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The purpose of this study was to determine the effect of high pressure (up to 600 MPa for 2 minutes at 20^oC) on the quality of three types of shellfish (mussels (Mytilus edulis), oysters (Crassostrea gigas) and prawns (Nephrops norvegicus) during storage for four weeks at 2^oC.

Mussels: If a psychrotrophic count of 10⁶-10⁷ is assumed as the level at which spoilage occurs then, from a microbiological viewpoint, the shelf-life of the mussels could be extended to 14 days using a pressure treatment of 500 MPa or higher.  This was confirmed by results from sensory analysis of the cooked mussels which found that while untreated, fresh mussels were most acceptable, the pressure treated (600 MPa) mussels were also acceptable after 2 weeks storage.

Oysters:  The samples had a low initial microbial count and numbers did not reach spoilage levels during four weeks storage in any of the pressure treated samples.  The sensory panel found the appearance of the pressure treated samples (> 400 MPa) to be significantly more acceptable than controls.  The panel also found that raw odour was not significantly changed by up to two weeks storage.  Thereafter there was a significant deterioration, although samples still remained acceptable.

Prawns:  Pressure treatment of >400 MPa gave a microbiological shelf-life of 14 days but enhanced melanosis.  A combination of dipping the prawns in 4% sodium metabisulphite followed by pressure treatment controlled the blackening.  Dipped prawns, treated at 600 MPa and cooked after 2 weeks storage had acceptable odour, appearance, flavour and texture, although they were not as acceptable as cooked, fresh samples.