Limoncello is an Italian lemon liqueur mainly produced in Southern Italy. It is also produced in Calabria, Abruzzo, Basilicata, Apulia, Sicily, Sardinia, Liguria, Menton in France, and the Maltese island of Gozo. It is also a popular homemade liqueur. Limoncello has usually a slightly turbid appearance, which originates from the presence of small (approximately 100 nanometers) essential oil droplets suspended in the drink. The spontaneous emulsification of hydrophobic essential oils in alcohol/water mixtures is often referred to as the ouzo effect.
Traditionally, limoncello is made from the zest of Femminello St. Teresa lemons, also known as Sorrento or Sfusato lemons. Lemon zest, or peels without the pith, is steeped in rectified spirit until the oil is released. The resulting yellow liquid is then mixed with simple syrup. Varying the sugar-to-water ratio and the temperature affects the clarity, viscosity, and flavor. Opaque limoncellos are the result of spontaneous emulsification (otherwise known as the ouzo effect) of the sugar syrup and extracted lemon oils.
Limoncello is the second most popular liqueur in Italy after Campari and has recently [when?] become popular in the United States, Canada, the United Kingdom, Australia, and New Zealand, where restaurants are now increasingly offering limoncello on their beverage and dessert menus.
The United States has seen a rise in commercial producers using California lemons which are grown year-round, with 90% of the United States lemon crops coming from California. A popular ingredient in cocktails, limoncello imparts a strong lemon flavor without the sourness or bitterness of pure lemon juice.
Limoncello is traditionally served chilled as an after-dinner digestive. Along the Sorrentine Peninsula and the Amalfi Coast, it is usually served in small ceramic glasses that are also chilled. This tradition has been carried into other parts of Italy. Limoncello is also used to make various cocktails, pastries, or ice cream.
Alcohol content can vary widely, especially among homemade variants, but the average alcohol content is between 25% and 30%. Wikipedia