Oyster
The oyster is a bivalve mollusc with thick, rough, irregular greyish or brownish shells. The top shell is larger and flatter than the lower one, which is concave and houses the body of the oyster. Oysters are classified as either flat or cupped, the flat varieties being more common in Europe.
Oysters are also prized for their magnificent pearls, which, unlike those of other molluscs, are large enough to be fashioned into jewellery. These pearls are formed when a grain of sand or a piece of the shell becomes lodged inside the oyster, which then secretes a nacreous liquid in order to protect itself from this foreign body. Inserting a tiny pearl inside the shell, thus prompting the oyster to secrete layers of calcium carbonate, produces cultured pearls. The most beautiful pearls are produced by the Pinctada genus, which lives in warm-water seas.
Oysters are either male or female, but it is not unusual for their gender to change at least once over the course of their lifetimes. Unlike mussels, oysters do not affix themselves to rocks or other objects by secreting a mass of silky threads, but rather by attaching themselves to other oysters or to a host. Capable of forming colonies, oysters feed on plankton, plants, and microscopic aquatic animals. Like all molluscs, they are particularly vulnerable to pollution.
Oysters thrive in both tropical and temperate seas, but those found in temperate waters mature less quickly, often taking as long as 4 - 7 years to grow to a length of 8 centimetres - a size sometimes attained by tropical oysters in only 2 years. The slow-growing oysters found in temperate waters are renowned for their flavour.
The ample, shiny flesh of oysters can be greyish brown, pearl gray, or beige, and may be even slightly green if the oyster has fed on seaweed. Its consistency changes during the reproductive season, it is often said that oysters are edible only during months that contain the letter "r" (from September to April); however, they are not actually inedible during the summer months, just less appetizing and more perishable. At any rate, this restriction is no longer always applicable - at least for cultivated oysters - because American researchers have invented a new genetic procedure that makes oysters sterile, effectively ending the reproductive cycle and eliminating the period during which they are less flavourful.
Oysters are often named for the areas they inhabit. Blue Point and Cape Cod oysters are among the most popular varieties in the United States, while Caraquet (named for Caraquet Bay in New Brunswick) and Malpeque (cultivated in Prince Edward island) oysters are renowned in eastern Canada. Likewise, the most sought-after Australian varieties are the Sydney Rock oysters and Tasmanian oysters.
Relatively easy to breed, oysters have been grown in oyster beds for over 2,000 years and were first cultivated on a large scale by the Romans and the Gauls. Today the leading oyster-producing countries are the United States, Japan, Korea, and France, but the oyster is also farmed in numerous other countries, including South Africa, Australia, New Zealand, and Canada.
Hold the oyster firmly in one hand, with the rounded side down so that less liquid is lost. Insert the blade of the knife between the shells, near the hinge. Twist the blade to separate the shells, and then cut the muscle that joins them together. Next slip the blade of the knife underneath the oyster to detach it from the shell. All that remains to be done is to remove any fragments of shell that may be stuck to the oyster. You may want to protect your hand with a glove, a cloth, or thick paper, in case the knife slips.
Oysters are easier to open if heating them in a medium oven for 30 to 60 seconds, steaming them for a few seconds, or microwaving them on high power for 1 minute softens the adductor muscle. Before opening oysters, scrub them with a brush under cold running water. Never soak oysters in water, because they can die if they open and their liquid drains out.
It is impossible to assess the freshness of oysters without opening them. Never eat oysters unless they are firm and plump, and are stored in clear liquid that has a pleasant odour.
Preshelled oysters can be eaten raw if they are very fresh, but they are often less flavourful than unshelled oysters and are more suitable for use in cooked dishes. Although canned smoked oysters are sold "ready to eat," they can also be rinsed and marinated.
Oysters are also prized for their magnificent pearls, which, unlike those of other molluscs, are large enough to be fashioned into jewellery. These pearls are formed when a grain of sand or a piece of the shell becomes lodged inside the oyster, which then secretes a nacreous liquid in order to protect itself from this foreign body. Inserting a tiny pearl inside the shell, thus prompting the oyster to secrete layers of calcium carbonate, produces cultured pearls. The most beautiful pearls are produced by the Pinctada genus, which lives in warm-water seas.
Oysters are either male or female, but it is not unusual for their gender to change at least once over the course of their lifetimes. Unlike mussels, oysters do not affix themselves to rocks or other objects by secreting a mass of silky threads, but rather by attaching themselves to other oysters or to a host. Capable of forming colonies, oysters feed on plankton, plants, and microscopic aquatic animals. Like all molluscs, they are particularly vulnerable to pollution.
Oysters thrive in both tropical and temperate seas, but those found in temperate waters mature less quickly, often taking as long as 4 - 7 years to grow to a length of 8 centimetres - a size sometimes attained by tropical oysters in only 2 years. The slow-growing oysters found in temperate waters are renowned for their flavour.
