Maillard reaction

The Maillard reaction is the chemical browning that produces the deep flavour and colour of seared meat, toasted bread, roasted coffee, dark beer, and chocolate. Discovered by French chemist Louis-Camille Maillard in 1912.

The reaction: amino acids (from proteins) combine with reducing sugars at high heat to produce a cascade of new flavour compounds — roughly 1000 distinct molecules have been identified. The colour follows the chemistry; the same reactions that produce flavour also produce melanoidins (brown polymers).

Practical Maillard:

• Starts around 140°C (285°F). Below this, browning is via caramelisation (sugar alone, no protein involvement) or doesn’t happen at all.
• Accelerates at low moisture. Water buffers temperature at 100°C; you need to drive off surface moisture before Maillard ramps up. This is why “pat dry before searing” is the universal advice.
• Slows at very high heat (above ~190°C) as carbonisation takes over and bitter compounds dominate.

Caramelisation (sugar alone) is the related but distinct reaction — happens at ~170°C, no protein needed. Onion caramelisation, dulce de leche, and crème brûlée all rely on caramelisation rather than Maillard.