Asparagus is a seasonal vegetables and its bursts in the coastal area harvested in April and May, and in the inland area in May and June. Asparagus is a herbaceous, perennial plant growing to 100–150 cm (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 four to 15 together, in a rose-like shape. 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.
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. It may also be quickly grilled over charcoal or hardwood embers, and 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.Asparagus can also be pickled and stored for several years. Some brands label shoots prepared in this way as “marinated”.
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
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.
Cream of asparagus soup
Asparagus, a light chicken or vegetable stock and milk or cream are primary ingredients. The cooked asparagus may be puréed or pulped in its preparation, and some preparations may combine both puréed and solid forms of asparagus, such as cooked asparagus tips. Puréed versions may be strained through a sieve to remove stray stringy asparagus matter. The use of thick pieces of asparagus can enhance the flavor of puréed versions of cream of asparagus soup, as can the use of fresh asparagus while it is in season (during spring). It may be thickened using a roux, and some versions may omit milk and use extra stock, along with additional roux to thicken the soup. It may be served garnished with cooked asparagus tips, croutons, sour cream, crème fraîche, herbs such as chives, parsley and tarragon, and other foods. Cold versions may contain cream stirred into the soup prior to serving, or may be topped with sour cream. Additional ingredients in its preparation may include half and half, light cream, evaporated milk, onion, garlic, lemon juice, celery, salt, pepper, leeks and herbs such as basil and parsley. Cheese may add flavor and thickness to the soup in versions that omit cream or milk. Sometimes rice is added.