and LC2 in the calcium form also showed a very high IRI activity. An overall comparison between the potassium and calcium forms indicates that κ-carrageenan or carrageenans with a high portion of consecutive κ-units show a higher IRI activity in the potassium form. In contrast, calcium ions seem to facilitate the IRI activity of ι-carrageenans and hybrid carrageenans rich in ι-units. These results suggest that the stabilization of the helical conformation of carrageenans is important for the IRI activity of carrageenans: Monovalent ions (especially potassium) were described to stabilize helices of κ-carrageenans , whereas calcium ions stabilize the helices of ι-carrageenans ). In the literature, varying IRI activities were observed for different carrageenan types: In a previous study, we found a lower IRI activity for ι-carrageenan compared to κ-carrageenan , while Kamińska-Dwórznicka et al. ( ) described a comparable activity of the two carrageenan types. However, the structure of the carrageenans used in the second study was not analyzed. As we also demonstrated in a previous study, the structural composition of commercial carrageenans shows considerable variation depending on the source . Furthermore, analyzed the IRI activity in a model food (sorbet) and not a defined model system which could also explain the different results (cations from the matrix may influence IRI activity). In a previous study, carrageenans with more than one structural unit also showed a considerable IRI activity . However, the samples used were inhomogeneous with regards to their associated