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.