What is the Maillard reaction? It’s why browned food tastes so good

• The Maillard reaction is a complex chemical reaction that scientists are still studying.
• Essentially, proteins attack reducing sugars to cause browning and create some of our favorite flavors.
• For better Maillard browning in your kitchen, pay attention to acidity levels and sugar.
• Visit Insider's Home & Kitchen Reference library for more stories.

If you've ever enjoyed a sip of coffee, reached for the browned bit of cheese in your quesadilla, or slow-cooked a brisket, you're already well-acquainted with the Maillard reaction, the complicated yet beloved chemical reaction that creates many of our favorite flavors.

"Maillard creates a lot of flavor compounds that we like and associate with comfort foods," says Pat Polowsky, a food scientist based in Madison, Wisconsin. "It also creates that signature brown color."

Along with the color, the Maillard reaction creates "roasted notes, nutty notes, and burnt aromas," according to Polowsky. It's that rich, resonant note in your coffee, the browned bits of the brisket, the extra flavor in the bread crust.

The Maillard reaction was discovered by French chemist Louis Camille Maillard in 1912, whose research originally focused on kidney disorders. (Fun fact: The Maillard reaction can happen inside the human body!)

Since then, Maillard has become almost a household name, thanks to his contribution to our understanding of how the Maillard reaction affects the flavor of our food.

We chatted with Polowsky and Sarah Tracy, a food historian and author of the forthcoming "Delicious: A History of Monosodium Glutamate and The Fifth Taste" for more on Maillard.

The science of the Maillard reaction

"You need two things for the Maillard reaction," says Polowsky, "Protein of some type - or even amino acid, just something protein-like - and a specific type of sugar called reducing sugars."

Polowsky explains that sucrose is not a reducing sugar, so browning in baking is not evidence of the Maillard reaction. The browning on your pepperoni pizza, however, is.

Some mistakenly say that the Maillard reaction requires heat. While the Maillard reaction is famous for its cooking applications, "you don't necessarily need heat," says Polowsky. "It can happen under normal temperatures, but it will take months to years." A can of shaker Parmesan, for instance, can go brown in your fridge if it sits for long enough.

In other words, heat triggers the process, and it's important in cooking applications, but it's not quite accurate to say that Maillard browning requires heat.

The Maillard reaction is extremely complicated, and the actual chemistry is still being studied, Polowsky says. There's a lot we still don't know.

But, in short, what we see in cooking is heat essentially egging on protein to attack sugar. The sugar kicks off a chain of reactions, which first are quite volatile, then eventually become more stable. This chemical process unlocks aroma and flavor that wouldn't have been detectable otherwise.

"You can initially prevent this under acidic conditions, under which protein can't attack as efficiently," Polowsky explains.

The antithesis to this is the traditional step of alkaline baths for pretzels and bagels. The alkalizing process encourages the Maillard browning that we know and love in those baked goods as well.

Though the Maillard reaction is talked about glowingly by chefs and food lovers, it's not always desirable. Polowsky cites the grated Parmesan and condiments like ketchup as foods that are susceptible to non-heat-driven Maillard browning that we generally don't want it from. The extra depth of flavor in ketchup may be tasty, but most people would find brown ketchup kind of icky.

Another example is Gatorade.

"Especially the Gatorade that they added protein to," he says. "Gatorade is not that acidic and has lots of sugars. If they're adding peptide or proteins for recovery, that can go brown, so they have to formulate it to prevent that."

What does the Maillard reaction taste like?

The Maillard reaction encourages layered, rich flavors that we associate with comfort. Think of the difference in flavor between a slice of bread and a piece of toast or between the interior of a baked potato and French fries.

The exact composition of amino acids and sugars makes each Maillard-browned food taste a little different, but there's a complexity to it that makes it extra appealing.

And though the Maillard reaction does lead to flavors we think of as caramelly, caramelization is a different process entirely.

"Caramelization needs much higher temperatures. It's literally just the sugar molecules breaking down. The sugar undergoes pyrolysis (turning into fire), breaking itself down into color pigments and flavor compounds. But, it doesn't need a protein to do it and happens at much higher temperatures."

A slow-roasted brisket, therefore, has undergone the Maillard reaction, but not technically caramelization.

Why do we like it so much?

For most of history, says Tracy, "the imperative to cook food was really the same as drying or salting it: to keep it from going bad, to make it more portable for travel, and to eat during the winter when fresh foods were scarce."

To even be able to cook food a certain way because we like its flavor better is a fairly modern luxury. Roasted brussels sprouts are far more popular than boiled, thanks to the Maillard reaction, but either will nourish our bodies.

Sometimes, Maillard is talked about in relation to umami, "the fifth taste" that encompasses savory flavors. It's not necessarily related to umami, though, says Polowsky, and umami could even be destroyed in the Maillard process. However, "it does create aroma and color cues that prime us to find umami." Amino acids are crucial to the Maillard reaction, and also to the functioning of our bodies.

"We eat with our eyes first," says Polowsky. The rich, nutty notes of a Sunday roast, the golden outside of croissants, and even the browning on French fries - all evidence that the Maillard reaction has occurred - let us know that thing is safe and satisfying to eat.

How to take advantage of the Maillard reaction

• Cook dry food at high heat. This more quickly triggers the Maillard reaction, allowing that rich, flavorful sear on something like a steak.
• Don't be afraid of corn syrup. Corn syrup, composed of glucose and fructose, is much better for Maillard browning than sucrose. In general, more varied types of sugars will help with the Maillard reaction because they encourage the proteins to attack more of the sugars.
• Let your cheese brown. Whether it's oozing out the sides of your grilled cheese and hitting the frying pan or you're creating a crust for your mac and cheese, that caramelly crunch will be the envy of the dish.
• Add acid later. Wait until after your food is cooked to add lemon or other acidic components. Acid inhibits Maillard browning.
• Add toasted components. Toast accompanying bread either in a toaster or by making it into crostini to add some Maillard reaction magic to your meal. Even the breadcrumbs you use to coat your chicken could benefit from a quick toast. Nuts, seeds, and spices can also be toasted before adding them to a dish.

Insider's takeaway

The Maillard reaction is a complex chemical process that we have to thank for some of our favorite foods. It's best harnessed with a combination of heat, reducing sugars, and amino acids, and results in the rich flavors in beer, coffee, brisket, steak, french fries, and many of our other favorite foods.

In your own cooking at home, make sure to wait until your food is cooked to add acidic components like a lemon squeeze, and in general, don't be afraid of browning. It's not burning, it's becoming more flavorful!

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