Asparagus

Asparagus officinalis
Wild Asparagus in Austria
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Asparagales
Family:	Asparagaceae
Genus:	Asparagus
Species:	A. officinalis
Binomial name
Asparagus officinalis L.

Steamed Asparagus prepared with roasted pine nuts.

Asparagus officinalis with dewdrops.

Asparagus officinalis is a spring vegetable. A flowering perennial ^[1] plant species in the genus Asparagus in the lily family, like its allium cousins, onions and garlic, it is native to most of Europe, northern Africa and western Asia.^[2][3][4] and is widely cultivated as a vegetable crop.

Biology

Asparagus is a herbaceous perennial plant growing to 100–150 centimetres (39–59 in) tall, with stout larissa stems with much-branched feathery foliage. The "leaves" are in fact needle-like cladodes (modified stems) in the axils of scale leaves; they are 6–32 millimetres (0.24–1.3 in) long and 1 millimetre (0.039 in) broad, and clustered 4–15 together. The root system is adventitious and the root type is fasciculated. The flowers are bell-shaped, greenish-white to yellowish, 4.5–6.5 millimetres (0.18–0.26 in) long, with six tepals partially fused together at the base; they are produced singly or in clusters of 2–3 in the junctions of the branchlets. It is usually dioecious, with male and female flowers on separate plants, but sometimes hermaphrodite flowers are found. The fruit is a small red berry 6–10 mm diameter, which is poisonous to humans.^[5]

Plants native to the western coasts of Europe (from northern Spain north to Ireland, Great Britain, and northwest Germany) are treated as Asparagus officinalis subsp. prostratus (Dumort.) Corb., distinguished by its low-growing, often prostrate stems growing to only 30–70 centimetres (12–28 in) high, and shorter cladodes 2–18 millimetres (0.079–0.71 in) long.^[2][6] It is treated as a distinct species Asparagus prostratus Dumort by some authors.^[7][8]

History

Asparagus has been used from early times as a vegetable and medicine, owing to its delicate flavour and diuretic properties. There is a recipe for cooking asparagus in the oldest surviving book of recipes, Apicius’s third century AD De re coquinaria, Book III. It was cultivated by the ancient Egyptians, Greeks and Romans, who ate it fresh when in season and dried the vegetable for use in winter. Asparagus is pictured on an Egyptian frieze dating to 3000 B.C. France’s Louis XIV had special greenhouses built for growing it.^[9]

It lost its popularity in the Middle Ages but returned to favour in the seventeenth century.^[10]

Uses

Culinary

Three types of asparagus on a shop display, with white asparagus at the back and green asparagus in the middle. The plant at the front is Ornithogalum pyrenaicum, is commonly called wild asparagus, and sometimes "Bath Asparagus".

Only young asparagus shoots are commonly eaten: once the buds start to open the shoots quickly turn woody and become strongly flavoured.

Asparagus is low in calories and is very low in sodium. It is also a good source of vitamin B6, calcium, magnesium and zinc, and a very good source of dietary fiber, protein, vitamin A, vitamin C, vitamin E, vitamin K, thiamin, riboflavin, rutin, niacin, folic acid, iron, phosphorus, potassium, copper, manganese and selenium. The amino acid asparagine gets its name from asparagus, the asparagus plant being rich in this compound.

The shoots are prepared and served in a number of ways around the world, typically as an appetizer^[11] or vegetable side dish. In Asian-style cooking, asparagus is often stir-fried. Cantonese restaurants in the United States often serve asparagus stir-fried with chicken, shrimp, or beef, and also wrapped in bacon. Asparagus may also be quickly grilled over charcoal or hardwood embers. It is also used as an ingredient in some stews and soups. In the French style, it is often boiled or steamed and served with hollandaise sauce, melted butter or olive oil, Parmesan cheese or mayonnaise. Tall, narrow asparagus cooking pots allow the shoots to be steamed gently, their tips staying out of the water. In recent years, almost as a cycle dating back to early culinary habits, asparagus has regained its popularity eaten raw as a component of a salad.^[12]

Asparagus can also be pickled and stored for several years. Some brands may label shoots prepared this way as "marinated."

The bottom portion of asparagus often contains sand and dirt and as such thorough cleaning is generally advised in cooking asparagus.

Green asparagus is eaten worldwide, though the availability of imports throughout the year has made it less of a delicacy than it once was.^[6] However, in the UK, due to the short growing season and demand for local produce, asparagus commands a premium and the "asparagus season is a highlight of the foodie calendar."^[13] In continental northern Europe, there is also a strong seasonal following for local white asparagus, nicknamed "white gold".

