The next time you put your steak on to sizzle remember you’re actually performing your very own scientific experiment. The Maillard (pronounced like my-yard) reaction is what happens when the protein in meat, for example, is heated to 310°F or higher and is what causes your meat to turn brown. But whilst it is sometimes called the ‘browning reaction’ as it turns foods brown, the important part of the Maillard reaction isn't the colour, but the flavours it creates.
The name comes from French chemist Louis Camille Maillard, who discovered the process at the beginning of the 20th century.
The Maillard reaction doesn't just happen with meat either, from roasting coffee beans to making pork crackling, the Maillard reaction is responsible for the flavour and colour of lots of different foods, from caramel made from milk and sugar to maple syrup and even beer and self-tanning products!
It’s not a single reaction but a complicated set of reactions where hundreds of different flavour compounds are created. It's all about amino acids reacting with reducing sugars to create these flavour compounds which are then broken down to create even more new flavour compounds and so on. The creation of these flavour compounds is key in the heating, including baking and frying, of nearly all foods.
Different foods have a different and distinct set of flavour compounds created during the Maillard reaction.
So whilst two foods both undergo the Maillard reaction, the different amounts of simple sugars and amino acids in the food will produce difference smells, which is why frying fish doesn't smell the same as roasting coffee.
It also means that foods cooked in different ways will have different flavours, i.e., boiling or poaching of fish for example (which won't produce a Maillard reaction) will create a different flavour than if you roasted or grilled it.