Molecular Gastronomy: Exploring the Science of Flavor (9 page)

best choice is citric acid, in its salt form, in a proportion of 1–2%. Do this and

you can be sure your fondue will be a success.

46 | secrets of the kitchen

9Roasting Beef

Allowing meat to rest after cooking causes the juices that have been re-

tained in its center to ow outward to the dry periphery.

m a n y h o m e c o o k s t o d a y are pressed for time. Their haste prevents

them from eating good roasts of beef, for example, for they often neglect an in-

dispensable step after cooking: letting the meat rest, with the door of the oven

open. Omitting this step means that the meat will be tough and dry. Profes-

sional cooks are well aware that letting meat rest is essential if it is to be tender,

but they believe this is because, in the process of cooking, the juices want to

“escape” the heat of the oven and consequently flow back into the center of the

meat. Letting meat rest afterward therefore is seen as a way of ensuring that its

fluids will be thoroughly redistributed. Why should this be true? What really

happens when we roast a piece of meat?

Let’s examine the matter with the cold and clinical eye of a physical chem-

ist. Chemists know that meat is composed of cells, or muscle fibers: sacs filled

mainly with water that contain molecules responsible for metabolism and

contraction. These cells are sheathed with collagen and grouped together in

bundles, which themselves are grouped together in larger bundles. Naturally

this is a simplified description; animal muscle also contains fatty matter, blood,

and so on.

How does the muscle structure react when it is heated? Because heat is

introduced into a roast by conduction, air being heated in an oven to a tempera-

ture of about 200°c (392°f), the water evaporates from the outer layer inward

to a point where the temperature is 100°c (212°f). This crusty, desiccated outer

| 47

layer is thin. Closer to the center, the temperature slowly rises during cooking,

and the structure of the meat is transformed by degrees because the various

proteins in the meat coagulate at different temperatures. From 70°c (158°f),

for example, myoglobin, which transports oxygen in the blood, is oxidized: The

ferrous iron it contains is transformed into ferric iron, with the result that the

meat turns pink. At 80°c (176°f) the cell walls begin to break down, bringing

the myoglobin into contact with oxidant compounds and causing the meat’s

color to change to brown.

Can blood accumulate in the heart of the roast? When a temperature of

50°c (122°f) is reached in the outside layer, the collagen contracts, compress-

ing the juices inside (although the degree of compressibility is small because

the juices are mainly water) and expelling the juices of the periphery outward.

The center of the roast, composed of liquids and largely incompressible solids,

cannot receive these juices. Anyone who is not convinced of this has only to

roast a few pieces of beef, weigh them, and determine their density before and

after cooking.

Good Advice, Bad Reasoning

These steps are instructive. First of all, one notices that a roast shrinks

when cooked in the usual manner, losing almost a sixth of its weight. This

loss results from the elimination of the meat’s juices, which are expelled by

both contraction of the collagen and evaporation of peripheral water. Note that

this observation fatally undermines the theory of cauterization, which holds

that the coagulated surface of the meat seals in its internal juices. Near the

turn of the twentieth century, for example, Mme. E. H. Gabrielle, author of
La

cuisinière modèle,
remarked, “Put the roast on the spit before a very hot fire,

in order to sear and tighten the pores of the meat, which thus conserves its

juices.” Similarly, the great French chef August Escoffier (1846–1935) wrote in

his book for home cooks,
Ma cuisine
(1934), that the purpose of browning is

“to form around the piece a sort of armature that prevents the internal juices

from escaping too soon, which would cause the meat to be boiled rather than

braised.” Both views are mistaken. Not only does the notion of “pores” have

no anatomical basis, but measurement shows that the loss of juices actually

increases with cooking.

48 | secrets of the kitchen

Empirical analysis also establishes that juices do not flow back to the center

of the roast; the density of the cooked center does not differ significantly from

that of raw meat. This means that the center has undergone little or no modi-

fication during cooking (which is not surprising in the case of French-style

roasts, which remain almost raw in the center) and also that the center is full

of juices compressed by the shrinking of the collagen.

Why, then, is it a good idea to let meat rest after cooking? Weighing the

center and outside portions of roasts, we find that the cooked center loses more

juice while resting than do the peripheral parts (which, having already been

dried out, are less likely to lose any). Letting the meat rest therefore does re-

distribute juices from the center outward so that the outer parts regain their

tenderness. But this is not because cooking had previously forced fluids to flee

to the center.

Given that the juiciness of the meat depends on the amount of juice it has,

why not use a syringe to reinject the juices that have drained out from the

roast during cooking? Seasoned with salt and pepper, these juices would give

the meat a taste it never had—except in the old days, when cooks used to lard

meats before cooking with seasoned pieces of bacon.

Roasting Beef
| 49

10

Seasoning Steak

As with the controversy in
gulliver’s travels
over how to crack open an

egg, there are two opposing schools in the matter of how to grill a steak:

those who salt it before cooking and those who salt it afterwards.

w h e n y o u g r i l l a s t e a k, naturally you salt it. But when? Before putting

the meat on the grill? During cooking? Just before eating it?

Cooks are naturally inclined to respond on the basis of their own experi-

ence, but sometimes this is insufficient. As Oscar Wilde remarked, experience

is the sum of all our past errors; as long as errors are not recognized, they re-

main alternative truths. Therefore it helps to conduct experiments in which the

various parameters are controlled—the only way to cut to the heart of things,

meat among them.

