of Algiers as professor of biological chem-

istry and toxicology, teaching there until his sudden death in Paris. The reaction that

bears his name was announced in a three-page paper published by the French Academy

of Sciences in 1912.

maillard reaction: A transformation that begins with the reaction of a sugar and

an amino acid. What follows is very complicated, however, and a complete description

would fill several volumes. It suffices for our purposes here simply to say that once an

Amadori or a Heyns rearrangement has taken place (depending on the nature of the re-

active sugar), several parallel paths lead to the formation of brown compounds, notably

the ones found on the surface of meats that are cooked at high temperatures.

meat: Roughly speaking, a packet of elongated sacs, or muscle fibers. These sacs contain

water and proteins, as in the case of egg whites. The muscle fibers are supported by a

tissue, collagen, that is made of elongated (rather than globular) proteins and that dis-

solves when heated in water.

membrane: The lining of living cells, consisting of a double layer of phospholipids in

which various molecules are dispersed, notably proteins and sugars.

microwaves: Electromagnetic waves that were first harnessed by radar. Engineers ob-

served that pigeons that flew in front of the antenna were cooked, which led to the de-

velopment of microwave ovens. These utensils are the only ones used in cooking today

whose principles were not understood in the Middle Ages.

milk: Mainly water, but it also contains fats dispersed in the form of droplets that are too

small to be seen individually by the naked eye, and proteins, also microscopic in size,

that are aggregated in micelles.

monosodium glutamate: A compound used by Asian cooks because it produces a

remarkable taste called umami.

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| 345

muscle fibers: The slender elongated cells (up to 20 centimeters long) found in

meats.

m y ofibrils: Cellular complexes of actin and myosin that are responsible for muscle

contraction.

m y oglobin: A muscle protein that contains an iron atom, just as chlorophyll contains a

magnesium atom.