The Maillard Reaction in Reducing Sauces
We reduce liquids all the time in recipes as a way of concentrating flavor. In our Mexican Pulled Pork recipe, we reduced the braising liquid we had used to cook the pork until it took on the thick, syrupy consistency of a glaze and its flavor deepened dramatically. As familiar as the benefits of reducing liquids are to us, the glaze's intense taste made us wonder: Was all that rich flavor derived simply from evaporating the water from the braising liquid, or was there a more complex dynamic at work?
A chat with our science editor revealed the answer: The reduction's richness is in part due to the same process that makes a seared steak taste so good—the Maillard reaction. When the proteins and sugars in meat (or most any foodstuff) are subjected to a high enough temperature (around 300 to 500 degrees), they combine, leading to browning and the creation of hundreds of new flavor compounds.
In our carnitas recipe, proteins and sugars are pulled from the pork by the braising liquid, which also contains sugars from lime and orange juices. After the meat is removed, the liquid is boiled to evaporate all the water. With the water removed, the temperature of the glaze can rise higher than water's boiling point of 212 degrees, eventually kicking off the Maillard reaction. The result: a viscous, highly concentrated glaze with exceptional depth of flavor.