Characterization of gelatin gels induced by high pressure

Gelatin gels made from cod and megrim skins were formed using high pressure and subsequent cooling at 7°C during 16–18 h. Pressure treatments were carried out at two temperatures (20 and 7°C) and 200, 300 and 400 MPa. Turbidity, gel strength and viscoelastic properties of these gels were studied. Gelatin gels from megrim showed lower degree of turbidity, independent of the treatment, only small significant differences were observed amongst them. In cod gelatins turbidity decreased as pressure increased, being higher at higher temperature. Gel strength of gelatin gels from megrim was about three times higher than gels from cod. High-pressure treatments improved gel strength only in gelatin gels from cod. However, in gels from megrim, which has high gelling capacity in comparison to cod gelatins, gel strength values of pressurized gels were lower than the control. Melting and gelling points did not vary substantially with pressure although values tend to improve. Initial values of G′ and G″ at 5°C after setting during 16–18 h were higher for megrim gelatins than cod gelatins except for high-pressure treated cod (400 and 200 MPa, 20°C) that showed the highest value. Gelation mechanism appears to be different between pressure- and heat-induced gels and they affect different to bonds that stabilise or destabilise the gel network. The properties of the resulting gelatins are also influenced by the initial collagen (that is different depending on the fish species and amino and imino acid content) and by the concrete treatment process.