Key Lime Pie

A crust made from crushed crackers is filled with a mixture in which the tartness of lime and the sweetness of sweetened condensed milk are in balance. Key lime pie, emblematic of the Florida Keys in the United States, is a dessert with a pale filling made from egg yolks, citrus juice and preserved milk. The small, round Key lime belongs to a different lineage from the common Persian lime. Its flesh is yellowish green, strongly acidic and distinctively aromatic. The filling, made by mixing condensed milk with the juice and egg yolks, turns pale yellow rather than bright green, and this too comes from the colors of the fruit and the egg yolks. Beyond its color, the filling is also distinctive because it combines dairy with citrus.

Combining condensed milk, egg yolks and lime juice and pouring the mixture into the crust

The basic method for the oven-baked version follows this order: sweetened condensed milk and egg yolks are mixed until smooth, the juice is added, and the mixture is poured into a graham cracker crust. The acid in the juice acts on the milk proteins and changes the viscosity, and the egg yolks set when heated, making the filling firm enough to slice. The process differs from that of a tart in which lemon curd is first cooked in a pan and then used as the filling. Because condensed milk adds sugar and milk solids at the same time, it cannot be replaced with the same amount of unsweetened milk.

The crust is not made of folded layers of flour and butter like pie pastry, but of fine crumbs of baked goods pressed together. Some versions are topped with whipped cream and others with meringue. The leftover egg whites can be used for meringue, but meringue is not a required finish for every version.

A 1964 Florida postcard carries a recipe in which beaten egg whites are folded into a filling of condensed milk, egg yolks and lime juice. The filling is poured into a baked pie shell, topped with meringue made from separate egg whites, and baked until browned. It is one example of egg whites being used both in the filling and on top.

Preserved milk on the islands and where Key limes are grown

In an era when fresh milk was hard to obtain on the islands, condensed milk, which keeps well, was used for making sweets. Today, Key limes are not grown only locally. A powerful hurricane in 1926 destroyed much of the islands’ commercial plantings, which never recovered to an industrial scale, and current commercial production is mainly in Mexico and Brazil. Today, fruit grown outside the islands is also used in pies in the Keys. Old no-cook recipes (ingredient proportions and methods) are also mentioned, but thickening by acid is not the same as the effect of heating. Current baked recipes call for baking the pie in the oven, letting it cool slightly and then refrigerating it.

Who was “Aunt Sally”?

A Keys legend holds that the pie was made by “Aunt Sally,” who was connected to the Curry family. Local historian Tom Hambright suggests that she may have refined a fishermen’s sweet, while food writer David Sloan regards her not as a servant but as Sarah, the wife of Curry’s son. Opinions also differ on who Sally was and how she was involved in making the pie.

The fishermen’s sweet that Sloan describes combined, in a cup, the condensed milk, limes and dry Cuban-style bread that fishermen took with them on fishing trips lasting several days. Because it used preserved milk and stale bread that was broken up and moistened, Sloan himself suggests it may have been more like a pudding than the modern baked pie. It is an origin story tied to island life, in which a meal eaten aboard a boat turned into a dessert of a grand household.

The theory of a condensed milk company origin and the records that remain in the Keys

Pastry researcher Stella Parks drew attention to “Magic Lemon Cream Pie,” which a New York condensed milk company popularized in 1931. Her theory is that, because its composition of citrus juice, condensed milk and eggs is similar, the local limes may have been substituted for the lemons. Parks considered it possible that the method of making pies with shelf-stable dairy products spread from the condensed milk company.

Countering this, Sloan cites a listing for “lime pie, ten cents” at the Green Lantern Tea Room in the January 27, 1926 issue of the Key West Citizen. At the very least, an item named “lime pie” was being sold in the Keys before 1931.

He also presents the Blackwell family recipe from the August 25, 1939 issue of the Miami Herald, which includes eggs, lime juice, condensed milk, a baked crust and meringue, along with an explanation that the family had used it for more than half a century. Records of pies sold in the Keys and accounts of methods handed down in families remain, separate from the theory that the pie originated with the condensed milk company.

Chosen as the state pie

Florida designated it the official state pie by a 2006 law, which took effect on July 1 of that year. In the mid-20th century it was also served as a celebrated slice at the Fern Inn in Islamorada and became known to visitors to the islands as well. The state designation marked the moment this regional specialty became an official symbol.

A related pie made with lemon, and a frozen chocolate-coated version

For the “Magic Lemon Meringue Pie” that Eagle Brand currently publishes, egg yolks are combined with lemon zest, sweetened condensed milk and juice, and the mixture is poured into a baked crust or a graham cracker crust and baked. The pie is then topped with egg-white meringue and baked again. Although limes and lemons are different fruits, the similar compositions of juice, preserved milk and eggs can be compared.

Kermit’s shop in the Keys also sells an item made by putting a slice of pie on a stick, freezing it and coating it in chocolate. A cold chocolate surface covers the cracker crust and the tangy dairy filling. This item turns a pie served on a plate into something that can be held in the hand and eaten, and it differs not only in its topping but also in its temperature and in how it is eaten.

Glossary