The lemon (Citrus limon) is a wonderfully versatile citrus fruit has close to limitless uses in the kitchen. Its mouth puckering acidity adds balance to many savoury dishes, and when teamed with sugar, it provides a wonderfully tangy note to sweet dishes as well.
There are three main varieties of lemon. The Lisbon, eureka and meyer.
- The Lisbon lemon is perhaps the most popular variety. It has a thin skin and plenty of piquantly sour flesh. The Lisbon grows to a medium size; that is around 120 mm in length. It grows on a moderately sized tree, of up to 3 metres, which bears an abundance of nasty thorns.
- The eureka is a large lemon, which has a thicker skin than the Lisbon and contains sharply acidic juice. It is the most sour lemon variety. The eureka is the most popular commercial variety as it grows on a large tree (5 metres) which contains relatively fewer thorns and crops heavily in the summer months, making it ideal for mechanical harvesting.
- The meyer lemon's slightly orange tinted skin gives evidence of its heritage. It is a lemon-orange hybrid. Meyers are almost round as opposed to the common oval shape of a lemon. They have a thin skin and sweeter juice than the other varieties.
Lemons are anatomically very similar to other citrus fruits. The outer peel or skin is almost always a vibrant yellow colour. Underneath this layer is the albedo, or white pith. Depending on the variety and growing conditions, this can range from very thin (1-2 mm) to quite thick indeed (20 mm). Inside is the juice bearing flesh that is broken down into segments that are known as carpels. These contain juice vesicles and the seeds. Each carpel is divided by a thin membranous layer.
The lemon is native to central and Southeast Asia. Sources vary widely between India, Malaysia and southern China. The citron (C. medica), a huge, thick-skinned super lemon was brought back to Europe in the 3rd Century BC, by Alexander the Great, but it wasn't until the Middle Ages that the lemon was introduced to Europe by returning Crusaders.
Ascorbic acid, or vitamin C is one of the principal nutrients in lemons, a fact long recognized by mariners. They would routinely issue lemons to their crew to ward off scurvy, a vitamin C deficiency.
On a flippant note, the ever-enlightening Larousse Gastronomique claims that it was tradition for pre-18th Century French schoolboys to present lemons to their master at the end of year. Try that today.
Flavour and uses
So what gives a lemon its delightfully sour flavour? Lemons have a fairly low pH. At 2.1, they are well into the acid spectrum. But most citrus fruits are the same. What sets the lemon apart is it's amazingly low sugar content. At 1% sugar, they don't have the ability to mask the perceived sourness as other citrus fruits can.
Many keen cooks would be aware that rubbing certain fruits and vegetables with lemon juice after cutting prevents them from browning. Artichokes, potatoes, apples and pears are the most usual suspects. Few however, are aware of how lemons do this. The browning of these fruits and vegetables is due to a bothersome enzyme, polyphonoloxidase, which causes phenolic compounds in the plant tissue to rapidly oxidize. Polyphonoloxidase is missing in citrus fruits, melons and tomatoes. More importantly, the enzyme responsible is inhibited by highly acidic conditions, particularly malic acid, but also citric acid and ascorbic acid, which lemons have in abundance.
In the kitchen, lemons are close to ubiquitous. Few cooks would go for more than a few days without including lemon in a recipe. A tip for maximizing the amount of juice extracted from a lemon (and indeed, all citrus fruits) is to warm them before juicing. A warm lemon can provide as much as twice the juice of a cold one. Try briefly microwaving or pouring boiling water over lemons before juicing to maximize your yield.
Lemon peel, or zest contains wonderfully pungent essential oils that will give a dish heightened citrus complexity. Try adding the zest to your next lemon recipe, be it sweet or savoury. There are several methods of zesting a lemon. A handy kitchen gadget is the citrus zester. It is a small handled tool that has a flat stainless steel protrusion at one end. This section is slightly tapered at the tip and contains 5 or 6 holes. Simply drag the zester across the lemon skin and the zest comes away in attractive strips. Alternatively, you can grate the skin on the finest holes of a kitchen grater. The third method is to peel the skin with a vegetable peeler. Finely chop the zest, removing as much of the bitter albedo as possible.
If you want to try some lemon recipes, Everything2, of course, has them in abundance. Here are a few to get you started.