However, commercial carrageenans were used in previous studies and a structural characterization has not been conducted in all cases. An analysis of IRI activity of carrageenans characterized by NMR spectroscopy suggested that ι-carrageenan exhibited a lower IRI activity than κ-carrageenan. Furthermore, carrageenans with different structural units (,  and, in part, ) showed different levels of IRI activity . However, NMR spectroscopy cannot distinguish between carrageenan mixtures and hybrid carrageenans. In a previous study, we demonstrated that commercial carrageenans show considerable structural heterogeneity and that carrageenan types specified by the manufacturer do not necessarily reflect the actual structural composition . Several samples specified as -carrageenans were actually - or -- hybrid carrageenans. Our investigation also revealed that commercial carrageenans contain different types of cations.