Influence of cations on texture, compressive elastic modulus, sol-gel transition and freeze-thaw properties of kappa-carrageenan gel

The influences of 4 mono- and di-valent cations (K⁺, Na⁺, Mg²⁺ and Ca²⁺) on the mechanical, sol-gel transition and freeze-thaw properties of κ-carrageenan gel were investigated. Texture profile analysis results demonstrated that the texture behavior of gelatinized κ-carrageenan was obviously influenced by the cation types and concentrations and the influence of K⁺ was the greatest. The gelling temperature (T_g) of κ-carrageenan gel showed a positive correlation with cation concentrations and the influence of K⁺ was still the largest. However, the viscosities of κ-carrageenan gels evoked by divalent cations were higher than monovalent cations. Furthermore, cations reduced freeze-thaw stability of κ-carrageenan gels and followed the same influence tendency as viscosities. It was proposed that divalent cations form direct crosslinking between κ-carrageenan helices while monovalent cations only bind single sulphate groups on κ-carrageenan molecules. There were more junction zones in divalent cations invoked gels. Furthermore, K⁺ and Ca²⁺ cations showed apparent synergistic effect in the research.