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Giving Thanks for the Maillard Reaction

Photo by Element5 Digital on Unsplash

Thanksgiving dinner is a production. One cousin is in charge of both roasting and deep-frying the turkeys. Because the crispy Brussels sprouts with apples and cranberries I brought one time were a hit, I am expected to deliver those every year. Two countertops are covered in desserts, from Connecticut-made chocolates to the requisite pumpkin pies. Roasting marshmallows on the bonfire while the adults have a beer is a tradition, followed by a cup or two of coffee.

Besides thanking everyone for their role in making this happen, we have to thank science.

The Maillard reaction is named after French chemist Louis-Camille Maillard, who discovered this in 1912, though it took for John E. Hodge a few decades later to explain how the chemistry worked.

The Maillard reaction is actually a sequence of multiple reactions between amino acids (the building blocks of protein) and sugars when heated at a high enough temperature for moisture to evaporate.

As explained in Chemical & Engineering News, the Maillard reaction has three stages: “First, the carbonyl group of a sugar reacts with an amino group on a protein or amino acid to produce water and an unstable glycosylamine. Then, the glycosylamine undergoes Amadori rearrangements to produce a series of aminoketose compounds. Last, a multitude of molecules, including some with flavor, aroma, and color, are created when the aminoketose compounds undergo a host of further rearrangements, conversions, additions, and polymerizations.”

When this happens, the aroma, flavor, and color change. Even the texture changes. It is what turns bread to toast, Sugar Maple sap into syrup. There is a range of aromatic and flavor compounds, and these vary based on the type of sugars and amino acids, as well as cooking time and temperature.

J. René Coffee Roasters trailer at the Connecticut Science Center

Jose René Martinez, owner of J. René Coffee Roasters, explains what the Maillard reaction means for coffee: “When roasting, the Maillard reaction occurs when reducing sugars and amino acids bind around the 140-200℃ (284-392℉) temperature mark. Many of the flavor compounds in coffee are developed during this very critical stage.”

“Around 170℃/338℉ and upward,” René says, “coloring or ‘browning’ of coffee begins. Compounds, including melanoidins, as well as aromatic compounds begin to develop during this stage. The reactions that occur during this phase are critical to the complexity of aromas in roasted coffee, which is why a roaster must carefully monitor the rate at which these changes occur when roasting.”

René tells us that “as a roaster, [his] job is to carefully monitor the Maillard Reaction during a coffee roast to ensure that the vital aromatic flavor compounds are occuring in such a way that maximizes the pleasant tasting flavor notes we love so much in coffee.”

“From green coffee inspections to eliminating unripened beans to extreme focus during the development phase of roasting, we have to be diligent in our efforts,” René says. “Otherwise it will lead to underwhelming or poor tasting coffee.”

Next time you sip an espresso or nibble on a chocolate chip cookie, you will know what is responsible for the great taste!


Happy Thanksgiving! Celebrate the Maillard reaction with a visit to the J.René Coffee Roasters trailer in the Connecticut Science Center lobby. It’s open Tuesday through Friday, 8:30AM – 3:00PM, and Saturday & Sunday, 9:00AM – 3:30PM (except holidays). Drop by after experiencing the Science Center’s exhibits, or if you’re just passing through on your way to work. 


Kerri Provost is a Communications Research Associate at the Connecticut Science Center who is outdoors whenever possible and is currently attempting to walk every block of Hartford. She is the co-producer of Going/Steady, a podcast about exploring The Land of Steady Habits and beyond.