Allium cepa is a biennial plant with adventitious and fibrous roots and 3–8, distichous, glaucous leaves. The bulb is made of concentric, enlarged fleshy leaf bases. The outer leaf base dries and becomes thin and variously coloured, forming the protective coat, while the inner leaf bases thicken when the bulb develops. The mature bulb can be globose, ovoid or elongate and its size varies depending on the cultivar.
The genus Allium is very large and consists of many wild edible species(only a small fraction is cultivated commercially),and is widely distributed over temperate zones in the northern hemisphere.
The plant portion commonly used is the bulb, which is utilized as a food ingredient to give flavour and aroma to a great variety of dishes. The bulb is eaten raw or cooked. The leaves and the flowers of the plant are also edible and are often used in salads. The seeds of the plant are sprouted and eaten as well. Onion is used as food and spice in diets of almost all cultural areas.
Onion nutritional composition is very complex. It has-been shown that it is one of the major sources of dietary flavonoids in many countries. Specifically, onion has been characterised for its flavonol quercetin and quercetin derivates. Moreover, it is rich in other bioactive compounds such as frutooligosaccharides and sulfur compounds.
Allium
cepa L. or onion
