Onion (Allium cepa L.)

 

Used plant part

Bulb (subterranean leaves). Superterranean green leaves display the same aroma, but are slightly less intensive; in their culinary use, they equal chives.

Plant family

Alliaceae (onion family).

Sensoric quality

In fresh state, spicy, pungent and lachrymatory. For more information on hot and pungent spices, see sichuan pepper.

Main constituents

Fresh onions contain only traces (0.01%) of essential oil, which mostly consists of sulfur compounds: Ethyl and propyl disulfides, vinyl sulfide and other sulfides and thioles. The lachrymatory principle is variously identified as thiopropanal-S-oxid (CH3-CH2-C(SO)H) or its tautomer propenyl sulfenic acid (CH3-CH=CH-SOH). This substance is released from its precursor S-1-propenyl-L-cysteine sulfoxide as a reaction to cell damage; this mechanism is very similar to that in garlic.

Origin

Onion seems to originate from West or Central Asia. In Europe, it is known since the bronze ages (see poppy on the Homeric epics); together with garlic, onion it is mentioned in the oldest part of the Bible, the Pentateuch (see pomegranate).

Etymology

The origin of late Latin cepula (diminutive form of cepa) is unclear, but it is the source of the Italian and German names; the similarity of German zwei "two" is purely coincidental.
French, English and Dutch names derive from late Latin unio "onion", probably related to unus "one" because of the single, perfectly shaped onion bulb in contrast to the multitude of garlic cloves.

The second element of Swedish rödlök is further discussed under garlic. Its first element röd "red" serves to distinguish onion from garlic, which is termed vitlök, where vit means "white". This usage is closely paralleled in Indonesian, where bawang putih "garlic" and bawang merah "onion" are formed with adjectives putih "white" and merah "red".

All the names of shallots derive from the West Asian city Askalon; it is, however, not clear whether shallots in truth have their origin in West Asia. The German regional name Klöben is related to English cleave, referring to the several sub-bulbs of shallot. The same element is also found in Knoblauch, the German name of garlic.
Onion certainly is a borderline case between spices and vegetables; I have, however, included it to this list because it is an indispensable ingredient to nearly every cuisine of the world, and it is used for large spectrum of different dishes.

Pastes prepared by grinding onions together with a variety of spices are known in quite many countries. Since raw onions easily turn bitter, such pastes must be prepared fresh and used without much delay; alternatively, they can be preserved by adding some acid (e.g., vinegar or lemon juice). Indonesia displays a great variety of onion-based spice pastes (bumbu, see lemon grass); from the New World, Jamaican jerk is the most famous example. (see allspice). Both concoctions are mostly used to marinate meat or fish.

 

Onion plants www.botanikus.de

In India, onion is the basis of most sauces and gravies. Nearly every North Indian recipe starts with the same procedure: Fry chopped onions slowly, add spices (frequently fresh garlic and ginger and dried spices like coriander, cumin, nigella, turmeric, black cardamom, chiles) and fry until the onion turns golden. The mixture (wet masala) may afterwards be pureed, simmered with tomatoes or yoghurt, or just added to boiling vegetables or meat. It is part of the art of Indian cooking to estimate spice amounts in advance; if you take too much or too little, the error will become manifest only in the last phase of cooking, when corrections are difficult to make.

In the Imperial cuisine of Northern India (moghul cuisine, see black cumin), gravies are prepared in a similar way; yet aromatic spices (cinnamon, Indian bay-leaves and cloves) are used more lavishly at the cost of pungent chiles.

Gravies based on onion are prepared in another way in Burma, whose unique situation between China, India and Thailand has given rise to a unique cuisine. The dishes called "curries" in Burma are meat cubes or vegetables braised in a rich spicy gravy prepared in advance: Onions, vinegar, garlic, fresh ginger, cumin, coriander and of course chiles are blended to a smooth paste and fried in sesame oil until the fat separates from the gravy. By the long frying procedure, Burmese curries acquire a very complex taste not easily found in the cuisines of other contries.

By frying, onion changes its taste and turns more sweet and aromatic; the flavour develops best after long frying in comparatively cool fat. Fried onion rings are popular in Central Europe as a decoration, e.g., for German mashed potatoes, but they are also known in Vietnam and especially in Indonesia, where nasi goreng (fried rice) is nearly always topped with them. After removal of the fat used for frying, they can be stored for several hours without losing their crispy texture, provided they are kept in an air-tight container.

Onions may also be dried, in which case they again change their flavour and turn more garlic-like. Onion powder is a rather popular spice in the South of the US and in México, and forms part of commercially available chile-con-carne spice mixtures (together with cumin, oregano, garlic, pepper and chiles).

Shallots stem from a closely related plant, Allium ascalonicum. They are smaller and grow in clusters with up to five bulbs; their taste is somewhat finer and less pungent. Shallots are most popular in Northern France, where they are essential for sauces based on red wine. Contrasting the usage of ordinary onion, shallots are never fried (because the French believe them to turn bitter on frying), but mostly cooked or braised (e.g., for sauces made from red wine). Shallots are called for by the classic recipe sauce béarnaise (see tarragon).

Quite many Far Eastern cookbooks suggest to use shallots instead of onions, since the latter are closer to Asian onions both with respect to size and flavour. Shallots are particularly suited to substitute onions in the Indonesian spice paste bumbu (see lemon grass).