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he Portuguese oyster, Crassostrea angulata, is a species of oyster found in the southwest Iberian Peninsula, closely related to the Pacific oyster. Although first identified as a native European species, genetic studies have suggested the Portuguese oyster originated from the Pacific coast of Asia and was introduced to Europe by Portuguese trading ships in the 16th century. The species is usually found in coastal river mouths and estuaries.
Prior to decimation by iridoviral disease in 1969, C. angulata was extensively cultivated in France and Portugal as part of the edible oyster industry. The Pacific oyster, which is more resistant to the disease, was introduced in the 1970s and has since replaced C. angulata as the main commercial species. The Portuguese oyster is cultured commercially in Taiwan.
Some types of oysters are commonly consumed cooked or raw, and in some locales are regarded as a delicacy. Some types of pearl oysters are harvested for the pearl produced within the mantle. Windowpane oysters are harvested for their translucent shells, which are used to make various kinds of decorative objects.
Oysters can be eaten on the half shell, raw, smoked, boiled, baked, fried, roasted, stewed, canned, pickled, steamed, or broiled, or used in a variety of drinks. Eating can be as simple as opening the shell and eating the contents, including juice. Butter and salt are often added. Poached oysters can be served on toast with a cream roux. In the case of Oysters Rockefeller, preparation can be very elaborate. They are sometimes served on edible seaweed, such as brown algae.
Care should be taken when consuming oysters. Purists insist on eating them raw, with no dressing save perhaps lemon juice, vinegar (most commonly shallot vinegar), or cocktail sauce. Upscale restaurants pair raw oysters with mignonette sauce, which consists primarily of fresh chopped shallot, mixed peppercorn, dry white wine and lemon juice or sherry vinegar. Like fine wine, raw oysters have complex flavors that vary greatly among varieties and regions: salty, briny, buttery, metallic, or even fruity. The texture is soft and fleshy, but crisp on the palate. North American varieties include Kumamoto and Yaquina Bay from Oregon, Duxbury and Wellfleet from Massachusetts, Malpeque from Prince Edward Island, Canada, Blue Point from Long Island, New York, Pemaquid from Maine, Rappahannock River from Virginia, Chesapeake from Maryland and Cape May oysters from New Jersey. Variations in water salinity, alkalinity, and mineral and nutritional content influence their flavor profile.
Oysters are an excellent source of zinc, iron, calcium, and selenium, as well as vitamin A and vitamin B12. Oysters are low in food energy; one dozen raw oysters provides only 460 kilojoules (110 kilocalories). They are rich in protein (approximately 9 g in 100 g of Pacific oysters). Two oysters (28 grams or 1 ounce) provide the Reference Daily Intake of zinc and vitamin B12.
Traditionally, oysters are considered to be an aphrodisiac, partially because they resemble female sex organs. A team of American and Italian researchers analyzed bivalves and found they were rich in amino acids that trigger increased levels of sex hormones. Their high zinc content aids the production of testosterone.
