Asparagus

Asparagus or garden asparagus, scientific name Asparagus officinalis, is a spring vegetable, a flowering perennial^[1] plant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and asparagus in the Asparagaceae. Asparagus officinalis 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 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 mm (0.24–1.26 in) long and 1 mm (0.039 in) broad, and clustered 4–15 together, in a rose-like shape.^[5]The root system is adventitious and the root type is fasciculated. The flowers are bell-shaped, greenish-white to yellowish, 4.5–6.5 mm (0.18–0.26 in) long, with six tepals partially fused together at the base; they are produced singly or in clusters of two or three 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. ^[6]

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 cm (12–28 in) high, and shorter cladodes 2–18 mm (0.079–0.709 in) long.^[2][7] It is treated as a distinct species, Asparagus prostratus Dumort, by some authors.^[8][9]

History

Asparagus has been used as a vegetable and medicine, owing to its delicate flavour, diuretic properties, and more. It is pictured as an offering on an Egyptian frieze dating to 3000 BC. In ancient times, it was also known in Syria and in Spain. Greeks and Romans ate it fresh when in season, and dried the vegetable for use in winter; Romans even froze it high in the Alps, for the Feast of Epicurus. Emperor Augustus created the "Asparagus Fleet" for hauling the vegetable, and coined the expression "faster than cooking asparagus" for quick action.^{[Note 1][10][11]} A recipe for cooking asparagus is in the oldest surviving book of recipes, Apicius’s third-century AD De re coquinaria, Book III.

The ancient Greek physician Galen (prominent among the Romans) mentioned asparagus as a beneficial herb during the second century AD, but after the Roman empire ended, asparagus drew little medieval attention.^{[12][Note 2]} until al-Nafzawi's The Perfumed Garden. That piece of writing celebrates its (scientifically unconfirmed) aphrodisiacal power, a supposed virtue that the Indian Ananga Ranga attributes to "special phosphorus elements" that also counteract fatigue. By 1469, asparagus was cultivated in French monasteries. Asparagus appears to have been hardly noticed in England until 1538,^{[Note 2]} and in Germany until 1542.^[11]

The finest texture and the strongest and yet most delicate taste is in the tips.^[13] The points d'amour ("love tips") were served as a delicacy to Madame de Pompadour.^[14] Asparagus became available to the New World around 1850, in the United States.^[11]

Uses

Asparagus

Nutritional value per 100 g (3.5 oz)
Energy	85 kJ (20 kcal)
Carbohydrates	3.88 g
Sugars	1.88 g
Dietary fibre	2.1 g
Fat	0.12 g
Protein	2.2 g
Vitamins
Vitamin A equiv. beta-carotene lutein zeaxanthin	(5%) 38 μg (4%) 449 μg 710 μg
Thiamine (B1)	(12%) 0.143 mg
Riboflavin (B2)	(12%) 0.141 mg
Niacin (B3)	(7%) 0.978 mg
Pantothenic acid (B5)	(5%) 0.274 mg
Vitamin B6	(7%) 0.091 mg
Folate (B9)	(13%) 52 μg
Choline	(3%) 16 mg
Vitamin C	(7%) 5.6 mg
Vitamin E	(7%) 1.1 mg
Vitamin K	(40%) 41.6 μg
Trace metals
Calcium	(2%) 24 mg
Iron	(16%) 2.14 mg
Magnesium	(4%) 14 mg
Manganese	(8%) 0.158 mg
Phosphorus	(7%) 52 mg
Potassium	(4%) 202 mg
Sodium	(0%) 2 mg
Zinc	(6%) 0.54 mg
Link to USDA Database entry
Units μg = micrograms • mg = milligrams IU = International units
Percentages are roughly approximated using US recommendations for adults. Source: USDA Nutrient Database

Only young asparagus shoots are commonly eaten: once the buds start to open ("ferning out"), the shoots quickly turn woody.^[15]

Water makes up 93% of asparagus's composition.^[16] Asparagus is low in calories and is very low in sodium. It is a good source of vitamin B₆, calcium, magnesium and zinc, and a very good source of dietary fibre, protein, beta-carotene, vitamin C, vitamin E, vitamin K, thiamin, riboflavin, rutin, niacin, folic acid, iron, phosphorus, potassium, copper, manganese and selenium,^[17][18] as well as chromium, a trace mineral that enhances the ability of insulin to transport glucose from the bloodstream into cells. The amino acid asparagine gets its name from asparagus, as the asparagus plant is relatively rich in this compound.

