The lemon (Citrus × limon) is a hybrid in cultivated wild plants. It is the common name for the reproductive tissue surrounding the seed of the angiosperm lemon tree. The fruit are used primarily for their juice, though the pulp and rind (zest) are also used, primarily in cooking and baking. Lemon juice is about 5% acid, which gives lemons a sour taste and a pH of 2 to 3. This makes lemon juice a cheap, readily available acid for use in educational science experiments.

　　Description

　　A lemon tree can grow up to 10 meters (33 feet), but they are usually smaller. The branches are thorny, and form an open crown. The leaves are green, shiny and elliptical-acuminate. Flowers are white on the outside with a violet streaked interior and have a strong fragrance. On a lemon tree, flowers and ripe fruits can be found at the same time.[1]

　　Lemon fruit are oval. When ripe, they have a bright yellow nose, a layer of pith underneath and a paler yellow segmented interior. Small seeds commonly known as 'floopies' are found within the fruit.

　　History

　　William-Adolphe Bouguereau Girl Holding LemonsThe lemon is a cultivated hybrid deriving from wild species such as the citron and mandarin. When and where this first occurred is not known. The citron – apparently the fruit described in Pliny's Natural History (XII, vii.15) as the malum medicum, the "medicinal fruit" – seems to have been the first citrus fruit known in the Mediterranean world. Depictions of citrus trees appear in Roman mosaics of North Africa, but the first unequivocal deSCRIPTion of the lemon is found in the early 10th-century Arabic treatise on farming by Qustus al-Rumi. The use and cultivation of the lemon, by the Cantonese (Southern Barbarians) is noted in the early 12th century. At the end of the 12th century, Ibn Jami', personal physician to the Muslim leader Saladin, wrote a treatise on the lemon, after which it is mentioned with greater frequency in the Mediterranean. However, it is believed that the first lemons were originally cultivated in the hot, semi-arid Deccan Plateau in Central India.

　　The origin of the name "lemon" is through Persian (Limu [pronounced with long e and short u]), akin to the Sanskrit nimbuka. They were cultivated in Genoa in the mid-15th century, and appeared in the Azores in 1494. More recent research has identified lemons in the ruins of Pompeii. Lemons were once used by the British Royal Navy to combat scurvy, as they provided a large amount of Vitamin C.

　　In food preparation

　　LemonsLemon, raw, without peel Nutritional value per 100 g (3.5 oz)

　　Energy 30 kcal 120 kJ

　　Carbohydrates 9 g

　　- Sugars 2.5 g

　　- Dietary fiber 2.8 g

　　Fat 0.3 g

　　Protein 1.1 g

　　Water 89 g

　　Vitamin C 53 mg 88%

　　Citric acid 5 g (Percentages are relative to US recommendations for adults. )

　　Both lemons and limes are regularly served as lemonade or limeade, its equivalent, or as a garnish for drinks such as iced tea or a soft drink, with a slice either inside or on the rim of the glass. Only lemons, however, are used in the Italian liqueur Limoncello. A wedge of lemon is also often used to add flavor to water. The average lemon contains approximately 3 tablespoons of juice. Lemons warmed to room temperature before squeezing (in a microwave or by leaving on a counter) increases the amount of juice that can be extracted. Storing lemons at room temperature for long periods makes them more vulnerable to mold.

　　Lemon juice is typically squeezed onto fish dishes; the acidic juice neutralizes the taste of amines in fish by converting them to nonvolatile ammonium salts.

　　In addition, lemon juice is widely used, along with other ingredients, when marinating meat before cooking: the acid provided by the juice partially hydrolyzes the tough collagen fibers in the meat (tenderizing the meat), though the juice does not have any antibiotic effects.

　　Some people like to eat lemons as fruit; however, water should be consumed afterwards to wash the citric acid and sugar from the teeth, which might otherwise promote tooth decay and many other dental diseases. It can be used on its own or with oranges to make marmalade.

　　Lemons also make a good short-term preservative, commonly used on sliced apples. This keeps the fruit crisp and white for about a day, preventing the unappetizing browning effect of oxidization. This helps to prolong the usage of the fruit.

　　Chemistry

　　D-limoneneLemons and other citrus fruits contain amounts of different chemicals and are thought to have some health benefits. They contain a terpene called D-limonene which gives their characteristic lemon smell and taste. Lemons contain significant amounts of citric acid; this is why they have a low pH and a sour taste. They also contain Vitamin C (Ascorbic acid) which is essential to human health. 100 milliliters of lemon juice contains approximately 50 milligrams of Vitamin C (55% of the recommended daily value) and 5 grams of citric acid.

　　Lemons can be processed to extract oils and essences.

　　Health benefits

　　Some sources state that lemons contain unique flavonoid compounds that have antioxidant and anti-cancer properties.[3] These may be able to deter cell growth in cancers. Limonins found in lemons could also be anti-carcinogens.

　　Because of its high Vitamin C content, lemon has been touted in alternative medicine as a tonic for the digestive system, immune system, and skin.[citation needed]

　　There is a belief in Ayurvedic medicine that a cup of hot water with lemon juice in it tonifies and purifies the liver.

　　In a Japanese study into the effects of aromatherapy, lemon essential oil in vapour form has been found to reduce stress in mice.