• Blast freezing. Very cold air (minus 25° to minus 40°F) is circulated over a product that has been placed in trays or on racks in an enclosed space. Often the product is carried on conveyor belts through a horizon tal tunnel or vertically in an ascending spiral. Tunnel belt speed varies with product size. IQF fillets are often blast frozen, as are larger dressed fish, like salmon. 
  •  Cryogenic freezing. An advanced, accelerated form of blast freezing in which individual products (e.g., shrimp, fillets) are exposed to super-cold air or, more common ly, to sprays of liquid nitrogen or carbon dioxide at temperatures of minus 150°F or colder. Cryogenic freezing offers distinct quality benefits, including a taste and texture more resembling fresh seafood. 
  • Plate freezing (or contact freezing). Employs refriger ant flowing through parallel, hollow metal plates. The plates are gently squeezed together for maximum contact to produce a flat, frozen package. Fish blocks, layerpacks, shatterpacks and cellopacks are commonly frozen this way, as are blocks of shrimp and scallops. Plate-frozen products freeze in two to four hours at minus 40°F. 
  • Brine freezing. Product is immersed in a brine solution that has been mechanically chilled to 0°F. The saltwater, which remains liquid to minus 6°F, surrounds and quickly freezes odd-shaped products like crab clusters and legs. The technique can also be used to freeze packaged products. Immersion brine freezing is generally employed aboard tuna purse seiners for at-sea freezing.