Alaska Pollock Fish Protein Gels as Affected by Refined Carrageenan and Various Salts

Refined iota and kappa carrageenans were added (0, 0.25, 0.5, 0.75 and 1.0%) to Alaska pollock surimi and combined with various salts (NaCl, KCl or CaCl₂, respectively) at 2%. Sample pastes were subjected to dynamic rheology (temperature sweep heating 20-80C and cooling 80-20C). Gel properties (breaking force, penetration distance and water retention ability [WRA]) were measured at 0, 3, 6 and 9 freeze/thaw cycles. The effect of salt type indicated that NaCl significantly (P<0.05) increased force values, whereas KCl increased (P<0.05) penetration distance. WRA was improved (P<0.05) by KCl, followed by NaCl and CaCl₂, respectively. Kappa carrageenan increased (P<0.05) force values. However, adding kappa and iota carrageenans tended to decrease penetration distance. Iota carrageenan (0.25-1.0%) generally increased (P<0.05) or did not significantly (P>0.05) affect WRA compared to kappa carrageenan. Utilizing KCl and NaCl combined with kappa and iota carrageenans could increase gel strength and WRA. Practical Applications: Iota carrageenan tended to improve or maintain water retention ability of Alaska pollock fish protein gels during extended freeze/thaw cycles compared to when kappa carrageenan was added. However, kappa carrageenan tended to improve force values or gel strength of Alaska pollock fish protein gels. Therefore, a mixture of kappa and iota carrageenans should be evaluated to maximize the respective properties and optimize the amount of each carrageenan type in order to improve functionality of Alaska pollock fish protein gels. In addition, further study to utilize a combination of NaCl and KCl rather than a single salt type could further maximize the functionality of an iota-kappa carrageenan blend in Alaska pollock fish protein gels.