Maillard reaction
Also searched as: browning, roasted aromas, crust, searing
In short: In strong heat, protein and sugar react with each other. This creates brown colour and hundreds of roasted aromas.
Like a campfire with wet wood: first the water has to go, then it burns. As long as the surface is wet, it boils at 100 °C, however hot the pan is.
Water is evaporating. The surface is stuck at 100 °C; no browning yet.
- 100 °Cwater evaporates, surface is stuck
- 140 °Cbrowning begins
- 190 °Cturns bitter and burns
Below 100 °C none of this happens yet. From 100 °C: water evaporates, surface is stuck.
What happens
From about 140 °C, building blocks of protein combine with sugar into hundreds of new aroma compounds and brown colour. As long as there is water on the surface, it stays stuck at around 100 °C, because the water has to evaporate first. Only once it is dry does the temperature rise and browning begin. Alkaline conditions speed up the reaction.
Why it matters
The crust on a steak, bread crust, roasted onions, coffee, roast vegetables: almost everything that tastes savoury and roasted comes from here.
Rules of thumb
- Pat the surface dry before it goes into the pan.
- Preheat the pan properly and do not overcrowd it.
- Leave it alone at first until the crust releases by itself.
- A pinch of baking soda speeds up browning, e.g. with onions.
Levers
Common mistakes
- Overcrowding the pan: juice runs out and the meat stews grey instead of frying.
“Searing seals in the juices.” Not true. The crust is not watertight. Searing brings flavour and colour, not juice.
In practice
Meat
Pat dry, hot pan, a little at a time. A full pan cools down and the meat turns grey.
Bread
Steam at the start keeps the crust soft so the loaf can rise. Then bake dry and it browns. Pretzels get so dark because the lye is alkaline.
Vegetables
Dry vegetables well and do not overload the tray. A pinch of baking soda browns onions faster.
Coffee and tea
When roasting, Maillard and run together. Lightly roasted tastes nutty, dark roasted toasty to bitter.
- Harold McGee: On Food and Cooking (2004), Kapitel Fleisch
- Royal Society of Chemistry: The Maillard reaction