Kitchen Mysteries: Revealing the Science of Cooking

Cooking and Science

Venial Sins, Mortal Sins

Add the cheese béchamel to the egg whites, beaten into stiff peaks, without collapsing them! Such vague instructions in a soufflé recipe often make amateur cooks nervous. How to avoid collapsing those laboriously beaten egg whites? In our ignorance, we begin by using what we think is a gentle—that is, slow—technique. The egg whites and the béchamel do not mix easily, so we stop before we have a homogeneous blend or we stir the two ingredients so long that the egg whites collapse. In both cases, the effect is the same: the soufflé is ruined.

Where does the fault lie? With the cookbook that takes for granted such simple techniques, known to professionals but not sufficiently mastered by the general public? With the neophyte, who naively, even presumptuously, ventures into a discipline that is not so simple as it seems?

Difficulties like those encountered in preparing a soufflé do not jeopardize our access to the realm of taste, and even the cookbook’s scant instructions mark only a venial sin. With a little research, the novice will soon track down an explanation of the basic culinary techniques, and, reassured, she or he will come around to accepting—even to wishing—that cookbooks not all repeat the same advice, which he once considered them to be lacking.

On the other hand, more troubling, it seems to me, are such terse phrases as Mix the egg yolks two by two into the cheese béchamel sauce thus prepared. Why two by two? And why not six at once if I am in a hurry? This time, the explanation is nowhere to be found. Experience alone demonstrates the validity (or not!) of the advice. A few attempts to break the rule will return the audacious cook to the wisdom of the ancients, but he will remain intellectually frustrated if he is as curious as he is epicurean.

In this work, I want to share with you the explanations that science offers for those empirical precepts handed down from chef to chef and from parent to child. Better understood, the bits of advice and suggested techniques that cookbook authors offer in passing will be better respected. Knowing the reasons behind them, you will be able to follow recipes considered difficult for their thousands of fundamental trifles and achieve results you never expected. You will learn to adapt recipes to the ingredients available to you; sometimes you will even modify proposed techniques according to the available utensils. Feeling equal to the task, you will be more confident and more relaxed, and you will be able to call into play all your innate creativity.

Canard à la Brillat-Savarin

To whet your appetite by giving you the chance to verify that an infusion of science can have its usefulness in cooking, I offer you a recipe that compensates for the inadequacies of the microwave: a quick canard à l’orange.

Who has not taken a bland, gray, tasteless piece of meat from his microwave? Should we prohibit the use of microwaves for cooking meat and restrict them to reheating prepared dishes? It would be a shame to deprive ourselves of their advantages (quick, economic, energy-efficient cooking), but we must learn the specific possibilities this new kind of cooking offers, so that we do not ask it for more than it can give. As the old, politically incorrect proverb says, even the most beautiful woman in the world can only give what she has.

Microwave cooking is no great mystery. Very simply, microwaves heat the specific parts of food that contain lots of water. In other words, if we are not careful and put a piece of meat in a microwave oven, we will only succeed in steaming it. What a shame to turn duck or beef tenderloin into stew!

Why are microwaves so deficient when used in this way? Because they skip over one of the three fundamental functions of cooking. Cooking must, of course, kill microorganisms and make tough, fibrous, or hard-to-digest foods assimilable. But it must also make food taste good.

If grilling works wonderfully, it is precisely because it fulfills these roles simultaneously. First, the surface of the meat hardens because the surface juices evaporate while the meat proteins coagulate. Second, the meat’s constituents react chemically to form vividly colored molecules but also odorant or tasty ones. In other words, a flavorful and colored crust is formed. Within the piece of meat, the collagen molecules that toughen the meat are broken down.¹ The meat becomes tender. If the meat is seared, that is, cooked quite rapidly, the juices at its center do not disperse too much toward the exterior, and the meat retains its succulence and its juiciness. Biting into the meat will break the muscle fibers so that internal juices are released, bathing the mouth in a wave of delicate sensations.

Let us recognize in passing some principal chemical reactions in cooking, Maillard reactions, to which I will often return in this book: acted upon by heat, the molecules of the family to which our table sugar belongs (wrongly called carbohydrates, because these compounds are not strictly speaking made of carbon and water) and amino acids (the individual links in those large protein molecules) react and produce various odorant and tasty molecules. In cooking, this is one of the reactions we utilize to add savor even when we do not add flavorings to our dishes.

