How Molecular Gastronomy Works

­Molecular gastro­nomy is a rela­tively new term, one that has caused much confusion and controversy. Some of the confusion comes from trying to put a modern spin on a m­uch-older word. That word is gastronomy, which, since the 19th century, has described the art of selecting, preparing, serving and enjoying fine food. If preparing food is an art form, then it must be an activity requiring creative skill and imagination, not technical expertise. And yet gastronomy, like astronomy and agronomy, say, seems to describe a rigorous, scientific field of study.

In 1989, Nicholas Kurti and Hervé This decided to intentionally emphasize the scientific elements of cooking by coining the term molecular and physical gastronomy. The addition of the words "molecular" and "physical" cast cooking in a new light. It was no longer magic and artistry, but molecules obeying well-known processes that describe the behavior of all solids, liquids and gases. Suddenly, the "art" of selecting, preparing, serving and enjoying fine food became the "science" of doing so.

This described molecular and physical gastronomy as the physics and chemistry behind the preparation of a dish, and he began testing the scientific validity of cooking rules and old wives' tales in a research environment that was part kitchen, part high-tech lab. He also organized the first International Workshop on Molecular and Physical Gastronomy in 1992 and presented the first doctorate in molecular and physical gastronomy at the University of Paris in 1996.

Not everyone embraced the field. Some critics complained that the new field overemphasized the scientific processes of cooking and failed to acknowledge intangible aspects of the craft, such as a chef's intuition or spontaneity. Others simply said it was too difficult and complex for average cooks in average kitchens. One such critic has been William Sitwell, the editor of Waitrose Food Illustrated. Sitwell argues that the modern interpretation of gastronomy lies beyond the grasp of most food lovers and home cooks. Even Heston Blumenthal, who applies the science of cooking to great success, has questioned the accuracy of the term.

­In 1998, after Nicholas Kurti passed away, Hervé This officially changed the name of the fledgling field from molecular and physical gastronomy to just molecular gastronomy. He also began to ease his strictly scientific definition of the field. Today, This acknowledges that cooking involves more than just science and technology. It also involves art and love -- components that aren't so easily described by the behavior of atoms and molecules. In this new framework, molecular gastronomy is more properly defined as the "art and science" of selecting, preparing, serving and enjoying food. Others prefer a more fanciful definition, such as the science of deliciousness, which suggests that perception and emotion are just as important in cooking as physics and chemistry.

­The emotional side of cooking may be difficult to quantify, but the science is becoming better understood every day. We'll begin to explore some of the science next.

Chemists classify all matter into three groups: elements, compounds and mixtures. An element, such as carbon, hydrogen or oxygen, can't be broken down into other substances. A compound is composed of two or more ­elements joined chemically in a definite proportion. Compounds -- water, ammonia and table salt are examples -- have properties that are separate and distinct from their constituent elements. Finally, a mixture is a combination of su­bstances that aren't held together chemically and, as a result, can be separated by physical means, such as filtration or sedimentation.

All prepared food dishes are examples of a mixture known as a colloid. A colloid is a material composed of tiny particles of one substance that are dispersed, but not dissolved, in another substance. The mixture of the two substances is called a colloidal dispersion or a colloidal system. The accompanying table shows some of the most important types of colloids you come across in cooking.

­The colloidal systems described above involve only two phases, or states of matter -- gas and liquid or solid and liquid. Sometimes, especially in food preparation, more than two phases are involved. Such a colloidal system is known as a complex disperse system, or CDS. The classic example is ice cream, which is made by churning a mixture of mil­k, eggs, sugar and flavorings as it is slowly chilled. The churning disperses air bubbles into the mixture by foaming and breaks up large ice crystals. The result is a complex substance involving solids (milk fats and milk proteins), liquids (water) and gases (air) in at least two colloidal states.

To aid in the description of complex disperse systems found in food preparation, Hervé This devised a method -- a CDS shorthand, if you will -- that could be used for any dish. His method abbreviates phases with letters and uses symbols and numbers to represent processes and sizes of molecules, respectively. For example, the shorthand for aioli sauce, a mayonnaiselike emulsion of olive oil flavored with lemon juice and garlic, would be written as:

O[10-5, 10-4] ÷ W[d > 6 x 10-7] 

O[10^-5, 10^-4] ÷ W[d > 6 x 10^-7] 

The O stands for "oil," the W for "water." The forward slash means "dispersed into." The numbers indicate sizes of the molecules. Showing molecule sizes is important because the size of solid particles in a colloid helps determine its properties. The particles dispersed in milk range from 3.9 x 10^-8 to 3.937 x 10^-5 inches (1 x 10^-7 to 1 x 10^-4 centimeters) in diameter.

