Earlier, in my review of Hyde and Co., I mentioned a most un-English fellow, Maillard – to be precise, Louis Camille Maillard (1878 – 1936). He was a doctor and chemist, and a decorated one as well, at least in his native France. But in our time he is best known for something foundational to pretty much all sorts of cooking. Indeed, Maillard’s discovery, along with that of Ikeda Kikunae (more on him later), probably counts as the foundation of flavour chemistry – the first scientific attempts to figure out what we talk about when we talk about flavour.
It all started in 1912, when Maillard undertook a project to study the reactions between amino acids, the building blocks of proteins, and sugars, the basic fuel of all living things. Mixing a dose of glucose and a dose of glycine, he heated the mixture and observed that it turned brown. (He probably also observed that it smelled good, but this is speculation.) The next year, Maillard published a paper outlining some of the products of the sugar-amino acid reaction.
Given how much emphasis the French place on good food, it’s a little weird that more significance was not placed on this discovery. But that’s what happened, actually; Maillard himself never really looked into the process of the reaction in his paper, or examined its applications in the context of cooking. The work he started would not be further developed and understood until the 1950s, when an American chemist named John Hodge actually figured out how the reaction works.
Even though it’s called the Maillard reaction, it is actually a general term for a vast range of reactions which produce a kaleidoscope of deliciousness. To give an idea of how fundamental the Maillard reaction is to cooking, all of the following derive some part of their flavour or fragrance from it:
- Grilled meat
- French fries
- Caramelised onions
- Roasted coffee beans
- Anything with wok hei
- Soy sauce
- Whisky and beer
- Mature cheese
- Mature ham
The Maillard reaction can take place at room temperature, but it is very slow. Therefore soy sauce, where the reaction is crucial, can take months to mature properly. Add heat, however, and you can speed things up a lot, especially as the food heats to around 140 degrees Celsius.
The heat helps to break proteins down into amino acids, which then react with sugars over a three step process. Each sugar reacts its own way, and each amino acid also reacts its own way; so by permutation, you can get hundreds and hundreds of flavour compounds just from grilling a nice piece of sirloin. The picture below shows the three steps, and some of the products; it is estimated that six hundred products of the Maillard reaction come together to give us the flavour known as ‘perfectly browned steak’.
In terms of actually cooking food, the Maillard reaction is important for just about everything that uses dry heat. Processes that use wet heat, like boiling, steaming or cooking something sous vide, will not brown, because the food will never be hotter than the boiling water, namely 100 degrees Celsius. As mentioned above, that’s not quite hot enough for the reaction to proceed at its peak.
Since it also causes foods to go brown, the Maillard reaction can be confused with caramelisation, but the two things are rather different. The difference is probably clearest when making butterscotch or salted caramel, if you melt the sugar first. As the sugar syrup goes brown, it gives off a fragrance; this is pure caramelisation, which only requires sugars to be heated. Once you take butter and cream and throw it in to sizzle in the hot syrup, you add milk proteins, which are the second ingredient required; the new fragrance that comes from that is contributed by the Maillard reaction
Of course, if you then continue heating the butterscotch, eventually the smell will go from complex and fragrant to bitter and acrid, and the colour goes from nicely brown to black. As the temperature rises, both caramelisation and the Maillard reaction give way to pyrolysis, or charring.
Cooking with dry heat (frying, grilling, roasting, baking etc.) is therefore a delicate balance between the three processes and the temperature at which they dominate. Too low, and something is cooked without having any flavour (too little Maillard). Too high, and you get a blackened hunk of carbon (it’s all pyrolysed).
It’s always amazing to know that some of the most complex, alluring and different flavours that humans can taste all spring from the same family of reactions. Since taste is evolved for animals to figure out the best, most nutritious foods, one has to wonder why humans love the products of the Maillard reaction so much; after all, we are the only animals that cook our food and therefore deliberately induce the reaction.
Or maybe it’s the other way round. Since cooking makes food easier to digest, and is generally an advantageous thing for humans to do, we learned to love the smells that cooking produces, especially when it involves the proteins and sugars that we need to survive.
The warm waft of freshly baked bread in the murky hours of morning. The seductive, smooth scent of meat and fish sitting over hot coals as the sun sets over a nearby sea. The heady aroma of wok hei, springing out at us from a freshly served plate of char kuay teow. We learn that these smells are good, and we can’t get enough of them.
Anyway, I’ve just managed to make myself hungry and am off to find something to eat. Have a lovely weekend ahead, and enjoy the fruits of the Maillard reaction!