To make a canard à l’orange worthy of its name, the microwave will not suffice. Since microwaves heat water in particular and do not increase internal temperatures to more than 100°C (212°F, the boiling point of water) in ordinary culinary conditions, they do not promote Maillard reactions. In the canard à la Brillat-Savarin that I am suggesting you make, the microwave will only be used for the braising, after a quick turn in the frying pan.

Control your desire to discover this much anticipated recipe and grant me a few lines to introduce you briefly to the one to whom I have dedicated it, one of the greatest gastronomes of all time, the author of the Treatise on the Physiology of Flavour, which every gourmand ought to have read.²

His mother was a blue ribbon chef named Aurore (hence the name of the sauce), but Jean-Anthelme Brillat (1755-1826) took the name Savarin from one of his aunts, as a condition for becoming her heir. Because of the French Revolution, his was a turbulent career. After spending some time in exile in the United States, he returned to France, where he was named adviser to the French Supreme Court in 1800. Two years before his death, he published the book that made him famous and from which I will draw many precepts, quotations, and anecdotes in the pages that follow.

Now for that duck recipe. Begin with thighs that you have grilled in clarified butter over a very hot flame but for a very short time, long enough to allow a lovely golden crust to appear. The clarification of butter, that is, melting butter slowly and using only the liquid fatty portion of the melted product, is useful as butter thus treated does not darken during cooking. After the first grilling process, the meat is still inedible because the center remains raw, and we know that duck must be cooked! Using a paper towel, blot the fat from the surface of the thighs, and, using a syringe, inject the center of the meat with Cointreau (better yet, with Cointreau into which you have dissolved salt and infused pepper). Place the thighs in a microwave for a few minutes (the precise amount of time will vary according to the number of pieces and the power of the oven). During the cooking process, the surface of the meat will dry slightly and need no further treatment. On the other hand, the center of the meat will be braised in an alcohol vapor and flavored with orange (my own personal taste also prompts me to stud the flesh with cloves before microwaving it).

Spare yourself the trouble of making a sauce: it is already in the meat. No need to flambé: the alcohol has already permeated the flesh. Check your watch: you will see that putting science to work has cost you no time; quite the contrary. Furthermore, it has rejuvenated an old recipe by making it lighter.

Horresco Referens

³

If the book you are now holding in your hands explains a few mysteries of cooking, it nevertheless sheds no light on many areas. Foods are a complex mix, hard to analyze chemically. For example, Maillard reactions operate simultaneously in hundreds of compounds. The chemical combinations are countless, as are the products formed. And certain molecules present in minimal concentrations in foods perform brilliant solo parts in the grand symphony of flavors.

The natural world is so rich that cooking will always remain an art, in which work and intuition will sometimes lead to miracles. A plant like sage, for example, contains more than five hundred odorant compounds. Many a roux will thicken in our saucepans before we ever determine the exact role of these compounds in the flavor. Simple calculations show that the exploration of food combinations, compounds, and flavors will never come to an end.

So does science have no place in the kitchen? Not at all! The knowledge it produces offers simple principles that apply to the different classes of food. It explains many procedures. What you will discover here is the useful information it can provide us for eating well.

This book is not concerned with the composition of food, however. Dietary books annoy gourmands because their immediate objective is not gustatory pleasure. Often the long lists of ingredients, the tables of food constituents, in terms of fats, carbohydrates, proteins, and trace minerals, serve no purpose because they do not help answer the main question: how do the various culinary operations transform foodstuffs? How do these operations simultaneously render fibrous or indigestible foodstuffs not only assimilable but also delicious?

