Nothing fishy about UHP processing shelf life findings

Quality of salmon flesh was assessed after exposure to UHP 200, 400, or 600 Megapascal (MPa) compared with no UHP and 30 days of storage at 4 °C.

The use of UHP at levels greater than or equal to 400 MPa improved the color, hardness, and chewiness of the flesh, said the researchers.

Salmon flesh quality analyses included the degree of changes in interspacing of muscle bundles, color, texture profiles (hardness, chewiness, cohesiveness, and elasticity) and microbial growth.

UHP does not require heat, preserves the quality of salmon flesh, and allows for an increase in the chilled storage period.

Total aerobic plate count (TPC), lactobacilli, and yeast were assessed in salmon fillets.

UHP treatment and salmon quality​

Relationship between UHP treatment and salmon flesh quality was investigated.

There are many preservation methods for salmon, such as hot or cold smoking, vacuum- or modified atmosphere-packaging (MAP), freezing, and canning.

Although current methods may improve food safety, the quality of the salmon flesh may be decreased, said the researchers.

Vacuum-packaging or MAP for salmon flesh storage are commonly used due to increasing demands for raw fish. However, these methods are not perfect for fish preservation, as microorganisms remain after packaging, and the resulting shelf-life is short.

Lightness of salmon fillets exposed to 400 and 600 MPa and stored at 4 °C after 30 days increased significantly (P < 0.05) as compared to UHP applied at lower values.

Chewiness rose (P <0.05) with increasing pressure, especially at 400 and 600 MPa.

Cohesiveness and elasticity showed low force values and did not change in any treatment group.

Microbiological changes​

Initially, the TPC and the yeast count were <​100 CFU/g, whereas lactobacilli counts were below the detection limit of 10 CFU/g.

At 200 MPa, the total bacterial count decreased by 30%, but the yeast count did not change. At 400 and 600 MPa, microbial counts were initially below the detection limit, however, the counts increased significantly (P ​< ​0.05) during storage at 4 °C.

All the microorganisms (total colonies, lactobacilli, and yeast) decreased in all groups after 30 d of storage at 4 °C in a pressure-dependent manner (<​100 at 600 MPa).

The researchers said the results indicated that microorganisms can be controlled initially by UHP treatment and may extend the shelf life of treated fillets.

“After 30 d of storage at 4 °C, salmon flesh treated with UHP at >400 MPa showed positive effects on color change, texture profile change, and inhibition of microorganism proliferation. ​

“We conclude that UHP (>400 MPa) is a useful method for salmon flesh preservation for markets.” ​

Source: Journal of Food Science

Online ahead of print, DOI: 10.1111/1750-3841.12714​

“Changes in Salmon (​Oncorhynchus keta​) Flesh Quality Following Ultra-High Pressure Treatment and 30 d of Chilled Storage​”

Authors: Dae-Hun Park, Jong-Gi Jung, Bo-Ram Jung, Gyeyeop Kim, Honggyun Lee, Hyeon-A. Kim, and Mi-Ae Bang