Triple sec is a liqueur made from the dried peels of Curaçao oranges. The is used to describe any generic beverage made from Curaçao oranges, and technically specialty beverages like Cointreau, Curaçao, and Grand Marnier are all simply forms of triple sec. Many liquor stores and major markets carry generic triple secs, along with fancier branded versions of this liqueur, and it is a common staple in most bars as well.
To make this liqueur, producers need dried skins of Curaçao oranges, oranges unique to the island of Curaçao in the Caribbean. The history of the Curaçao orange begins in Spain, where orange farmers selectively bred oranges to produce the famously sweet Valencia Orange. When Spanish settlers moved to Curaçao, they brought some of their favorite oranges with them, and discovered to their chagrin that the fruit turned out extremely bitter in the climate and soil conditions of the island.
The oranges were allowed to run wild on the island, since no one could come up with a use for them. In the mid 1800s, however, someone seized upon the idea of marinating the dried skins of Curaçao oranges in alcohol and then distilling the results to create a liqueur. The result was an early form of triple sec, which in turn generated a demand for the once-useless bitter oranges of Curaçao. Today, demand is so high that many distilleries use bitter orange peels from other varieties of orange to make this liqueur, with Curaçao liqueur being the only version which is certifiably made with Curaçao oranges.
Classically, the orange peels are steeped for 24 hours in a plain alcohol before being distilled three times to make an extremely concentrated liqueur. Sugar is often added to triple sec to cut the bitterness of the oranges, and the clear beverage may be colored to make it more visually interesting. Some producers also add other spices and flavorings to the beverage.
The quality of this orange-flavored beverage varies considerably. Some brands are good enough to drink on their own as aperitifs or digestifs, while others are more suitable for mixing with other drinks. Triple sec is an ingredient in a broad array of mixed drinks, and it is also sometimes used in cooking to flavor various foods. Triple sec-soaked cakes, for example, are a not uncommon sight during the holidays in some regions of the world.