Thermal gelation properties of two different composition sardine (Sardina pilchardus) muscles with addition of non-muscle proteins and hydrocolloids

A Thermal Scanning Rigidity Monitor was used to study heat gelation in two sardine minces (S1 and S2) differing in compositional properties (fat content (S1 = 4.3%, S2 = 9.6%) and water content (S1 = 76.5%, S2 = 72.0%)), protein functionality (soluble protein (S1 = 62.6%, S2 = 49.8%) and viscosity (S1 = 3140 cP, S2 = 2323 cP)), as well as the contribution to gelation of a number of non-muscle proteins (egg white, soy protein, sodium caseinate, wheat gluten) and hydrocolloids (iota-carrageenan and starch). The batter of the mince, characterised by higher protein solubility and viscosity and lower fat content (S1), exhibited greater structural stability at temperatures above 50 °C. The addition of gelling ingredients always produced an increase in maximum rigidity values, except in the case of sodium caseinate or starch-containing batters of mince with low protein solubility and viscosity (S2), where the rigidity is considerably inferior throughout the experimental temperature range. Of the non-muscle proteins assayed, batters contanining egg white presented the highest rigidity at maximum gelation peak, mainly in the low quality mince (S2). Iota-carrageenan also increased rigidity considerably with respect to the controls. Addition of starch gave less rigidity than iota-carrageenan, although it helped stabilise the formed gel at high temperatures (80 °C).