The Dish on the Maillard Reaction

I’ve been told that I am the home economics teacher you’ve always wanted. As a chef and culinary educator, I started the Retro Rad cooking movement to encourage all of you to dig through your mother’s recipe boxes, dust off your pressure cookers and crock pots, and take the old and make it new.

Recently I was asked to explain what actually happens while food is being cooked. What is the “magic” that occurs when we brown our food and sear it to perfection?

Close your eyes and breathe in deeply. While you exhale, imagine the smell of meat grilling, dim sum pan-frying, fish broiling, coffee roasting, and bread baking. Every human feels a primordial “perking up” when they experience this sensation. As proteins start heating up, your surroundings become aromatic, and all your senses are activated. Your eyes open wide and your ears tune in to explain the dark toasty notes filling your nostrils.

It’s all the result of the Maillard reaction and caramelization.

Until the early 1900s, not much thought was given to the heating or “browning” of food. That began to change in 1912 when French chemist Louis- Camille Maillard identified that the amino acids in proteins found in our food react with reducing sugars when introduced to elevated temperatures. In doing so, he set the foundation for food science and changed the way we look at steak forever.

There are basically two types of reactions that occur when food is heated, the aptly named Maillard reaction and caramelization. Both are referred to as nonenzymatic browning and differ from enzymatic browning, which occurs through chemical changes without heat, like fermentation.

We are playing Mad Scientist every time we tie on aprons and turn up the heat. Those special odors, flavors, textures, and colors that occur during the browning of our food are the result of what Nobel Prize winner Jean-Marie Lehn refers to as “the most widely practiced chemical reaction in the world.”

The Maillard reaction is the effect amino acids and sugars produce when the surface temperature of food is raised to more than 300˚. What begins as a simple chemical reaction quickly becomes very complicated. The molecules produced keep reacting in ever more complex ways and generate literally hundreds of various molecules. These rearranged amino acids and sugars exude the potent aromas, tastes, and colors associated with roasting, baking, and frying.

Though similar in effect and often appearing simultaneously, there is one very distinct difference between caramelization and the Maillard reaction. Caramelization occurs when sugars react with sugars. A basic example of caramelization is the browning of a crème brulee. Sugars chemically reorganize between 310°–338˚. As the heat increases, the electrons break apart and reorganize causing a noticeably darker color, richer flavors, and more intense aromatics.

So, what determines which reaction will occur? The ratio of the Maillard reaction to caramelization that takes place depends on the amino acid/protein and sugar/carbohydrate content of the foods you are cooking. Carrots and onions for example, have lots of sugars, so roasting these root vegetables will result in considerably more caramelization than Maillard compounds. Seared steak, on the other hand, will have become browned and flavor-enriched mostly from the Maillard reaction.

When cooking, high temperatures are key and the food must be fairly dry on its outside surface. Foods cooked by wet methods will only reach 212°, the boiling point of water. This means, when creating that delicious seared flavor, boiling and steaming are out while roasting, broiling, grilling, sautéing, and frying are in. Pat meat and veggies dry with a paper towel before placing in the oven or a hot skillet. Also, be sure not to crowd the skillet or roasting pan, which may cause moisture to accumulate.

As delicious as it is, you might think that raising the temperature even higher would enhance caramelization and the Maillard reaction. It does to a point, but above 355° a different set of reactions occurs. The technical term is pyrolysis, but we all call this burning. Although a lot of us like foods a little charred, with too much pyrolysis comes bitterness. The black compounds that pyrolysis creates may also be carcinogenic, so go easy on the charring.

Harold McGee, author of On Food and Cooking, reminds us that there is much to be learned when it comes to the chemistry of cooking. We find references to the Maillard reaction and caramelizaton in most basic cooking methods. However, there are numerous chemical reactions taking place when food is browning and they are still “not very well understood.”

Give Yourself a Hand When Determining Doneness

Rare (Kate Atherton) Rare: The internal temperature of rare beef is about 140˚. When meat is rare, it will feel soft and yielding, like the flesh between your thumb and index finger when you pinch them together.

Medium Rare (Kate Atherton) Medium Rare: The internal temperature of medium rare beef is about 150˚. When meat is medium rare, it will feel a bit resistant to the touch, like the flesh between your thumb and middle finger when you pinch them together but less soft and yielding than rare.

Medium (Kate Atherton) Medium: The internal temperature of medium beef is about 160˚. When meat is medium, it will feel increasingly taut, like the flesh between your thumb and ring finger when you pinch them together but less soft and yielding than medium rare.

Well Done (Kate Atherton) Well-Done: The internal temperature of well-done beef is about 170˚. When meat is well done, it will yield only slightly to the touch, like the flesh between your thumb and little finger when you pinch them together, but less soft and yielding than medium.