The shoots are prepared and served in a number of ways around the world, typically as an appetizer^[19] 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. Asparagus may also be quickly grilled over charcoal or hardwood embers. It is also used as an ingredient in some stews and soups. In recent years asparagus eaten raw, as a component of a salad, has regained popularity.^[20]

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

Stem thickness indicates the age of the plant, with the thicker stems coming from older plants. Older, thicker stalks can be woody, although peeling the skin at the base removes the tough layer. Peeled asparagus will however poach much faster.^[21] The bottom portion of asparagus often contains sand and dirt, so thorough cleaning is generally advised before cooking.

Green asparagus is eaten worldwide, though the availability of imports throughout the year has made it less of a delicacy than it once was.^[7] In Europe, however, the "asparagus season is a highlight of the foodie calendar"; in the UK this traditionally begins on 23 April and ends on Midsummer Day.^[22][23] As in continental Europe, due to the short growing season and demand for local produce, asparagus commands a premium price.

White asparagus in continental northwestern Europe

Asparagus is very popular in the Netherlands, Spain, France, Poland, Belgium, Germany, Austria, Italy and Switzerland, and is almost exclusively white; if not, it is specified by the local language term for "green asparagus". White asparagus is the result of applying a blanching technique while the asparagus shoots are growing. Compared to green asparagus, the locally cultivated so-called "white gold" or "edible ivory" asparagus, also referred to as "the royal vegetable",^[14] is less bitter and much more tender. Freshness is very important, and the lower ends of white asparagus must be peeled before cooking or raw consumption.

To cultivate white asparagus, the shoots are covered with soil as they grow, i.e. earthed up; without exposure to sunlight no photosynthesis starts, so the shoots remain white in colour.

Only seasonally on the menu, asparagus dishes are advertised outside many restaurants, usually from late April to June. For the French style, asparagus is often boiled or steamed and served with hollandaise sauce, melted butter or olive oil, Parmesan cheese or mayonnaise.^[24] Tall, narrow asparagus cooking pots allow the shoots to be steamed gently, their tips staying out of the water.

During the German Spargelsaison or Spargelzeit ("asparagus season" or "asparagus time"), the asparagus season that traditionally finishes on 24 June, roadside stands and open-air markets sell about half of the country's white asparagus consumption.^[25]

Cultivation

Since asparagus often originates in maritime habitats, it thrives in soils that are too saline for normal weeds to grow. 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 has thin stems.^[26]

A new breed of "Early Season Asparagus" that can be harvested two months earlier than usual was announced by a UK grower in early 2011.^[27] This variety does not need to lie dormant and blooms at 7 °C (45 °F) rather than the usual 9 °C (48 °F).

The blanching of white asparagus is obtained by the labor intensive hilling cultivation method, to distinguish its gastronomical qualities from those of the green plant, which is the same botanical variety.

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

Companion planting

Asparagus is said to be a useful companion plant for tomatoes as the tomato plant repels the asparagus beetle. Asparagus may repel some harmful root nematodes that affect tomato plants.^[28]

Commercial production

The top asparagus importers (2011) were the United States (174,609 tonnes), followed by the European Union (external trade) (94,292 tonnes), and Canada (23,265 tonnes).^[29]

China is the world's largest producer: in 2012 (7,350,000 tonnes), at a large distance followed by Peru (376,645 tonnes), and Mexico (119,789 tonnes).^[29] U.S. production was concentrated in California, Michigan and Washington.^[29][30] The annual production for white asparagus in Germany is 57,000 tonnes (61% of consumer demand).^[31]

Celebrations

The green 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.^[32]

Many German cities hold an annual Spargelfest (asparagus festival) celebrating the harvest of white asparagus. Schwetzingen claims to be the "Asparagus Capital of the World" and during its festival an Asparagus Queen is crowned. The Bavarian city of Nuremberg feasts a week long in April, with a competition to find the fastest asparagus peeler in the region. This usually involves generous amounts of the local wines and beer being consumed to aid the spectators' appreciative support.^[33]

Vernacular names and etymology

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.^{[Note 2]} 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".