In one chapter of his book, Brillat-Savarin writes, Here I meant to insert a little essay on food chemistry, and to have my readers learn into how many thousandths of carbon, hydrogen, and so forth, both they and their favorite dishes could be reduced; but I was stopped by the observation that I could hardly accomplish this except by copying the excellent chemistry books which are already in good circulation.⁴ Is that really what stopped the great gastronome? Or, rather, was he applying the maxim he gives in his introduction? I have barely touched on the many subjects which might have become dull.⁵

Reactions in the Saucepan

Having considered what this book’s subject will not be, let me move on to its central theme: science and cooking. Cooks are rarely scientists, and sometimes science frightens them. Nevertheless, the marvelous thing about science is that its subjects and its laws are simple. Notwithstanding a few explorations into the composition of matter, it asks us only to accept that our universe is composed of molecules, which in turn are composed of atoms.

That we have known since middle school. We also know that atoms are linked by chemical bonds, more or less strong according to the types of atoms. Among the atoms in a single molecule, these forces are generally strong, but between two neighboring molecules, they are weak. Often when a substance is heated moderately, only the bonds between neighboring molecules are broken. Water in the form of ice, for example, is a uniform arrangement of water molecules.

When ice is heated, the energy supplied is enough to break the bonds between the water molecules and create a liquid in which the molecules still form a coherent mass but move in relationship to one another.

In the liquid created in this way, the molecules themselves are not transformed. The water molecules in the liquid water are identical to the water molecules in the ice. Then, as the water is heated further, it evaporates more and more, until it boils at 100°C (212°F), under ordinary pressure. The energy provided is enough to overcome the forces of cohesion binding the water molecules.

Again, however, in each molecule, the oxygen atom remains linked to two hydrogen atoms. This type of transformation is physical, not chemical, in nature. The water molecule remains a water molecule.

What the cook must keep in mind, however, is that foods are sometimes heated so much that chemical reactions can be produced as well. That is, molecules can be broken up and atoms rearranged, creating new molecules. I have already mentioned Maillard reactions, but they are not the only kind. Foods are chemical mixtures (and what is not a chemical mixture in our environment?), and the qualities we attempt to modify through cooking are manifestations of the chemical properties of these mixtures. When odorant compounds form on the surface of a roast, that is the result of a chemical reaction. When mushrooms darken after being cut, that is the result of a chemical reaction (enzymatic, but we shall return to this).

One reaction? Rather, a set of countless reactions, but we may simplify the analysis by using the biochemical classifications: carbohydrates, fats, proteins, water, mineral elements. The austerity of this decomposition allows for an overall understanding of the phenomena. Food chemistry is still in its infancy, and chemists are working hard to discover which reactions take place in foods. They are still only seeing the tip of the iceberg. We are very ignorant about the chemistry of cooking.

Universal Gastronomy

Nevertheless, there are some famous forerunners. In the mid-eighteenth century, the French cook Menon referred to the art of cooking, insisting on the need for experience and theory. In 1681, Denis Papin (1647-1712) invented the pressure cooker in the process of trying to discover a way to make stock from bones. The English philosopher Francis Bacon gave his life for cooking by trying to take advantage of a snowstorm to study the preservative effect of the cold. He stopped at a farm, bought a chicken, and stuffed it with snow. But he caught cold during the experiment and died of bronchitis fifteen days later.

Brillat-Savarin surveyed the scene in his time, and his admirable treatise contains a few errors that I will occasionally rectify, always paying tribute to the old master. On the other hand, I will not discuss the documents of the microbiologist Edouard de Pomiane (1875-1964). Pomiane was very popular in the 1930s, writing best sellers and creating one of the first radio programs focusing on questions of science and cooking. He believed he had invented a new science, which he called gastrotechnie, or gastrotechnology. This science encompassed nothing more than what Brillat-Savarin had already considered in his definition of gastronomy: Gastronomy is the intelligent knowledge of whatever concerns man’s nourishment.⁶ (Incidentally, it is not generally known that the word gastronomy comes from the title of a Greek work, Gastronomia , written by a contemporary of Aristotle, Archestratus, who had compiled a kind of Michelin guide for the ancient Mediterranean area; Joseph Berchoux [1765-1839] introduced the word into French in 1800.)

Today, the science of cooking is progressing thanks to methods of analysis perfected in the last few decades that can detect compounds present in minuscule concentrations that nevertheless play a major role in the flavor of foods. Yet it remains true that we know the temperature at the center of the planets and the sun better than the temperature at the heart of a soufflé. One of the cofounders of the scientific discipline called molecular gastronomy (the other being myself), the late Nicholas Kurti (1908-1998), a physicist at Oxford University and a member of London’s very old and very respectable Royal Society, reminds us of this paradoxical fact. How to explain the paradox? I tend to think that we sometimes fear that cooking does not fall within chemistry’s domain.

