What You Need to Know
During heating, water evaporates around 100 °C while milk proteins and sugars concentrate. At 120–130 °C Maillard reactions brown the milk solids, generating nutty aromatics such as lactones and pyrazines. Continued heating above ~170 °C scorches the solids, degrading flavor compounds and forming acrylamide.
The Science
Primary Reaction
Maillard reaction (browning of milk proteins and sugars) and water evaporation