A history of Key Lime Pie
Key Limes, also known as Mexican or West Indian Limes (Citrus aurantifolia) are thought to have originated in Southeast Asia, probably making their way across the ocean on one of Christopher Columbus's expeditions. Seeds flourished in the warm Florida climate especially around Key West.
However, in 1926 a hurricane struck the lime groves virtually wiping them out. The growers replanted with Persian limes (Citrus latifolia) which, unlike the small, very thorny Key limes, were easier to pick and transport. Persian limes which are readily available in today's shops are oval with a dark green, thick rind and less acidic than Key limes.
Only a few genuine Key lime trees are still in existence in the Florida Keys. Key limes are round, with thin yellowish-green skins, about the size of ping-pong ball, juicer, more tart, aromatic and acidic. Key limes are now chiefly grown commercially outside the United States, returned as concentrates and then reconstituted.
There are numerous stories about the origin of the pie. One popular version is that it was created by millionaire William Curry's cook, Aunt Sally, in the mid-19th century. There might be some truth in the story as it was about that time that sweetened condensed milk was invented in 1856. There is also a suggestion that the pie was adapted from an old Caribbean dessert made from sour oranges. (See Condensed Milk below.)
Key West has little pasture for grazing cattle, and in those days of no refrigeration, milk and cream were in short supply. Hardly surprising then that the advent of condensed milk was a boon to the cooks of Key West, especially when they realised that the reaction between the condensed milk and the acidic lime juice caused the mixture to thicken naturally.
Originally the pies would have had a shortcrust pastry base but Graham Cracker crumbs appear to be the norm today. However, a crust made from crushed chocolate cookies is also making its appearance on dining tables.
The pie's topping also caused some controversy – whether to add a meringue or cream topping, or leave it plain. Meringue probably came about from frugal housewives wishing to use up the left-over egg whites from the egg yolks that go into the 'custard' filling; cream became an option after the advent of refrigeration. One thing that unites all serious cooks is that absolutely no artificial colouring should be used in the filling – its colour should be pale yellow from the juice of the limes (bottled is fine) and egg yolks.
There is also a debate as to whether the pie should be baked. Originally the pie was not baked, but with fears of salmonella from raw eggs many cooks prefer to bake their pies for about 10 minutes, before serving it chilled -some cooks even pop the pie in the freezer for 15 minutes chilling before serving.
The Graham Cracker - the preferred choice in North America for many cooks as the base for cheesecakes and desserts such as Key Lime Pie - was the creation of the Rev. Sylvester Graham, a Presbyterian minister in Bound Brook, New Jersey.
Graham was a vegetarian, much concerned with the nation's health and moral well-being. He advocated a special vegetarian health diet to include fibre-rich bread specially milled from the whole wheat, its bran and wheat germ having been coarsely ground and combined with the more finely ground endosperm. The resulting brown flour, known as Graham flour, had a coarse texture with a sweetish, nutty flavour. The bread, made from this flour was certainly healthier than the over- refined, chemical additive white loaves that were the fashion of the age.
Graham introduced the Crackers that bear his name, and whose main ingredient is Graham flour, in 1829 as part of his health regime.
Today's Graham Crackers are more likely to be made from refined, bleached flour sweetened by honey or sugar, and considered to be more of a snack than a health food.
(The nearest United Kingdom equivalent to Graham Crackers is Digestive Biscuits. However, it is becoming increasingly easy to buy Graham Crackers in the UK either on line or in specialist stores and some supermarkets.)
Condensed and Evaporated Milk
Drinking fresh milk prior to the middle of the 19th century was a dangerous business. Hygiene standards were poor and without refrigeration milk rapidly spoiled.
But things were to change following a transatlantic crossing made by Gail Borden in 1852. The crossing was rough and the cows carried on board ship were unable to give milk because of sea-sickness.
By 1854 Borden had devised a way of preventing milk from souring. By heating it and thereby condensing it, he found that the milk would survive for three days. It took him another couple of years to realise that in fact it was the heating process that was killing the bacteria that caused the milk to spoil. Adding sugar also helped to hinder the bacteria growth. Borden was granted the patent for sweetened condensed milk in 1856.
It was John Baptist Meyenburg, a Swiss who had emigrated to the United States, who took the process one stage further by producing unsweetened condensed milk. Meyenburg, realised his ambition of canning unsweetened condensed milk in 1885.
1892 saw Borden adding evaporated milk to his product line. Seven years later in 1899 with Meyenburg's help, Elbridge Amos Stuart discovered a way of producing canned, sterilised, evaporated milk.
But who it was who discovered that a chemical reaction between the condensed milk and citrus juice causes the mixture to thicken, is not recorded!