Molecular Gastronomy: Exploring the Science of Flavor (49 page)

sensation by altering the real acidity of the food (as measured by its ability to dissolve

metals, for example). Acidity therefore is better characterized in units of pH, with the

aid of small strips of paper and electrodes connected to a measuring device (two items

that deserve a place in modern cooking, by the way). Because lentils cook better in a

basic than an acid medium, you can adjust the pH of the cooking water with the aid of

bicarbonate soda and, once the cooking is done, add vinegar to neutralize the unsavory

taste of the bicarbonate.

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actin: An important protein in cooking because it is abundant in meats and fish. It acts

in concert with myosin in the elongated cells of muscle fibers as an essential agent of

muscle contraction.

albumen: The white of an egg—but if you look at it you will see that it’s yellow. Why

did our ancestors choose such an ill-suited word? In the
Viandier,
a fourteenth-cen-

tury French cookbook, the egg white was called “albun,” from the Latin
alba,
meaning

“white.” An egg can have different colors, of course, depending on what the hen eats.

In a cookbook from the eighteenth century one reads that in spring, when the hen eats

beetles, the egg white is bitter and green.

albumin: An old word, formerly used in cookbooks to denote what today are called pro-

teins. The term is now reserved for globular proteins such as ovalbumin, the principal

protein of albumen.
See also
Egg white.

amino acids: The building blocks of proteins. Some twenty kinds are found in cooking.

amylopectin: Along with amylose, one of the two molecules that are the principal con-

stituents of starch. Instead of being a mere linear chain of glucose subunits, it has a

branching structure, also made of glucose subunits.

amylose: A glucose polymer. Amylose molecules are composed of long chains of identi-

cal subunits of glucose molecules.

aroma: There us no consensus among specialists concerning the meaning of this term.

In the view of some authorities it is the name of the sensation created by volatile mol-

ecules released during mastication that rise up through the retronasal fossae into the

nose. But others, a majority, take it to describe a part of the overall sensation of flavor.

When you drink wine, for example, and perceive a flavor of green pepper, you say that

it has a green pepper aroma. This effect is caused by both odorant and taste molecules

that stimulate the trigeminal nerve (producing a sensation of freshness, for example).

Here I use the term to refer to a distinctive sensation that is a component of the overall

flavor of a food or wine.

a scorbic acid: Also known as vitamin C. It is responsible for the antioxidant properties

of lemon juice, in which it is present in large quantities (37 milligrams per 100 grams).

Instead of using lemon juice to prevent pears, bananas, and apples from browning, why

not use ascorbic acid? It’s cheaper and much more efficient.

aspartame: A sweetener made by the conjunction of two amino acids, l-aspartic acid and

l-phenylalanine methylene. This molecule in itself furnishes proof that there is not just

one sweet taste but many. Taste it and see for yourself!

a stringency: Characteristic of a molecule that binds with salivary proteins and sup-

presses their lubricating action, producing the sensation of a dry, tightened mouth.

Many polyphenols are astringents because their hydroxyl (–oh) groups bind with such

proteins. If you take a sip of a very astringent wine, swirl it around in your mouth for a

few seconds, and then spit it out into a glass, you will see precipitates—proteins bound

to tannins.

338 | gloss ar y

autoxidation: An essential chemical reaction that causes fats to turn rancid. Because

it is self-catalyzing, the reaction takes place quickly. To retard it, protect foods against

exposure to oxygen, light (whose ultraviolet rays promote autoxidation), and certain

metals.

bases: Purists are alarmed when these are said to be the opposite of acids, yet it is easier

and more helpful to describe them in this way. Pedantry is not always a sign of clarity:

Who will understand me, apart from those who already know, if I say that acids release

protons whereas bases capture them?

bitter: This annoyingly vague word is used to denote one of the sensations given by the

gustatory papillae. Why annoyingly vague? Because each of us has a very particular

impression of tastes and because we do not know which tastes go to make up the flavor

of a given dish. In the mouth foods release volatile molecules that travel up to the nose

through the retronasal fossae along with molecules that give a sensation of spiciness,

while mechanical and thermal sensors in the mouth detect texture and temperature.

We therefore have an overall sensation that is customarily called flavor, but no one has

ever succeeded in identifying its component tastes in the course of everyday eating and

drinking. The problem is compounded by the fact that we now know there is not just

one bitter taste but several; electrophysiologists recently demonstrated that the papillary

cells that detect quinine (a “bitter” molecule), for example, differ from those that detect

denatonium benzoate (another “bitter” molecule).

boiling: Not the same thing as evaporation. For example, a bowl of water left to sit out

for a long time is emptied through the evaporation of the water at room temperature. By

contrast, evaporation accompanies boiling when a pan of water is placed over high heat.

At what temperature does water simmer? Knowing the answer is important because

meat is more tender when it is simmered.

browning: Meats heated at high temperatures brown, as do apples that are cut up and

left uncovered, as does sugar that is heated. Browning has various causes, including

oxidation, enzymatic reactions caused by polyphenoloxidases, Maillard reactions, and

thermal degradation.

butter: A substance that was long considered to be emulsion in which water is dispersed

in fatty matter in the form of casein-coated droplets. (Water molecules account for

roughly 15–20% of its mass and triglyceride [fat] molecules
roughly 80%.) But this view

is wrong because at room temperature some of the fat is solid. Butter is better thought

of as an emulsion trapped in a solid network, that is, an emulsion contained by a gel.

c alcium: This chemical element is found in ionized rather than neutral form in foods,

for it has lost two electrons. This divalence makes it an interesting ion, in part because

it can bond simultaneously with two pectin molecules, which means that it hardens not

only vegetables but also jams. Calcium therefore is neither good nor bad. It is up to the

cook either to use it or to seek to eliminate it, keeping in mind that it is readily trapped

with citrate ions, for example.

