Physical and rheological properties of fish gelatin gel as influenced by κ-carrageenan

Physical and rheological properties of fish gelatin (FG) (5%, w/v) gel containing κ-carrageenan (CG) at different levels (0%, 25%, 50%, 75% and 100% of total solid) were studied. Gel strength and hardness of FG/CG mixed gel increased with increasing CG content, while springiness of mixed gel decreased when CG was higher than 25% (P < 0.05). Rheological measurements revealed that the value of elastic modulus Gʹ of FG/CG mixed gel decreased as CG content increased. This could be associated with the phase separation between the two biopolymers present in the mixed gels as visualised by confocal laser scanning microscopy (CLSM). Moreover, gelling and melting temperatures also increased as the levels of CG increased (P < 0.05). However, the addition of carrageenan lowered the lightness (L*-value) but increased the redness (a*-value) of mixed gel samples. Based on fourier transform infrared (FTIR) spectra, the interaction between FG and sulphate groups of CG occurred. This study shows that the addition of 50% CG could improve the gelling property of fish gelatin gel by increasing gel strength and melting temperature.