Effect of Kappa-Carrageenan on the Gelation of Horse Mackerel (T. Murphyi) Raw Paste Surimi-Type

Gelation of fresh (unfrozen) raw surimi-type paste (RS paste) from horse mackerel (T. murphyi) was studied in the presence of-carrageenan (0.5, 1, 2% C) and KCl (0.5-2%) as a substitute for NaCl. Gelation was traced by measuring the storage modulus (G) during heating-cooling cycles. Variations in G during the heating stage of the mixed system RS-C characterised the presence of a phase separation in this stage due to C solubilitation (at about 50°C) as well as to RS gelation (35-80°C) in the mixture. It was also observed that when C was added as a single ingredient, it inhibited RS gelation as a function of its concentration (2%). Nevertheless, during the cooling stage, the final G value for the RS-2% C mixed system was greatly increased. This reinforcing would be caused by further (cold) C gelation in the mixture. It is theorised that C might act by forming ‘packed’ microgels within the RS protein gel network, which is favoured upon application of a moderate (40°C, 60min) thermal treatment rather than when an extreme (90°C, 20min) treatment is applied. On the other hand, although KCl enhanced gelation of the 2% C solution, addition of this salt to the RS-2% C mixture did not improve its gelation. Rheological information was complemented with observation of the resulting structures by scanning electronic microscopy (SEM).