Carrageenans with both κ and ι structural units also showed significant IRI activity. A high IRI activity was observed for the potassium forms of carrageenans with a high portion of consecutive κ units. However, conversion into the calcium form in part even improved the properties of hybrid carrageenans. Our results also suggested that not only the portion of the individual structural elements are important but also the abundance and length of the corresponding blocks. The results of this study lay the basis for a targeted extraction of carrageenans to optimally exploit their functionality. Future work could focus on the application of structurally defined carrageenans in different food products.