High pressure processing extend the shelf life of milkfish flesh during refrigerated storage

Milkfish has become most often associated with histamine fish poisoning recently in Taiwan, but no information regarding the use of high pressure for preservation on this fish flesh. The microbial quality and physicochemical properties of milkfish flesh pressurized at 200, 300, 400, 500, and 600 MPa for 5 min were evaluated. In addition, the retardation effects in microbial growth and quality loss of pressurized milkfish flesh stored at 4 °C and 15 °C were investigated. The results showed that the L* (lightness), W (whiteness), ΔE (color difference), and texture (hardness, cohesiveness and chewiness) of fish flesh increased significantly with the increase in pressure, whereas the a* (redness) value of samples significantly decreased, indicating that high pressure can cause negative effects in texture and color of fish flesh. Furthermore, the aerobic plate count (APC), psychrotrophic bacteria count (PBC), and coliform decreased with the increase in pressure. The samples pressurized more than 300 MPa had significantly lower levels of total volatile basic nitrogen (TVBN) than unpressurized sample. In addition, high pressure above 300 MPa delayed the production in TVBN and histamine content in milkfish flesh stored at low temperatures (4 °C and 15 °C), whereas the delaying effect on the increase of APC and PBC was significant at higher pressures (>400 MPa). However, compared with 15 °C, high pressure combined with low temperature storage at 4 °C more significantly delayed the changes in microbial and chemical quality. In conclusion, the results indicated that pressurization at 400 MPa for 5 min on milkfish flesh was able to prevent deterioration and quality loss, and extend the shelf life during storage at low temperatures, even though it can cause changes to fish flesh texture and color.