As proof, I offer an experiment carried out among friends, to improve wines. The physical chemist at Dijon’s Institut National de la Recherche Agronomique (INRA), Patrick Etiévant, had discovered that two important molecules in the flavor of well-aged burgundy were paraethylphenol and paravinylphenol. I acquired these molecules from a chemical products retailer, planning to add them to a poor-quality wine. The only comment I got from my guinea pigs was: That smells like a chemical. An astonishing remark, because isn’t everything a chemical? The foods we eat, the tools we cook with, we ourselves?

Well, it is time to discover the very substance of cooking, avoiding remarks like it is methylmercaptan that makes urine smell after eating asparagus. What puts us off here is less the trivial nature of the remark than its uselessness in terms of cooking. To know that asparagus contains methylmercaptan does not help us cook it. Likewise, to know that the external parts of potatoes contain alkaloids like solanine or chaconine simply allows us to eat better, not to cook better. This book aims only to promote the latter.

In this book, I examine the proven techniques, assemble the physical and chemical explanations, and do my analyses, seeking to understand without always believing that the solution given is definitive. Excuse this guide’s inadequacies if you discover any, and, through your letters, help me compile improvements for the next edition. In doing this, you will be helping all gourmands, of which, naturally, I am one. Finally, please excuse me for sometimes being a bit academic. Like Brillat-Savarin, I am well aware that to speak without pretension and to listen with kindness, that is all that is necessary for time to flow sweetly and swiftly.

My huge regret is my inability to explain the genius of the great chefs, gifted with a sixth sense for harmonizing ingredients and creating unexpected associations and surprisingly happy combinations. A veal scallop to which one adds, at the end of the cooking, a little white wine to deglaze the pan ... and a drop of pastis? The miracle happens: a superb taste emerges. The art of cooking is not a matter of succeeding with the soufflé every time but of suspecting that pastis will transform a veal scallop. The rest is just the first course in cooking.

Mysterious as it is to many of us, this first course in cooking is indispensable if we are to devote ourselves to the study of tastes and flavors without being afraid of the béarnaise sauce turning or the soufflé collapsing on us at the last minute. When we master these things, we can follow in the footsteps of our great forebears.

The New Physiology of Flavor

The Prehistory of Tastes

Before digging into the main course—the methods of preparation—let us make a little detour useful to understanding how we eat, because we will be better cooks if we know how to distinguish the various sensations that dishes produce: tastes and flavors, colors, scents, aromas.

Aristotle knew everything, but what did he know about tastes? Let us entrust ourselves to this old philosopher. Tirelessly traversing the lyceum with his disciples, he worked up an appetite and turned his metaphysical mind toward gourmand meditations: there are in the tastes as in the colors, on the one hand, the simple kinds which are also the opposites, that is, the sweet and the bitter; on the other hand, the kinds derived either from the first, like the unctuous, or from the second, like the salty; finally, halfway between these last two flavors, the sour, the pungent, the astringent, and the acid, more or less; these seem to be, in effect, the different tastes.

Aristotle is not the only authority to have appreciated oral sensations. In particular, in the eighteenth century the great Linnaeus also applied his talents to tastes, but paradoxically the most famous of systematicians, the father of botanical classification, lacked some systematic spirit, because he mixed together the moist, the dry, the acid, the bitter, the fatty, the astringent, the sweet, the sour, the viscous, the salty. He put them all pell-mell in the same bag for us, this mix of tastes and mechanical sensations.

A Frenchman deserves the credit for establishing a little order in the domain of oral impressions. In 1824 the great chemist Michel-Eugene Chevreul (1786-1889), famous especially for his work on fats, distinguished the olfactory, gustatory, and tactile sensations. He recognized that the perception of hot or cold is distinct from that of sweet or bitter. He separated out the tactile sensations of the oral cavity, as well as the proprioceptive sensations (for example, toughness). With Chevreul, the taste of physiologists—one component of flavor—was distinguished from everyday sensation,