Behind the browning of toast, chocolate, steak and even your favorite coffee beans.
By Robert Lindsay and Rich Hartel
1. What do toast, raisins, caramels, chocolate and beer all have in common? They are all examples of the Maillard reaction, a chemical process that occurs when certain foods are cooked or processed. Triggered by the interaction of reducing sugars and proteins within foods, the Maillard reaction helps create the unique colors and flavors of all of the above items. It’s also one of the key reactions at work when grilling red meats or roasting coffee beans.
2. Think of it as what browning can do for you. People have known since ancient times that foods take on new aromas and tastes as they brown. But it was only in the last century that someone figured out why. In 1913, French chemist Louis-Camille Maillard discovered that under high heat carbon atoms from reducing sugars such as lactose, glucose and fructose combine with nearby amino acids to form new compounds. While processes like carmelization can produce similar pigments, these chemical recombinations produce rich, savory flavors that are unique to grilled, fried or roasted foods.
3. The Maillard reaction is an indispensable tool of the flavor industry. Maillard-induced flavors are often meaty, brothy, roasty, toasty, nutty or gravy-like in taste and smell, making them useful as natural ingredients to add flavor to processed foods. Food chemists use industrial processes to create and capture these unique flavor compounds, which are commonly added to a variety of foods. And there’s more where those flavors came from. Many of the compounds created by Maillard reactions—including some important to flavor—have yet to be characterized.
4. It can be fast—or slow. While Maillard reactions occur quickly in cooking, they can also unfold over longer periods of time in foods stored at lower temperatures. The flavors that emerge in ripening cheese, for example, are due in part to the Maillard reaction. It’s also the secret to Serrano ham, a raw meat that is dry-cured for several months to bring out smoky flavors.
5. Yeah, but it’s a dry heat. If you’re looking to master the Maillard reaction in your cooking, it’s important to create the right environment for a little food chemistry. The reaction moves fastest at high temperatures with little moisture and neutral to slightly alkaline conditions. Water tends to slow or stop the reaction, which is why boiling doesn’t cause foods to brown. So turn on the grill and enjoy the results.
Robert Lindsay and Rich Hartel have a combined 60-plus years of teaching, research and outreach experience with CALS’ food science department. Lindsay, a retired professor of food science, is an expert on flavor chemistry who has identified pathways for the formation of flavors in dairy, seafood and vegetables. Hartel is a professor of food engineering who studies crystalline structures in food. In 2008, he co-authored the book Food Bites: The Science of the Food We Eat, with his daughter, Annakate Hartel.