After developing his system, Hervé This undertook a thorough analysis of French sauces. Most cookbooks will tell you that there are hundreds of French sauces, which are generally classified into white sauces, brown sauces, tomato sauces, the mayonnaise family and the hollandaise family. This discovered that all the French classical sauces belong to only 23 groups based on the type of CDS used to make the sauce. Not only that, This found that it was possible to move backward from a formula to a brand-new sauce never before prepared in any kitchen. In other words, you can use This' CDS system to invent new recipes from scratch.

­Understanding colloids is just the beginning. Molecular gastronomists take advantage of other scientific principles to prepare world-class dishes. We'll cover those next.

­Molecular gastronomists use ­special techniques, ing­redients and cooking principles to encourage certain chemical reactions to occur. These reactions, in turn, produ­ce startling new flavors and textures. One popular technique is cooking meat sous vide, a French term that means "under vacuum." Here's how it works: First, you pour water in a pan and heat it to a low temperature. The exact temperature varies depending on the type and thickness of the meat, but it never exceeds the boiling poin­t of water (212 degrees F, 100 degrees C). For steak, the water temperature will be about 140 degrees F (60 degrees C). Next, you place your meat, along with seasonings, into a heat-safe plastic bag, seal it and place it in the hot-water bath. The meat ­cooks slowly in the heated water and retains its moisture. After approximately 30 minutes, you remove the meat from the bag and place it in a hot frying pan. Sear the meat briefly on each side before serving. When you cut into the meat, you will find it to be juicy, tender and delicious.

An­other interesting technique is spherification, which involves making liquid-filled beads that, to use the words of a writer at Gourmet magazine, "explode in the mouth with a pleasingly juicy pop" [source: Abend]. Ferran Adrià, the chef of El Bulli Restaurant in Spain, first developed the technique and has since perfected it for a variety of dishes. Spherification relies on a simple gelling reaction between calcium chloride and alginate, a gumlike substance extracted from brown seaweed. For example, to make liquid olives, you first blend calcium chloride and green olive juice. Then you mix alginate into water and allow the mixture to sit overnight to remove air bubbles. Finally, you delicately drop the calcium chloride/olive juice mixture into the alginate and water. The calcium chloride ions cause the long-chain alginate polymers to become cross-linked, forming a gel. Because the calcium chloride/olive juice mixture enters the alginate in the shape of a droplet, the gel forms a bead. The size of the bead can vary dramatically, making it possible to create jelly-shelled equivalents of everything from caviar to gnocchi and ravioli.

Flash freezing can also be used to create fluid-filled fare. It's simple: Expose food to extremely low temperatures, and it will be frozen on the surface, liquid in the center. The technique is typically used to develop semifrozen desserts with stable, crunchy surfaces and cool, creamy centers. At Chicago's Alinea restaurant, chef Grant Achatz uses flash freezing to create a culinary delight consisting of a frozen disk of mango purée surrounding a core of roasted sesame oil. As a San Francisco blogger and food lover relates, the dish arrives with instructions: "We were instructed to allow the whole thing to melt away on our tongues. An extraordinary dance of sweet, tangy, salty, icy, creamy, oily ..." [source: Gastronomie].

Flavor juxtaposition is one of the most important tenets of molecular gastronomy. Hervé This says juxtaposition can be used to intensify a more flavorful ingredient by pairing it with a much less flavorful ingredient. Or, you can combine two dominant flavors, such as chocolate and orange, to reinforce the taste of both. Either way, understanding the molecules responsible for flavors is helpful. Molecular gastronomists have learned that foods sharing similar volatile molecules -- those that leave food as a vapor and waft to our nose -- taste good when eaten together. This concept has led to some unusual flavor pairings, like strawberry and coriander, pineapple and blue cheese, and cauliflower (caramelized) and cocoa.

­If you wan­t to test some of these techniques, you'll need the right equipment. On the next page, we'll review some essential tools of the molecular gastronomist.

­The recipe for liquid olives, which calls for 1.25 grams (0.04 ounces) of calcium chloride, 200 grams (7 ounces) of green olive juice, 2.5 grams (0.09 ounces) of alginate and 500 grams (18 ounces) of water, sounds more like the materials list of a high school chemistry experiment and hints at one important piece of equipment every molecular gastronomist must have: a scale. A good digital scale is indispensable and can even be used for nonculinary tasks, such as evaluating nutritional content or even calculating postage.

Here are some other tools you might need to master molecular gastronomy:

Of course, you'll need to have a well-stocked spice rack to accompany your high-end gadgets. We've already discussed alginate and calcium chloride -- the two chemicals needed for spherification. Another important gelling agent is methylcellulose, which congeals in hot water, then becomes liquid again as it cools. Emulsifiers are a must for maintaining a uniform dispersion of one liquid in another, such as oil in water. Two popular emulsifiers are soy lecithin and xanthan gum. Finally, more and more molecular gastronomists are turning to transglutanimase, a chemical that causes proteins to stick together. Because meat is protein, chefs can do inventive things with transglutaminase, such as removing all fat from a steak and gluing it back together or fashioning noodles from shrimp meat.

