Authentic Key lime pie is yellow, not green (green means artificial food coloring and flavoring). Photo by David Hsu | Dreamstime.
Updated August 2009
Key Lime: The Sassy Ingredient In One Of America’s Favorite Pies
Plus Easy Recipes
An Overview Of The Lime
We are unabashed fans of Key lime pie. We love it so much, we often make the filling alone, to serve crustless in pots de crème or ramekins (for a grandiose presentation, you can use martini glasses, and for a “deconstructed” Key lime pie, sprinkle the top with graham cracker crumbs). The peak season for Key limes is June through August, so you can find this special fruit in your market now and use these delicious and easy recipes.
Key limes (Citrus aurantifolia Swingle), also known as Mexican limes and West Indies limes, are grown in the Florida Keys (plus Mexico and the West Indies, in case that isn’t apparent). They are much smaller than the standard supermarket lime known as the Persian or Tahitian lime (Citrus latifolia). You can see the relative sizes in the photo at the right, the Persian lime in the center and the Key lime at the right. Both are the only two acid, or sour, limes in world trade.
Left to right: the sweet lime, Persian lime and Key lime. Key limes have thin skins and yellow flesh. The juice is more sour than Persian limes, and the flesh contains many more seeds
The Key lime has a higher acidity, a stronger aroma, and a thinner rind than the Persian lime (Citrus x latifolia). While each food has a unique, compared to other limes, the Key lime is tart rather than sour. Some ascribe bitterness to it, but we’d say it has a milder quality, and therefore just right for desserts.
There are other major varieties of limes that can be found in the U.S. The rangpur lime (Citrus X limonia Osbeck) from the Pacific Rim, which is generally candied or pickled and, in the west, most popular in marmalade; the kaffir lime (Citrus hystrix), whose leaves are used in Thai, Malaysian and Indonesian cuisines; the sweet lime or limetta (Citrus limettioides), a hybrid between a Mexican lime and a sweet lemon or sweet citron, grown in California and Italy and eaten as a fruit in South America, India and North Africa. See the different types of limes in our Lime Glossary.
The History Of The Key Lime Pie
The recipe for Key lime pie, a lime custard pie, was created in Key West. There were no cattle on the island, and canned milk, first marketed by Borden’s in 1859, was used for all purposes. The original Key lime pie was a no-bake pie; the acid from the lime juice curdled and set the egg yolks.
Today, Key lime pie is the state pie of Florida and the official dessert of Key West, where there are variations of the recipe, including those with meringue topping and/or a pastry crust (believed to be the original crust)—plus a lively debate as to which is the “correct” form of the pie.
While Key limes seem rare and exotic today, they were grown commercially in southern Florida until they were wiped out in a 1926 hurricane. The growers replanted with the hardier and easier* Persian lime trees.
*Persian limes are not only easier to grow, but easier to pick because they have no thorns, and easier and more economical to ship due to their much thicker skin.
Authentic Key lime pie has a firm custard texture and a pale yellow color. Many people use bottled Key lime juice; but as with anything, the difference between bottled and fresh-squeezed juice makes the difference between a decent and a spectacular pie. The good news is that, you can squeeze the juice and freeze it for up to three months. Until next Key lime season, you can substitute Persian limes in this recipe (but the flavor of Key limes is more bright and special, which is why people pay more for them).
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