Maillard reaction
The Maillard reaction is a chemical reaction between amino acids and reducing sugars to create melanoidins, the compounds which give browned food its distinctive flavor. Seared steaks, fried dumplings, cookies and other kinds of biscuits, breads, toasted marshmallows, and many other foods undergo this reaction. It is named after French chemist Louis Camille Maillard, who first described it in 1912 while attempting to reproduce biological protein synthesis. The reaction is a form of non-enzymatic browning which typically proceeds rapidly from around 140 to 165 °C. Many recipes call for an oven temperature high enough to ensure that a Maillard reaction occurs. At higher temperatures, caramelization and subsequently pyrolysis become more pronounced.
https://en.wikipedia.org/wiki/Maillard_reaction