Fish products are highly vulnerable to enzymatic spoilage and developing toxic bacteria. They are sold: fresh with a very short shelf life; packaged in modified atmospheres; or frozen and then packaged. Most fish are sold frozen and overwrapped with films such as OPP, PET, or HDPE to prevent moisture loss. Fish high in fat content require PVDC added to the base film.
Most fresh fish is sold unpackaged, but a complex, safe, modified atmosphere packaging system has been developed but is rarely used. The film involved must possess high oxygen permeability and LDPE has this characteristic.