High pressure processing extend the shelf life of fresh salmon, cod and mackerel

• High pressure processing (HPP) extend the microbial shelf life of fish.
• The TBARS-level in salmon, cod and mackerel was differently affected by HPP.
• Acid phosphatase showed no change in activity after HPP (500 MPa) and storage.
• HPP induced different levels of change in various fish species.

High pressure processing (HPP) is used on several types of seafood, though its potential for extending the shelf life of fresh fish has not been fully exploited. This study compared the effect of HPP (200 and 500 MPa, 120 s) on salmon, cod and mackerel. Immediately after processing, and during storage up to 26 days different analysis were carried out to evaluate the microbiological shelf life, oxidation, acid phosphatase level and pH of the different fish species during the storage period. For cod and mackerel, HPP at 500 MPa restrained the bacterial flora and it did not reach spoilage level, opposite to the salmon samples exposed to 500 MPa. Analysis of TBARS is often used as a measure of lipid oxidation. The TBARS-level was differently affected by pressure in salmon and cod. HPP at 200 MPa did not have any effect on the oxidation level in salmon during the storage period while this was observed for cod. The TBARS level in mackerel was high, independent of pressure treatment or not. Phosphatase activity in fish has been suggested to be related to freshness. The acid phosphatase (ACP) levels in control samples showed significant differences between salmon and cod. For salmon both control and samples treated at 200 MPa showed a decrease in ACP level at day 11 compared with day 0, whereas the HPP500 values were even throughout the study. This latter observation was also the case for cod treated at 500 MPa. This study have shown that HPP induce different levels of changes in various fish species.