The effect of rosemary extract and omega-3 unsaturated fatty acids on the properties of gels made from the flesh of mackerel (Scomber scombrus) by high pressure and heat treatments

Gels made from the flesh of mackerel (Scomber scombrus) and fortified with rosemary extract and omega-3 unsaturated fatty acids were studied in connection with high pressure/thermal treatments. Elasticity and breaking deformation were significantly higher in pressure-induced gels (300 MPa, 25 °C, 15 min), while hardness was considerably lower. For gels without ingredients the fraction solubilised with 8 M urea and 2% β-mercaptoethanol was larger in the pressurised samples, indicating more covalent bonding in heat-induced gels which could not be disrupted by the solubilising agent. Scanning electron microscopy showed that pressure-induced gels generally presented a structure more compacted than heat-induced gels. The high pressure activated lipid oxidation, the antioxidant effect of rosemary being evident in all samples.