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Processing
Oysters are eaten in fresh condition in the half shell in many countries. The oysters
are processed in several ways.
Frozen oysters: After
depuration whole oysters (shell-on) are frozen by spreading them in a single layer
of trays in an air blast freezer with polypropylene film stretched over each tray.
Frozen whole oysters packed in polythene bags remain in good condition for six months
in cold storage at -25°C. The liquid within the shell acts as a glaze to protect
the meat from dehydration. Shucked oyster meat is also frozen either in blocks or
individually.
Canned oysters: Oyster
meat is chilled, washed and blanched in 3% brine containing 0.1% citric acid for
4 to 5 min. The blanched meat is packed in cans, and hot 2% brine with 0.1% citric
acid is added to the cans. The cans are seamed, sterilized at 115°C for 25 min
and immediately chilled and stored.
Smoked oysters: The
meat is washed, treated with 5% brine for 5 min, drained, dipped in edible oil,
spread in a single layer on a nylon wire mesh, drained again and loaded into a smoking
chamber. The meat is held in dense smoke and maintained at a temperature of 40°C
for 30 min and later at 70°C for 90 min. The smoked oysters are filled in cans
with hot refined oil. The cans are seamed, sterilized at 115°C for 25 min and
immediately chilled and stored.
Oyster stew: Oysters,
which are too large or badly cut while shucking, or those in low condition, are
prepared as for canning but are chopped into small pieces and added to milk and
spices.
Oyster processing unit
Byproducts and utilization
The two shell valves constitute about 85% of the total weight of oyster and contain
52-55% calcium oxide. They are used in the manufacture of calcium carbide, lime,
fertilizers and cement. They are useful spat collectors in oyster culture. The shells
are broken to pieces and used as poultry grit.
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