­Now we're ready to put everything together. In the next section, we'll present three recipes for a molecular gastronomy-inspired meal.

­It's not the goal of molecular gastronomists to reduce cooking to a collection of dry c­alculations and lifeless formulas. Rather inventive cooks are trying to make their­ creations e­v­en tastier, with the help of a new technique or by tweaking an old favorite. Let's see how they might ­transform this traditional meal.

­Caviar, the classic upscale hors d'oeuvre, is prepared from the eggs of certain fish species. With a little kitchen chemistry, you can enjoy a new­ kind of caviar -- apple caviar -- first developed by Ferran Adrià, the chef of El Bulli Restaurant who experimented with spherification.

Here's the basic recipe; you can find detailed instructions on the StarChefs Web site. Gather one-and-a-quarter pounds of golden apples, along with some alginate, baking soda, water and calcium chloride. Puree the golden apples, freeze for half an hour and then skim off the impurities and strain. Next, add the alginate to the apple juice while heating. Remove from heat and add the baking soda. Now prepare a calcium chloride solution by dissolving calcium chloride in water. Finally, use a syringe to add your apple juice mixture to the calcium chloride solution one drop at a time. As you do, you should see beads, or "caviar," form. Cook for a minute in boiling water, strain and rinse in a cold-water bath.

For the main course, we're going to have duck à l'orange. The classic French recipe directs you to roast the bird in an oven for about two hours. Roasting browns the meat and adds flavor through a series of chemical changes known as Maillard reactions. These reactions cause sugars and amino acids in the meat to cross-link. This, in turn, creates the compounds responsible for the pleasing color and flavor. Unfortunately, cooking meat at high temperatures also has some negative effects. Most notably, the muscle fibers contract and shorten, forcing out water and making the meat tougher.

A molecular gastronomist overcomes this by taking advantage of microwave technology. When meat is prepared in a microwave, it warms to 212 degrees F (100 degrees C) and remains at that temperature as long as it contains water. Microwaving meat is faster and more efficient than roasting, but doesn't produce the beneficial Maillard reactions. To get the best of both worlds, molecular gastronomists would brown the meat first in a skillet, inject Cointreau (an orange-flavored liqueur) into each piece with a syringe, then finish the cooking in the microwave.

Homemade vanilla ice cream is last. The best ice cream has abundant air bubbles and small ice crystals, which makes the finished product light and smooth. Traditionally, you would place your ingredients in an automatic ice cream maker to churn and freeze the mixture. Churning folds air into the material and breaks up ice crystals. But there's a limit to how cold an average machine can get. Most rely on your kitchen freezer, which reaches a temperature of 0 degrees F (-18 degrees C). A molecular gastronomist uses a simpler technique: He or she pours liquid nitrogen directly into the ingredients, which will flash freeze the mixture and create extra-small ice crystals that result in the smoothest ice cream possible.

If you're dying to make this classic dessert in a cutting-edge way, start with a basic recipe, like this one from the Food Network. After you've prepared the ice cream mixture, don your safety glasses and gloves and add liquid nitrogen while stirring with a wooden spoon. Stop when the ice cream reaches your desired thickness.

­Up n­ext, we'll talk about some chefs who have embraced molecular gastronomy.

­

Anyone can learn and apply the techniques of molecular gastronomy to basic dish­es and preparations. If we re-examine one of the pasta-cooking rules we presented in the introd­uction, you can see h­ow the application of a little science can save time and energy. Adding oil to boiling water does not, in fact, prevent pasta from clumping. Why? Because oil and water don't mix, which means the oil stays on the surface, far from the cooking noodles. Instead, add a tablespoon of something acidic, such as vinegar or lemon juice. A weak acid inhibits the breakdown of starch and reduces stickiness.

­

­For many people, this will be the extent of their hands-on involvement with molecular gastronomy. But that doesn't mean they won't appreciate the products of molecular gastronomy. Luckily, there are several chefs around the world who readily embrace physics and chemistry in the kitchen. The accompanying table lists some of the most renowned chefs who apply the principles and techniques of molecular gastronomy. But be forewarned: If you decide to visit one of these restaurants, you'll need to make reservations weeks or even months in advance. You should also be prepared to pay handsomely -- $200 a head or more -- for the experience.

If, after dining at one of these molecular gastronomy hotspots, you decide you want to become an avant-garde chef yourself, there are options. A few universities are introducing molecular gastronomy programs for postgraduate students. For example, the University of Nottingham has partnered with Heston Blumenthal to create a doctoral track. The three-year course of study provides a unique blend of science and gastronomy, with ideas and inventions devised in the laboratory being tested and refined at the Fat Duck. Several cooking schools are also incorporating molecular gastronomy in their courses. At the French Culinary Institute in New York City, students can learn about sous vide techniques, hydrocolloids and other applications of food and technology.

­Either way, as a student of cooking or as a lover of fine food, molecular gastronomy is sure to open up new vistas -- and awaken your palate to a new definition of delicious.