German botanical illustration of asparagus

Medicinal

The second century physician Galen described asparagus as "cleansing and healing."

Nutrition studies have shown that asparagus is a low-calorie source of folate and potassium. Its stalks are high in antioxidants. "Asparagus provides essential nutrients: six spears contain some 135 micrograms (μg) of folate, almost half the adult RDI (recommended daily intake), 20 milligrams of potassium," notes an article in Reader's Digest. Research suggests folate is key in taming homocysteine, a substance implicated in heart disease. Folate is also critical for pregnant mothers, since it protects against neural tube defects in babies. Several studies indicate that getting plenty of potassium may reduce the loss of calcium from the body.

Particularly green asparagus is a good source of vitamin C. Vitamin C helps the body produce and maintain collagen, the major structural protein component of the body's connective tissues.

"Asparagus has long been recognized for its medicinal properties," wrote D. Onstad, author of Whole Foods Companion: A Guide for Adventurous Cooks, Curious Shoppers and Lovers of Natural Foods. "Asparagus contains substances that act as a diuretic, neutralize ammonia that makes us tired, and protect small blood vessels from rupturing. Its fiber content makes it a laxative too." It should be noted, however, that ammonia only "makes us tired" if we are in end stage liver failure.

Cultivation

Green asparagus for sale in New York City.

Since asparagus often originates in maritime habitats, it thrives in soils that are too saline for normal weeds to grow in. Thus a little salt was traditionally used to suppress weeds in beds intended for asparagus; this has the disadvantage that the soil cannot be used for anything else. Some places are better for growing asparagus than others. The fertility of the soil is a large factor. "Crowns" are planted in winter, and the first shoots appear in spring; the first pickings or "thinnings" are known as sprue asparagus. Sprue have thin stems.^[14]

White asparagus, known as spargel, is cultivated by denying the plants light while they are being grown. Less bitter than the green variety, it is very popular in the Netherlands, France, Belgium and Germany where 57,000 tonnes (61% of consumer demands) are produced annually.^[15]

Purple asparagus differs from its green and white counterparts, having high sugar and low fibre levels. Purple asparagus was originally developed in Italy and commercialised under the variety name Violetto d'Albenga. Since then, breeding work has continued in countries such as the United States and New Zealand.

In northwestern Europe, the season for asparagus production is short, traditionally beginning on April 23 and ending on Midsummer Day.^[16]

Companion planting

Asparagus is a useful companion plant for tomatoes. The tomato plant repels the asparagus beetle, as do several other common companion plants of tomatoes, meanwhile asparagus may repel some harmful root nematodes that affect tomato plants.^[17]

Commercial production

Asparagus output in 2005 shown as a percentage of the top producer (China – 5,906,000 tonnes).
     100      10      1

As of 2007, Peru is the world's leading asparagus exporter, followed by China and Mexico.^[18] The top asparagus importers (2004) were the United States (92,405 tonnes), followed by the European Union (external trade) (18,565 tonnes), and Japan (17,148 tonnes).^[19] The United States' production for 2005 was on 218.5 square kilometres (54,000 acres) and yielded 90,200 tonnes,^[20] making it the world's third largest producer, after China (5,906,000 tonnes) and Peru (206,030 tonnes).^[21] U.S. production was concentrated in California, Michigan, and Washington.^[20] The crop is significant enough in California's Sacramento-San Joaquin River Delta region that the city of Stockton holds a festival every year to celebrate it, as does the city of Hart, Michigan, complete with a parade and asparagus queen. The Vale of Evesham in Worcestershire is heralded as the largest producer within Northern Europe, celebrating like Stockton, with a week long festival every year involving auctions of the best crop and locals dressing up as spears of asparagus as part of the British Asparagus Festival.^[22] There is also a city festival in the Bavarian city of Nuremberg held for a week in April held in honour of the locally produced white asparagus i.e. "Spargel".There is a competition to find the fastest spargel peeler in the region and usually involves generous amounts of the local wines and beer being consumed to aid the spectators appreciative support.^[23]

Vernacular names and etymology

Asparagus in Mildura, Victoria, Australia

Mature native Asparagus with seed pods in Saskatchewan, Canada

Asparagus officinalis is widely known simply as "asparagus", and may be confused with unrelated plant species also known as "asparagus", such as Ornithogalum pyrenaicum known as "Prussian asparagus" for its edible shoots.

