Carrageenans and alginate effects on properties of combined pressure and temperature in fish mince gels

Sulphated polysaccharides (kappa- and iota-carrageenan) and sodium alginate added to blue whiting mince were subjected to three different pressure/heat treatments in order to determine the functionality of each one in mince gel. The effect of the gelling treatment was largely dependent on the hydrocolloid used. In general, gelation at atmospheric pressure induced gels that were more adhesive, harder (except in the case of iota-carrageenan) and yellower, and less cohesive. Lower pressure conditions (200 MPa, 10°C, 10 min) produced more cohesive gels with higher breaking deformation and lower elasticity; these gels also had the highest values of work of penetration (especially those containing iota-carrageenan). Higher pressure conditions (375 MPa, 37°C, 20 min) induced gels with the lowest hardness; all other characteristics were similar in some cases to pressurized gels at lower gelling conditions and in others to heat-induced gels. The carrageenans (iota or kappa) appeared to form a reticular structure in the heat-induced gels, which was not observed with alginate. In the pressurized gels, iota-carrageenan was in globular form, indicating that it had not gelled; kappa-carrageenan, on the other hand, formed small, fine reticular structures. Alginate formed a fine, dense network in the higher treatment conditions, but this was not observed in the lower treatment conditions. From a technological standpoint, the composite system offers new potential, due not only to the added hydrocolloid but also to the treatment applied.