Plate Freezing:

Also known as contact freezing, plate freezing employs refrigerant flowing through parallel, hollow metal plates that are in direct contact with prepackaged (boxed) seafood, gently compressing it so the product is not crushed or deformed. Pressurized contact with the plates not only speeds up the rate of freezing, it also produces a smooth, flat surface on the faces of of a block of fish by preventing the expansion that normally occurs during freezing. The pressure also diminishes voids or air spaces that could be a focal point for rancidity (oxidation) and could result in irregular fish sticks or portions being cut from these blocks. Voids that fill with water can present hazards during deep-frying of seafood products, resulting in explosive splattering when chunks of ice are placed in hot oil. Products to be plate-frozen are prepackaged in a uniform shape in boxes, that normally wind up about 2 1/2" thick following compression. Plate-frozen products freeze in about two to four hours at minus 40 degrees F. Plate freezing is used to create blocks of products like shrimp, scallops or fish fillets, the later of which can be offered as a solid block or packaged as layerpacks, shatterpacks or cellopacks.