The
name oyster is used for a number of different groups of mollusks which grow
for the most part in marine or brackish water. Inside a usually highly-calcified
shell is a soft body. The gills filter plankton from the water. Strong adductor
muscles are used to hold the shell closed.
Oysters
are highly prized as food, both raw and cooked, and have
a reputation as an aphrodisiac due to the high
content of zinc they contain. Perhaps the definitive work on oysters as food is
Consider
the Oyster, by M. F. K. Fisher.
True
oysters
The "true
oysters" are the members of the family Ostreidae, and this includes
the edible oysters, which mainly belong to the genera Ostrea,
Crassostrea, Ostreola or
Saccostrea.
Examples are the Edible
Oyster, Ostrea edulis (others are just as edible); the Olympia Oyster Ostreola
conchaphila; Wellfleet oyster and
the Eastern Oyster Crassostrea
virginica.
Oysters
as edibles
Special
knives for opening raw, live, oysters, such as this one, have a short and stout
blade. Oysters
can be eaten raw, or boiled, fried, roasted, stewed, canned, pickled, or broiled.
Preparation can be as simple as opening the shell, while cooking can be as spare
as adding butter and/or salt,
or can be very elaborate.
Like
all shellfish, oysters have an extremely short shelf-life, and should be fresh
when consumed. Precautions should be respected when eating them (see below). Purists
insist on eating oysters raw, with no dressing save perhaps lemon juice or vinegar.
Raw oysters are regarded like wines in that they have complex flavors that vary
greatly among varieties and regions: some taste sweet, others salty or with a
mineral flavor, or even like melon. The texture is soft and fleshy, but crisp
to the tooth.
Oysters
are generally an expensive food in places where they aren't harvested, and often
they are eaten only on special occasions, such as Christmas. Whether oysters are
predominantly eaten raw or cooked is a matter of cultural preference. In the United
States today, oysters are usually cooked before consumption; canned smoked oysters
are widely available as preserves with a long shelf life. Raw oysters were, however,
once a staple food along the East Coast of the US, and are still easily found
in states bordering the ocean. Oysters are nearly always eaten raw in France.
Fresh
oysters must be alive just before consumption. There is a simple criterion: oysters
must be tightly closed; oysters that are already open are dead and must be discarded.
Opening oysters requires skill, for live oysters, outside of the water, shut themselves
tightly with a powerful muscle. The generally used method for opening oysters
is to use a special knife (called a shucking knife), with a short and thick blade,
inserting the blade (with some moderate force and vibration if necessary) at the
hinge in the rear of the shell, and sliding it upward to cut the adductor muscle
(which holds the shell closed). Inexperienced cooks can easily slip and injure
themselves; this is said to be a significant cause of domestic accidents in the
Christmas season in France.
An
alternative to opening raw oysters before consumption is to cook them in the shell
– the heat kills the oysters and they open by themselves. Cooked oysters are savory
and slightly sweet-tasting, and the varieties are mostly equivalent.
A
piece of folk wisdom concerning oysters is that they are only safe to eat in months
containing the letter 'r.' This is because oysters spawn in the warmer months,
from roughly May to August. They are safe to eat at all times of the year, although
their flavor when eaten raw can be somewhat watery and bland during spawning season.
Oysters from the Gulf of Mexico spawn throughout the year, and are generally best
cooked.
Pearl
oysters
Although
all oysters (and, indeed, many other bivalves) can secrete pearls, those from edible
oysters are commercially valueless. The Pearl Oysters come from a
different family, the Pteriidae
(Winged Oysters). Both cultivated
and natural pearls are obtained from these oysters, though some other mollusks,
for example freshwater
mussels, also yield pearls of commercial value.
Dermo
"Dermo"
(Perkinsus marinus)
is marine disease of oysters, caused by a protozoan parasite. It is a prevalent pathogen of oysters,
causing massive mortality in oyster populations and poses a significant economic
threat to the oyster industry.
Other
molluscs named "oyster"
A
number of other molluscs not falling into either of these groups have common names
that include the word "oyster", usually because they either taste or look like
oysters, or because they yield noticeable pearls. Examples include:
