Key lime pie is an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 dessert

Dessert

In cultures around the world, dessert is a course that typically comes at the end of a meal, usually consisting of sweet food. The word comes from the French language as dessert and this from Old French desservir, "to clear the table" and "to serve." Common Western desserts include cakes, biscuits,...

 made of key lime

Key lime

The Key lime is a citrus species with a globose fruit, 2.5–5 cm in diameter , that is yellow when ripe but usually picked green commercially. It is smaller, seedier, has a higher acidity, a stronger aroma, and a thinner rind than that of the Persian lime...

 juice, egg yolk

Egg yolk

An egg yolk is a part of an egg which feeds the developing embryo. The egg yolk is suspended in the egg white by one or two spiral bands of tissue called the chalazae...

s, and sweetened condensed milk in a pie

Pie

A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients....

 crust. The traditional Conch

Conch (people)

Conch , was originally a slang term for native Bahamians of European descent.Several theories have been proposed for the origin of the term:*After the American Revolution, many loyalists migrated to the Bahamas...

 version uses the egg whites to make a meringue

Meringue

Meringue is a type of dessert made from whipped egg whites and sugar, occasionally some recipes may call for adding an acid such as cream of tartar or a small amount of vinegar and a binding agent such as cornstarch found in icing sugar which may be added in addition to the corn starch which...

 topping. The dish is named after the small key limes (Citrus aurantifolia

Key lime

The Key lime is a citrus species with a globose fruit, 2.5–5 cm in diameter , that is yellow when ripe but usually picked green commercially. It is smaller, seedier, has a higher acidity, a stronger aroma, and a thinner rind than that of the Persian lime...

'Swingle') that are naturalized throughout the Florida Keys

Florida Keys

The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...

. While their thorns make them less tractable, and their thin yellow rind more perishable, key limes are more tart and aromatic than the common Persian lime

Persian lime

Persian lime , also known as Tahiti lime or Bearss lime , is a citrus fruit sold simply as a "lime" in the United States...

s seen year round in most U.S. grocery stores.

Key lime juice, unlike regular lime juice, is a pale yellow. The filling in key lime pie is also yellow, largely due to the egg yolks.

During mixing, a reaction between the condensed milk and the acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

ic lime juice occurs which causes the filling to thicken on its own without requiring baking. Many early recipes for key lime pie did not instruct the cook ever to bake the pie, relying on this chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 (called souring

Souring

Souring is a cooking technique that uses exposure to an acid to effect a physical and chemical change in food. This acid can be added explicitly , or can be produced within the food itself by a microbe such as Lactobacillus.Souring is similar to pickling or fermentation, but souring typically...

) to produce the proper consistency of the filling. The acid in the lime juice actually "cooks" the pie. Today, in the interest of safety due to consumption of raw eggs, pies of this nature are usually baked for a short time. The baking also thickens the texture more than the reaction alone.

History

Key lime pie was invented in the late 19th century in Key West, Florida

Key West, Florida

Key West is a city in Monroe County, Florida, United States. The city encompasses the island of Key West, the part of Stock Island north of U.S. 1 , Sigsbee Park , Fleming Key , and Sunset Key...

. The creator of key lime pie is Fern Butters (1892-1975). It was believed that William Curry, a ship salvager and Key West's first millionaire, had a cook named Aunt Sally. Aunt Sally created the pie. However, some believed that Sally changed the pie that local sponge fishermen already created.

The first recipe for key lime pie was recorded in the 1930s. Key lime pie is made with canned sweetened condensed milk, since fresh milk was not a common commodity in the Florida Keys

Florida Keys

The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...

before modern refrigerated distribution methods.

Legislation

In 1965, Florida State Representative Bernie Papy, Jr., introduced legislation calling for a $100 fine to be levied against anyone advertising key lime pie that is not made with key limes. The bill did not pass.

In 2006 both the Florida House of Representatives and the Florida Senate passed legislation {HB 453} and {SB 676} effecting that key lime pie is the "Official Pie of the State of Florida", as of July 1, 2006.