The Sanskrit name of Asparagus is shatavari and it has been historically used in India as a part of Ayurvedic medicines.

In East Asia, Asparagus officinalis is known as lùsǔn (蘆筍, simplified 芦笋) in Mandarin Chinese, louhséun (露筍) in Cantonese, and lô͘-sún (蘆筍) in Hokkien/Taiwanese. In Thai it is known as nǭmai farang (หน่อไม้ฝรั่ง IPA: [nɔ̀ː máj fà râŋ]), and in Vietnamese as măng tây which literally mean "European bamboo shoots" and "Western bamboo shoots", respectively. The green asparagus is commonly used in Chinese-American cuisine and Thai cuisine.

In Turkish, asparagus is known as "kuşkonmaz," literally "bird can't land," in reference to the shape of the plant.

Effects on urine

The effect of eating asparagus on urine has long been observed:

"[Asparagus] cause a powerful and disagreeable smell in the urine, as every Body knows." (Treatise of All Sorts of Foods, Louis Lemery, 1702)^[34]

"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)^[35]

"A few Stems of Asparagus eaten, shall give our Urine a disagreable Odour..." ("Letter to the Royal Academy of Brussels," Benjamin Franklin, c. 1781)^[36]

Asparagus "...transforms my chamber-pot into a flask of perfume." Marcel Proust (1871–1922)^[37]

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 from others, so some people excreted odorous urine after eating asparagus, and others did not. In the 1980s three studies from France,^[38] China and Israel published results showing that producing odorous urine from asparagus was a common 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.^[39] However, a 2010 study^[40] found variations in both production of odorous urine and the ability to detect the odour, but that these were not tightly related. It is believed most people produce the odorous compounds after eating asparagus, but only about 22% of the population have the autosomal genes required to smell them.^[41][42][43]

In 2010, the company 23andMe published a genome-wide association study on whether participants have "ever noticed a peculiar odor when you pee after eating asparagus?"^[44] This study pinpointed a single-nucleotide polymorphism (SNP) in a cluster of olfactory genes associated with the ability to detect the odor. While this SNP did not explain all of the difference in detection between people, it provides support for the theory that there are genetic differences in olfactory receptors that lead people to be unable to smell these odorous compounds.

Chemistry

Certain compounds in asparagus are metabolized to yield ammonia and various sulfur-containing degradation products, including various thiols and thioesters,^[45] which give urine a characteristic smell.

Some^[46] of the volatile organic compounds responsible for the smell are:^[47][48]

• methanethiol
• dimethyl sulfide
• dimethyl disulfide
• bis(methylthio)methane
• dimethyl sulfoxide
• 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.^[49] 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. The smell has been reported to be detectable 15 to 30 minutes after ingestion.^[50][51]

Gallery

• 

  Wild asparagus sauteed with garlic, naam plaa and soy sauce

• 

  In the Netherlands and Northern Germany, asparagus is often eaten together with ham, boiled egg, potatoes and a melted butter sauce

• 

  Cream of asparagus soup

• 

  Asparagus officinalis with dewdrops

• 

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

• 

  Asparagus for sale.

See also

• Cream of asparagus soup
• List of companion plants

Notes

References

External links

Wikimedia Commons has media related to Asparagus officinalis.

Wikibooks Cookbook has a recipe/module on Asparagus

Wikisource has the text of the 1911 Encyclopædia Britannica article Asparagus.

• Kew Species Profile: Asparagus officinalis (garden asparagus)
• PROTAbase on Asparagus officinalis
• Asparagus officinalis – Plants for a Future database entry
• World Asparagus Situation and Outlook PDF (55.0 KB) – 2005 USDA report
• Asparagus Production Management and Marketing – commercial growing (OSU bulletin)