The ample, shiny flesh of oysters can be greyish brown, pearl gray, or beige, and may be even slightly green if the oyster has fed on seaweed. Its consistency changes during the reproductive season, it is often said that oysters are edible only during months that contain the letter "r" (from September to April); however, they are not actually inedible during the summer months, just less appetizing and more perishable. At any rate, this restriction is no longer always applicable - at least for cultivated oysters - because American researchers have invented a new genetic procedure that makes oysters sterile, effectively ending the reproductive cycle and eliminating the period during which they are less flavourful.
Oysters are often named for the areas they inhabit. Blue Point and Cape Cod oysters are among the most popular varieties in the United States, while Caraquet (named for Caraquet Bay in New Brunswick) and Malpeque (cultivated in Prince Edward island) oysters are renowned in eastern Canada. Likewise, the most sought-after Australian varieties are the Sydney Rock oysters and Tasmanian oysters.
History
Eaten since prehistoric times, the oyster was a particular favourite of the Romans, the Celts, and the Greeks. In ancient Greece, oysters were used as ballots as well as food: electors voted by scratching their choices onto the surface of the shells.Relatively easy to breed, oysters have been grown in oyster beds for over 2,000 years and were first cultivated on a large scale by the Romans and the Gauls. Today the leading oyster-producing countries are the United States, Japan, Korea, and France, but the oyster is also farmed in numerous other countries, including South Africa, Australia, New Zealand, and Canada.
Nutritional Value
Oysters are rich in vitamin B12, iron, zinc, and copper. They are said to be especially nourishing and are reputed to have regenerative and invigorating properties. Some people even consider them an aphrodisiac.Buying
Do not buy fresh unshelled oysters unless they are still alive and full of water. Live oysters are usually closed, and if they are slightly open, will close when tapped. Oysters that are filled with water are quite heavy. Oysters are also shelled and sold either fresh or frozen, by the kilogram. Shelled fresh oysters should be firm, fleshy, and shiny, and the liquid in which they are stored should be clear, not milky. Shelled oysters are more expensive, but none of the flesh is wasted. Oysters are usually classified according to their size and shape, not their flavour.Storage
Shelled oysters stored in their own liquid will keep for about 10 days in the refrigerator and for about 3 months in the freezer, depending on how fresh they are when purchased. However, they should be eaten as soon as possible. Unshelled oysters can be kept for up to 6 weeks in a container covered with a damp cloth. Never store them in a bag or a tightly sealed container because they will be unable to breathe. Oysters cannot survive at temperatures lower than 1°C or higher than 14°C. Never freeze unshelled oysters.Preparing
Opening oysters requires a certain amount of skill. Oyster knives have solid handles and thick blades specially designed for opening the shells. (If you use an ordinary kitchen knife, the odds of cutting yourself are greater and the knife can break.) Use a knife with a stainless-steel blade to avoid transferring the taste of metal to the oysters.Hold the oyster firmly in one hand, with the rounded side down so that less liquid is lost. Insert the blade of the knife between the shells, near the hinge. Twist the blade to separate the shells, and then cut the muscle that joins them together. Next slip the blade of the knife underneath the oyster to detach it from the shell. All that remains to be done is to remove any fragments of shell that may be stuck to the oyster. You may want to protect your hand with a glove, a cloth, or thick paper, in case the knife slips.
Oysters are easier to open if heating them in a medium oven for 30 to 60 seconds, steaming them for a few seconds, or microwaving them on high power for 1 minute softens the adductor muscle. Before opening oysters, scrub them with a brush under cold running water. Never soak oysters in water, because they can die if they open and their liquid drains out.
It is impossible to assess the freshness of oysters without opening them. Never eat oysters unless they are firm and plump, and are stored in clear liquid that has a pleasant odour.
Cooking
Oysters can be cooked, but they become rubbery and pasty if even slightly overcooked. To cook them, plunge them into boiling liquid and immediately remove the saucepan from the heat, leaving the oysters in the liquid for just a few minutes. If you decide to cook them a little more, allow them to simmer for a few minutes, but do not bring the liquid to a boil or the oysters will become hard and shrivelled. They should never be cooked for longer than 5 minutes. As soon as the edges of the oysters start to curl up, remove them from the liquid.Using
Oysters are usually eaten raw, either plain or with a little lemon juice or pepper. Cooked oysters are delicious hot or cold. Prepared in many different ways, oysters are often used in soups, pates, and sauces or cooked au gratin.Preshelled oysters can be eaten raw if they are very fresh, but they are often less flavourful than unshelled oysters and are more suitable for use in cooked dishes. Although canned smoked oysters are sold "ready to eat," they can also be rinsed and marinated.
