What is Maillard browning?

The chemistry behind why baked surfaces turn brown and develop roasted, savory flavors. Named after French chemist Louis Camille Maillard, who described the reaction in 1912. Amino acids (protein) react with reducing sugars (glucose, fructose, but NOT sucrose directly) at temperatures starting around 280°F / 140°C, kicking into high gear at 310°F / 155°C and above. The reaction produces hundreds of flavor compounds — roasted notes, browning pigments, toasted aromas — that are responsible for the flavor of bread crust, brownie tops, seared meat, and roasted coffee. Distinct from caramelization (which is sugar breaking down on its own at higher temps, around 320-360°F / 160-180°C). Both reactions happen on a brownie surface during baking and combine to create the crackly mahogany top crust that defines a good fudge brownie.