The English word "asparagus" derives from classical Latin, but the plant was once known in English as sperage, from the Medieval Latin sparagus. This term itself derives from the Greek aspharagos or asparagos, and the Greek term originates from the Persian asparag, meaning "sprout" or "shoot". Asparagus was also corrupted in some places to "sparrow grass"; indeed, the Oxford English Dictionary quotes John Walker as having written in 1791 that "Sparrow-grass is so general that asparagus has an air of stiffness and pedantry". In Gloucestershire and Worcestershire it is also known simply as "grass". Another known colloquial variation of the term, most common in parts of Texas, is "aspar grass" or "asper grass". In the Midwest United States and Appalachia, "spar grass" is a common colloquialism. Asparagus is commonly known in fruit retail circles as "Sparrows Guts", etymologically distinct from the old term "sparrow grass", thus showing convergent language evolution.

It is known in French and Dutch as asperge, in Italian as asparago (old Italian asparagio), in Portuguese as aspargo, in Spanish as espárrago, in German as Spargel, in Hungarian as spárga.

The Sanskrit name of Asparagus is shatavari and it has been historically used in India as a part of Ayurvedic medicines. In Kannada, it is known as ashadhi, majjigegadde or sipariberuballi.

In Thailand it is known as no mai farang (Thai: หน่อไม้ฝรั่ง), and in Vietnam măng tây which literally means "European bamboo shoots" and "Western bamboo shoots" respectively. The green asparagus is normally used in Thai cuisine.

Urine effects

The effect of eating asparagus on the eater's urine has long been observed:

"[Asparagus] cause a filthy and disagreeable smell in the urine, as everybody knows." (Treatise of All Sorts of Foods Louis Lemery, 1702)^[24]

"asparagus... affects the urine with a foetid smell (especially if cut when they are white) and therefore have been suspected by some physicians as not friendly to the kidneys; when they are older, and begin to ramify, they lose this quality; but then they are not so agreeable" ("An Essay Concerning the Nature of Aliments," John Arbuthnot, 1735)^[25]

Asparagus "...transforms my chamber-pot into a flask of perfume." Marcel Proust (1871–1922) ^[26]

There is debate about whether all (or only some) people produce the smell, and whether all (or only some) people identify the smell. It was originally thought this was because some of the population digested asparagus differently than others, so that some people excreted odorous urine after eating asparagus, and others did not. However, in the 1980s three studies from France,^[27] China and Israel published results showing that producing odorous urine from asparagus was a universal human characteristic. The Israeli study found that from their 307 subjects all of those who could smell 'asparagus urine' could detect it in the urine of anyone who had eaten asparagus, even if the person who produced it could not detect it himself.^[28] Thus, it is now believed that most people produce the odorous compounds after eating asparagus, but only about 22% of the population have the autosomal genes required to smell them.^[29][30][31]

Chemistry

Asparagus foliage turns bright yellow in autumn

Certain compounds in asparagus are metabolized giving urine a distinctive smell due to various sulfur-containing degradation products, including various thiols, thioesters, and ammonia.^[32]

The volatile organic compounds responsible for the smell are identified as:^[33][34]

• methanethiol,
• dimethyl sulfide,
• dimethyl disulfide,
• bis(methylthio)methane,
• dimethyl sulfoxide, and
• dimethyl sulfone.

Subjectively, the first two are the most pungent, while the last two (sulfur-oxidized) give a sweet aroma. A mixture of these compounds form a "reconstituted asparagus urine" odor. This was first investigated in 1891 by Marceli Nencki, who attributed the smell to methanethiol.^[35] These compounds originate in the asparagus as asparagusic acid and its derivatives, as these are the only sulfur-containing compounds unique to asparagus. As these are more present in young asparagus, this accords with the observation that the smell is more pronounced after eating young asparagus. The biological mechanism for the production of these compounds is less clear.

The onset of the asparagus urine smell is remarkably rapid. It has been estimated to start 15 to 30 minutes after ingestion.^[36][37]

See also

• Spargel
• List of companion plants

References

External links

• California Asparagus Commission
• PROTAbase on Asparagus officinalis
• Asparagus officinalis – Plants for a Future database entry
• World Asparagus Situation and OutlookPDF (55.0 KB) – 2005 USDA report
• Asparagus Production Management and Marketing – commercial growing (OSU bulletin)
• How to grow asparagus in your garden Guide to growing Asparagus in your garden
• Asparagus Breeding Program at Rutgers, the State University of New Jersey
• Asparagus effect on urine article