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.

pH and the speed of the reaction: alkalinity dramatically accelerates Maillard. The classic example is pretzels — a brief dip in a sodium hydroxide or baking soda bath raises the surface pH to ~12, which is why the crust browns far darker and faster in the oven than a plain bagel does at the same temperature. Adding a pinch of baking soda to a hamburger patty before searing produces the same effect on a smaller scale. Conversely, acidic ingredients (lemon juice on chicken, vinegar in a marinade) slow Maillard and produce less brown crust at the same heat. Restaurant cooks adjust this consciously; home cooks often don’t realise the marinade is fighting the sear.

Acrylamide — the health-policy footnote: very high-temperature Maillard reactions on starchy foods (potatoes, bread crusts, coffee) produce trace acrylamide, classified by the IARC as “probably carcinogenic to humans”. Real-world dietary exposure is low, but the EU and UK published guidance in 2018 recommending lighter browning on commercial fried products. Domestically, this means “golden, not dark” rather than burnt crusts — a marginal change for most diets but a meaningful one for people who eat large quantities of fried starchy foods. Related: oven temperature converter, Gas Mark. Reference: Hodge JE, J Agric Food Chem, 1953.

Worked example

Sear a 200 g ribeye in a cast-iron pan. Step one — surface dry: blot with paper towels and salt 40 minutes ahead so surface moisture is wicked off (wet meat in a 180°C pan steams to ~100°C until the surface dehydrates, then jumps to pan temperature; this is the “why isn’t it browning” failure mode). Step two — preheat pan to ~230°C (smoking lightly), add a thin film of high-smoke-point oil. Step three — lay the steak down and do not move it for 90 seconds. With a 230°C surface and a dry contact patch, Maillard runs hard for 60-90 seconds before water trapped in the meat reaches the surface and stops the reaction. Flip, repeat. The crust you can scrape with a knife is the visible product of perhaps 0.5 g of amino-acid-plus-sugar polymerisation — but it’s 80% of the perceived flavour of the dish.

When and why it matters

Most home-cooking complaints about “bland meat” or “pale chicken” are Maillard failures, not seasoning failures. The three diagnostic questions: is the surface dry before the meat touches the pan, is the pan hot enough (water flicked on should sizzle and skitter, not pool), and is the meat in contact with the pan rather than steaming under its own crowded juices. Restaurants brown in small batches at high heat for precisely this reason. The same chemistry is why oven-roasting at 160°C produces grey chicken skin and the same bird at 220°C produces brown crispy skin — below ~140°C surface temperature, Maillard simply doesn’t run regardless of how long you cook. Reference: EFSA — Acrylamide in food.