Stress relaxation behaviour and structural changes of muscle tissues from Gilthead Sea Bream (Sparus aurata L.) following high pressure treatment

Sea Bream muscle tissue was subjected to different high pressure treatments, and rheological changes were monitored during storage by means of the stress relaxation test. The best fit was obtained by application of the three term Maxwell exponential model, followed by the Nussinovich model. The application of 300 and 400 MPa pressures appeared to enable preservation of elasticity and stiffness of fish muscle during storage, compared to untreated samples. On the contrary, samples treated at 200 MPa underwent a decrease in elasticity during storage. The water holding capacity of dorsal muscle was also assessed, and it was found to decrease with increasing pressures. Immunoblot studies performed on the main structural proteins revealed that a pronounced time-dependent degradation of desmin, observed in untreated samples, could be prevented by treatment at 400 MPa. Taken together, our results strongly suggest that high pressure treatments inactivate degrading enzymes acting on proteins that are related to tissue integrity preservation, texture quality, and water holding capacity.