Glossary
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caramel: A delicious brown product that is classically obtained by the thermodegradation

of ordinary sugar (sucrose). Different caramels can be obtained depending on the acid-

ity or alkalinity of the medium in which a sugar is heated. Sugars such as glucose and

fructose yield distinct flavors from those of sucrose. I love the fructose flavor!

caramelization: A term that cooks use indifferently to denote the browning of meats

and the thermal degradation of sugars. Yet the chemical reactions are quite different in

the two cases. If progress is to be made in the domain of cooking, its terminology must

be made more exact: A cat is not a dog, and it would be a poor biologist who confused

the two.

caseins: Proteins present in milk, where they are assembled into calcium phosphate–ce-

mented aggregates known as micelles.

cell: Roughly speaking, a small sac filled with water. The wall of the cell is essentially a

double layer of phospholipid molecules. A closer look reveals that cells contain a host

of interesting molecules, including proteins, sugars, lipids, and desoxyribonucleic acid

(dna), which makes these sacs living entities.

chemistry: A science of central importance to us as human beings, for it is what al-

lows us to live. In fact, it allows us to live for two reasons: On one hand, our organ-

ism functions only by virtue of a coordinated set of chemical reactions; on the other

hand, cooking is a form of chemistry that creates the foods that we consume. Chemistry

sometimes is defined as the science of the transformations of matter, but this is an

exaggeration: Many biological phenomena (the act of chewing, for example) and many

of the phenomena of particle physics (the annihilation of a particle and its antiparticle)

are transformations of matter (in the first case food is divided up, in the second matter

is converted into energy) that do not involve chemistry. It is nonetheless accurate to say

that chemistry creates its own subject matter and that it is concerned with the structure

of atoms and molecules.

chlorophyll: A platelet-like molecule, with a tail and a magnesium atom at the center,

that contributes to the color of green vegetables. The magnesium atom can be dis-

lodged by a hydrogen ion during cooking in an acidic medium. This replacement of

magnesium by hydrogen is accompanied by a change of color: The food turns from

green to brown.

chocolate: Let’s not kid ourselves: It’s almost impossible for chocolate lovers to stay

slim. Chocolate is composed mainly of fat (which accounts for roughly 30 grams of ev-

ery 100 grams of dark chocolate) and sugar (60 grams). This bare description neglects

the fact that chocolate has remarkable organoleptic properties and physical properties

that are no less wonderful. For example, its fats melt in the mouth (at 37°c [99°f]) but

not in the hand (at 34°c [93°f]). Mineral fats are sometimes added, but very few arti-

sanal or industrial producers show their customers the courtesy of honestly and clearly

admitting on their labels the difference between true chocolate and chocolate enriched

with fats other than cocoa butter, a situation that seems to bother only me.

340 | gloss ar y

clarification: A medieval culinary procedure that consists of adding egg white to a

stock (wines are also clarified, but here we are concerned chiefly with cooking) and then

heating it. The egg white traps the particles that cloud the stock, making it possible to

obtain a fairly clear result by means of a final filtering. Rather than waste perfectly good

eggs, we can use good laboratory filters instead.

coagulation: A transformation whose culinary prototype is the transformation of the

egg white, a transparent yellow liquid, into a cooked egg white, an opaque white solid.

collagen: In meats, a fibrous tissue that sheathes muscle fiber cells. It is composed of

proteins that are braided in triple strands, which combine in a way vaguely similar to

cellulose fibers in paper. When meat is cooked, the thermal agitation breaks the bonds

between collagen proteins, and they pass into solution (the bouillon subsequently gela-

tinizes as it cools because the proteins recombine with one another).

concentration: A term that refers to both a physical phenomenon and a form of mea-

surement. The phenomenon is the grouping together of entities in space or time. Thus,

for example, there is a concentration of spectators in a stadium for a sporting event. Ob-

viously molecules can also be concentrated, particularly in herbs; for example, anethol

molecules are numerous in fennel. Concentration measures this effect. In cooking, the

term often is used in connection with the cooking of a piece of meat. This is an odd

way of talking: Juices come out from a roast rather than becoming concentrated inside,

odorant and taste molecules are formed as a result of chemical reactions only on the

surface, and the temperature inside the roast is lower than that of the oven. What, then,

is being concentrated here?

conduction: In cooking, this phenomenon occurs principally by means of heating: The

thermal agitation of molecules on the surface of a food is communicated to neigh-

boring molecules inside. These molecules in their turn disturb molecules still further

inside, and so on. This is why the internal temperature of foods progressively rises as

they are cooked.

convection: A phenomenon that accelerates exchanges of heat in a liquid by virtue

of differences in density between hot and cold parts. A broth cools rapidly because

the liquid at the surface cools from contact with the air, so that its density increases;

it then falls to the bottom of the bowl, while the hot liquid rises, then cools, and falls

to the bottom. By contrast, a thick soup cools thoroughly only at the surface because

its viscosity prevents convection. You can create a remarkable gastronomic sensation

with a fragrant liquid (wine or hot chocolate, for example) if you put some of the liquid

in a glass at room temperature and then, having heated the rest, gently pour it in the

glass. Because of differences in density, stratification occurs between the two liquids.

Although it is not visible, you will be able to perceive the effect as you drink.