Do you like toast better than bread? Roasted coffee more than green beans? A perfectly grilled steak better than steak tartare? There is one important chemical reaction that makes your cooked food taste better than raw food and there are four things you can do to make your favourite steak taste even better.
That reaction is the Maillard reaction. The Maillard reaction is probably one of the most important chemical reactions that takes place when you cook food and also one of the most mysterious. The Maillard reaction is one of three chemical reactions that results in your food turning brown. It also results in the production of lots of flavour compounds, called the melanoidins.
Maillard? What the hell does that mean?
Chemical reactions are generally named for the process they describe (i.e. the oxidation reaction) or after some dude who discovered it (I say dude because only four named chemical reactions are named after women). The Maillard reaction is named after French physician and chemist Louis Camille Maillard. He discovered and first described the reaction in 1912, while trying to explain what happens when amino acids react with sugar at high temperatures, but its importance in the chemistry of food was not fully realised until the 1950s.
It is commonly known as the Maillard reaction; however it is actually a series of reactions that occur at the same time or one after another in your food as you cook it. There are a few essential components for the Maillard reaction, and one that sets it apart from one of the other key browning reaction, caramelisation, although they can both occur together.
For the Maillard reaction to take place you need three things: sugar, an amino acid and heat. The sugar can be a small sugar, like sucrose, glucose or fructose or can be tied up in a bigger carbohydrate molecule like starch. The amino acid can be a free amino acid or more commonly part of a protein chain. And this is where the Maillard reaction differs from caramelisation. The Maillard reaction requires protein whereas caramelisation occurs in the absence of protein. Think of torching the top of a crème brûlée and the sugar turning brown. That is caramelisation because the reactant is sugar in the absence of protein.
Many different factors also play a role in the Maillard reaction and thus in the final colours and flavours; types of amino acids and sugars, acidity, temperature, time, presence of air, water and other food components are also important in the products formed. During cooking, hundreds of different flavour compounds are created. These compounds in turn break down or react with more amino acids to form yet more new flavour compounds. Each type of food has a very distinctive set of flavour compounds that are formed during the Maillard reaction.
How to make the most of the Maillard reaction
Don’t forget the protein
Protein is why the Maillard reaction can become complicated and why it can result in many different flavours and aromas. There are many different amino acids and they occur in different proportions in different foods, and the type of amino acid determines the resulting flavour. As a result of different amino acids and the sequential nature of the reactions, hundreds of different flavour compounds are created. For examples cysteine, a sulfur-containing amino acid abundant in red meat, reacts with sugars to form sulfur containing compounds which are important components of roasted meat flavour – why roast beef tastes and smells different from roast chicken and baking bread.
When cooking the surface temperature of your food must get above 110°C.
Although the Maillard reaction can happen at room temperature, it is very slow. It requires a heat of at least 110°C to happen rapidly. This is because it requires a large amount of energy to force the initial reaction between the sugar and amino acids to occur.
Since water boils at 100°C, water is the enemy of the Maillard reaction. If you are cooking in water, it will be hard for the Maillard reaction to occur because the temperature of your food will never get above 100°C. The presence of surface moisture also influences the reaction. The surface moisture of food steams, which lowers the temperature, slows the reaction and reduces the amount of browning.
Furthermore, only the surface of your food will ever get hot enough for the Maillard reaction to take place. The moist inside of meat, vegetables and dough will never exceed 100°C. That is why the outside of your bread crusts up and becomes brown while the inside is white and fluffy. That is also why all your recipes tell you to brown the meat, vegetables and flour before adding any liquid to stews and curries. You want the Maillard reaction to do its flavour forming thing before you limit the temperature of your cooking to less than 100°C. Conversely, if you want to emphasize the natural flavours of food, avoid the Maillard reaction and the intense but less individualized browning flavours it creates by avoiding by high temperatures, using long slow cooking or moist techniques like boiling, steaming and braising.
There is an exception to this rule and that happens when you change the acidity or alkalinity of the liquid that you are boiling your food in, or you greatly increase the cooking time. For example, the base liquid for brewing beer, a water extract of barley malt that contains reactive sugars and amino acids from the germinated grains, deepens in colour and flavour with several hours of boiling.
Reduce the moisture content of your food.
So, like I said above, water is the enemy of the Maillard reaction and moisture on the surface of your food will prevent it from getting to the required temperatures for the Maillard reaction to readily take place. So it follows that if you reduce the moisture content of your food, especially on the surface, you will get a better reaction.
So how do you reduce the moisture content on the surface of your food? This works best with meat and the general consensus is to leave you meat in an environment that is lacks moisture you will get a dryer surface and tastier dinner. Max Veenhuyzen at the Guardian suggests leaving your roast chicken uncovered in the fridge for a few hours before cooking to dry the skin out – his mum’s secret.
Tim Ferris recommends drying your steak for a few hours or overnight by dry brining it. Coat one side with salt and sit uncovered, salty side up in your fridge. Salt draws out the water. Then about 90 minutes before cooking, put the steak in the freezer for 45 minutes, elevated and unwrapped so all surfaces are exposed, like on a cake rack on a plate to catch drippings. Any leftover surface moisture evaporates rapidly in the dry atmosphere in the freezer.
Add sugar/carbohydrate to your food.
One way to increase the reaction rate is to increase the heat. Another is to increase the reactants. So sprinkling sugar or a source of sugar like corn flour or corn starch is another way to make the most of the Maillard reaction.
Cook’s Illustrated rubs steaks in salt and corn starch and then puts them in the freezer for 30 minutes. While he salt helps draw extra moisture to the surface, the corn starch absorbs moisture and promotes the development of an especially crisp crust because the starches in the corn starch enhance browning by adding more sugars to the Maillard reaction.