Have you ever wondered why a crusty steak, a crispy golden-brown loaf of bread, a perfectly fried french fry all taste amazing? All of these achieve their texture and flavor to an interesting phenomenon called the Maillard reaction, discovered and named after French chemist, Louis-Camille Maillard. It's obvious that cooked food tastes different than raw food, but food cooked perfectly golden-brown has a distinct flavor, creating hundreds of flavour and aroma compounds, making food taste better.
To understand this further, let's take a look at the chemistry behind this reaction. All food can be broken down into three simple categories - sugar, protein, and water. Upon reaching 150ºC, the sugar begins one of the three sub-reactions of the Maillard reaction. The sugar reacts with an amino group on a protein forming a glycosylamine. The product of this reaction then undergoes two other reactions, finally producing reductones, essential for the charred-cooked flavor food gives. If you've ever noticed your coffee tastes a little darker or burnt, it means the beans were likely roasted too long. This permeating flavor throughout the food essentially differentiates a boiled steak from a beautifully seared one.
But now, more onto the different effects of the Maillard reaction. For example, in coffee, melanoidins (products of the Maillard reactions) contribute to mouthfeel and color. The reducing of sugars and amino acids essentially reason why burnt food tastes bad - as almost everything in the food has denatured, there is really nothing left to taste.
Additionally, the most notable effect of the Maillard reaction is the change in color. A burnt steak is black, an over-charred toast is incinerated into ash, the longer the reaction takes place, the darker the color. This all revolves around the key factor of the reaction – heat. The length of time the reaction takes place above 150ºC, the darker the food will become. However, as we know, the graph of flavor looks more like a parabola than a straight line, and our goal as cooks is always to try to get as close to the apex as possible.