Some argue that introducing salt beforehand gives it time to penetrate, so

that the meat is seasoned, if not quite all the way through, then at least much of

the way. Others are equally convinced that salting meat before cooking causes

its juices to be drawn out by osmosis. Meat is composed of cells—muscle fi-

bers—that contain water, proteins, and all the other molecules necessary to

cellular life. If the meat is placed in contact with salt at the outset, the naysayers

claim, then the fact that the concentration of water in the meat is greater than

in the surrounding layer of salt means that the water will osmotically migrate

toward the salt, drying out the meat.

But that is not all. Not only would the meat gradually lose its juices, but

during the course of their escape it would be partly boiled in them, instead of

being grilled, so that it would not brown properly. It would also lose tender-

ness, which depends on the concentration of water in food. Some participants

50 |

in the seminar on molecular gastronomy that I have been conducting in Paris

for several years have mentioned a harmful effect on the internal color of the

meat, noting that the juice that comes out from the meat is made up largely

of blood (along with intracellular water). However, advocates of the water loss

theory sometimes forget that muscle fibers are sheathed in a supporting tissue

known as collagen.

The structure of different cuts of meat (beef ribs, beefsteak, pork chops,

and so on) is so varied that the question must be refined. Let’s consider two

simple and useful examples, a thin piece of red meat such as steak and the

white meat of a fowl, and measure three things: the rate at which the salted

meat discharges (“sweats”) water, the amount of weight lost, and the residual

amount of salt in the meat.

Coating, Sprinkling, and Sweating

Let’s begin by considering the first question: How much juice comes out of

the meat in the presence of salt? Drench pieces of red and white meat in table

salt and let them sit, weighing them at regular intervals. The results probably

will vary depending on the meat selected, which may have been cut along the

axis of the fibers (with the grain), perpendicularly (against the grain), or diago-

nally (across the grain). Naturally, water will drain out more readily if the fibers

have been opened up. In the case of the red meat, the type of steak matters, too.

For example, a rib steak ought to lose more than a flank steak.

With flank steak we find that the discharge of water is very slow, whereas

white meat such as chicken loses 1% of its weight in the first thirty minutes

after salting. Of course, what happens to salted meats left to sit at room tem-

perature is very different from what occurs during cooking, but the results

are plain enough: There is no disgorging of liquid, even though the meat has

been coated with salt. In the case of actual cooking, when one would season

it with only a small amount of salt, the purging action would be weaker still.

Thus it appears that salt has no notable effect—a provisional but nonetheless

probable conclusion. You can salt your flank steak when you like, without fear

of its drying out.

Turning to the second question, whether the salt penetrates the steak dur-

ing cooking, consider the experiments I have conducted in collaboration with

Rolande Ollitrault of the École Supérieure de Physique et Chimie in Paris and

Seasoning Steak
| 51

Marie-Paule Pardo and Éric Trochon of the École Supérieure de Cuisine Fran-

çaise. We salted the same cut of meat before and after cooking, measuring the

loss of juice and, most importantly, analyzing the pieces of cooked meat with

a scanning electron microscope and a device for detecting chemical elements

by means of X-rays.

X-ray analysis reveals the presence of various chemical elements (notably

sodium and chlorine in the case of kitchen salt), making it possible to deter-

mine whether the salt diffuses through the meat. Again, the answer is clear:

Rather than penetrating to the center, it actually passes out of the meat during

cooking. On the other hand, when a piece of meat that has been trimmed of

fat is placed on the grill, a very small amount of metal is observed to enter the

outer layer of the meat.

The nature of meats is so varied that the more subtle effects of preparation

and cooking may make themselves felt only insofar as they suit our desires

and answer to our illusions. “Nature,” in the sybilline words of Leonardo da

Vinci (anticipating Hamlet), “is full of infinite reasons that were never in ex-

perience.” This does not mean that experimentation must be abandoned. It

means that experiments must be carefully designed so that the fire of truth

may be discovered beneath the smoke of subjective experience and individual

opinion.

52 | secrets of the kitchen

11

Wine and Marinades

Beef marinates better in red wine than in white wine.

i t i s s a i d t h a t f i s h m u s t b e c o o k e d in white wine but that red wine

should be used to marinate and cook tough meats in order to tenderize them.

It is also said that parsley must not be used if the marinating process lasts

more than two days and that one should not roast marinated meats because

roasting dries them out. How far should we credit these familiar dictums?

Japanese physical chemists recently provided partial corroboration. Experi-

ments conducted some twenty years ago in France, at the Institut National

de la Recherche Agronomique station in Clermont-Ferrand, showed that beef

is tenderized by prolonged immersion in acid solutions, which dissolve col-

lagen and various other proteins principally responsible for the toughness of

raw meats while ionizing these proteins, increasing the amount of water they

retain. Vinegar is not the sole ingredient of such marinades, however, and the

role of wine in particular remained mysterious. Two researchers in the depart-

ment of home economics at the University of Koshien in Japan, Kazudo Okuda

and Ryuzo Ueda, completed the French study after first examining the effect

on meats of fermented products such as vinegar and soy sauce.

Preliminary investigations established that the mass, water content (the

tenderness of meats depends particularly on their juiciness, which is to say