Asparagus – Asparagus officinalis
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Asparagus officinalis is a spring vegetable, a flowering perennial 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, and is widely cultivated as a vegetable crop.
Asparagus shoot before becoming woody
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 (0.24–1.3 in) long and 1 mm (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 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.
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 (0.079–0.71 in) long. It is treated as a distinct species, Asparagus prostratus Dumort, by some authors. A remarkable adaptation is the edible asparagus, while in the Macaronesian Islands several species, (A. umbellatus, A. scoparius, etc.), are preserved the original form, a leafy vine; in the Mediterranean, the asparagus genus has evolved into thorny species.
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. Still in ancient times, it was known in Syria and in Spain. Greeks and Romans ate it fresh when in season and dried the vegetable for use in winter; Romans would even freeze it high in the Alps, for the Feast of Epicurus. Emperor Augustus reserved the “Asparagus Fleet” for hauling the vegetable, and coined the expression “faster than cooking asparagus” for quick action. 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. 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, and in Germany until 1542.
The finest texture and the strongest and yet most delicate taste is in the tips. The points d’amour (“love tips”) were served as a delicacy to Madame de Pompadour. Asparagus became available to the New World around 1850, in the United States.
|Nutritional value per 100 g (3.5 oz)|
|Energy||85 kJ (20 kcal)|
|– Sugars||1.88 g|
|– Dietary fibre||2.1 g|
|Vitamin A equiv.||38 ?g (5%)|
|– beta-carotene||449 ?g (4%)|
|– lutein and zeaxanthin||710 ?g|
|Thiamine (vit. B1)||0.143 mg (12%)|
|Riboflavin (vit. B2)||0.141 mg (12%)|
|Niacin (vit. B3)||0.978 mg (7%)|
|Pantothenic acid (B5)||0.274 mg (5%)|
|Vitamin B6||0.091 mg (7%)|
|Folate (vit. B9)||52 ?g (13%)|
|Choline||16 mg (3%)|
|Vitamin C||5.6 mg (7%)|
|Vitamin E||1.1 mg (7%)|
|Vitamin K||41.6 ?g (40%)|
|Calcium||24 mg (2%)|
|Iron||2.14 mg (16%)|
|Magnesium||14 mg (4%)|
|Manganese||0.158 mg (8%)|
|Phosphorus||52 mg (7%)|
|Potassium||202 mg (4%)|
|Sodium||2 mg (0%)|
|Zinc||0.54 mg (6%)|
|Link to USDA Database entry Percentages are roughly approximated from 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.
Water makes up 93% of Asparagus’s composition. 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, 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 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, almost as a cycle dating back to early culinary habits, asparagus has regained its popularity eaten raw as a component of a salad.
Asparagus can also be pickled and stored for several years. Some brands may 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 and peeling the skin at the base will remove the tough layer. Peeled asparagus will poach much faster, however. 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. 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. As in continental Europe, due to the short growing season and demand for local produce, asparagus commands a premium.
Typical serving of asparagus with Hollandaise sauce and potatoes.
Asparagus is very popular in the Netherlands, Spain, France, Poland, Belgium, Germany, Italy and Switzerland, and is almost exclusively white—else, it is specified by the local language term for “green asparagus”. Compared to the latter, the locally cultivated so-called “white gold” or “edible ivory”, also referred to as “the royal vegetable”, is less bitter and much more tender. Freshness is highly regarded, and it must be peeled before cooking or raw consumption.
To cultivate white asparagus, the shoots are covered with soil as they grow; without exposure to sunlight there is no photosynthesis, and 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. 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, 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.
German botanical illustration of asparagus
The second century physician Galen described asparagus as “cleansing and healing”.
Nutrition studies have shown 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 (?g) 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 women, since it protects against neural tube defects in babies. Studies have shown that people who have died from Alzheimer’s Disease have extremely low to no levels of folate. Several studies indicate 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.”
Water from cooking asparagus may help clean blemishes on the face if used for washing the face morning and night. From John Heinerman’s Heinerman’s New Encyclopedia of Fruits and Vegetables: “Cooked asparagus and its watery juices are very good for helping dissolve uric acid (causes gout) deposits in the extremities, as well as inducing urination where such a function may be lacking or only done on an infrequent basis. Asparagus is especially useful in cases of hypertension where the amount of sodium in the blood far exceeds the potassium present. Cooked asparagus also increases bowel evacuations.”
South Korean scientists discovered asparagus can help with hangovers. Research to be published in the Journal of Food Science says extracts taken from leaves and shoots were found to boost levels of key enzymes that help break down alcohol.
Green asparagus for sale in New York City
Harvest in Hockenheim, Germany
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.
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. 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 countries such as the United States and New Zealand.
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.
Asparagus output in 2005 shown as a percentage of the top producer (China)
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 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.
The effect of eating asparagus on the urine has long been observed:
- “[Asparagus] cause a filthy and disagreeable smell in the urine, as every Body knows.” (Treatise of All Sorts of Foods, Louis Lemery, 1702)
- “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)
- “A few Stems of Asparagus eaten, shall give our Urine a disagreable Odour…” (“Letter to the Royal Academy of Brussels,” Benjamin Franklin, c. 1781)
- Asparagus “…transforms my chamber-pot into a flask of perfume.” Marcel Proust (1871–1922)
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, 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 himself. However, a 2010 study 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.
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?” 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.
Asparagus foliage turns bright yellow in autumn
Certain compounds in asparagus are metabolized to yield ammonia and various sulfur-containing degradation products, including various thiols and thioesters, which give urine a characteristic smell.
Some of the volatile organic compounds responsible for the smell are:
- dimethyl sulfide
- dimethyl disulfide
- 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. 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.