The sulfate contents (calculated from the sulfur contents) of the cation-exchanged carrageenans were slightly different from the unmodified carrageenans. For IC3 and C2, a clearly higher sulfate content was observed after cation-exchange. This can be explained by the presence of sucrose and glucose in the unmodified samples. These low molecular weight compounds are added for the standardization of the carrageenans and are removed by the precipitation step during the cation exchange. For all other samples, the sulfate content was comparable or in some cases even lower than in the unmodified samples. The partially lower contents can be explained by small amounts of salt in the samples. This is also supported by a comparison of the sulfate contents from ICP-OES and the theoretical sulfate content (calculation based on the structure). However, small amounts of salt are not expected to influence the determination of the IRI activity significantly: The salt excess in the monocationic carrageenans would lead to a salt concentration of about 0.2 -2.4 mM in a 1 mg/mL carrageenan solution. demonstrated that low concentrations of salt (0.3 mM KCl) do not significantly influence IRI activity, whereas high concentrations (30 mM KCl or 100 mM NaCl) lead to a significant increase in ice crystal diameter. Given that the salt concentration of the samples used in this study is notably lower than 30 mM, it can be assumed that the effect on IRI activity is minimal.