Impact of Freezing Process on Salt Diffusivity of Seafood: Application to Salmon (Salmo salar) Using Conventional and Pressure Shift Freezing

The depression of the melting temperature of ice under pressure permits to obtain a rapid freezing of foods. The expected benefit lies in reduced water diffusion from the intra- toward the extracellular media, resulting in a reduced drip loss during thawing. Beside, the modification of the cellular structure induced by ice formation may affect the mass diffusivity of the flesh. In the present study, salmon was used as a model food. Slabs of salmon (1-cm thick) were frozen using blast air and pressure shift freezing at 200 MPa. The impact of the freezing process on the mass diffusivity of salt was evaluated using an aqueous solution (NaCl, 3% w/w). Results indicate that the effective mass diffusivity was slightly increased in comparison to non-frozen flesh when a rapid freezing process was used. This may be attributed to a change in the permeability of cell membranes caused by freezing and high pressure.